FILE: <bc-38.htm> GENERAL INDEX [Navigate to MAIN MENU ]
[For
educational purposes only; do not review, quote or abstract]
BIOLOGICAL CONTROL OF NOXIOUS PLANTS AND WEEDS
(Contacts)
----Please CLICK
on
desired underlined categories [ to search for Subject Matter,
depress Ctrl/F ]:
|
[Please refer also
to Related
Research #1, #2 ] |
|
Introduction In the United States there are 500 major species of
noxious plants (weeds) which cause an estimated annual loss of around $8
billion (Chandler 1980, Goeden & Andrés 1999). These plants infest
cropland, rangeland, recreational and aquatic sites and vary in their
economic importance and need for control. Cultural and chemical controls for
noxious plants are effective but temporary at best, if not uneconomical.
There is also a growing awareness that herbicidal treatments might be harmful
to the environment including humans. Herbicide resistance spreads rapidly
when very effective compounds are used. Thus, control of noxious plants is no
longer a matter of improved plant kill; planning and ingenuity are required
to minimize immediate losses without inviting incursions by replacement weed
species. Aldrich (1984) commented that noxious plants (weeds) are part of
dynamic ecosystems continually evolving in response to natural and cultural
control pressures. Biological control is a proven method of controlling
noxious plants, and there an a large volume of literature devoted this
approach. Quadrennial international symposia and their proceedings
continually update knowledge about this discipline. Goeden & Andrés
suggest that biological control continues to offer promise and expanded
application in reducing losses due to noxious plants. Biological noxious plant control involves the study of
relationships among such plants, their associated organisms and the
environment, followed by the manipulation of selected species (natural
enemies) to the detriment of the target plant species. Attention focuses on
those plant/natural enemy relations that have coevolved to the degree that
natural enemies cannot exist or would have little environmental impact in the
absence of their host. Goeden & Andrés suggest that coevolved natural
enemies that have developed a high degree of host specificity have proven the
safest to use, are least likely to damage nontarget plant species and are
most suitable for regulating the plant's abundance. Biological control
researchers go to considerable effort to match natural enemies to their host
plants in problem environments, seeking combinations and devising
manipulations most detrimental to the target plants. Presently all biological
control activity involving plants in Australia is regulated by the Biological
Control Act of 1984, which details how plants targeted for biological control
are to be open to public review before the release of biological control
agents (Cullen & Delfosse 1984, Turner 1985). The natural enemies used in biological control are
self-perpetuating only in the presence of their plant hosts and then only
within the limits set by the environment. According to definitions for
biological control (Smith 1919, 1948, DeBach 1964), the ability of natural
enemies to regulate noxious plant or arthropod populations in a
self-sustaining, density-dependent manner sets biological control apart from
other methods of control. The methodology used in biological plant control consists
of six parts: (1) assuring proper identification of the target plant, (2)
charting its geographic range, (3) characterizing the habitats it infests,
(4) ascertaining the losses caused by the plant, (5) determining the degree
of control required, and (6) compiling a list of natural enemies already
present or reported elsewhere. Both advantages and disadvantages are, however, associated
with biological control of noxious plants. Advantages include (1) the
introduced agents perpetuate and distribute themselves throughout the plant's
range, (2) the impact of host-specific agents is focused on a single plant
species without harm to other plants, (3) the cost of developing biological
control is relatively inexpensive compared to much higher costs for other approaches
(Harris 1979, Andrés 1977), (4) the agents are non polluting, energy
efficient and biodegradable, (5) the knowledge generated during pre release
and evaluation studies contributes to a broader understanding of plant
ecosystems and environmental factors regulating natural communities.
Disadvantages are (1) once established in an area an introduced agent cannot
be extirpated from the environment, (2) a host specific agent will control
only one species in a noxious plant species complex, (3) impact of the agent
is usually slow, requiring 3-4 years before control is achieved, (4) an agent
may expand its host range to include closely related nontarget plants and (5)
the establishment, spread and impact of a biological control agent is
determined by the quality of the environment and the host, and cannot be
predicted. Introducing New Natural Enemies For
Biological Control Naturalized noxious plants often have few host specific natural
enemies capable of effectively regulating their abundance. Additional species
of natural enemies may be sought in the plant's native range and introduced
to the problem areas. This approach is common worldwide, and has led to the
introduction of numerous plant-feeding insects and mites, and recently, plant
pathogens and nematodes (Julien 1982, 1987). Finding and introducing
phytophagous organisms requires thorough preintroduction studies to assure
that control can be achieved and that economically and ecologically important
plants will not be adversely affected. Several authors have listed the
guidelines for introducing such natural enemies (Zwölfer & Harris 1971,
Frick 1974, Andrés et al. 1976, Klingman & Coulson 1983, Schroeder &
Goeden 1986). Goeden & Andrés list the following steps in this approach:
(1) Project Selection. Once released, introduced natural enemies
cannot be restricted to parts of the plant's geographic range. Before
undertaking studies that may lead to natural enemy introduction there must be
assurance that the plant has few, if any, redeeming virtues and that there is
little or no public opposition to the project (Turner 1985). (2) Search
For Natural Enemies. A list of organisms recorded from the target plant
is compiled from literature and museum records, which is followed by field
surveys and studies of associated organisms in selected parts of the plant's
native range. Such organisms are collected, identified and checked in the
literature and museum records. Candidate species are selected for further
study. (3) Host Range & Biological Studies. Biological studies
involving various aspects of behavior such as feeding and oviposition, are
conducted in the laboratory in efforts to determine host plant range. Tested
are cultivated and ecologically important plant species, with special
attention on close taxonomic relatives (Wapshere 1974a). (4) Summary of
Host Range Studies. A summary of the natural enemy's taxonomy, behavior,
biology and host plant relationships is prepared in a special report. These
reviews are prepared in the United States by the U. S. Department of
Agriculture, Animal & Plant Health Inspection Service, Technical Advisory
Group (USDA, APHIS-TAG), Hyattsville, Maryland, as well as relevant state
Departments of Agriculture and universities. A recommendation is made on
whether or not to import the candidate organism. (5) Importation and
Release. After approval, natural enemies are collected from the same
field populations that constituted the test material and transferred to a
domestic quarantine. Univoltine or difficult to culture species are
identified and examined to assure that they are free from parasites and
entomogenous pathogens. Species which are amenable to culture are reared for
one generation before being liberated. Quarantine processing is labor
intensive and often restricts the number of biological control agents that
can be examined. Release sites are selected on the basis of climate, habitat,
freedom from disturbance and other factors in order to enhance chances for
establishment. (6) Evaluation. Evaluations are given on success of
establishment, field reproduction and damage inflicted against the target
plant. Noxious plants may have dozens of associated natural
enemies, with some species attacking only the flowers and fruit, while others
attack the leaves, stems, branches, crowns or roots. Zwölfer (1988) reported
that the guild of agents attacking the flower heads and achenes of an
asteraceous thistle may include monophagous to oligophagous species that vary
in their impact on the host plant. Pre introduction studies help determine
which species are sufficiently host specific for biological control purposes
and suggest the best sequence for importation. An agent's host finding
capability and competitiveness with other flower head infesting species can
be very important (Zwölfer & Harris 1971, Harris 1973, Goeden 1983). Conservation of Biological Control
Organisms Sometimes indigenous or exotic natural enemies feed and reproduce
on a noxious plant host yet do not provide effective biological control.
However abundance of an associated agent might be effectively enhanced to
provide localized reduction of a plant. For example, DDT has been used
selectively to eliminate Exochomus sp., a coccinellid beetle predator
that restricted the potential of an introduced cochineal insect, Dactylopius
opuntiae (Cockerell), to control the prickly pear cacti, Opuntia
ficus-indica (L.) Miller and O. tardispina
Griffiths in South Africa (Annecke et al. 1969, Moran & Zimmerman 1984).
Reducing the coccinellid predators allowed the cochineal insects to increase
in number and the cacti were effective controlled. On the other hand many
indigenous species have complements of natural enemies which themselves are
controlled by parasitoids, predators and environmental factors. A thorough
understanding of plant/natural enemy/environment relationships is required in
order to manipulate aspects of the relationship to favor the agent's impact.
In general this is not been feasible because of the high cost involved. Augmentation of Natural Enemies Supplemental releases of a natural enemy may increase its
abundance and time its impact against a noxious plant. This approach was not
widely practiced until the discovery that an endemic fungus, Colletotrichum
gloeosporioides (Penz.) Sacc. (Melanconiales), could be cultured and
applied to northern jointvetch, Aeschynomene virginica (L.)
B.S.P. (Leguminosae), a noxious plant of rice in the southeastern United
States (Daniel et al. 1973). This work stimulated the search for indigenous
pathogens associated with other noxious plants (Charrudattan & Walker
1982, Templeton et al. 1978). The impact of the moth, Bactra verutana
Zeller could be enhanced by supplementing existing field populations with
large numbers of this insect against purple nutsedge, Cyperus rotundus
L. in cotton (Frick & Chandler 1978). Although experimental control was
demonstrated, the method proved too expensive to be practical. History of Plant Control with Natural
Enemies Following is a summary of historical events in the
biological control of noxious plants derived from Goeden & Andrés (1999): For most of its history, the biological control of noxious
plants was the domain of a rather small, dedicated group of broadly versed
entomologists (DeBach 1964), which began rather by accident. The earliest
record of the biological control of a noxious plant involved the intentional
introduction of the cochineal insect, Dactylopius ceylonicus
(Green) to northern India from Brazil in 1795 in the false belief that it was
D. coccus Costa, a species cultured commercially as a source of
carmine dye. Instead of reproducing well on the cultivated, spineless prickly
pear cactus, Opuntia ficus-indica (L.) Miller, D.
ceylonicus readily transferred to its natural host plant, O. vulgaris
Miller, that had become widespread in India when it escaped cultivation in
the absence of its South American natural enemies. Once the value of D.
ceylonicus as a biological control agent was recognized, it was
introduced in 1836-1838 to southern India, where it brought about the first
successful, intentional use of an insect to control a noxious plant. Shortly
before 1865, D. ceylonicus also was transferred from India to
Sri Lanka which resulted in the successful control of O. vulgaris
throughout the island (Goeden 1978, Moran & Zimmerman 1984). Attention next shifts to Hawaii where Albert Koebele was
hired as foreign explorer after helping to achieve the spectacularly
successful biological control of the cottony-cushion scale on citrus in
California during the late 1890's (Doutt 1958, 1964). Koebele explored the
jungles of southern Mexico during 1902 for insects feeding on lantana (Lantana
camara L., Verbenaceae). Lantana was an ornamental plant of Central
and South American origins that had escaped from cultivation to become a
serious pest in Hawaii. Koebele shipped 23 species of insects to Hawaii
(Goeden 1978). Koebele suffered problems of extreme temperatures, unscheduled
shipping delays, pathogens and other contaminants (Perkins & Swezey
1924). Upon their arrival by ship in 1903, the insects Koebele collected were
liberated directly on lantana plants in the field without host specificity
tests. Eight species, including some of the most effective natural enemies of
lantana, were reported established on this plant throughout the islands by
1905 (Andrés & Goeden 1971, Goeden 1978, Julien 1982). Procedures for exploration of natural enemies of an alien
plant in its country or countries of origin were pioneered in the lantana
project. The lantana seed fly, Ophiomyia lantanae (Froggatt)
(Diptera: Agromyzidae), was transferred from Hawaii to New Caledonia in
1908-1909 and to Fiji in 1911 (Rao et al. 1971). These shipments marked the
beginnings of a tradition of transfer projects (DeBach 1964), involving
biological control agents of proven worth to other countries with the same
noxious plants. Three more species of lantana insects were then transferred
from Hawaii to Fiji during 1922-1928 (Rao et al. 1971). An attempt was made to introduce D. ceylonicus
to Australia from Ceylon and India in 1903, without success (Goeden 1978,
Moran & Zimmerman 1984). Then an intensive Australian effort on the
biological control of prickly pear cacti (Opuntia spp.) began in
1913-1914, when the two membered Prickly-Pear Travelling Commission surveyed
the insects and pathogens associated with these plants in Java, Sri Lanka,
India, East Africa, South Africa, the Canary Islands, littoral Mediterranean
countries, the United States, Mexico and parts of Central America, the West
Indies, South America and Hawaii (Johnston & Tryon 1914). This effort of
worldwide exploration for natural enemies of a group of noxious plants
remains unequalled in scope of geographic coverage. Biological control of the prickly pear cacti, Opuntia
inermis deCandolle and O. stricta Haworth in Australia
ranks as one of the most successful projects in biological control of noxious
plants. The project followed the initial efforts of the Prickly Pear
Travelling Commission, which first recognized the potential value of what was
later to become the principal natural enemy, the moth, Cactoblastis cactorum
(Berg) (Lepidoptera: Pyralidae). The principal entomological effort in this
biological control project occurred during the 1920's when North and South
America, particularly the southern United States, Mexico and Argentina, were
thoroughly explored for potentially useful, cactus-feeding insects. More than
150 species of cactus insects eventually were collected and studied, many of
which were new to science. From 1921 to 1925, 48 species were imported into
Australia, of which 19 were liberated and 11 became established. A single consignment of C. cactorum was
imported from Argentina in 1925. Large scale mass culture and host plant
specificity tests with useful and weedy plant species were undertaken for the
first time in a biological control project. Cactoblastis cactorum
became widely established following the distribution of more than 2.7 billion
mass reared and field collected eggs between 1925 and 1933. Almost 90% of the
original stands of O. inermis and O. stricta were
destroyed by 1934 through larval feeding by this moth, supplemented by
airborne, soft-rot bacteria for which the borers provided entrance wounds
into infested plants. Virtually complete control of the cacti was achieved in
Queensland and northern New South Wales involving 24 million ha of formerly
infested land that was restored to agricultural use (Dodd 1940, Goeden 1978,
Moran & Zimmerman 1984). The spectacular success of Cactoblastis cactorum
tended to eclipse the benefits derived from other cactus insects used in
biological control, notably several species of cochineal insects (Moran &
Zimmerman 1984). For example, Dactylopius ceylonicus was
successfully reintroduced to Australia during 1913-1915 and virtually
eliminated O. vulgaris as a rangeland weed in Queensland. Both C.
cactorum and Dactylopius spp. were transferred during the mid
1920's and 1930's to countries where prickly pear cacti also were introduced
pests: Indonesia, Mauritius, New Caledonia, Reunion and South Africa (Rao et
al. 1971, Greathead 1971, Goeden 1978). In South Africa and Mauritius these
early successful transfer projects led to the independent development of other
successful research projects in the biological control of noxious plants
(Greathead et al. 1971, Goeden 1978, Julien 1982, 1987). Another noteworthy success following the prickly pear
cactus effort was the biological control of Koster's curse, Clidemia hirta
(L.) D.Don (Melastomataceae). This shrub, native to the West Indies and
tropical America, became a serious problem on Fiji. Following a preliminary
survey of insects attacking C. hirta and allied
Melastomataceae, Liothrips urichi Karny was selected as a
promising biological control agent and its life history and host plant
relationships intensively studied in Trinidad during 1927-28. Potted C.
hirta infested with the thrips were shipped in cold storage to Fiji in
1930. Upon arrival the thrips were transferred directly to plants in the
field. Field releases continued throughout 1930. By 1932-33, several hundred
hectares of thrip stunted C. hirta had been overgrown by plant
competitors of greater forage value. Shaded and greatly weakened by thrips
attack these weeds were soon defoliated and killed. Regrowth was readily
located and attacked by L. urichi. By 1937 the competitive
ability of the C. hirta was permanently impaired by continued
thrips attack except in a few shaded and wet areas (Simmonds 1937, Rao et al.
1971, Goeden 1978, Julien 1982). New Zealand joined the list of Commonwealth countries
sponsoring original research on biological control of noxious plants in the
1920's. Studies were initiated of insects attacking gorse, Ulex europaeus
L. (Leguminosae) in England in 1926 and the introduction and successful
colonization of the seed weevil, Apion ulicis Forster was
accomplished during 1929-31. Surveys of insects attacking blackberries (Rubus
spp., Rosaceae) in Europe and North America were conducted during the mid
1920's, but no species were thought safe enough for introduction and the
project was abandoned. Beginning in 1927 and continuing into the 1930's,
diapausing pupae of the cinnabar moth, Tyria jacobaeae (L.), a
defoliator of tansy ragwort, Senecio jacobaea L. (Asteraceae),
were introduced into New Zealand from England, but establishment was not
attained. Australia also received T. jacobaeae from New Zealand
during 1929-32, beginning a series of colonizations that continued into the 1950's
and 1960's. Efforts to establish this moth were precluded by the predatory
activity of native insects, mainly scorpion flies (Goeden 1978, Julien 1982). In Australia the success of the prickly pear biological
control stimulated an attack on other widespread introduced rangeland noxious
plants, including cocklebur, Xanthium strumarium L.
(Asteraceae). Explorations for natural enemies began in the United States
during 1929. St. Johnswort, Hypericum perforatum L.
(Hypericaceae) was targeted in 1926 with explorations in England. The
cocklebur project yielded only partially successful biological control while
varying results with different introduced insects were obtained with St.
Johnswort (N. Clark 1953, L. R. Clark 1953). Basic studies performed on the St.
Johnsworth project set a pattern for contemporary Australian projects in
biological control. The natural enemies and technology transferred from this
project contributed to the development of biological control of noxious
plants in North America. Prior to World War II, a framework was developed for
the rapid expansion of biological control efforts that were conducted after
1950. The first biological control effort against plants in the continental
United States was developed by H. S. Smith, which involved the introduction
of insects to control native prickly pear cacti, Opuntia littoralis
(Engelmann) Cockerell, and O. oricola Philbrick, and various
hybrids, on rangeland of Santa Cruz Island in southern California (DeBach
1964). Phytophagous insects originating from the California mainland and in
Texas were introduced to Santa Cruz island beginning in 1940, but successful
biological control was attained only after Dactylopius opuntiae,
native to Mexico and the southern California coast, was introduced in 1951
from Hawaii ex Australia ex Mexico (Goeden et al. 1967, Goeden 1978, Goeden
& Ricker 1981). Biological control efforts were reduced during World War
II to a few transfer projects. For example, the leaf beetle, Chrysolina
hyperici (Förster) was transferred from Australia to New Zealand in
1943 for the biological control of St. Johnswort. In 1944 the introduction of
several insect species from Australia was made to California for specificity
testing and release during 1945-46 for the biological control of St.
Johnswort, which became known as Klamath weed. The work was organized by J.
K. Holloway of the USDA and H. S. Smith of UC, Riverside. Successful
biological control of Klamath weed, primarily caused by the defoliating leaf
beetle, Chrysolina quadrigemina (Suffrian), rivaled the
Australian success with prickly pear cacti. This success primarily was
responsible for fostering the establishment and expansion of biological
noxious plant control in North America (Huffaker 1957). The first intentional
introduction of an insect for plant control was made in Canada in 1950 with
the importation of Chrysolina quadrigemina and C. hyperici
from California to control St. Johnswort (Smith 1951). Within a decade after
the liberation of C. hyperici and C. quadrigemina,
the Klamath weed had been reduced in status from an extremely important
rangeland scourge to that of an occasional roadside plant, and now occurs at
less than 1% of its former density and has been removed from the list of
noxious plants in California (Holloway & Huffaker 1949, 1951). Its present occurrence primarily along
roadsides is linked to disturbance there of the phytophagous biological
control agents (E. F. Legner, unpub. data). Efforts were resumed in Hawaii in 1945 to control Eupatorium
adenophorum Sprengel (Asteraceae) with the introduction of the stem
gall forming fly, Procecidochares utilis Stone, which
presumably was recommended for introduction to Hawaii by A. Koebele 20 years
earlier. This successful introduction was followed by a series of projects
undertaken by the Entomology Division of the Hawaii Department of
Agriculture, making Hawaii a center of activity in the biological control of
noxious plants during the 1950's and 1960's. Plants that were targeted for
biological control in the 1950's were the Christmas berry, Schinus terebinthifolius
Raddi (Anacardiaceae); elephant's foot, Elephantopus mollis
Humboldt, Bonplaud & Kuth (Anacardiaceae); sourbush, Pluchea odorata
(L.) Cassini (Asteraceae); melastoma, Melastoma malabathricum
L. (Melastomataceae); firebush, Myrica faya Aiton (Myricaceae);
and emex, Emex australis Steinheil and E. spinosa
Campdera (Polygonaceae). Substantial to complete biological control of emex
was achieved at 600-1,200 m elevations with the weevil, Apion antiquum
(Gyllenhal) introduced from South Africa in 1957 (Davis 1966). The rest of
these six projects and several contemporary transfer projects on biological
control in Hawaii are unfortunately poorly documented (Goeden 1978, Julien
1982, 1987). A successful project was begun near the end of World War
II on black sage, Cordia macrostachya (Jacquin) Roemer &
Schultes (Boraginaceae), an introduced plant pest in sugarcane fields on the
island of Mauritius. Preliminary surveys of the insect fauna of black sage
and related plant species was conducted in the West Indies during 1944-46.
Following detailed life history studies and host specificity tests, the leaf
beetle, Metrogaleruca obscura DeGeer was introduced to Mauritius
from Trinidad in 1947 (Simmonds 1950). The beetle populations multiplied
rapidly and by 1950 had spread over the entire island, causing heavy
defoliation which killed or weakened plants so that they were replaced by
competing plant species. A seed feeding wasp Eurytoma attiva
Burks also was introduced in 1959-50 (Williams 1960). Defoliation and seed
destruction by these introduced insects have continued to prevent the
regeneration of black sage (Simmonds 1967, Goeden 1978, Julien 1982). Until this time most plants targeted for biological
control were introduced and perennial in relatively undisturbed rangeland.
However, starting in Australia, Canada and the United States in the late
1950's, projects were initiated on aquatic and semiaquatic weeds, annuals and
biennials, cropland and ruderal weeds. For example, the first aquatic plant
targeted for biological control with insects was alligatorweed, Alternanthera
phylloxeroides (Martius) Grisebach (Amaranthaceae). The first annual
plant targeted for biological control with insects in North America was
puncturevine, Tribulus terrestris L. (Zygophyllaceae). A
classic Commonwealth of Biological Control study by Zwölfer (1965) of the
insect fauna of Canada thistle, Cirsium arvense (L.) Scopoli
and other wild Cynareae (Asteraceae) in Europe which was sponsored by the
Canada Department of Agriculture during the early 1960's, formed the
foundation for a number of biological control projects targeted on introduced
thistles in Canada and the United States (Schröder 1980). These included
annual, biennial and perennial species of Carduus, Centaurea, Cirsium
and Silybum (Goeden et al. 1974a). These projects have continued with
mixed results. Especially interesting is the successful biological control of
musk thistle, Carduus nutans L., attained with the introduced
seedhead weevil, Rhinocyllus conicus L. in Canada (Harris
1984a) and Virginia (Kok & Surles 1975). Introduced spurges, Euphorbia spp. (Euphorbiaceae),
of Eurasian origins, were targeted for biological control in Canada in the
early 1960's with the first introduction of the hawk moth, Hyles euphorbiae
L. from Germany in 1965 (Harris 1984b). The biological control of rush
skeletonweed, Chondrilla juncea L. (Asteraceae) in Australia is
another important advancement. This project was the first to involve the
intentional international transfer of a phytopathogen for the biological
control of a plant, i.e., the rust fungus Puccinia chondrillina
Bubak & Sydenham (Uredinales) between Italy and Australia in 1971 for the
successful biological control of a noxious plant. This project also was one
of the first to target a plant pest of cropland (dryland wheat). It
established procedures for testing phytopathogens for host specificity under
quarantine conditions and involved the first intentional importation in 1971
of a phytophagous mite, Eriophyes chondrillae for biological
control (Cullen 1974, 1978). Scope of Biological Noxious Plant
Control Target Plants.--101 species of plants have been targeted for biological
control (Julien 1982, Julien et al. 1984). Thirty-three plant families are
represented among the 101 species, 25 of which belong to the Asteraceae and
19 of which are Cactaceae. The other 31 families are represented by five or
fewer species (Julien et al. 1984). Only about 22% of what Holm et al. (1977) consider to be
18 of the world's worst plant pests have been targeted for biological
control, i.e. Convolvulus arvenis L. (Convolvulaceae), Cyperus
esculentus L. and C. rotundus (Cyperaceae), and Eichhornia
crassipes (Martius) Solms-Laubach (Pontederiaceae) (Pemberton 1980).
Success was achieved only against the water hyacinth, E. crassipes,
while the other three projects have been unsuccessful (Julien 1982). It was also
noted that biological control of plant pests has not yet had a single project
against a noxious grass (Pemberton) despite grasses (Graminaceae) comprising
10 of the world's 18 worst plants according to Holms et al. (1977). Two
grasses, Digitaria sanguinalis (L.) Scopoli and Panicum dichotomiflorum
Michaux, were included among the some 80 species or species groups of plants
listed by Goeden et al. (1974a) as having been targeted, without success, for
biological control in the United States and Canada. Noxious grasses traditionally have not been considered
suitable for biological control because many are close relatives of important
cultivars. The chances of finding arthropod natural enemies able to
discriminate among such closely related, potential host plants are considered
remote. However, phytopathogens offer promise for control of noxious
graminaceous plants, as some are very host specific (e.g., rust fungi).
Noxious plants that are least amenable to biological control include those in
highly disturbed habitats, submersed aquatic plants (with apparently few host
specific natural enemies), highly toxic plants for which tolerable densities
are too low to be obtained by natural enemies, minor plants of limited
distribution that do not threaten to invade other areas, and plants whose
eradication is sought (Harris 1971, Frick 1974, Goeden 1977). Most noxious plants successfully controlled with
introduced natural enemies were introduced plant species (Julien 1982, Julien
et al. 1984). Only four species of native plant pests have been successfully
controlled with intentionally introduced organisms: Opuntia dillenii
(Ker-Gawler) Haworth (Cactaceae) on the island of Nevis in the West Indies
(Simmonds & Bennett 1966); O. littoralis and O. oricola
on Santa Cruz Island off southern California (Goeden et al. 1967, Goeden
& Ricker 1981); and O. triacantha (Willdenow) Sweet on the
islands of Antigua, Monserrat and Nevis in the West Indies (Simmonds &
Bennett 1966, Bennett 1971). All four of these native plants are prickly-pear
cacti (subgenus Platyopuntia) which along with other Cactaceae as
Moran & Zimmerman (1984) observed, are unusual among terrestrial plants
as regards their insect relations. Natural Enemies
Employed.--Julien (1982)
listed 174 biological control projects directed against the 101 noxious plant
species previously noted. Of these, 151 (87%) used exotic organisms
introduced against 82 plant species, and 23 (13%) used native organisms
against 26 plant species. There were 171 species of insects in seven orders
and 38 families comprising 98% of all releases of natural enemies and 96% of
all species of natural enemies released for biological control of these 101
plants. Most released species were in the Coleoptera, Lepidoptera, Diptera
and Hemiptera (Homoptera & Heteroptera), in decreasing order. There were
very few species of Orthroptera, Thysanoptera and Hymenoptera utilized. Of the 69 colonized species of Coleoptera, 60 species of
Lepidoptera, 20 species Diptera and 16 species of Hemiptera, 65%, 55%, 70% and
66% became established and 29%, 20%, 19% and 44% were effective as biological
control agents, respectively. The 10 families of insects that contained the
most species released for biological control of plants in decreasing order
were Chrysomelidae, Curculionidae, Pyralidae, Dactylopiidae, Tingidae,
Tephritidae, Cerambycidae, Noctuidae, Apionidae, Agromyzidae, Gelechiidae and
Tortricidae. Moran & Zimmerman (1984) reported that 63 species of
cactophagous insects were introduced worldwide for biological control of 22
species of Cactaceae, with 19 (30%) being successfully established. In
Australia there were 54 species and South Africa 24 species of insects
introduced for cactus control. Phytopathogens.--The decade of the 1970's saw increased efforts to use phytopathogens,
especially fungi, for biological control of aquatic and terrestrial noxious
plants (Charudattan 1978, Freeman & Charudattan 1981, Charudattan &
Walker 1982). Julien (1982) listed four phytopathogens that were imported for
biological control of noxious plants worldwide. Two of these pathogens were
accidental introductions, while the other two, both rust fungi, provide
examples of successful control of alien terrestrial plants with intentionally
introduced natural enemies. The introduction of Puccinia chondrillina
into Australia in 1971 for the biological control of rush skeletonweed has
already been mentioned. The high degree of host specificity exhibited by P.
chondrillina prevented the direct transfer of the Australian material
to control the two forms of rush skeletonweed found in the western United
States. Surveys in Europe uncovered a strain of P. chondrillina
that attacked the predominant form of the plant in the United States (Emge et
al. 1981). Another example is the successful biological control of
weedy blackberries, Rubus constrictus Lefevre & Mueller
& R. ulmifolius Schott (Rosaceae), with Phragmidium violaceum
(Schultz) Winter introduced from Germany to Chile in 1973 (Oehrens 1977).
Biological control of Hamakua pamakani, Aegeratina riparia
(Regel) King & Robinson (Asteraceae) was obtained with the pathogen Cercosporella
sp. (Uredinales) imported from Mexico to Hawaii in 1975 (Trujillo 1985). Charudattan (1984) discussed plant pathogens that could be
used as microbial herbicides. This strategy employs alien or native pathogens
which are mass cultured and applied as inundative inocula on target plant
pests. Successful examples include Collectotrichum gloeosporioides
f.sp. aeschynomene, registered and sold as CollegoTM for
control of northern jointvetch, Aeschynomene virginica on rice
and soybeans in Arkansas (Templeton et al. 1978); Phytophthora citrophthora
(R.E. & E.H. Smith) Leonian (Peronosporales), registered and sold as
DevineTM for control of milkweed vine, Morrenia odorate
(Hook. & Arn.) Lindle in Florida citrus (Ridings et al. 1978). Misc. Natural
Enemies.--There have
been two species of mites (Acarina) used successfully in the biological
control of noxious plants. Tetranychus opuntiae Banks was an
accidental introduction on prickly pear cacti in Australia. Eriophyes chondrillae
was the first mite species intentionally transferred between continents for
biological control of plants (Cullen 1974, 1978). An eriophyid mite, E.
boycei Keifer was exported from California to the Soviet Union in 1971
and 1972 for the biological control of ragweeds, Ambrosia spp.
(Asteraceae), but it was not released (Goeden et al. 1974b). Comroy (1982)
gave additional examples of native and introduced mites attacking weeds in an
attempt to demonstrate their efficacy as biological control agents. Although nematodes are well known as plant pest few
species are used as biological control agents. Only Paranguina picridis
Kirjanova & Ivanova has been used (Julien 1982, Julien et al. 1984). This
species, obtained from the Soviet Union, was released in restricted field
trials in Quebec, Saskatchewan, Canada in 1976 to control Russian knapweed, Centaurea
repens L. (Asteraceae). The nematode was successfully transferred from
central Asia to the Crimea and reportedly yielded good control of Russian
knapweed (Kovalev 1973). Experimental use was made of Nothanguina phyllobia
Thorne by augmenting its naturally occurring populations with large number of
infectious larvae to control silverleaf nightshade, Solanum elaeagnifolium
Cavanilles (Solanaceae) in Texas (Orr 1980). The introduction of N. phyllobia
into Australia and South Africa is under consideration. Other invertebrate natural enemies have limited use as
nonselective grazers in biological control of aquatic plants, including
crayfish, snails and tadpole shrimp (Andrés & Bennett 1975, Takahashi
1977). A vertebrate herbivore, the grass carp, Ctenopharyngodon idella
(Curvier & Valenciennes) (Pisces: Cyprinidae), has yielded mixed results
in different countries when introduced against mixes of aquatic plants
(Julien 1982). Seven other fish
species and the manatee complete the list of vertebrates that have limited
use in aquatic plant control of which the cichlid genera Tilapia and Sarotherodon
have shown the greatest control potential (Pictures) (Andrés &
Bennett 1975, Julien 1982, Legner 1983, 1986; Garcia & Legner 1999, Misc.
Research ). One report discusses
how fish converted noxious pests to edible protein (Legner 1980) Geese, sheep
and goats have long been used as managed grazers of terrestrial plants (King
1966). Biological Control Organizations in
Noxious Plant Control Goeden & Andrés (1999) detail the various world
organizations devoted to biological control of noxious plants. They disclose
more than 70 countries which were involved in 499 releases of introduced
natural enemies for biological control. References pertaining to
organizations are Julien (1982) Julien et al. (1984), Coulson (1985),
Schroeder & Goeden (1986) The biological control of noxious plants has deployed
phytophagous insects from seven insect orders. Of these the least successful
have been Lepidoptera, which because they are so large, are thought to be
more susceptible to generalist predators (Bernays & Moran 1996). Although
of initial importance for accelerating control of target plants, the
intrinsic rate of increase is not thought to be very important for
establishment. However, the level of specialization on the host plant may be
important. This degree of specialization may also be due to relatively
greater use of the plant for protection by highly adapted, specialized
species of phytophagous insects. Protection from abiotic events and predators
may involve internal feeding, galling, host-specific crypsis and many
specialized uses of particular features of the host plant. Monophagy (host
specificity) has to precede complex adaptive specializations, and specificity
is very important for restriction of the biological agent to the target
plant. Extreme specialization is not as common as monophagy among insects and
is not easy to measure. Characteristics of plants which make them vulnerable
to biological control are not easy to identify, especially as biological
noxious plant control has been dominated by relatively few target plants (= Opuntia
spp., Lantana spp. and Compositae). Finding patterns of biological
attributes of insect herbivores which were used in biological control and
among their host plants has not been possible. This is thought to be in part
because of the problem of trying to generalize among taxa and life forms with
unequal representation, which. Bernays & Moran (1996) state, "We
conclude that biological control of weeds remains an art dependent for
success on the judgment of the gifted naturalist with relevant experience." Bernays & Moran (1996) reviewed the biological
attributes of phytophagous insects, deriving their information primarily from
Julien (1982, 1987), Julien et al. (1984), and Moran (1986). The attributes
of plants that contribute to their status as weeds have been discussed by
Groves & Burdon (1986), McDonald et al. (1986), Mooney & Drake
(1986), Kornberg & Williamson (1987) and Joenje et al. (1987). Crawley
(1983) listed the main groups of vertebrate and invertebrate herbivorous
fauna and recorded the frequency of herbivory in these groups. Also, the mode
of feeding and the parts of the plant eaten were characterized. Phytophagous
species predominate among insects. Strong et al. (1984) estimated that ca.
25% of all known living species of animals and plants are plant-feeding
insects. The biological control of noxious plants has involved insects 96% of
the time. Establishing Phytophagous
Biological Control Agents There is no agreement about the proportions of
phytophagous species represented in each of the seven orders of insects that
include phytophagous species and which have been used in biological control.
Chapman's (1982) estimate for the phytophagous insect fauna of Great Britain
is considered the most reliable based on authoritative records of the feeding
habits of each species, and includes almost the entire British insect fauna.
Bernays & Moran (1996) show various tables which detail these data. In
making such lists, it is difficult to define phytophagy precisely, especially
for species that are mainly wood and seed feeding. There are differences in
the proportions of phytophages in different taxa in different geographical
regions, and limited knowledge of the fauna and their feeding habits. The
data suggest that high proportions of releases of Lepidoptera and Coleoptera
have failed to establish, and there have been an exceptionally large number
of introductions of phytophagous Coleoptera species worldwide. Diptera have a
good record of successful establishment. Julien et al. (1984) provided an estimate of effectiveness
of each of the releases of biological control agents from the success ratings
of Moran & Zimmermann (1985). Apparently the Dactylopiidae (Homoptera)
used widely as biological control agents against cacti, have the best record
of insect biological control agents. Also indicated is that large percentage
of releases of Pyralidae (Lepidoptera) are effective, but the data are biased
by the outstanding and repeated success of the cactophagous moth, Cactoblastis
cactorum against Opuntia spp. in many parts of the world. Other
pyralids have not been very successful. There have been 111 species of noxious targeted for
biological control using phytophagous insects, including 25 species against
which native phytophagous organisms have been used (Julien 1987). These
plants are in 33 families with the majority of target species in the
Compositae and Cactaceae (25 & 22 species, respectively), and with five
or fewer target plants in each of the other families (Julien 1984). No
success was achieved against target weed species in 11 plant families. Almost
2/3rds of all successful biological control attempts using insect herbivores
have been targeted at Lantana camara (Verbenaceae), cacti and
Asteraceae Compositae. About 25% of all the releases that resulted in establishment
of phytophagous insects for biological plant control have been on Lantana
camara, ca. 23% on 22 species of Opuntia (Cactaceae), 10% on 12
species of thistles and knapweeds (Asteraceae) and about 6% on St. John's
wort, Hypericum perforatum. There is a correlation between the
proportion of phytophagous insects species introduced for biological control
of noxious plants and the proportion that successfully established: the
greater the number of species introduced the greater the chances of
establishment. The overall probability of successful establishment of a
phytophagous insect for biological control of noxious plants has been ca.
0.71. This estimate was also given by Julien et al. (984) for all
invertebrate organisms and fungi used in noxious plant suppression. The
overall establishment rate has been greater in the case of composite plants
other than thistles and knapweeds (0.88), and in biological control of
aquatic plants (0.90). Phytophagous Insect Feeding
Habits Southwood (1978) and Strong et al. (1984) point out that
there are special evolutionary problems facing herbivorous insects. The most
general of these problems is the low nutrient content of plant tissues,
especially protein (McNeill & Southwood 1978, Lawton & McNeill 1979,
Lee et al. 1983). Phytophagous insects feed on a variety of plant diets, from
seed and fruit tissue, which is relatively rich in nutrients, to mature
leaves and wood, which have low levels of all available nutrients. Many
phytophagous insects are so well adapted to a generally low protein diet that
high levels may even be harmful (Broadway & Duffey 1986). Phloem feeding
insects encounter different problems as there are extreme variations in
nutrients and secondary compounds within a plant and within a leaf. Other
problems include genetic variation, age, climate, soil and time of day. Diet variability may be the greatest difficulty
confronting plant feeding insects. Somatic mutations were considered by Denno
& McClure (1983) as an evolutionary advantage for plants in their ability
to change under selection pressure by insect herbivores. Mobile insects may
have an advantage over sessile species in making selections, and there are
many examples of adaptability of herbivores (Jermy 1987) and few examples of
learning ability in relation to nutrient needs (Waldbauer et al. 1984, Lee
& Bernays 1988). Herbivorous insects that have been used in the biological
control of noxious plants include sap-suckers, miners, chewers, borers and
gall-formers that damage leaves, stems or cladodes, reproductive parts or
roots. Of all successful establishments, species where the immature stages
and the adults damage the host have been involved in 60% of the cases; for
37% the immature stages alone are involved, and species in which adults along
cause damage accounted for only 3% of the cases. The distribution of the main
feeding motes for the immature stages of insect herbivores used in the
biological control of weeds is given in table form by Bernays & Moran (1996).
Apparently feeding habit does not greatly affect the chances of establishment
of the herbivorous insects used in biological control. The differences in the
proportions for immature insects that feed by sucking simply reflects the
large number of cases where released sucking insects have established against
Lantana and against the Opuntia spp. For all weeds combined,
stem-boring species established more often than they failed and species which
feed on the leaves or cladodes of their host plants failed more often than
they established. These patterns do not include Lantana nor Opuntia,
however. There has been a significantly higher rate of
establishment for phytophages whose immature stages feed on seeds or fruits
and a highly significant increase in the number of releases that failed when
herbivorous insects were used whose immature stages feed on the roots of
their hosts, and relatively small number of releases have involved species
whose immature stages feed on stems. These statistics all exclude Opuntia
spp. and Lantana spp. as previously. Specificity to Host
Plant Host plant specificity is stressed in biological control
of noxious plants. Most insect herbivores are more or less host specific, i.e.,
they feed on plant species within a family or subfamily or lower taxon
(Chapman 1982). This may be influence partly by ecological factors rather
than an inability to feed and develop on certain plants. Some insects have
microhabitat limitations that greatly restrict the avai8lable foods, and some
herbivorous species are restricted in their use of plants by the action of
predators (Smiley & Wisdom 1985). Such ecological restriction is shown by
the fact that host plant range is usually greater under laboratory conditions
than in the field even with some seemingly monophagous species. In the
laboratory 53% of insect biological control agents were shown to increase the
number of species of host plants on which they could complete their
development; the remaining 47% were assumed to be restricted entirely by
plant characteristics. Plant physical appearance can be limiting, but for the
most part, host plant acceptance and rejection is determined by chemical
factors, especially plant secondary compounds (Dethier 1982). The most
specific feeders may respond positively to chemicals typical of their host
plants, but they are also inhibited from feeding by features of nonhosts
(Bernays & Chapman 1987a). Sensitivity to deterrents increases markedly
with specificity and it is likely, although unproven, that dependence on key
host compounds also increases with specificity. The absolute dependence on
particular compounds by monophagous species is considered rare, because of
the ability of most specific insects to eat nutrient mixtures without host
specific chemicals and to oviposit on neutral substrates. Feeding or oviposition inhibition may be due to repellents
acting from a distance, but more usually it is by deterrents in the surface
waxes of the plant, or within the living tissues. In some host specific
insects, volatile compounds, wax components or internal constituents are
specific attractants, phagostimulants or oviposition stimulants (Juniper
& Southwood 1986). The neural basis of host plant choice has been reviewed
by Dethier (1982), Hanson (1983) and Schoonhoven (1987). Such mechanisms are
considered variable, although specificity appears dominated by deterrent
inputs from nonhost chemicals. Information transmitted by certain deterrent
cells, which are sensitive to a wide range of plant secondary compounds, can
lead to rejection behavior or, in some cases, the compounds may cause a
decline in the input from cells signalling favorability (Dethier 1982,
Mitchell 1987). During the course of evolution, loss of sensitivity to
certain deterrents may be associated with a change in host us to plants
containing these compounds. A taxon that has been well studied this way is a
species group in the lepidopteran genus Yponomeuta (van Drongelen
1979). In this group, the ancestral host plants and more recent host
associations are well understood. Loss of sensitivity to particular secondary
compounds in recently adopted plant host species could accompanied the
behavioral switch to these hosts. Therefore, it seems that the derived insect
species have been permitted to use the new plant species, and in these
insects there do not seem to be essential compounds in the chosen hosts. Schoonhoven (1982) found that specific signalling
compounds which occur in the hosts of some insect herbivores evoke responses
from highly sensitive receptors. There are not enough examples to generalize,
but the clearest cases of this phenomenon occur in the most recent
specialized insect herbivores, such as Chrysolina spp. (Rees 1969).
The tarsi have receptors particularly sensitive to the host chemical,
hypericin, which occurs on the leaf surfaces of Hypericum spp. Genetic or experimentally based variation in sensitivity
to deterrents may yield some information on the importance of the rejection
response; for instance, population variation or cases of habituation, imply a
limited importance of deterrents, and probably a relatively low degree of
obligate specialization on the host plants. Unvarying deterrence, on the
other hand, would indicate a greater specialization. Up to now variation has
been greater in herbivorous insects with a wider host range (Jermy 1987).
But, adequate genetic variance was found in the specific bruchid beetle Callosobruchus
maculatus for artificial selection of larvae onto a new host in 16
generations (Wasserman & Futuyma 1981). The diversity of compounds involved in behavioral
responses of herbivorous insects may be viewed as convenient cues that enable
the insects to reject the nonhost with minimum delay and improve host finding
(Van Emden 1978). In more cases they are seen as plant defenses, which
insects may overcome, and if they do they may turn the defense into a useful
positive cue. On evolution and poly/monophagy, Huffaker et al. (1971)
stated, "Evolution has served both to promote monophagy and to promote
and maintain polyphagy in relation to the organisms and their environment.
The value of a broad diet is obvious; if one food (prey) is scarce another
can be substituted. By their very nature, specialists are better adapted to
utilize a specific prey at low prey densities in maintaining their own
populations. They are more closely synchronized in their habits, haunts and
seasonal life phases, and are normally better attuned in nutritional needs,
reproductive potential and searching behavior to effectively utilize their
prey at a minimal prey density. Thus, they are more effective and reliable
biological control agents..." The earliest insect herbivores are
believed to have been polyphagous, having arisen from a variety of ancestors
feeding on mixtures of pollen, fungi and decaying plant and animal matter
(Strong et al. 1984). Now the vast majority of phytophagous insects have
relatively restricted host ranges; probably over 90% feed on only one or two
plant families, while over 70% feed on only one or two genera (Chapman 1982),
and a significant proportion feed on only one species with the accompanying
risk of resource limitation. There are thought to be important advantages for
insects in having a limited host range, and it is usually assumed that
specialization for dealing with plant chemistry is the principal one
(Berenbaum 1986). Becoming adapted to detoxify the defenses of one group of
plants and being nutritionally specialized for dealing with them, is expected
to involve a loss of capability to deal with other groups of plants (Levins
& MacArthur 1969, Scriber 1983). The theories of chemical coevolution of
plants and their insect herbivores have been the subject of many reviews
(Feeny 1975, Rhoades 1979, 1983). May factors may drive evolution of host plant
specialization. The adaptive link between deterrence of herbivorous insects
by plant secondary compounds and their detrimental effects on insects is
rather weak (Mitter & Futuyma 1983, Bernays & Chapman 1987b). There
are many biologically active compounds that deter feeding by insects, but
which appear to have no detrimental effects when they are ingested. Because
deterrents have a major role in the behavior of host plant selection, the
implication is that rejection is triggered something other than avoiding
toxins. Supporting this reasoning are, e.g., force-feeding on nonhosts often
allows adequate growth and development (Waldbauer et al. 1984); there have
been numerous host switches by insect herbivores to unrelated plants (Strong
et al. 1984); artificial selection for host changes has been shown (Futuyma
& Gould 1979, Wasserman & Futuyma 1981); insects have versatile and
effective means of dealing with plant secondary compounds 9Bernays 1981,
1982); and habituation to deterrents has been shown in a number of insect
herbivores (Jermy et al. 1982). From the nutritional standpoint, monophagous
species of insects do not appear to have any advantage in terms of growth
rates, and may even be at a relative disadvantage (Futuyma & Philippi
1987). If the present patterns of restricted host range do not
always result from the need to specialize because of plant chemistry, other
pressures and reasons must exist that give the specialist insect herbivore an
edge. They believe that these reasons should be sought in the major causes of
mortality in herbivorous insects. Differential mortality on different hosts
due to variation in protection from natural enemies is considered a
possibility and has been shown in some cases (Smiley & Wisdom 1985, Price
et al. 1986, Lawton 1986). Host Plant Ranges Weed control specialists formulated a hypothesis for
selection pressure which influences a restricted host range. In it generalist
natural enemies are thought to drive the process forward, and it was believed
possible to demonstrate that specialized prey specific parasitoids are
relatively more important. Evidence stems from work by Bernays & Graham
(1988), and Bernays (1988). Another option for herbivores under pressure from
prey specific parasitoids is to switch host plants. Maintenance of sufficient
flexibility may allow switching to occur repeatedly and if tracking by the
parasitoid is effective, polyphagy may result. Thus in some cases a return to
polyphagy would be driven by specialist parasitoids. The overall proportions
of specialist and generalist herbivores might be a reflection of the relative
mortality from specialist parasitoids and generalist predators. Switching to other hosts is a problem in the introduction
of herbivorous insects used in biological control. However, switching may be
unlikely, or at any rate would be a lengthy evolutionary process. This is
because the herbivore, having been introduced without its specialist
parasitoids, may lack the normal pressures to cause a switch. Species that
have developed extreme dependence on one plant species have shown only
limited adaptability for switching, however. Analysis of Biological
Control Projects It is estimated the proportion of introductions that
resulted in successful establishment of insect biological control agents for
each insect family. It is regular for the number of such establishments to be
about double the number of failures. A detailed analysis from Julien (1982)
was made of more than 500 case of definite establishment or definite failure
to establish. Insect families represented by less than three introductions
were omitted from the analysis, and the remainder were divided into those
that are mainly or wholly monophagous/oligophagous, such as Chrysomelidae,
Tephritidae and Pyralidae, and those with polyphagous species such as
Noctuidae, Arctiidae, Gelechiidae and Agromyzidae. The ratios of successful
establishments to failures were 2.6 "0.1 for the first group and 0.7 " 0.1 for the second, although all species analyzed were
specialists because as biological control agents they were originally
accepted for their host specificity. It is possible that species from
families in which polyphagy is common are less specialized and less adapted
to making use of host plants for protection from an array of mortality
factors. Differences in these ratios are not thought to be due to
nutritional factors, since all the developmental characteristics and the
fecundity of insect herbivore species analyzed from a data base gathered at Silwood,
England showed no significant differences between insect species that
successfully established and those that failed to establish. Relative to
biological control and to factors in the new environment of the introduced
herbivore, generalist predators and parasitoids and abiotic factors will be
of primary importance since the specialist natural enemies have been
carefully excluded. In the majority of cases for biological control agents,
the impact of natural enemies is unknown. Julien (1982), however, noted the
importance of predation in many of the cases where the agent was from one of
the more polyphagous families and Goeden & Louda (1976) provided a
summary of what was known 15 years ago. Crawley (1986) listed generalist
predators along with abiotic factors as the major causes of establishment
failure, and several analyses indicated that climate affected species that
failed more than species that established. If degree of specialization is important in the
establishment of a biological control agent, then it might be expected that
monophagous species would be more successful than oligophagous species. The
Silwood, England data showed that of 540 introductions for biological control
of plants, 36% involved agents that fed in their native habitats on only one
plant species or subspecies; 52% were restricted to a single genus or species
group and the remainder fed on more than one genus. But there are no
significant differences in these patterns when the cases of establishment are
compared with those that failed. Reasons could relate to the additional
complication that in a number of instances the agent was deliberately
introduced onto a plant species other than the original host plant (Goeden
& Kok 1986, Moran et al. 1986). The numerous insect species used in controlling Lantana
camara appear to be monophagous but this plant is probably a species
complex (Stirton 1977, Spies & Stirton 1982), and the degree of
specificity of its herbivores may have to be categorized differently. Also an
insect that feeds on one species of host plant rather than on five is not
necessarily more extreme in its level of specialization. Important plant
features for a highly specialized insect may be shared by related plant
species in one genus. For example, many species of Hypericum contain
hypericin, which is used by species of Chrysolina as a recognition
factor, and the data indicate that this is a relatively extreme case of
specialization. On the other hand, Lantana camara varieties
differ in their complexes of volatile compounds as determined by small to
humans, and such differences may explain why many insect herbivores are so
selective among these varieties. It is possible, however, that the level or
degree of specialization of the phytophagous insect species is important in the
eventual process of establishment of a biological control agent, although
measuring this parameter is impossible. It may only be possible to detect and
test this by such means as chemoreceptor screening, or by tests for predator
avoidance. Insects feeding on fruits and seeds or that form galls are more
specific than leaf feeders (Janzen 1978, 1981). This may be associated with
such factors as small size, which favors success biological plant control
agents or level of specialization required to deal with phenological and
chemical factors that may provide extreme constraints (Janzen 1969, Huffaker
et al. 1976). Herbivore Ecological
Attributes It was concluded by Crawley (1986) from an analysis of
Silwood, England data that "the most pronounced patterns to emerge from
an analysis of wed control agents relate to the insects' intrinsic rate of
increase. Species with higher values of Ri are more likely to depress weed
abundance to low levels." It was also maintained that the likelihood of
establishment is most influenced by Ri. A reexamination of the same data was
made from the Silwood Project to investigate quantitatively the components of
Ri and to detect differences between introduced insect herbivore species that
established and those that failed to establish. No significant differences
were found in fecundity, generation time, voltinism or longevity. On the
other hand, size was a significant factor in the successful establishment or
failure to establish: small insects were much more likely to establish than
large insects. Crawley (1986) made the point that intrinsic rate of increase
showed a close negative correlation with body size, but the importance of
size relates to something other than the intrinsic rate of increase since the
generation time is not different in the two groups and yet it is this
component of Ri that should be most influenced by size. Alternative reasons for the importance of size in
establishment of introduced herbivores may relate to causes of mortality.
Climatic factors should affect large insects less (Scriber & Feeny 1979),
and diseases seem unimportant in general. Since specialist natural enemies
have been excluded, the answer may be related to the influence of generalist
predators and parasitoids. Of all the failures of insect herbivores to
establish among the biological control projects that were examined from an
analysis of data from Silwood, England, only one was shown to be mainly
limited by a parasitoid, so that predation may be the important factor. This
makes intuitive sense when considering that the attractiveness of large prey
to a variety of predators such as birds and lizards. Only speculation is
possible on the identity of the main predators of relatively large insect
herbivores, most of which are Lepidoptera. The importance of predators among
species of this order compared with those of other groups may be grater
because the large exposed eggs are particularly vulnerable to ant predation
(Hoffmann 1981, Robertson 1985), the surface feeders, which predominate among
the Lepidoptera, are vulnerable to generalist predators and the larger late
instars may be particularly vulnerable to vertebrate predation (Dempster
1984). Considering established biological control agents, a
higher proportion tend to be distributed over a wider geographic range in
their native home than is the case for those that did not establish. They
also tend to be found at many sites on a local level and to be very abundant
in general in their country of origin. Biological attributes underlying these
differences are unknown, but it is thought that wider distribution involves
at least a generally greater tolerance of climatic extremes. The role of
natural enemies in regulating the herbivores in their native homes was
compared for species that became successfully established as biological
control agents and for those that failed. Of 453 cases analyzed, there were
no significant patterns or trends of any kind. Plant Attributes Bernays (1985) from a comparison of the number of species in
different plant families and the number of major weed species in the same
families, suggested that most important weed species are in the more recently
evolved plant families. For example, the Polygonaceae and Cyperaceae have
more weedy species than expected by chance and the Poaceae contains a
relatively large number of noxious plant species. There are probably many
reasons for this including physiological aggressiveness and resistance to
grazing damage. There are also good biological reasons for not attempting to
control graminoid plants with introduced arthropods. They are not rich in
numbers of insect species and tend to have a smaller proportion of specialist
herbivores. Only one attempt has been made to control a noxious grass and it
failed (Julien et al. 1984). Other than grasses, the greatest number of noxious plants
are in the Asteraceae but not in much greater proportion than is expected by
chance (Bernays 1985). But many noxious plant species occur in the Cactaceae,
and most of these are in the genus Opuntia (Julien et al. 1984, Moran
& Zimmermann 1984). Several factors may have contributed to the
aggressiveness of cacti and may have contributed to their status as pests:
(1) they are successful competitors, especially in dry areas, poor soils or
in mismanaged or botanically disturbed areas; (2) they are succulents and
have morphological and physiological adaptations including a waxy cuticle,
shallow roots, and CAM photosynthetic mechanisms to resist drought; (3) they
reproduce and distribute readily by seed and/or vegetative propagules; and
(4) the thorns provide a very successful protection from grazing animals. In
addition, as with other alien pestiferous species, it is perhaps of major
importance that they were released into their respective areas of
introduction without the associated natural insect fauna (Moran &
Zimmermann 1984). No phytophagous insects outside the new world (the native
home of all cacti) have adapted to Cactaceae as permanent hosts (Moran 1980) Qualities of noxious plants that make them likely
candidates for successful control by herbivores are variable. Moran et al.
(1986) summarized some of the attributes of such plants that may be important
in the context of biological control with herbivorous insects. They commented
that native plants have less chance of being controlled than aliens, although
there are some exceptions such as the control of the native Leptospermum
scoparium in New Zealand (Julien 1982), and that perennials provide a
stable permanent habitat for herbivorous insects and appear to have been more
susceptible to biological control than annuals. However, there are also
exceptions such as Tribulus terrestris in the southwestern
United States. Also of importance in biological control is the taxonomic
isolation of the plant. Moran et al. (1986) discussed the practical value of
this attribute in relation to screening insect herbivores for biological
control, but there may also be biologically relevant traits of taxonomically
isolated species. There may be a greater number of specialist herbivores on
taxonomically isolated plants because of a longer coevolutionary history of
insects with them (Strong et al. 1984). But this may only be important if the
taxonomic isolation is accompanied by structural, chemical or phenological
differentiation relevant to the insect herbivores. A monospecific genus in
the Poaceae may be more similar to its other family members than a
monospecific genus in the Asteraceae or Verbenaceae. This may be one of the
reasons why grass feeders tend to feed on many more genera than do
phytophages that feed on dicotyledonous plants (Bernays & Barbehenn
1987). There is some controversy about whether greater
specialization of a phytophagous insect to a particular host increases or
diminishes its chances of success as a biological control agent against an
alien plant. It is considered that a greater degree of specialization may
provide better protection from a wide range of mortality factors, and this
may enhance the phytophages' chances of survival. Hokkanen & Pimentel
(1984) argued that insect biological control agents that utilize different
but related species to the target weed may be more successful biological
control agents of plants than insect herbivore species introduced onto
conspecific host plants. Goeden & Kok (1986) and Moran et al. (1986) have
contested these ideas, as has been discussed in a previous section. Dennill
& Moran (1988) provided evidence from insect-plant associations in
agriculture that highly specialized insects (those with an old evolutionary
association with their host plants, as was the terminology used by Hokkanen
& Pimentel 1984) and less specialized herbivores (those with the
potential of forming new associations with target plants that are not among
their original hosts) can be equally damaging to their hosts and thus have
utility as biological control agents. Dennill & Moran (1988) also
contended that because many of the insect herbivores involved in recent
associations have a restricted host range, there need not be any additional
risk associated with their introduction. PHYTOTOXINS FROM PLANT PATHOGENS Genetically modified bacteria have been inoculated into
American elm trees to protect the trees from Dutch elm disease, but the same
technology could be applied to hastening the destruction of target noxious
plants (see Strogel 1991). The innate weed-killing powers of living
microorganisms has intrigued researchers in the quest for environmentally
compatible alternatives to chemical herbicides. Strobel (1992) diesucced the
biological approach that would bypass the need to release whole organisms and
would reduce risks that pathogens might later adapt to nontarget host plants.
In place of organisms, the approach deploys substances produced by microbes,
namely weed-damaging compounds called phytotoxins. After the
phytotoxins are extracted from pathogens, the toxins can be sutdied
individually for their modes of attack. Once the chemical structure of these
compounds are known, they might be synthesized, thus escaping the need to
collect or maintain colonies of pathogens to produce weed-killing materials
(Strobel 1991). It is that possible that many derivatives also might be
synthesized to improve the effectiveness of the original toxins. For further
details on this innovative approach to biological weed control, please also
refer to Charudattan (1990), Charudattan & Walker (1982), Hoagland
(1990), Kenfield et al. (1988), Stierle et al. (1988). REFERENCES: [ Additional
references may be found at MELVYL Library ] Anonymous. 1968. Principles of plant and animal pest control.
Vol. 2. Weed Control. Nat. Acad. Sci. Wash. D.C. Publ. 1597: 471 p. Aldrich, R. J. (ed.). 1984. Weed crop ecology. Breton, North
Scituate, Mass. Andrés, L. A. 1977. The economics of biological control of weeds.
Aq. Bot. 3: 111-23. Andrés, L. A. 1978. Biological control of puncturevine, Tribulus
terrestris (Zytgophyllaceae): post introduction collection records of Microlarinus
spp. (Coleoptera: Curculionidae), p. 132-36. In: T. E. Freeman (ed.),
Proceedings of the IV Intern. Symposium on Biological Control of Weeds, 1976,
Gainesville, Florida. Andrés, L. A. & G. W. Angelet. 1963. Notes on the ecology and
host specificity of Microlarinus lareynii and M. lypriformis
(Coleoptera: Curculionidae) and the biological control of puncture vine, Tribulus
terrestris. J. Econ. Ent. 56: 333-40. Andrés, L. A. & F. D. Bennett. 1975. Biological control of aquatic
weeds. Ann. Rev. Ent. 20: 31-46. Andrés, L. A. & C. J. Davis. 1974. The biological control of
weeds with insects in the United States. Commonw. Inst. Biol. Contr. Misc.
Publ. 6: 11-25. Andrés, L. A. & R. D. Goeden. 1971. The biological control of
weeds by introduced natural enemies, p. 143-64. In: C. B. Huffaker
(ed.), Biological Control. Plenum Press, New York. Andrés, L. A., C. J. Davis, P. Harris & A. J. Wapshere. 1976.
Biological control of weeds, p. 481-93. In: C. B. Huffaker & P. S.
Messenger (eds.), Theory and Practice of Biological Control. Academic Press,
New York. Annecke, D. P., M. Karny & W. A. Burger. 1969. Improved
biological control of the prickly pear, Opuntia megacantha
Salm-Dyck, in South Africa through use of an insecticide. Phytophylactica 1:
9-13. Baloch, G. M. & Sana-Ullah. 1974. Insects and other organisms
associated with Hydrilla verticillata (L.f.) L.C.
(Hydrocharitaceae) in Pakistan. Commonw. Inst. Biol. Contr. Trinidad, Misc.
Publ. 8: 61-6. Beckendorf, S. K. & M. A. Hoy. 1985. Genetic improvement of
arthropod natural enemies through selection, hybridization or genetic
engineering techniques, p. 167-87. In: M. A. Hoy & D. C. Herzog
(eds.), Biological Control in Agricultural IPM Systems. Academic Press,
Orlando, Florida. Bellows, T. S., Jr. & T. W. Fisher, (eds) 1999. Handbook
of Biological Control: Principles and Applications. Academic Press, San
Diego, CA. 1046 p. Bennett, F. D. 1966. Investigations on the insects attacking
aquatic ferns, Salvinia spp. in Trinidad and northern South America.
Proc. S. Weed Conf. 19: 497-504. Bennett, F. D. 1970a. Recent investigations on the biological
control of some tropical and subtropical weeds. Proc. 10th Brit. Weed Contr.
Conf. p. 660-68. Bennett, F. D. 1970b. Insects attacking waterhyacinth in the West
Indies, British Honduras and the USA. Hyacinth Contr. J. 8(2): 10-13. Bennett, F. D. 1971. Some recent successes in the field of
biological control in the West Indies. Revista Peruana de Entomol. 14:
369-73. Bennett, F. D. 1974. Biological control, p. 99-106. In: D.
S. Mitchell (ed.), Aquatic Vegetation and Its Use and Control. UNESCO, Paris. Bennett, F. D. & H. Zwölfer. 1968. Exploration for natural
enemies of water hyacinth in northern South America and Trinidad. Water
Hyacinth Cont. J. 7: 44-52. Berenbaum, M. J. 1986. Post-ingestive effects of phytochemicals
on insects: on Paracelsus and plant products. p. 121-53. In: T.
A. Miller & J. Miller (eds.), Insect-plant Interactions. Springer-Verlag,
New York. 342 p. Bernays, E. A. 1981. Plant tannins and insect herbivores: an
appraisal. Ecol. Ent. 6: 353-60. Bernays, E. A. 1982. The insect on the plant: a closer look. p.
3-17. In: H. Visser & A. K. Mink (eds.), Insect-plant
relationships. Pudoc, Wageningen, Netherlands. 464 p. Bernays, E. A. 1985. Arthropods for weed control in IPM systems.
p. 373-88. In: M. A. Hoy and D. C. Herzog (eds.), Biological Control
in Agricultural IPM Systems. Academic Press, New York. 589 p. Bernays, E. A. 1988. Host plant specialization in insects: The
role of predators. Ent. Expt. Appl. (in press). Bernays, E. A. & R. Barbehenn. 1987. Nutritional ecology of
grass foliage-chewing insects. p. 147-76. In: F. Slansky & J. G.
Rodriguez (eds.), Nutritional Ecology of Insects, Mites, Spiders and Related
Invertebrates. John Wiley & Sons, New York. 1016 p. Bernays, E. A. & R. F. Chapman. 1987a. Chemical deterrence of
plants. p. 107-16. In: J. Law (ed.), Molecular Entomology. UCLA
Symposia, Vol. 49, Alan Liss, Inc. 500 p. Bernays, E. A. & R. F. Chapman. 1987b. Evolution of deterrent
responses by phytophagous insects. p. 159-75. In: R. F. Chapman, E. A.
Bernays & J. G. Stoffolano (eds.), Perspectives in Chemoreception and
Behavior. Springer-Verlag, New York. Bernays, E. A. & M. Graham. 1988. On the evolution of host
plant specificity in phytophagous arthropods. Ecology (in press). Bernays, E. A. & V. C. Moran. 1996. Biological attributes of
plant-feeding insects used to control alien weeds. Technical Rept.,.
University of California, Berkeley, CA Bess, H. A. & F. H. Haramoto. 1958. Biological control of
pamakani Eupatorium adenophorum, in Hawaii by a tephritid gall
fly, Procecidochares utilis. 1. The life history of the fly and
its effectiveness in the control of the weed. Proc. X Intern. Congr. Ent.,
Montreal (1956)4: 543-48. Blackburn, R. D., D. L. Sutton & T. Taylor. 1971. Biological
control of aquatic weeds. J. Irrig. Darin. Div. A.S.C.E. 97(IR3): 421-32. Bock, H. H. 1969. Productivity of the waterhyacinth, Eichhornia
crassipes (Mart.) Solms. Ecology 50: 460-64. Bornemissza, G. F. 1966. An attempt to control ragwort in
Australia with the Cinnabar moth, Callimorpha jacobaeae (L.)
(Arctiidae: Lepidoptera). Aust. J. Zool. 14: 201-43. Broadway, R. M. & S. S. Duffey. 1986. The effect of dietary
protein on the growth and digestive physiology of larval Heliothis zea
and Spodoptera exigua. J. Insect Physiol. 32: 673-80. Brown, J. L. & N. R. Spencer. 1973. Vogtia malloi,
a newly introduced phycitid to control alligatorweed. Environ. Ent. 2: 521-23. Bucher, G. E. & P. Harris. 1961. Food plant spectrum and
elimination of disease of cinnabar moth larvae, Hypocrita jacobaeae
(L.) (Lep.: Arctiidae). Canad. Ent. 93: 931-36. Buckingham, G. & S. Passoa. 1985. Flight muscle and egg
development in waterhyacinth weevils, p. 497-510. In: E. S. Delfosse
(ed.), Proceedings of the VI International Symposium on Biological Control of
Weeds, 1984, Vancouver, B.C., Canada. Cameron, E. 1935. A study of the natural control of ragwort (Senecio
jacobaea L.). J. Ecol. 23: 265-322. Caresche, L. & A. Wapshere. 1974. Biology and host
specificity of the Chondrilla gall mite Aceria chondrillae.
Bull. Ent. Res. 64: 183-92. Center, T. D. 1982. The waterhyacinth weevils, Neochetina eichhorniae
and N. bruchi. Aquatics 4(2): 8, 16-19. Center, T. D. 1985. Leaf life tables: a viable method for
assessing sublethal effects of herbivory on waterhyacinth shoots, p. 511-24. In:
E. S. Delfosse (ed.), Proceedings of the VI International Symposium on
Biological Control of Weeds, 1984, Vancouver, B.C., Canada. Center, T. D. & W. C. Durden. 1981. Release and establishment
of Sameodes albiguttalis for the biological control of
waterhyacinth. Environ. Ent. 10: 75-80. Chandler, J. M. 1980. Assessing losses caused by weeds, p.
234-40. In: R. J. Aldrich (ed.), Proceedings of the E. C. Stakman
Communication Symposium, Univ. of Minnesota, St. Paul, Agric. Exp. Stn. Misc.
Publ. No. 7. Chapman, R. F. 1982. Chemoreception: The significance of receptor
numbers. Adv. Insect Physiol. 16: 247-356. Charudattan, R. 1978. Biological control projects in plant
pathology: a directory. Misc. Publ. Plant Path. Dept., Univ. of Florida,
Gainesville. 57 p. Charudattan, R. 1984. Microbial control of plant pathogens and
weeds. J. Georgia Ent. Soc. 19, No. 2: 28-40 (suppl.). Charudattan, R. 1986. Integrated control of waterhyacinth (Eichhornia
crassipes) with a pathogen, insects and herbicides. Weed Sci. 34:
26-30 (suppl. 1). Charudattan, R. & H. L. Walker (eds.). 1982. Biological
Control of Weeds With Plant Pathogens. John Wiley, New York. 293 p. Charudattan, R. 1990. Release of fungi: large-scale use of fungi
as biological weed control agents. In: Risk Assessment in Agricultural
Biotechnology: Proc. Internatl. Conf., Publ. No. 1928, Univ. Calif., Div. Agric.
& Nat. Res. Clark, L. R. 1953. The ecology of Chrysomela gemellata
Rossi and C. hyperici Forst., and their effect on St. John's
wort in the Bright District, Victoria. Aust. J. Zool. 1: 1-69. Clark, N. 1953. The biology of Hypericum perforatum
L. var. angustifolium DC. (St. John's wort) in the Ovens Valley,
Victoria, with particular reference to entomological control. Aust. J. Bot.
1: 95-120. Cofrancisco, A. F., Jr., R. M. Stewart & D. R. Sanders, Sr.
1985. The impact of Neochetina eichhorniae (Coleoptera:
Curculionidae) on waterhyacinth in Louisiana, p. 525-35. In: E. S.
Delfosse (ed.), Proceedings of the VI International Symposium on Biological
Control of Weeds, 1984, Vancouver, B.C., Canada. Commonwealth Scientific & Industrial Res. Organiz. 1971. Div.
Ent. Ann. Rept. 1970-1971. Canberra, A.C.T., Australia Coulson, J. R. 1971. Prognosis for control of water hyacinth by
arthropods. Hyacinth Control J. 9: 31-4. Coulson, J. R. 1977. Biological control of alligatorweed,
1959-1972. A review and evaluation. U. S. Dept. Agric. Tech. Bull. No. 1547.
98 p. Coulson, J. R. 1985. Information on U.S. and Canadian biological
control programs using natural enemies and other beneficial organisms. U. S.
Dept. Agric., Agric. Res. Serv. Biol. Contr. Doc. Center Info. Doc. 95 p. Crawley, M. J. 1983. Herbivory. The Dynamics of Animal-plant
Interactions. Blackwell Sci. Publ., Oxford. 437 p. Crawley, M. J. 1986. The population biology of invaders. Phil.
Trans. Roy. Soc. London, B314: 711-31. Cromroy, H. L. 1982. Potential use of mites in biological control
of terrestrial and aquatic weeds, p. 61-66. In: M. A. Hoy, G. L.
Cunningham & L. Knutson (eds.), Biological Control of Pests by Mites.
Univ of Calif. Press, Berkeley, CA. Cullen, J. M. 1974. Seasonal and regional variation in the
success of organisms imported to combat skeleton weed Chondrilla juncea
L. in Australia, p. 111-17. In: A. J. Wapshere (ed.), Proceedings of
the III International Symposium on Biological Control of Weeds, 1973,
Montpellier, France. Cullen, J. M. 1978. Evaluating the success of the programme for
the biological control of Chondrilla juncea in Australia, p.
233-39. In: T. E. Freeman (ed.), Proceedings of the IV International
Symposium on Biological Control of Weeds, 1976, Gainesville, Florida. Cullen, J. M. & E. S. Delfosse. 1985. Echium plantagineum:
catalyst for conflict and change in Australia, p. 19-25. In: E. S.
Delfosse (ed.), Proceedings of the VI International Symposium on Biological
Control of Weeds, 1984, Vancouver, B.C., Canada. Cullen, J. M., P. F. Kable & M. Catt. 1973. Epidemic spread
of a rust imported for biological control. Nature (London) 244: 462-64. Daniel, J. T., G. E. Templeton, R. J. Smith, Jr. & W. T. Fox.
1973. Biological control of northern jointvetch in rice with endemic fungal disease.
Weed Sci. 21: 303-07. Davis, C. J. 1966. Progress report: biological control status of
noxious weed pests in Hawaii--1965-1966. Hawaiian Dept. Agric. Mimeo. Rep. 4
p. Davis, C. J. & N. L. H. Krauss. 1966. Recent introductions
for biological control. Proc. Hawaiian Ent. Soc. (1965)19: 201-07. DeBach, P. 1964. The scope of biological control, p. 1-20. In:
P. DeBach (ed.), Biological Control of Insect Pests and Weeds. Reinhold, New
York. DeLoach, C. J. & H. A. Cordo. 1976. Life cycle and biology of
Neochetina bruchi, a weevil attacking waterhyacinth in
Argentina, with notes on N. eichhorniae. Ann. Ent. Soc. Amer.
69: 643-52. DeLoach, C. J. & H. A. Cordo. 1978. Life history and ecology
of the moth Sameodes albiguttalis, a candidate for biological
control of waterhyacinth. Environ. Ent. 7; 309-21. DeLoach, C. J. & H. A. Cordo. 1983. Control of waterhyacinth
by Neochetina bruchi (Coleoptera: Curculionidae: Bagoini) in
Argentina. Environ. Ent. 12: 19-23. Dempster, J. P. 1984. The natural enemies of butterflies. p. 97-104. In: R. I. Vane-Wright & P. R. Ackery
(eds.), The Biology of Butterflies. Academic Press, New York.. 429 p. Dennill, G. B. & V. C. Moran. 1988. Proceedings of VII
International Symposium on Biological Control of Weeds. E. S. Delfosse (ed.).
March 1988, Rome, Italy. (in press). Denno, R. E. & M. S. McClure (eds.). 1983. Variable plants
and herbivores in natural and managed systems. Academic Press, New York. 717
p. Dethier, V. G. 1982. Mechanism of host-plant recognition. Ent.
Expt. Appl. 31: 49-56. Dodd, A. P. 1940. The Biological Campaign against Prickly Pear.
Commonw. Prickly Pear Board, Brisbane, Australia. 177p. Dodd, A. P. 1959. The biological control of prickly pear in
Australia, p. 565-77. In: Biogeography and Ecology in Australia
(Monogr. Biol., Vol. VIII). W. Junk, The Hague, Netherlands. Doutt, R. L. 1958. Vice, virtue, and the Vedalia. Bull. Ent. Soc.
Amer. 4: 119-23. Doutt, R. L. 1964. The historical development of biological control,
p. 21-42. In: P. DeBach (ed.), Biological Control of Insect Pests and
Weeds. Reinhold Publ. Co., New York. Drongelen, W. van. 1979. Contact chemoreception of host-plant
specific chemical in larvae of various Yponomeuta species
(Lepidoptera). J. Comp. Physiol. 134A: 265-79. Dunn, P. H. 1978. Shortcomings in the classic tests of candidate
insects for the biocontrol of weeds, p. 51-56. In: T. E. Freeman
(ed.), Proceedings of the IV Intern. Symposium on Biological Control of
Weeds, 1976, Gainesville, Florida. Embe, R. G., J. S. Melching & C. H. Kingsolver. 1981.
Epidemiology of Puccina chondrillina, a rust pathogen for the
biological control of rush skeleton weed in the United States. Phytopathology
71: 839-43. Feeny, P. 1975. Biochemical coevolution between plants and their
insect herbivores. p. 3-19. In: L. E. Gilbert & P. H. Raven
(eds.), Coevolution of Animals and Plants. Univ. Texas Press, Austin. 246 p. Freeman, T. E. & R. Charudattan. 1981. Biological control of weeds
with plant pathogens. Prospectus, p. 293-99. In: E. S. Delfosse (ed.),
Proceedings of the V International Symposium on Biological Control of Weeds,
1980, Brisbane, Australia. Frick, K. E. 1969. Attempt to establish the ragwort seed fly in
the United States. J. Econ. Ent. 62: 1135-38. Frick, K. E. 1970. Ragwort flea beetle established for biological
control of tansy ragwort in northern California. Calif. Agr. 24(4): 12-13. Frick, K. E. 1974. Biological control of weeds: introduction,
history, theoretical and practical applications, p. 204-23. In: F. G.
Maxwell & F. A. Harris (eds.), Proceedings of the Summer Institute of
Biological Control of Plant Insects and Diseases. Univ. of Mississippi Press,
Jackson. Frick, K. E. & J. M. Chandler. 1978. Augmenting the moth (Bactra
verutana) in field plots for early-season suppression of purple
nutsedge (Cyperus rotundus). Weed Sci. 26: 703-10. Frick, K. E. & C. Garcia, Jr. 1975. Bactra verutana
as a biological agent for purple nutsedge. Ann. Ent. Soc. Amer. 16: 7-14. Frick, K. E. & J. K. Holloway. 1964. Establishment of the
cinnabar moth, Tyria jacobaeae, on tansy ragwort in the western
United States. J. Econ. Ent. 57: 152-54. Fullaway, D. T. 1959. Biological control of lantana in Hawaii, p.
70-75. In: Rept. Bd. Agr. & Forest., Hawaii. Bien. ending June 30,
1958. Futuyma, D. J. & F. Gould. 1979. Associations of plants and
insects in a deciduous forest. Ecol. Monogr. 49: 33-50. Futuyma, D. J. & T. E. Philippi. 1987. Genetic variation and
variation in responses to host plants by Alsophila pometaria
(Lepidoptera: Geometridae). Evolution 41: 269-79. Gilstrap, F. E. & R. D. Goeden. 1974. Biology of Tarachidia
candefacta, a Nearctic noctuid introduced into the U.S.S.R. for
ragweed control. Ann. Ent. Soc. Amer. 67: 265-70. Goeden, R. D. 1970. Current research on biological weed control
in Southern California. Commonw. Inst. Biol. Contr., Trinidad, Misc. Publ. 1:
25-8. Goeden, R. D. 1977. Chapter 4: Biological control of weeds, p.
43-47. In: B. Truelove (ed.), Research Methods in Weed Science. S.
Weed Sci. Soc., Auburn Printing, Auburn, Georgia. Goeden, R. D. 1978. Part II: Biological control of weeds, p.
357-545. In: C. P. Clausen (ed.), Introduced Parasites and Predators
of Arthropod Pests and Weeds. U. S. Dept. Agric. Handb. No. 480. Goeden, R. D. 1983. Critique and revision of Harris' scoring
system for selection of insect agents in biological control of weeds. Prot.
Ecol. 5: 287-301. Goeden, R. D. 1988. History of biological weed control. Biocontr.
News Info. 9: 55-61. Goeden, R. D. & L. A. Andrés. 1999. Biological control of
weeds in terrestrial and aquatic environments. In: Bellows, T. S., Jr.
& T. W. Fisher, (eds) 1999. Handbook of Biological Control: Principles
and Applications. Academic Press, San Diego, CA. Goeden, R. D. & R. L. Kirkland. 1981. Interactions of field
populations of indigenous egg predators, imported Microlarinus
weevils, and puncturevine in southern California, p. 515-27. In: E. S.
Delfosse (ed.), Proceedings of the V International Symposium on Biological
Control of Weeds, 1980, Brisbane, Australia. Goeden, R. D. & L. T. Kok. 1986. Comments on a proposed
"new" approach for selecting agents for the biological control of
weeds. Canad. Ent. 118: 51-58. Goeden, R. D. & S. Louda. 1976. Biotic interference with
insects imported for weed control. Ann. Rev. Ent. 21: 325-42. Goeden, R. D. & D. W. Ricker. 1967. Geocoris pallens
found to be predaceous on Microlarinus spp. introduced to California
for the biological control of puncturevine, Tribulus terrestris.
J. Econ. Ent. 60: 725-29. Goeden, R. D. & D. W. Ricker. 1970. Parasitization of
introduced puncturevine weevils by indigenous Chalcidoidea in southern
California. J. Econ. Ent. 63: 827-31. Goeden, R. D. & D. W. Ricker. 1973. A soil profile analysis
for puncturevine fruit and seed. Weed Sci. 21: 504-07. Goeden, R. D. & D. W. Ricker. 1976. The phytophagous insect
fauna of the ragweed, Ambrosia psilostachya, in southern
California. Environ. Ent. 5: 1169-77. Goeden, R. D. 1978. Biological control of weeds. p. 357-414. In:
C. P. Clausen (ed.), Introduced Parasites and Predators of Arthropod Pests
and Weeds: a World Review. USDA, ARS, Handbook 480. 524 p. Goeden, R. D. & D. W. Ricker. 1981. Santa Cruz
Island--revisited. Sequential photography records the causation, rates of
progress, and lasting benefits of successful biological weed control, p.
355-65. In: E. S. Delfosse (ed.), Proceedings of the V International
Symposium on Biological Control of Weeds, 1980, Brisbane, Australia. Goeden, R. D., C. A. Fleschner & D. W. Ricker. 1967.
Biological control of prickly pear cacti on Santa Cruz Island, California.
Hilgardia 38: 579-606. Goeden, R. D., L. A. Andrés, T. E. Freeman, P. Harris, R. L.
Pienkowski & C. R. Walker. 1974a. Present status of projects on the
biological control of weeds with insects and plant pathogens in the United
States and Canada. Weed Sci. 22: 490-95. Goeden, R. D., O. V. Kovalev & D. W. Ricker. 1974b.
Arthropods exported from California to the USSR for ragweed control. Weed
Sci. 22: 156-58. Groves, R. H. & J. J. Burdon (eds.). 1986. Ecology of
Biological Invasions: an Australian Perspective. Aust. Acad. Sci., Canberra.
166 p. Greathead, D. J. 1967. A list of the more important weeds of East
Africa. Commonw. Inst. Biol. Contr., Unpub. Mimeo. 7 p. Greathead, D. J. 1971. A review of biological control in the
Ethiopian Region. Commonw. Inst. Biol. Contr. Tech. Comm. No. 5: 1-172. Hanson, F. E. 1983. The behavioral and neurophysiological basis
of food plant selection by lepidopterous larvae. p. 3-23. In: S. Ahmad
(ed.), Herbivorous Insects: Host Seeking Behavior and Mechanisms. Academic
Press, New York. 257 p. Harley, K. L. S. 1969. The suitability of Octotoma scabripennis
Guer. and Uroplata girardi Pic. (Col.: Chrysomelidae) for the
control of lantana (Verbenaceae) in Australia. Bull. Ent. Res. 58: 835-43. Harley, K. L. S. & R. K. Kunimoto. 1969. Assessment of the
suitability of Plagiohammus spinipennis (Thoms.) (Col.:
Cerambycidae) as an agent for control of weeds of the genus Lantana
(Verbenaceae). I. Life history and capacity to damage L. camara
in Hawaii. Bull. Ent. Res. 58: 567-74. Harris, P. 1971. Current approaches to biological control of
weeds. Biological control programmes against insects and weeds in Canada
1959-1968. Commonw. Inst. Biol. Contr. Technol. Comm. No. 4: 79-83. Harris, P. 1973. The selection of effective agents for the
biological control of weeds. Canad. Ent. 105: 1495-1503. Harris, P. 1974. The impact of the cinnabar moth on ragwort in
eastern and western Canada and its implication for biological control
strategy. Commonw. Inst. Biol. Contr., Trinidad, Misc. Publ. 8: 119-23. Harris, P. 1976. Biological control of weeds: from art to
science, p. 478-83. In: Proceedings of the 15th International Congress
of Entomology, Washington, D. C. Harris, P. 1979. Cost of biological control of weeds by insects
in Canada. Weed Sci. 27: 242-250. Harris, P. 1984a. Carduus nutans L., nodding
thistle, and C. acanthoides L., plumeless thistle (Compositae),
p.115-26. In: J. S. Kelleher & M. A. Hume (eds.), Biological
Control Programmes Against Insects and Weeds in Canada 1969-1980. Commonw.
Agric. Bur., Slough, U.K. Harris, P. 1984b. Euphorbia esula-virgata
complex, leafy spurge and E. cuparissias L., cypress spurge
(Euphorbiacea), p. 159-69. In: J. S. Kelleher & M. A. Hume (eds.),
Biological Control Programmes Against Insects and Weeds in Canada 1969-1980.
Commonw. Agric. Bur., Slough, U.K. Harris, P. & D. P. Peschken. 1971. Hypericum perforatum
L., St. John's Wort (Hypericaceae). Commonw. Inst. Biol. Contr., Trinidad,
Tech. Commun. 4: 89-94. Harris, P. & G. L. Piper. 1970. Ragweed (Ambrosia
spp.: Compositae): its North American insects and possibilities for its
biological control. Commonw. Inst. Biol. Contr. Tech. Bull. No. 13: 117-40. Harris, P. & H. Zwölfer. 1968. Screening of phytophagous
insects for biological control of weeds. Canad. Ent. 100: 295-303. Harris, P., A. T. S. Wilkinson, M. E. Neary & L. S. Thompson.
1971. Senecio jacobaea L., Tansy Ragwort (Compositae). Commonw.
Inst Biol. Contr., Trinidad, Tech. Commun. 4: 97-104. Hasan, S. 1972. Specificity and host specialisation of Puccinia
chondrillina. Ann. Appl. Biol. 72: 257-63. Hasan, S. 1974a. First introduction of a rust fungus in Australia
for the biological control of skeleton weed. Phytopathology 64: 253-54. Hasan, S. 1974b. The powdery mildews as potential biological
control agents of skeleton weed, Chondrilla juncea L. Misc.
Publ. Commonw. Inst. Biol. Contr. 6: 114-19. Hasan, S. & A. J. Wapshere. 1973. The biology of Puccinia
chondrillina, a potential biological control agent of skeleton weed.
Ann. Appl. Biol. 74: 325-32. Hauser, W. J., E. F. Legner, R. A. Medved & S. Platt. 1976. Tilapia--
a management tool for biological control of aquatic weeds and insects. Bull.
Amer. Fisheries Soc. 1(2): 15-16. Hawaii Dept. of Agr. 1962. Noxious weeds of Hawaii. 89 p. Hawaii Dept. of Agr. 1963. Ann. Rept. 1962-63, Div. Plant Indust.
p. 49-69. Hawaii Dept. of Agr. 1965. Ann. Rept. 1964-65, Div. Plant Indust.
p. 10-12, App. V: 39-52. Hawaii Dept. of Agr. & Conservation. 1960. Ann. Rept. 1960.
Div. Ent. & Market, S-45. Hawkes, R. B. 1968. The cinnabar moth, Tyria jacobaeae,
for control of tansy ragwort. J. Econ. Ent. 61: 499-501. Hawkes, R. B. 1973. Natural mortality of cinnabar moth in California.
Ann. Ent. Soc. Amer. 66: 137-46. Hawkes, R. B., L. A. Andrés & W. H. Anderson. 1967. Release
and progress of an introduced flea beetle, Agasicles n. sp. to control
alligatorweed. J. Econ. Ent. 60: 1476-77. Hickling, C. F. 1965. Biological control of aquatic vegetation.
Pest Articles & News Summaries (C) 11: 237-44. Hoagland, R. E. (ed.). 1990. Microbes and microbial products as
herbicides. Amer. Chem. Soc. Hoffman, W. J. H. 1981. Release of Tucumania tapiacola
(Lepidoptera: Pyralidae) in South Africa against Opuntia aurantiaca:
the value of detailed monitoring. p. 367-73. In: Proc. V Intern.
Symposium on Biological Control of Weeds. 1980, Brisbane, Australia. 649 p. Hokkanen, H. & D. Pimentel. 1984. New approach for selecting
biological control agents. Canad. Ent. 116: 1109-21. Holloway, J. K. 1964. Projects in biological control of weeds, p.
650-70. In: DeBach, P. (ed.), Biological Control of Insect Pests and
Weeds. Reinhold, New York.In: DeBach, P. (ed.), Biological Control of
Insect Pests and Weeds. Reinhold, New York. Holloway, J. K. & C. B. Huffaker. 1949. Klamath weed beetles.
Calif. Agric. 3: 3-10. Holloway, J. K. & C. B. Huffaker. 1951. The role of Chrysolina
gemellata in the biological control of Klamath weed. J. Econ. Ent. 44:
244-47. Holloway, J. K. & C. B. Huffaker. 1952. Insects to control a
weed, p. 135-40. In: Insects-- The Yearbook of Agriculture, 1952. U.
S. Govt. Printing Office. Holm, L. G., L. W. Weldon & R. D. Blackburn. 1969. Aquatic
weeds. Science 166(3906): 699-709. Holm, L. G., D. L. Plucknett, J. V. Pancho & J. P. Herberger.
1977. The World's Worst Weeds, Distribution, and Biology. Univ. of Hawaii
Press, Honolulu. Hoy, J. M. 1949. Control of manuka by blight. New Zealand J. Agr.
79: 321-24. Hoy, J. M. 1964. Present and future prospect for biological
control of weeds. New Zealand Sci. Rev. 22(2): 17-19. Huffaker, C. B. 1953. Quantitative studies on the biological
control of St. John's worth (Klamath weed) in California. Proc. 7th Pac. Sci.
Congr. 4: 303-13. Huffaker, C. B. 1957. Fundamentals of biological control of
weeds. Hilgardia 27: 101-57. Huffaker, C. B. 1959. Biological control of weeds with insects.
Ann. Rev. Ent. 4: 251-76. Huffaker, C. B. 1964. Fundamentals of biological weed control, p.
631-49. In: DeBach, P. (ed.), Biological Control of Insect Pests and
Weeds. Reinhold, New York.In: DeBach, P. (ed.), Biological Control of
Insect Pests and Weeds. Reinhold, New York. Huffaker, C. B. 1967. A comparison of the status of biological
control of St. Johnswort in California and Australia. Mushi Suppl. 39: 51-73. Huffaker, C. B. & L. A. Andrés. 1970. Biological weed control
using insects. Tech. Pap. FAO Int. Conf. Weed Contr., June 22 - July 1, 1970,
Davis, Calif, p. 436-49. Weed Sci. Soc. Amer., Champaign, Illinois. Huffaker, C. B. & C. E. Kennett. 1959. A ten-year study of
vegetational changes associated with biological control of Klamath weed. J.
Range Manage. 12: 69-82. Huffaker, C. B., D. W. Ricker & C. E. Kennett. 1961.
Biological control of puncturevine with imported weevils. Calif. Agr. 15:
11-12. Huffaker, C. B., P. S. Messenger & P. DeBach. 1971. The
natural enemy component in natural control and the theory of biological
control. p. 16-92. In: C. B. Huffaker (ed.), Biological Control.
Plenum Press, New York. 511 p. Huffaker, C. B., F. J. Simmonds & J. E. Laing. 1976.
Theoretical and empirical basis of biological control. p. 42-80. In:
C. B. Huffaker & P. S. Messenger (eds.), Theory and Practice of
Biological Control. Academic Press, New York. 788 p. Huffaker, C. B., J. Hamai & R. M. Nowierski. 1983. Biological
control of puncturevine, Tribulus terrestris in California
after twenty years of activity of introduced weevils. Entomophaga 28:
387-400. Huffaker, C. B., D. Ricker & C. Kennett. 1961. Biological control
of puncture vine with imported weevils. Calif. Agric. 15: 11-12. Imms, A. D. 1931. Biological control. II. Noxious weeds. Trop.
Agr. (Trinidad) 8: 124-27. Inman, R. E. 1971. A preliminary evaluation of Rumex rust as a
biological control agent for Curly Dock. Phytopath. 61: 102-07. Ivannikov, A. I. 1969a. A nematode controlling Acroptilon picris.
Zaschch. Rast. (Moscow). p. 54-5. Ivannikov, A. I. 1969b. The fly Melanagromyza cuscutae
Hg.-- a pest of dodder in Kazakhstan. Vestn. Sel'skokhoz. Nauki (Alma Ata)
12: 85-8. [in Russian]. Jackson, D. F. 1967. Interaction between algal populations and
viruses in model pools-- a possible control of algal blooms. Presented at
ASCE Ann. Nat. Meet. Water Resources Eng. Statler Hilton, New York, 1967. Janzen, D. H. 1969. Seed eaters versus seed size, number,
toxicity and dispersal. Evolution 23: 1-27. Janzen, D. H. 1978. The ecology and evolutionary biology of seed
chemistry as it relates to seed predation. p. 103-06. In: J. B.
Harborne (ed.), Biochemical Aspects of Plant and Animal Coevolution. Academic
Press, New York. 435 p. Janzen, D. H. 1981. Patterns of herbivory in a tropical deciduous
forest. Biotropica 13: 271-82. Jermy, T. 1987. The role of experience in the host selection of
phytophagous insects. p. 143-57. In: R. F. Chapman, E. A. Bernays
& J. G. Stoffolano (eds.), Perspectives in Chemoreception and Behavior.
Springer-Verlag, New York. 207 p. Jermy, T., E. A. Bernays & A. Szentesi. 1982. The effect of
repeated exposure to feeding deterrents on their acceptability to
phytophagous insects. p. 25-32. In: J. H. Visser & A. K. Minks
(eds.), Insect-plant Relationships. Pudoc, Wageningen, Netherlands. 464 p. Joenje, W., K. Bakker & L. Vlijm. 1987. The ecology of
biological invasions. Proc. Koninklijke Nederlandse Academie van
Wetenschappen 90: 1-80. Johnson, E. 1932. The puncture vine in California. Univ. Calif.
Col. Agric. Expt. Sta. Bull. 528. 42 p. Johnston, T. H. & H. Tryon. 1914. Report on the prickly-pear
travelling commission, 1st November, 1912-30th April, 1914. Parliamentary
Paper, Comming, Brisbane, Australia. 132 p. Julien, M. H. (ed.). 1982. Biological Control of Weeds: a World
Catalogue of Agents and Their Target Weeds, 1st ed. Commonw. Agric. Bur.,
Slough, U.K. 108 p. Julien, M. H. (ed.). 1987. Biological control of weeds: a world
catalogue of agents and their target weeds, 2nd ed. Commonw. Agric. Bur.
Int., Wallingford, U.K. 150p. Julien, M. H., J. D. Kerr & R. R. Chan. 1984a. Biological
control of weeds: an evaluation. Prot. Ecol. 7: 3-25. Julien, M. H., R. C. Kassulke & K. L. S. Harley. 1984b. Lixus
cribricollis Boheman (Curculionoidea: Curculionidae) for biological
control of the weeds Emex spp. and Rumex crispus in
Australia. Entomophaga 27: 439-46. Juniper, B. & T. R. E. Southwood (eds.). 1986. Insects and
the Plant Surface. Edward Arnold, London. 360 p. Kenfield, D., G. Bunkers, G. A. Strobel & F. Sugawara. 1988.
Potential new herbicides-- phytotoxins from plant pathogens. Weed Technol.
2(4): 519-24. King, L. J. 1966. Weeds of the World, Biology and Control.
Interscience Publ., Inc., New York. 526 p. Kirkland, R. L. & R. D. Goeden. 1977. Descriptions of the
immature stages of imported puncturevine weevils, Microlarinus lareynii
and M. lypriformis. Ann. Ent. Soc. Amer. 70: 583-87. Kirkland, R. L. & R. D. Goeden. 1978a. Biology of Microlarinus
lareynii (Col.: Curculionidae) on puncturevine in southern California.
Ann. Ent. Soc. Amer. 70: 13-18. Kirkland, R. L. & R. D. Goeden. 1978b. Biology of Microlarinus
lypriformis (Col.: Curculionidae) on puncturevine in southern
California. Ann. Ent. Soc. Amer. 70: 65-69. Kirkland, R. L. & R. D. Goeden. 1978c. An insecticidal-check
study of the biological control of puncturevine (Tribulus terrestris)
by imported weevils, Microlarinus lareynii and M. lypriformis
(Col.: Curculionidae). Environ. Ent. 7: 349-54. Klingman, D. L. & J. R. Coulson. 1983. Guidelines for
introducing foreign organisms into the United States for biological control
of weeds. Bull. Ent. Soc. Amer. 29: 55-61. Kok, L. T. & W. W. Surles. 1975. Successful biological
control of musk thistle by an introduced weevil, Rhinocyllus conicus.
Environ. Ent. 4: 1025-27. Kornberg, H. & M. H. Williamson (eds.). 1987. Quantitative
aspects of the ecology of biological invasions. Phil. Trans. Roy. Soc. London
(B) 314: 501-742. Kovalev, O. V. 1968. Perspectives of weed biological control in
the U.S.S.R. Proc. 13th Int. Congr. Ent. Moscow II: 158-59. Kovalev, O. V. 1970. Biological control of Ambrosia weeds,
p. 354-55. In: Proceedings of the 7th International Congress of Plant
Protection, 1969, Paris, France. Kovalev, O. V. 1971. [Phytophages of ragweeds (Ambrosia
L.) in North America and their application in biological control in the
U.S.S.R.]. Zoologichesky Zhurn. 50: 199-209. [in Russian]. Kovalev, O. V. 1973. Modern outlooks of biological control of
weed plants in the U.S.S.R. and the international phytophagous exchange, p.
166-71. In: P. H. Dunn (ed.), "Proceedings of the III
International Symposium on Biological Control Of Weeds, 1971, Rome, Italy. Kovalev, O. V. 1974. Development of a biological method of
controlling weeds in the USSR and the countries of Europe, p. 302-309. In:
E. Fm. Shumakov, G. V. Gusev & N. S. Fedorinchik (eds.), Biological
Agents For Plant Protection. Publ. House "Kolos," Moscow. 408 p.
[in Russian]. Kovalev, O. V. 1980. Biological control of weeds:
accomplishments, problems and prospects. Zashchita Rasteniy. 5: 18-21. [in
Russian]. Kovalev, O. V. & L. N. Medvedev. 1983. Theoretical basis of
introduction of ragweed leaf beetles of the genus Zygogramma Chevr.
(Coleoptera: Chrysomelidae) in the USSR for biological control of ragweed.
Ent. Obozr. 62: 17-32. [in Russian]. Kovalev, O. V. & N. I. Nayanov. 1971. A moth against ragweed.
Zemledelie 6: 36. Kovalev, O. V. & T. D. Runeva. 1970. Tarachidia candefacta
Hubn. (Lepidoptera: Noctuidae), an efficient phytophagous insect for
biological control of weeds of the genus Ambrosia L. Acad. Sci.
U.S.S.R. Ent. Rev. 49: 23-36. [in Russian]. Kovalev, O. V. & V. I. Samus. 1972. Biology of Tarachidia
candefacta Hubn. and prospects of its use to control common ragweed.
U.S.S.R. Agric. Biol. 7: 281-84. [in Russian]. Kovalev, O. V. & V. V. Vechernin. 1986. Description of a new
wave process in populations with reference to introduction and spread of the
leaf beetle Zygogramma suturalis F. (Coleoptera:
Chrysomelidae). Ent. Obozr. 65: 21-38. [in Russian]. Krauss, N. L. H. 1962. Biological control investigations on
lantana. Proc. Hawaii. Ent. Soc. 18: 134-3 Lawton, J. H. 1986. Host plant influences on insect diversity:
the effects of space and time. p. 105-25. In: L. A. Mound & N.
Waloff (eds.), Diversity of Insect Faunas. Blackwells Publ., Oxford. 204 p. Lawton, J. H. & S. McNeill. 1979. Between the devil and the
deep blue sea: on the problem of being a herbivore. Symp. British Ecol. Soc.
20: 223-44. Lee, J. A., S. McNeill & I. H. Rorison. 1987. Nitrogen as an
ecological factor. Blackwells, Oxford. 470 p. Lee, J. C. & E. A. Bernays. 1988. Declining acceptability of
a food plant for the polyphagous grasshopper Schistocerca americana
(Drury) (Orthoptera: Acrididae): the role of food aversion learning. Physiol.
Ent. (in press). 1978 Legner, E. F. 1978.
Efforts to control Hydrilla verticillata Royle with herbivorous Tilapia zillii (Gervais) in Imperial County irrigation canals. Proc. Calif. Mosq. & Vector Contr. Assoc., Inc. 46: 103-104. 1979 Legner, E. F. 1979.
Considerations in the management of Tilapia for biological aquatic weed control. Proc. Calif. Mosq. & Vector Contr.
Assoc., Inc. 47: 44-45. 1980 Legner, E. F. 1980.
Myriophyllum growth in
irrigation canals following reductions of competitive Potamogeton by Tilapia zillii. Proc. Calif.
Mosq. & Vector Contr. Assoc., Inc. 48:
117. 1983 Legner, E. F. 1983.
Imported cichlid behaviour in California. Proc. Intern. Symp. on Tilapia
in aquaculture, Nazareth, Israel, 8-13 May,
1983. Tel Aviv Univ. Publ.
59-63. . 1986 Legner, E. F. 1986.
Importation of exotic natural enemies. In: pp. 19-30, "Biological Control of
Plant Pests and of Vectors of Human and Animal Diseases." Fortschritte der Zool. Bd. 32:
341 pp. 1995 Legner, E. F. 1995.
Biological control of Diptera of medical and veterinary importance. J. Vector Ecology 20(1): 59-120. 2000 Legner, E. F. 2000.
Biological control of aquatic Diptera. p. 847-870.
Contributions to a Manual of Palaearctic Diptera, Vol. 1, Science Herald, Budapest. 978 p. 1980 Legner, E. F.
& T. W. Fisher. 1980. Impact of Tilapia zillii
(Gervais) on Potamogeton pectinatus L., Myriophyllum spicatum
var. exalbescens Jepson, and mosquito
reproduction in lower Colorado Desert irrigation canals. Acta Oecologica, Oecol. Applic. 1(1): 3-14. 1981 Legner, E. F.
& C. A. Murray. 1981. Feeding rates and growth of the fish Tilapia zillii [Cichlidae] on Hydrilla
verticillata, Potamogeton pectinatus and Myriophyllum
spicatum var. exalbescens and interactions in irrigation canals in southeastern
California. J. Amer.
Mosq. Contr. Assoc. 41(2): 241-250. 1980 Legner, E. F.
& F. W. Pelsue, Jr. 1980. Bioconversion: Tilapia fish turn
insects and weeds into edible protein.
Calif. Agric. 34(11-12): 13-14. 1983 Legner, E. F. & F. W.
Pelsue, Jr. 1983. Contemporary appraisal of the population
dynamics of introduced cichlid fish in south California. Proc. Calif. Mosq. & Vector Contr.
Assoc., Inc. 51: 38-39. 1973 Legner, E. F., T. W.
Fisher & R. A. Medved. 1973. Biological control of aquatic weeds in the
lower Colorado River basin. Proc. Calif.
Mosq.
Contr. Assoc., Inc. 41: 115-117. 1975 Legner, E. F., W.
J. Hauser, T. W. Fisher & R. A. Medved.
1975. Biological aquatic weed
control by fish in the lower Sonoran Desert of
California. Calif. Agric.
29(11): 8-10. Leki…, M. 1970. The
role of the dipteron, Phytomyza orobanchia Kalt. (Agromyzidae),
in reducing parasitic phanerogam populations of the Orobanche genus in
Vojvodina. Contemp. Agr. 18(7-8): 59-68. Leki…, M. & Lj.
Mihajlivo…. 1970.
Entomogauna of Myriophyllum spicatum L. (Halorrhagidaceae), and
aquatic weed on Yugoslav territory. J. Sco. Agr. Res. 23(82): 59-74. Levins, R. & R. H. MacArthur. 1969. An hypothesis to explain
the incidence of monophagy. Ecology 50: 910-11. Liepolt, R. & E. Weber. 1971. Bischerige erfahrungen mit den
weissen amur (Ctenopharyngodon idella in Osterreich. Osterr.
Fisherei 24: 159-62. Mackie, R. 1957. The biology of Eumysia idahoensis
Mackie. Unpup. M.S. Thesis, Univ. of Idaho, Moscow. Maddox, D. M. 1968. Bionomics of an alligatorweed fleabeetle, Agasicles
sp., in Argentina. Ann. Ent. Soc. Amer. 61: 1299-1305. Maddox, D. M. 1976. History of weevils on puncturevine in and
near the United States. Weed Sci. 24: 414-16. Maddox, D. M. 1981. Seed and stem weevils of puncturevine: a
comparative study of impact, interaction, and insect strategy, p. 447-67. In:
E. S. Delfosse (ed.), Proceedings V International Symposium on Biological
Control of Weeds, 1980, Brisbane, Australia. Maddox, D. M. & L. A. Andrés. 1979. Status of puncturevine
weevils and their host plants in California. Calif. Agric. 33: 7-8. Maddox, D. M., L. A. Andrés, R. D. Hennessey, R. D. Blackburn
& N. R. Spencer. 1971. Insects to control alligatorweed, an invader of
aquatic ecosystems in the United States. BioScience 21: 985-91. Maddox, D. M., L. A. Andrés, R. D. Hennessey, R. B. Blackburn
& N. R. Spencer. 1971. Insects to control alligatorweed. Bioscience 21:
985-91. May, J. & J. N. Roney. 1969. Arizona Cooperative Insect
Survey. Rept. No. 33, Aug. 1969. Mayton, E. L., E. V. Smith & D. King. 1945. Nutgrass
eradication studies. IV. Use of chickens and geese in the control of
nutgrass, C. rotundus L. J. Amer. Soc. Agron. 37: 785-91. McDonald, I. A. W., F. J. Kruger & A. A. Ferrar (eds.). 1986.
The ecology and management of biological invasions. Proc. Natl. Synth. Symp.
on the Ecology of Biological Invasions. Oxford Univ. Press, Cape Town, S.
Africa. 324 p. McNeill, S. & T. R. E. Southwood. 1978. The role of nitrogen
in the development of insect/plant relationships. p. 77-98. In: J. B.
Harborne (ed.), Biochemical Aspects of Plant and Animal Coevolution. Academic
Press, London. 435 p. Miller, D. 1940. Biological control of noxious weeds of New
Zealand. Herb. Publ. Ser. Bull. 27: 153-57. Mitchell, B. K. 1987. Interactions of alkaloids with galeal
chemosensory cells of Colorado potato beetle. J. Chem. Ecol. 13: 2009-22. Mitter, C. & D. J. Futuyma. 1983. An evolutionary-genetic
view of host-plant utilization by insects. p. 427-60. In: R. F. Denno
& M. S. McClure (eds.), Variable Plants and Animals in Natural and
Managed Systems. Academic Press, New York. 717 p. Miyazaki, M. & A. Naito. 1976. Studies on the host
specificity of Gastrophysa atrocyanea Mot. (Col:
Chrysomelidae), a potential biological control agent against Rumex obtusifolius
L. (Polygonaceae) in Japan. Commonw. Inst. Biol., Trinidad, Misc. Publ. 8:
97-107. Mooney, H. A. & J. A. Drake (eds.). 1986. Ecology of
Biological Invasions of North America and Hawaii. Springer Verlag, New York.
321 p. Moran, V. C. 1980. Interactions between phytophagous insects and
their Opuntia hosts. Ecol. Ent. 5: 153-64. Moran, V. C. 1986. The Silwood international project on the
biological control of weeds. p. 65-8. In: E. S. Delfosse (ed.), Proc.
VI Intl. Symp. Biol. Contr. Weeds, 19-25 Aug 1984, Vancouver, Canada. Agric.
Canad. 885 p. Moran, V. C. & H. G. Zimmerman. 1984. The biological control
of cactus weeds: achievements and prospects. Biocontr. News Info. 5: 297-320. Moran, V. C. & H. G. Zimmermann. 1985. The biological control
of Cactaceae: success ratings and the contribution of individual agent
species. p. 69-75. In: E. S. Delfosse (ed.), Proc. VI Intl. Symp.
Biol. Contr. Weeds, 19-25 Aug 1984, Vancouver, Canada. Agric. Canad. 885 p. Moran, V. C., S. Neser & J. H. Hoffmann. 1986. The potential
of insect herbivores for the biological control of invasive plants in South
Africa, p. 261-68. In: I. A. W. MacDonald, F. J. Kruger & A. A.
Ferrar (eds.), The Ecology and Management of Biological Invasions in Southern
Africa. Oxford Univ. Press, Capetown. South Africa. 324 p. Oehrens, E. 1977. Biological control of the blackberry through
the introduction of rush, Phragmidium violaceum, in Chile. FAO
Plant Protection Bull. 25: 26-28. O'Neill, K. 1968. Amynothrips andersoni, a new
genus and species injurious to alligatorweed. Proc. Ent. Soc. Wash. 70:
175-83. Oosthuizen, M. J. 1963. The biological control of Lantana camara
L. in Natal. J. Ent. Soc. South Africa 27: 3-16. Orr, C. C. 1980. Nothanguina phyllobia, a nematode
biocontrol of silverleaf nightshade, p. 389-91. In: E. S. Delfosse (ed.),
Proceedings of the V International Symposium on Biological Control of Weeds,
1980, Brisbane, Australia. Pemberton, R. W. 1981. International activity in biological
control of weeds: patterns, limitations and needs, p. 57-71. In: E. S.
Delfosse (ed.), Proceedings of the V International Symposium on Biological
Control of Weeds, 1980, Brisbane, Australia. Penfound, W. T. & T. T. Earle. 1948. The biology of the
waterhyacinth. Ecol. Monogr. 18: 447-72. Perkins, B. D. 1973. Potential for waterhyacinth management based
on studies in Argentina. Proc. Tall Timbers Conf. Ecol. Anim. Contr. Habitat
Manage. 4: 53-64. Perkins, R. C. L. 1903. Enemies of lantana. Hawaii Livestock
Breeder's Assoc., First Ann. Mtg. Proc., Nov. 17-18, 1902: 28-35. Perkins, R. C. L. 1904. Later notes on lantana insects. Hawaii
Livestock Breeder's Assoc., 2nd Ann. Mtg. Proc., 1903: 58-61. Perkins, R. C. L. & O. H. Swezey. 1924. The introduction into
Hawaii of insects that attack lantana. Bull. Hawaiian Sugar Planters Assoc.
Expt. Station No. 16: 1-53. Price, P. W., M. Westoby, B. Rice, P. R. Atsatt, R. S. Fritz, S.
N. Thompson & K. Mobley. 1986. Parasitic mediation in ecological
interactions. Ann. Rev. Ecol. Syst. 17: 487-505. Rao, V. P., M. A. Ghani, T. Sankaran & K. C. Mathur. 1971. A review
of the biological control of insects and other pests in south-east Asia and
the Pacific Region. Commonw. Inst. Biol. Contr. Tech. Commun. No. 6: 1-149. Rees, C. J. C. 1969. Chemoreceptor specificity associated with
choice of feeding site by the beetle Chrysolina brunsvicensis
on its food plant, Hypericum hirsutum. Ent. Expt. Appl. 12:
565-83. Rhoades, D. F. 1979. Evolution of plant chemical defense against
herbivores. p. 3-54. In: G. A. Rosenthal & D. H. Janzen (eds.),
Herbivores. Their Interaction With Secondary Plant Metabolites. Academic
Press, New York. 718 p. Rhoades, D. F. 1983. Herbivore population dynamics and plant
chemistry. p. 155-220. In. R. F. Denno & M. S. McClure (eds.),
Variable Plants and Animals in Natural and Managed Systems. Academic Press,
New York. 717 p. Ridings, W. H., D. J. Mitchell, C. L. Schoulties & N. E.
El-Gholl. 1978. Biological control of milkweed vine in Florida citrus groves
with a pathotype of Phytophthora citrophthora, p. 224-40. In:
T. E. Freeman (ed.), Proceedings of the IV Intern. Symposium on Biological
Control of Weeds, 1976, Gainesville, Florida. Ritcher, P. O. & E. A. Dickason. 1964. The Aroga
epidemic in Oregon. Proc. Range Insect Meet. Albany, Calif. 4 p. Robertson, H. G. 1985. Egg predation by ants as a partial
explanation of the difference in performance of Cactoblastis cactorum
on cactus weeds in South Africa and Australia. p. 83-88. In: E. S.
Delfosse (ed.), Proc. VI Intern. Symposium on Biological Control of Weeds.
Vancouver, Canada, 19-25 Aug. 1984. Agric. Canad. 885 p. Rudakov, O. L. 1961. Pervye resultaty biologicheskoy borby as
povilikoy. Zashch. Rast. (Moscow) 6: 23-4. Sands, D. C. & A. D. Rovira. 1971. Modifying the virulence
and host range of weed pathogens. Proc. 3rd Int. Conf. Plant Pathogenic Bacteria,
Wageningen, The Netherlands. p. 50. Schoonhoven, L. M. 1982. Biological aspects of antifeedants. Ent.
Expt. Appl. 31: 57-69. Schoonhoven, L. M. 1987. What makes a caterpillar eat? The
sensory code underlying feeding behavior. p. 69-98. In: R. F. Chapman,
E. A. Bernays & J. G. Stoffolano (eds.), Perspectives in Chemoreception
and Behavior. Springer Verlag, New York. 107 p. Schröder, D. 1974. The phytophagous insects attacking Sonchus
spp. (Compositae) in Europe. Commonw. Inst. Biol. Contr., Trinidad, Misc.
Publ. 8: 89-96. Schröder, D. 1980. The biological control of thistles. Biocontr.
News Info. 5: 297-320. Schröder, D. & R. D. Goeden. 1986. The search for arthropod
natural enemies of introduced weeds for biological control--in theory and
practice. Biocontr. News Info. 7: 147-55. Scriber, J. M. 1983. Evolution of feeding specialization,
physiological efficiency and host races in selected Papilionidae and
Saturniidae. p. 373-412. In: R. F. Denno & M. S. McClure (eds.),
Variable Plants and Animals in Natural and Managed Systems. Cademic Press,
New York. 717 p. Scriber, J. M. & P. P. Feeny. 1979. The growth of herbivorous
caterpillars in relation to degree of feeding specialization and to growth
form of their food plants (Lepidoptera: Papilionidae and Bombycoidea).
Ecology 60: 829-50. Seaman, D. E. & W. A. Porterfield. 1964. Control of aquatic
weeds by the snail Marisa cornuarietis. Weeds 12: 87-92. Simmonds, F. J. 1950. Insects attacking Cordia macrostachya
(Jacq.) Roem. & Schult. in the West Indies. II. Schematiza cordiae
Barber (Coleoptera: Galerucidae). Canad. Ent. 81: 275-82. Simmonds, F. J. 1967a. Biological control of pests of veterinary
importance. Vet. Bull. 37: 71-85. Simmonds, F. J. 1967b. The economics of biological control. J.
Roy. Soc. Arts London 115(5135): 880-98. Simmonds, F. J. 1970a. Commonwealth Agricultural Bureaux,
Commonw. Inst. Biol. Contr. Ann. Rept. (1970). Simmonds, F. J. (ed.). 1970b. Commonw. Inst. Biol. Contr.,
Trinidad, Misc. Publ. 1. 110 p. Simmonds, F. J. & F. D. Bennett. 1966. Biological control of Opuntia
spp. by Cactoblastis cactorum in the Leeward Islands (West
Indies). Entomophaga 11: 183-89. Simmonds, H. W. 1937. The biological control of the weed, Clidemia
hirta, commonly known in Fiji as "the curse." Agric. J.
Dept. Agric., Fiji 8: 37-9. Smiley, J. T. & C. S. Wisdom. 1985. Determinants of growth
rate on chemically heterogenous host plants by specialist insects. Biochem.
Syst. Ecol. 13: 305-312. Smith, H. S. 1919. On some phases of insect control by the
biological method. J. Econ. Ent. 12: 288-92. Smith, H. S. 1948. Biological control of insect pests, p.
276-320. In: C. P. Clausen (ed.), Biological Control of Citrus
Insects, Vol. IV. The Citrus Industry, W. E. Reuther, E. C. Calaran & G.
E. Carman (eds.), University of California, Div. Agric. Sci., Berkeley. Smith, J. M. 1951. Biological control of weeds in Canada.
Canadian National Weed Commission, East Sector Proceedings 5: 95-7. Sneed, K. E. 1971. The white amur: A controversial biological control.
Amer. Fish Farmer 2(6): 6-9. Sobhian, R. & L. A. Andrés. 1978. The response of the
skeletonweed gall midge, Cystiphora schmidti (Diptera:
Cecidomyiidae), and gall mite, Aceria chondrillae (Eriophyidae)
to North American strains of rush skeletonweed (Chondrilla juncea).
Environ. Ent. 7: 506-08. Southwood, T. R. E. 1978. The components of diversity. Symp. Roy.
Ent. Soc. London 9: 19-40. Spies, J. J. & C. H. Stirton. 1982. Meiotic studies of South
African cultivars of Lantana camara. Bothalia 14: 113-17. Squires, V. R. 1969. Distribution and polymorphism of Tribulus
terrestris sens. lat. in Australia. Victorian Nat. 86: 328-34. Stein, H. 1987. Is the dismal science really a science? Discover
(November). p. 96-9. Stierle, A. C., J. H. Cardellina II & G. A. Strobel. 1988.
Maculosin, a host-specific phytotoxin for spotted knapweed from Alternaria
alternata. Proc. Natl. Acad. Sci. 85: 8008-11. Stirton, C. H. 1977. Some thoughts on the polyploid complex Lantana
camara L. (Verbenaceae). Proc. 2nd Natl. Weeds Conf. South Africa. p.
321-40. Strobel, G. A. 1991. Biological control of weeds. Scien. Amer.
265(1): 72-9. Strong, D. R., J. R. Lawton & T. R. E. Southwood. 1984.
Insects on Plants. Community Patterns and Mechanisms. Blackwell Publ.,
Oxford. 313 p. Takahashi, F. 1977. Triops spp. (Notostraca: Triopsidae)
for the biological agents of weeds in rice paddies in Japan. Entomophaga 22:
351-57. Templeton, G. E., D. O. TeBeest & R. J. Smith, Jr. 1978. Development
of an endemic fungal pathogen as a mycoherbicide for control of northern
jointvetch in rice, p. 214-16. In: T. E. Freeman (ed.), Proceedings of
the IV Intern. Symposium on Biological Control of Weeds, 1976, Gainesville,
Florida. Thomas, P. A. & P. M. Room. 1986. Taxonomy and control of Salvinia
molesta. Nature 320: 581-84. Trujillo, E. E. 1985. Biological control of Hamakua Pa-Makani
with Cercosporella sp. in Hawaii, p. 661-71. In: E. S. Delfosse
(ed.), Proceedings of the VI International Symposium on Biological Control of
Weeds, 1984, Vancouver, Canada. Tryon, H. 1910. The "wild cochineal insect," with
reference to its inurious action on prickly pear (Opuntia spp.) in
India, etc., and to its availability for the subjugation of this plant in
Queensland and elsewhere. Queensl. Agric. J. 25: 188-97. Turner, C. E. 1984. Conflicting interests and biological control
of weeds, p. 203-25. In: E. S. Delfosse (ed.), Proceedings of the VI
International Symposium on Biological Control of Weeds, 1984, Vancouver,
Canada. U. S. Army. 1965. Expanded project for aquatic plant control.
89th Congress, 1st Sess., House Doc. No. 251. 145 p. U. S. Dept. Agriculture. 1965. A survey of extent and cost of
weed control and specific weed problems. Agr. Res. Serv. ARS 34-23-1, August.
78 p. Van Zon, J. C. J. 1974. Studies on the biological control of
aquatic weeds in the Netherlands. Commonw. Inst. Biol. Contr., Trinidad,
Misc. Publ. 8: 31-8. Vogt, G. B. 1960. Exploration for natural enemies of
alligatorweed and related plants in South America. Special Rept. PI-4, U. S.
Dept. Agr., Agr. Res. Ser., Ent. Res. Div. Mimeo. 58 p. van Emden, H. F. 1978. Insects and secondary substances-- an
alternative viewpoint with special reference to aphids. p. 309-26. In:
J. B. Harborne (ed.), Biochemical Aspects of Plant and Animal Coevolution.
Academic Press, London. 435 p. Vogt, G. B. 1961. Exploration for natural enemies of
alligatorweed and related plants in South America. Special Rept. PI-5, U. S.
Dept. Agr., Agr. Res. Ser., Ent. Res. Div. Mimeo. 50 p. Waldbauer, G. P., R. W. Cohen & S. Friedman. 1984. Self
selection of an optimal nutrient mix from defined diets by larvae of the corn
earworm, Heliothis zea Boddie. Physiol. Zool. 57: 590-97. Wang, R. 1986. Current status and perspectives of biological weed
control in China. Chinese J. Biol. Contr. 1: 173-77. Wapshere, A. J. 1970. The assessment of biological control
potential of the organisms attacking Chondrilla juncea L.
Commonw. Inst. Biol. Contr. Trinidad, Misc. Publ. 1: 81-9. Wapshere, A. J. 1974a. A strategy for evaluating the safety of
organisms for biological weed control. Ann. Appl. Biol. 77: 201-11. Wapshere, A. J. 1974b. Host specificity of phytophagous organisms
and the evolutionary centers of plant genera and subgenera. Entomophaga 19:
301-09. Wapshere, A. J. 1974c. A comparison of strategies for screening
biological control organisms for weeds. Misc. Publ. Commonw. Inst. Biol.
Contr. 6: 151-58. Warren, R. & V. Freed. 1958. Tansy ragwort-- a poisonous weed.
Oregon St. Coll. Ext. Bull. 717: 3-5. Wassermann, S. S. & D. J. Futuyma. 1981. Evolution of host
plant utilization in laboratory populations of the southern cowpea weevil, Callosobruchus
maculatus Fabricius (Coleoptera: Bruchidae). Evolution 35: 605-17. Waterhouse, D. F. 1966. The entomological control of weeds in
Australia. Mushi 39 (Suppl.): 109-18. Waterhouse, D. F. (ed.). 1970. The Insects of Australia.
Melbourne Univ. Press, Melbourne, Australia. 1029 p. Weber, P. W. 1956. Recent introductions for biological control in
Hawaii. Proc. Hawaiian Ent. Soc. 16: 162-64. Weldon, L. W. 1960. A summary review of investigations of
alligatorweed and its control. U. S. Dept. Agr., Agr. Res. Ser. CR-33-60. 41
p. Williams, J. R. 1960. The control of black sage (Cordia macrostachya)
in Mauritius: the introduction, biology and bionomics of a species of Eurytoma
(Hymenoptera, Chalcidoidea). Bull. Ent. Res. 51: 123-32. Wilson, C. L. 1969. Use of plant pathogens in weed control. Ann.
Rev. Phytopath. 7: 411-34. Wilson, F. 1960. A review of the biological control of insects
and weeds in Australia and Australian New Guinea. Commonw. Inst. Biol. Contr.
Trinidad Tech. Commun. 1: 102 p. Wilson, F. 1964. The biological control of weeds. Ann. Rev. Ent.
9: 225-44. Yeo, R. R. & T. W. Fisher. 1970. Progress and potential for
biological weed control with fish, pathogens, competitive plants and snails.
Tech. Pap. FAO Int. Conf. Weed Control, June 21 - July 1, 1970, Davis,
Calif., p. 450-63. Weed Sci. Soc. Amer. Champaign, Illinois. Zeiger, C. F. 1967. Biological control of alligatorweed with Agasicles
n. sp. in Florida. Hyacinth Contr. J. 6: 31-4. Zettler, F. W. & T. E. Freeman. 1972. Plant pathogens as
biocontrols of aquatic weeds. Ann. Rev. Phytopath. 10: 455-70. Zwölfer, H. 1965. Preliminary list of phytophagous insects
attacking wild Cynareae (Compositae) in Europe. Commonw. Inst. Biol. Contr.
Tech. Bull. 1: 81-154. Zwölfer, H. 1968. Some aspects of biological weed control in
Europe and North America. Proc. 9th Brit. Weed Contr. Conf., p. 1147-56. Zwölfer, H. 1973. Competitive coexistence of phytophagous insects
in the flower heads of Carduus nutans, p. 74-81. In: P.
H. Dunn (ed.), Proceedings of the II International Symposium on Biological
Control of Weeds, 1971, Rome, Italy. Zwölfer, H. 1974. Competitive coexistence of phytophagous insects
in the flower heads of Carduus nutans L. Commonw. Inst. Biol.
Contr., Misc. Publ. 6: 74-80. Zwölfer, H. 1988. Evolutionary and ecological relationships of
the insect fauna of thistles. Ann. Rev. Ent. 33: 103-22. Zwölfer, H. & P. Harris. 1971. Host specificity
determination of insects for biological control of weeds. Ann. Rev. Ent. 16:
159-78. |