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137.  Derived from: Legner, E. F. 1975.  Ethology of Host Selection by Entomophagous Insects:  Effect on successful importation of entomophagous insects.  Proc. Workshop Ethology of Host Selection by Entomophagous Insects, Tifton, Georgia, March 1975.  pp. 14-18.

Summary

 

Importation activities for natural enemies stresses a consideration of certain fundamental principles and procedures derived from years of experience by investigators in classical biological pest control.  Considerations that serve in the formulation of an importation program are included.

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          The native habitat of a pest is the most likely source of its effective natural enemies.  If natural enemies maintain the density of the pest species in its original habitat at non-economic levels, then the restoration of such a balance in the country or area of its importation may be expected.  Foreign entomophagous arthropods should be secured from regions most similar ecologically to the region in which they are to be colonized.  However, biological control work to date indicates that species imported into subtropical or tropical regions from the temperate zone are more likely to become established than when importations are made in the reverse manner.  If the pest populations in the foreign country occur generally at low densities in habitats that are apparently favorable for its reproduction, the natural enemies of the pest are probably responsible for its scarcity.  The dominant species of natural enemy at minimum host densities is likely to be the most effective species.  In regions of pest scarcity the natural enemy responsible for such scarcity may be ascertained by the exposure of protected pest populations.

 

          The capacity of an entomophagous insect to control its host in the country of its importation cannot be definitely predicted prior to its actual introduction.  The evidence of effectiveness in the country of origin is of value only in determining the priority and sequence of collecting.  Natural enemies of phytophagous insects should be collected from the species (or varieties) of host plants on which they are to be established in the country of destination.  This is because the probability of attraction to certain host plants, as a habitat, is a first step in host finding, and because the phytophagous species may consist of two or more biological races or siblings characterized by specific host plants and specific parasites as with Pseudococcus maritimus, which includes a form that infests only the grape and which is specifically parasitized by Acerophagus natativentris (S. S. Flanders, pers. commun.).  The importation of an entomophagous species from one geographical area should not preclude its importation from a different area, since it has been demonstrated that a species may consist of two or more geographical forms differing in seasonal occurrence, reproduction capacity, and in kinds of hosts.  Importation work is not completed until all geographical races have been discovered, collected, and shipped to the new country.  There is also the possibility that natural enemies might adapt to a more significant population dampening role in the country of destination through gradual genetic change.

 

          Although one principal species may give effective control, such control may not be general until additional species that occupy niches outside the range of the principal species are imported.  The number of species in the natural enemy complex of a plant insect in its country of origin may be very large.  The number known to attack the oriental fruit moth, Grapholitha molesta Busck, in Japan and Korea is over 50 species of which half are primary in habit.

 

          In searching for entomophagous species it should be constantly borne in mine that host habitat finding is important to the success or failure of natural enemies in finding their hosts.  In the case of certain medically important pests the degree of synanthropy is important.  During host searching parasites often search first for the environment frequented by the host.  Odor associated with these habitats is usually the attracting force.  Host visibility only aids the parasite in pinpointing an object that has already exerted an attraction.  Many parasitic Hymenoptera will oviposit in any suitable insect located in its preferred habitat, the host plant occasionally being more attractive to the parasite than the host itself.  Honeydew produced by aphids and coccids also can attract parasites; moisture in the form of dew is required by many parasitic species.  Locomotion of the parasite may determine the extent to which the host habitat is selected and frequented.  Phytophagous hosts are sometimes rendered immune to successful parasitization by certain plants upon which they feed.  The plant on which the host is feeding may affect host selection, fecundity, and longevity of the parasite.

 

Pertinent References:

 

Askey, R. R. 1971.  Parasitic Insects.  Amer. Elsevier Publ. Co., Inc., New York.  316 p.

 

DeBach, P.  1964 (editor and contributor).  Biological Control of Insect Pests and Weeds.  Reinhold Publ. Co., New York.  844 p.

 

DeBach, P.  1974.  Biological control by Natural Enemies.  Cambridge Univ. Press.  323 p.

 

Flanders, S. E.   1937.  Habitat selection by Trichogramma.  Ann. Entomol. Soc. Amer. 30:  208-210.

 

Laing, J.  1937.  Host-finding by insect parasites.  1.  Observations of the finding of host by Alysia manducator, Mormoniella vitripennis and Trichogramma evanescens.  J. Anim. Ecol. 6:  298-317.

 

Legner, E. F.  1967.  The status of Nasonia vitripennis as a natural parasite of the housefly, Musca domestica.  Canad. Entomol. 99(3):  308-09.

 

Legner, E. F., R. D. Sjogren and I. M. Hall.  1974.  The biological control of medically important arthropods.  Crit. Rev. Environ. Contr. 4(1):  85-113.

 

Remington, C. L.  1968.  The population genetics of insect introduction.  Ann. Rev. Entomology 13:  415-426.

 

Salt, G.  1958.  Parasitic behaviour and the control of insect pests.  Endeavour 17:  145-148.

 

Simmonds, F. J.  1972.  Approaches to biological control problems.  Entomophaga 17(3):  251-264.

 

 

 

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