BERMUDA CEDAR SCALES
Carulaspis minima (Targioni-Tozzetti) & Lepidosaphes newsteadi (Sulc.) – Diaspididae
GO TO ALL: Bio-Control Cases
Two diaspidid species that were introduced into Bermuda, apparently on coniferous nursery stock imported from California in the early 1940's, devastated the natural forest of Bermuda cedar, Juniperus bermudiana. Carulaspis minima, which had been confused with the juniper scale, C. visci (Schrank), is a pest of Thuja, Juniperus, Cupressus, Sequoia, Callitris, and Biota. It is of apparent Palearctic origin, and has been recorded from the Mediterranean area and the south central Soviet Union. It was probably introduced into North America and Bermuda (Borkhsenius 1950, Balachowsky 1954, McKenzie 1956). In Bermuda this scale was first considered less dangerous than L. newsteadi because it occupied a smaller area than the latter pest and was more heavily attacked by parasitoids (Rosen & DeBach 1978). However, it soon proved to be the more injurious of the two and spread rapidly over the island, causing severe defoliation and tree mortality, in a case of complete biological control of a plant, as previously discussed. Several overlapping generations were reported to develop annually in Bermuda, with crawlers present continuously from August to November (Waterston 1947, Thompson 1947, Bennett & Hughes 1959).
Lepidosaphes newsteadi, a pest of pine, cedar, Abies and Picea of European origin, is widespread in central and western Europe, and reported also from Lebanon and Turkey. It was accidentally introduced into North America and Bermuda. The scale attacks only the needles, causing defoliation in heavy infestations. It is univoltine in Europe, fertilized females overwintering, then depositing an average of 31 eggs per female during the following spring. Crawlers hatch at the beginning of June and emergence of adult males takes place in the 2nd half of August, coinciding with the second molt of the females (Schmutterer 1951, Balachowski 1954). In Bermuda this species also killed Bermuda cedar (Waterston 1947). With both species being harmful to the Bermuda cedar, even in moderate infestations, and causing tree mortality within two years after the first sign of attack, these pests destroyed a large proportion of the trees on the island and threatened to make the Bermuda cedar extinct.
Bermuda cedars were considered valuable for tourism, and its extermination might have serious effect on the island economy. Biological control was thus initiated in 1946 against both scales. Initially introductions of natural enemies were made mainly against L. newsteadi, but in succeeding years the majority of the imported species were for C. minima. The biological control effort was one of the largest ever to be undertaken as far as numbers of species of natural enemies released against a pest and total numbers of individuals liberated.
Hemisarcoptes malus (Shimer), a predator of oystershell scale, was introduced from Canada against L. newsteadi in 1946. These shipments yielded 435 adults and immature stages for field release in Bermuda (Waterston 1947). These were supplemented in 1949 by 235 adults of Chilocorus spp. from California bearing hypopi of the mite, which were also released. Aphytis mytilaspidis (LeBaron), a parasitoid of oystershell scale, was introduced against L. newsteadi from Canada in 1947. Two additional parasitoids of oystershell scale, Anabrolepis zetterstedtii (Westw.) and Aphytis sp., were introduced against L. newsteadi in 1947 from Italy, and also Chilocorus bipustulatus (L.), a general predator of scale insects (Rosen & DeBach 1978).
In March 1947 shipments of two coccinellid predators, Lindorus lophanthae (Baisd.) and Orcus chalybeus (Bdvl.), were made from California. Both species appeared promising in feeding tests with C. minima. Additional importations from California the same year included the coccinellids Chilocorus distigma Klug., C. stigma Say, Exochomus quadripustulatus (L.) and Zagloba ornata (Horn), and the encyrtid parasitoid Habrolepis rouxi Compere. Several shipments of other ladybeetles, collected from bamboo, coconut and citrus, were made from Trinidad, British West Indies, in 1947, these comprising Azya trinitatis Mshll., A. luteipes Mulsant, Chnoodes sp. nr. cinctipennis Gorham, Cryptognatha nodiceps Mshall., Curinus coeruleus (Muls.), Pentilia sp., Poria sp., Prodilis sp., and a nitidulid Cybocephalus sp.. Chilocorus nigritus (F.) and Lindorus lophanthae, were obtained in Mauritius and liberated in Bermuda. In all 30,000 parasitoids and predators were imported and released by the end of June 1947.
Importations in 1948 included the predators Egius platycephalus Muls. and Chilocorus cacti (L.) from Puerto Rico, C. bipustulatus from France, and the parasite Aphytis sp. (Chinese origin) from California. Additionally, many of the species obtained in 1947 were released again in 1948, including large numbers of Hemisarcoptes malus.
A program of mass producing coccinellid and nitidulid predators for the Bermuda project was conducted in California during 1948-49. Shipments of the coccinellids Cephaloscymnus occidentalis Horn, Chilocorus bipustulatus, Lindorus lophanthae, Lotis nigerrima Casey, L. neglecta Muls., Microweisia saturalis (Schwarz), Pharoscymnus exiguus (Weise), Telsimia nitida Chapin, and Zagloba ornata, and the nitidulid Cybocephalus sp. (Chinese origin) were made during this period. About 318,000 individuals were received from California during 1949. A similar program was started in Bermuda, and 134,000 predators were reared and released there during that year.
Shipments of Pinus sylvestris foliage, heavily infested with Leucaspis newsteadi and Leucaspis loewi Colvée, were received from Switzerland in 1949. Of the parasitoids obtained from these shipments, 1,048 Prospaltella aurantii (How.) and smaller numbers of Aphytis mytilaspidis and Azotus sp. were released against both L. newsteadi and C. minima. Mass production of predators was continued in California and Bermuda in 1950. An additional species of Cybocephalus (South African origin) was obtained from California. Further introductions included Chilocorus bipustulatus, Scymnus sp., and Cybocephalus rufifrons Reitter from Portugal, Chilocorus stigma from Florida, and small numbers of the coniopterygid predator Semidalis aleyrodiformis (Steph) from England.
Predatory coccinellids that were liberated in 1951 from shipments received from Trinidad were Azya trinitatis, A. luteipes, Curinus coeruleus, Delphastus diversipes (Champ.), Zenoria revestita Muls., Pentilia insidiosa Muls., P. castanea Mulsant, Psyllobora confluens (F.), Cryptognatha nodiceps, C. tumidiventris Champ, Exochomus bisbinotatus Gorham, Chnoodes sp., Scymnus sp., and at least three unidentified species. Shipments from Jamaica comprised Chilocorus cacti, Exochomus jamaicensis Sic., E. ritchieri Sic., and Procula douei Muls., as well as Cycloneda sanguinea (L.) (an aphid feeder) and Scymnus sp. (a mealybug feeder). Of these, C. cacti was mass produced in Bermuda. Shipments of coccinellids, collected in Florida on juniper trees infested with C. minima and other scales, yielded Chilocorus stigma, Microweisia misella (Lec.), Cleis picta (Rand.), Cycloneda sanguinea, Coccinella novemnotata Hbst., and one unidentified species.
Predators that were mass produced in California and forwarded to Bermuda during 1951 were Lotis nigerrima, L. neglecta, Zagloba ornata, Pharoscymnus exiguus, Cephaloscymnus occidentalis, Lindorus lophanthae, Pentilia insidiosa and Cybocephalus sp. (Chinese origin).
The work was terminated in 1951 when the majority of cedar trees in Bermuda were dead or in the process of dying. Altogether over 50 species of predators and parasitoids were introduced into Bermuda during 1946-51. Almost 700,000 predators were mass produced in California (1948-51), and more than 1,700,000 were mass produced in Bermuda for release against the cedar scales (1949-51) (Bedford 1950, Thompson 1954, Bennett & Hughes 1959).
Lepidosaphes newsteadi which was originally considered the most dangerous pest of Bermuda cedar, declined rapidly and was almost completely displaced by C. minima by the end of 1948. The causes of this remarkable decline are not known. The introduced predatory mite, Hemisarcoptes malus, and a chytrid fungus, Myiophagus ucrainica, as well as competitive displacement by C. minima are thought to be possible causes. Hemisarcoptes malus was reported by Bedford (1950) to be established in Bermuda, although not in infestations on Bermuda cedar. Whatever the cause, L. newsteadi became very rare in Bermuda after 1948, except for an occasional isolated infestation.
Carulaspis minima covered the islands and infested practically every Bermuda cedar tree by the end of 1948. Of the numerous natural enemies that were introduced against this scale, only a few were permanently established. Lindorus lophanthae was one of these and increased rapidly, spreading to all parts. It seemed abundant and effective at times. Microweisia saturalis was also established, and became abundant in the western areas of the islands. Hemisarcoptes malus was recovered in 1956 from C. minima. Several other species were recovered some time after their release, and were reported to have reproduced in the field, but most eventually died out. A few species became established on various other hosts, but were unable to breed on C. minima. Severe hurricanes in the autumn of 1947 and 1948 probably contributed to the failure of many species to become established, and hastened the decline of Bermuda cedar trees by causing severe damage to the foliage. Predation by lizards (Anolis spp.) was suggested by Simmonds (1958d) as another possible factor in the failure of introduced coccinellids to become established in Bermuda.
Although L. lophanthae and M. suturnalis showed some promise of controlling C. minima wherever they became particularly abundant, the decline and eventual death of many infested trees was not prevented. The main objective of the project was to prevent the destruction of the natural forest, but this was not realized. Bermuda cedars were not completely eradicated, however, as healthy stands may still be found in certain parts of this extremely small group of islands. Seedings germinate in many areas. It is not known whether the survival of Bermuda cedar has been affected to any extent by the numerous natural enemies of C. minima introduced into the islands (Bedford 1950, Thompson 1954, Bennett & Hughes 1959). According to Thompson (1954) the results of the project have shown that predators may be much more host specific than generally thought. Rosen & DeBach (1978) wondered whether the failure of the project was not partly due to the fact that C. minima, the main target, was at that time misidentified as C. visci. Also the emphasis on predators to the near disregard of parasitoids may have been responsible for the lack of parasitoid establishment. Carulaspis is known to be commonly attacked by Aphytis sp. in Greece and California (DeBach 1946, Rosen & DeBach 1978).
The release of Azotus sp. is if particular interest as all the known species of that genus were thought to be hyperparasitic. (Also see Anonymous 1948, Bedford 1949, Waterston 1946).
REFERENCES: [ Additional references may be found at: MELVYL Library]
Anonymous. 1948. Plant pathology. Bermuda Rept. Dept. Agric. 1947: 10-12 (Abs. in REv. Appl. Ent. (A), 39: 148)
Balachowsky, A. 1954. Les Cochenilles Paléarctiques de la Tribu des Diaspidini. Inst. Pasteur, Paris. 450 p.
Bedford, E. C. G. 1949. Report of the plant pathologist, 1948. Bermuda Dept. Agric. Rept. 1948: 13-24. (Abs in Rev. Appl. Ent. (A), 39: 148).
Bedford, E. C. G. 1950. Report of the plant pathologist. Bermuda Dept. Agric. Rept. 1949: 11-19. (Abs. in Rev. Appl. Ent. (A) 39: 148.)
Bennett, F. D. & I. W. Hughes. 1959. Biological control of insect pests in Bermuda. Bull. Ent. Res. 50: 423-36.
Borkhsenius, N. S. 1950. Unarmored and armored scales of the U.S.S.R. (Coccoidea). Akad. Nauk S.S.S.R., Opred. Faun. S.S.S.R. 32: 1-250.
DeBach, P. 1964. Some species of Aphytis Howard (Hymenoptera: Aphelinidae) in Greece. Ann. Inst. Phytopath. (Benaki) (n.s.) 7: 5-18.
McKenzie, H. L. 1956. The Armored Scale Insects of California. CAlif. Insect Survey Bull. 5. 209 p.
Rosen, D. & P. DeBach. 1978. Diaspididae. In: C. P. Clausen (ed.), Introduced Parasites and Predators of Arthropod Pests and Weeds: a World Review. U. S. Dept. Agric., Agric. Handbk. No. 480. 545 p.
Schmutterer, H. 1951. Zur Lebensweise der Nadelholz-- Diaspididen (Homoptera, Coccoidea, Diaspididae, Diaspidinae) und ihrer Parasiten in den Nadelwäldern Frankens. Ztschr. f. angew. Ent. 33: 111-36.
Simmonds, F. J. 1958. The effect of lizards on the biological control of scale insects in Bermuda. Bull. Ent. Res. 49: 601-12.
Thompson, W. R. 1947. Interim report on two scales attacking the Bermuda cedar. Bermuda Dept. Agric. 3 p. (Abs. in Rev. Appl. Ent. (A), 38: 85).
Thompson, W. R. 1954. Biological control work on cedar scale in Bermuda. In: 6th Commonwealth Ent. Conf. Rept., London: 89-93.
Waterston, J. M. 1946. Report of the plant pathologist (Bermuda) for the year 1945. Bermuda Dept. Agric. 12 p. (Abs. in Rev. Appl. Ent. (A), 36: 48).
Waterston, J. M. 1947. Report of the plant pathologist (Bermuda) for the year 1946. Hamilton Dept. Agric. 18 p. (Abs. in Rev. Appl. Ent. A), 37: 37).