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HOLLY LEAFMINER

Phytomyza ilicis Curtis -- Agromyzidae

(Contacts)

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Holly leafminer invaded British Columbia, Canada, where it damaged leaves of English holly in commercial and urban plantings. There were five parasitoids liberated on Vancouver Island during 1936-1938 and on mainland Canada in 1939 (Clausen 1978). Four species became established, with Chrysocharis gemma (Walker) and Opius ilicis Nixon being most important. About 90% parasitization was caused by C gemma on Vancouver Island while O. ilicis contributed ca. 90% of the parasitization on the mainland. These parasitoids usually prevent serious damage to English holly in ornamental plantings, and Turnbull & Chant (1961) considered this a complete biological control success. However, in commercially produced holly, the parasitoids did not give completely satisfactory control (Dahlsten & Hall 1999), therefore Turnbull & Chant (1961) and Munroe (1971) consider biological control as partially to substantially successful in commercial plantings.

Clausen (1978) remarked that the study of the natural enemies of the holly leaf miner in England and their subsequent behavior when introduced into British Columbia, demonstrated the risks and inherent difficulty in trying to judge, on the basis of studies in the native home of a pest and its natural enemies, the potential of each element of the latter when introduced into a new environment. Chrysocharis gemma was the dominant species in England, averaging 30-40% parasitism, with a maximum of 71%. On the other hand, the parasitization by O ilicis in England ranged from 0-0.3%, it being so scarce that on any basis of comparison it would have been completely ignored, or at least would have been put at the bottom of any priority list for introduction. However, it was fully effective on the mainland of British Columbia, as did C. gemma on Vancouver Island. Cameron (1941) discussed competition between O. ilicis and C. gemma, and stated that the latter is dominant when both occur in individual hosts. He concluded that the total mortality effected by the two parasitoids is greater than that which would be attained by C. gemma alone, since the mortality by O. ilicis, however small, represents kill of hosts not parasitized by C. gemma.

For further details on this biological control effort, please see the following (Cameron 1939, 1941; Downes & Andison 1940, McLeod 1954, 1962; Turnbull & Chant 1961).

REFERENCES: [Additional references may be found at: MELVYL Library ]

Cameron, E. 1939. The holly leaf-miner (Phytomyza ilicis Curt.) and its parasites. Bull. Ent. Res. 30: 173-208.

Cameron, E. 1941. The biology and post-embryonic development of Opius ilicis n. sp., a parasite of the holly leaf-miner (Phytomyza ilicis Curt.). Parasitol. 33: 8-39.

Clausen, C. P. 1978. Agromyzidae. In: C. P. Clausen, (ed.), Introduced parasites and predators of arthropod pests and weeds: A world review. U. S. Dept. of Agriculture, Agric. Handbk. No. 480. 545 p.

Dahlsten, D. L. & R. W. Hall. 1999. Biological control of insects in outdoor urban environments. In: Bellows, T. S. & T. W. Fisher (eds.), Handbook of Biological Control: Principles and Applications. Academic Press, San Diego, New York. 1046 p.

Downes, W. & H. Andison. 1940. The establishment in British Columbia of parasites of the holly leaf miner, Phytomyza ilicis Curtis. J. Econ. Ent. 33: 948-49.

McLeod, J. H. 1954. Statuses of some introduced parasites and their hosts in British Columbia. Ent. Soc. Brit. Columbia Proc. (1953) 50: 19-27.

McLeod, J. H. 1962. A review of the biological control attempts against insects and weeds in Canada. Part I. Biological control of pests of crops, fruit trees, ornamentals, and weeds in Canada up to 1959. Commonwealth Inst. Biol. Control, Tech. Commun. 2: 1-33.

Munroe, E. G. 1971. Chap. 48. Status and potential of biological control in Canada. p. 213-55. In: Biological control programmes against insects and weeds in Canada, Commonwealth Inst. Biol. Contr. Tech. Comm. No. 4: 266 p.

Turnbull, A. L. & D. A. Chant. 1961. The practice and theory of biological control in Canada. Canad. J. Zool. 39: 697-753.