Integrated pest management of Liriomyza trifolii: Influence of avermectin, cyromazine, and methomyl on leafminer ecology in celery

Abstract

The impact of weekly applications of avermectin, cyromazine and methomyl on Lyriomyza trifolii (Burgess) and an associated complex of six parasite species was evaluated in celery, Apium graveolens L. Avermectin suppressed leafminer populations, but did not adversely affect (1) seasonal per cent parasitism, (2) adult parasite mortality, or (3) survival and emergence of immature parasites from treated foliage. Although cyromazine use also reduced L. trifolii density, significant reductionsin survival and emergence of immature parasites greatly diminished the potential for biological control by lowering the seasonal per cent parasitism and increasing the L. trifolii: parasite ratio. Methomyl application for control of lepidopterous larvae increased leafminer density and reduced the seasonal percent parasitism by reducing survival of adult parasites. Species composition of the parasite complex was least affected by avermectin and methomyl. Cyromazine significantly reduced the relative abundance of some key parasite species. Major parasite species included species in the family Eulophidae: Diglyphus intermedius (Girault), D. begini (Ashmead), Chrysonotomyia ( Achrysocharella) punctiventris (Crawford), Chrysocharis parksi Crawford and C. ainsliei Crawford, and the family Pteromalidae: Halticoptera circulus (Walker). The potential for incorporation of these compounds into an integrated pest management program for celery and tomatoes, Lycopersicon esculentum Mill., is discussed.