Parasitism of natural populations of Liriomyza helianthi spencer and Calycomyza platyptera (Thomson) (Diptera : Agromyzidae)

The population dynamics and parasitoid assemblages of two leafminers, Lirio myza helianthi Spencer and Calycomyza platyptera (Thomson) (Diptera: Agromy zidae), were examined over a 3-year period. Leafminers were sympatric and o ccurred together on the same two host plants, Helianthus annus L. and Xanth ium strumarium L., at our study sites in northern California. Sixteen speci es of parasitoids were reared from the two leafminers and mortality from pa rasitoids was substantial, averaging about 74%. The most common species, su ch as Diglyphus spp. and Neochrysocharis arizonensis Crawford, show no bias in association with a particular leafminer or plant species. Of the remain ing parasitoids, most were usually associated with a particular leafminer s pecies (e.g., Opius dimidiatus [Ashmead] on L. helianthi). Only one parasit oid of the seven most common taxa (Chrysocharis ainsliei Crawford) was stro ngly associated with a particular host plant species (H. annuus) in either leafminer host. In addition, a review of the literature found that parasito id assemblages in natural, unmanaged habitats tended to be more species ric h than assemblages of parasitoids on leafminers in agricultural habitats, a lthough significant heterogeneity occurs among studies. Nevertheless, the m ost common genera of parasitoids attacking leafminers (Diglyphus, Chrysocha ris, Neochrysocharis, Opius) are prevalent in both habitats. Given the simi larity in assemblages of many of the parasitoids attacking leafminers in ma naged and natural habitats and frequent proximity of the two habitats, ther e exists the potential for exchange of natural enemies among habitats, pote ntially enhancing pest control in agricultural areas. (C) 2001 Academic Pre ss.