A tritrophic analysis of host preference and performance in the polyphagous leafminer Liriomyza huidobrensis

VALLADARES GRACIELA; SALVO ADRIANA; VIDELA MARTIN

Foz do Iguassu Brasil

Congreso; International Congress of Entomology; 2000

Most species in Agromyzidae (Diptera) show close association to a species or genus of plant host. Liriomyza huidobrensis (Blanchard) is one of the rare polyphagous species as well as one of the most important pests in the family. Oviposition preferences of this leafminer within its local host range in Central Argentina were analysed, considering consequences for larval development and translation of such plant insect relationships into the third trophic level (parasitoids). Infestation levels, suggesting apparent preferences, were estimated from field samples taken fortnightly in various crops at Córdoba (Argentina) along 2 years. Larvae were reared to asses percentage parasitism, and to measure adult body size of leafminer and parasitoids. In laboratory tests, host preferences and larval performance (as development time, survival, pupal weight and adult size) were further assessed, on three selected plant species (Vicia faba, Phaseolus vulgaris, Cucurbita maxima). L. huidobrensis was recorded on 24 crop species, its intensity noticeably varying among them. Adult leafminers were significantly bigger on plants were the species was more abundant. Parasitoid assemblages on the leafminer differed among host plants, regarding number of species (2-12 Hymenoptera species, their richness being associated to sample size), parasitism rate (between 2% and 77%, being independent of host abundance or number of species involved), and relative representation of the main parasitic species. Average body size of particular parasitoid species significantly increased on plants where leaf mining larvae were also bigger. In the laboratory, L. huidobrensis female consistently preferred V. faba for feeding and ovipositing. Larval development time was significantly shorter, while survival was 2.5 times higher and adults reached bigger size on the former plant than on other hosts. In almost every aspect considered, a pattern of decreasing preference and performance on V. fava - P. vulgaris – C. maxima was observed, in coincidence with the tendency for infestation levels observed in the field. From these observations, Liriomyza huidobrensis appears as a very efficient generalist, being able to select the most adequate plant host from among its wide range, and developing greater populations on such hosts. Plant host suitability did not seem to be obviously altered by parasitoids, although some parasitoids benefited from the higher performance of the leafminers, attaining bigger body size on plants were their hosts were bigger.