Evaluation of generational percent parasitism on Lyonetia clerkella (Lepidoptera

Abundance of live, dead and parasitized larvae of the peach leafminer, Lyonetia clerkella (Linnaeus), was investigated at 2 or 3-day intervals from April to November 1994 and April to October 1995. The proportions of infested leaves were determined by a binomial sampling in peach orchards under different management intensities, and subsequently the infested leaves were sampled to ascertain the fate of each leafminer through individual rearing in the laboratory. The seasonal prevalence showed seven discrete generations in both years. The number of larvae entering each generation was estimated by a stage-frequency analysis. From that estimate, as well as from an estimate of the number of parasitized larvae, the generational percent parasitism was determined for each generation and throughout the year. The yearly result was about 9% parasitism in the insecticide-sprayed orchards and about 19% in the unsprayed orchards. The relationship between host and parasitoid densities in successive generations showed a tendency toward counterclockwise rotation. Furthermore, the relationship between host density and percent parasitism exhibited a delayed density-dependent process in a host-parasitoid system.