Functional Response of Two Populations of Trissolcus vassilievi (Mayr) on Sunn Pest Eggs (Eurygaster integriceps Puton)

Egg parasitoids have important role in reducing pest populations. Trissolcus vassilievi (Mayr) is one of the most important biological control agents of the sunn pest. In this study, two populations of both the parasitoid and the host, one from Tabriz and the other from Varamin were used. The functional response experiments were carried out for both populations as well as progeny obtained by reciprocal crosses between them (Tabriz females×Varamin males vs. Varamin females×Tabriz males). The total time of experiment considered to be either 6 or 24 h. Logistic regression analysis revealed that the functional response of T. vassilievi was from type III in all treatments. Parameter estimation also revealed that searching rate (b) and handling time (Th) was close to each other in all treatments. Experiment time had no considerable effect on parasitism rate and only unrealistically increased the handling time and decreased the line slope of the attack rate. Maximum attack rate varied between 42 and 45 in original populations while it reached to a maximum of 47.5 in crossed populations. Handling time was longer and, parameter b was smaller in Tabriz wasps. This may suggest that attack rate increases more rapidly in Varamin wasps. In other words, they have stronger density dependent response. Host effect was not significant among treatments. This study showed that Varamin wasps have a minor superiority in terms of attack rate and handling time.