Effects of pipunculid parasitism on the population dynamics of the green rice leafhopper, Nephotettix virescens DISTANT

Abstract

The effect of pipunculid parasitism on the population dynamics of the green rice leafhopper, Nephotettix virescens was studied in asynchronous rice planting areas of Central Java and Bali, Indonesia. The parasitism rate of N. virescens adults was higher in migrant-producing, 1st and 2nd generations in paddy fields than in the other generations which were mainly composed of immigrants from outside. These included populations obtained in seed beds, paddy fields of 1-4 weeks after transplanting and ratoon fields of 1-4 weeks after harvest. Since the parasitism occurs mainly in the nymphal stages, the above results indicate a suppression of migratory activities of parasitized N. virescens. The parasitism rate of 1st generation adults was related positively with the adult density and negatively with the percentage of mature females among parasite-free females. The effects of a higher emigration rate of healthy adults on the parasitism rate of resident populations were analyzed with mathematical models. The results showed that the role of pipunculid parasitism as a factor stabilizing or destabilizing population fluctuations of N. virescens is quite limited.