Anastatus japonicus Ashmead, a potential biological control agent of Riptortus pedestris (Fabricius)

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is a significant pest of soybean production in China. While biological control would be a desirable means to manage this pest, little research on the use of parasitoids against R. pedestris has been done. In this study, for the parasitoid Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae), we measured the parasitism rate in R. pedestris, the emergence rate of parasitoid progeny, and mortality of eggs from host-feeding. Parasitoids of different ages were assessed against R. pedestris eggs of various ages under laboratory conditions. In addition, the development and longevity of A. japonicus reared on R. pedestris egg were also measured. We found the maximum parasitism rate of A. japonicus was 54.6% on R. pedestris egg. And the maximum emergence rate of A. japonicus was 50.0% from all offered R. pedestris eggs. Mortality from parasitoid host-feeding was 43.8% when 1-day-old R. pedestris eggs were offered to 6-day-old A. japonicus parasitoids. For older eggs, parasitism rates were lower, making 1-day old eggs the optimal host age for use in mass rearing. Longevity of the offspring (F₁) generation of A. japonicus were 10 (males) and 23 (females) days. The developmental times of the F₁ offspring were 21.9 (males) and 21.7 (females) days. The parasitism rate and the rate of mortality due to host feeding caused by parasitoid progeny (F₁) generation were 56.3, and 43.8%, respectively. Among all the eggs parasitized not subjected to host feeding, 98.5% yielded adult parasitoids. Among all emerging A. japonicus, the sex ratio (as % female) in the F₂ generation was 45%, which was significantly higher than that in the first generation (F₁) (18%). These results suggest that A. japonicus could be a potential biological control agent for use against R. pedestris.