Differential susceptibility of Riptortus pedestris (F.) and its two egg parasitoids to flonicamid

Abstract

Flonicamid a systemic insecticide acts as a feeding inhibitor against sucking insect pests. Now it is registered against soybean aphids in Korea and can be also used to control Riptortus pedestris (F.), a major pest of soybean. Here, we compared the susceptibility of R. pedestris and its two egg parasitoids, Ooencyrtus nezarae Ishii and Gryon japonicum (Ashmead), to flonicamid. The median lethal concentrations for 2nd and 4th instar nymphs of R. pedestris were 0.03 and 1.3 g/L, respectively, after 48 h of feeding. The toxicity indices for 2nd and 4th instar nymphs, and adult R. pedestris fed with 0.5 g/L flonicamid were 1.8, 1.5, and 1.5 times more toxic than that of the water control, while those for O. nezarae and G. japonicum were just 1.1 and 1.2 times more toxic than that of the control, respectively. In conclusion, flonicamid is more toxic to nymphs than adult stages of R. pedestris, but it is relatively safe to its egg parasitoids, thus can be used as an effective strategy for conservation biological control against R. pedestris.