Gryon japonicum (Ashmead), an egg parasitoid of Riptortus clavatus (Thunberg) is an economically important pest of various crops. As a conservational biological control, non-viable refrigerated eggs of R. clavatus were released to enhance parasitism by the parasitoid in soybean field. Since fenitrothion is an insecticide broadly used against R. clavatus, we investigated the effect of fenitrothion on the parasitization of refrigerated host eggs by G. japonicum. The acute toxicity of fenitrothion was compared with seven pesticides by topical application, exposure to residue, and oral ingestion. Fenitrothion, spinosad, cyfluthrin, carbosulfan and thiamithoxam caused 100% mortality within 24 hours by topical application. Fenitrothion was also highly toxic to G. japonicum when ingested orally. In sublethal effects of fenitrothion on G. japonicum in refrigerated and fresh host eggs, adult emergence of G. japonicum decreased by 12% and 34%, respectively, compared to control when the fenitrothion was applied on 8th day after parasitization. Parasitism on refrigerated eggs after a day of fenitrothion spray was higher as compared to the fresh eggs. However, parasitism on both refrigerated and fresh eggs significantly reduced when the parasitoids were provided with the fenitrothion sprayed eggs after an hour. In conclusion, there is no negative effect of fenitrothion on the parasitization by G. japonicum.

• Md. Abdul Alim(School of Bioresource Sciences, Andong National University)
• Un Taek Lim(School of Bioresource Sciences, Andong National University)