Neem oil antifeedant and insecticidal effects on Oebalus poecilus (Hemiptera: Pentatomidae) males and females

Abstract

The antifeedant and insecticidal effects of two commercial neem (Azadirachta indica) oil formulations (Dalneem and Nim-I-Go) to Oebalus poecilus were evaluated on irrigated rice. To evaluate the antifeedant effect, both formulations were tested at 1% and 2% (v/v) concentration levels. The insecticidal effect was evaluated at 0.5%, 1%, 2%, and 4% (v/v) concentrations of Dalneem, by ingestion. Both experiments were conducted with four replications by treatment, containing one panicle and adult insects segregated by gender (two insects per plot for the antifeedant effect and five for the insecticidal effect). Both products were efficient, reducing the damage caused by insects. Insects fed less on the panicles treated with neem oil, causing lower number of feeding sheaths per panicle and lower percentage of damaged grains than the control. Spikelets weight was higher in panicles treated with neem oils. Females caused significantly higher damage than males in controls, for numbers of feeding sheaths and for the feeding deterrence index. Only at the 4% (v/v) concentration level, Dalneem caused adult mortality higher than in the control. Results showed that neem oil formulations, at > 1% (v/v) concentration, can be used to reduce the quantitative and qualitative damages caused by O. poecilus in lowland rice.