Field efficacy of biorational insecticides, azadirachtin and Bt, on Agrotis segetum (Lepidoptera: Noctuidae) and its carabid predators in the sugar beet fields

Agrotis segetum (Denis & Schiffermüller) is an important polypahgous pest of sugar beet fields in many regions of world including Iran. Biorational pesticides are good and safe alternatives to the chemical insecticides which are compatible with goals of IPM programs. In this study, efficacy of three biorational pesticides, Azadirachtin (NeemAzal®), Bt (Bactospeine®) and Bt (Biolep®), and a conventional chemical insecticide, deltamethrin (Decis® EC), was studied on pest population and damages as well as carabid beetle population as its important predators in sugar beet field during two agricultural seasons (2015 and 2016). Sampling of the pest egg batches, larvae and the carabid beetles was carried out at 1 day before treatment (DBT) and 1, 3, 7 and 10 days after treatment (DAT). Finally, total yield and sugar content of sugar beet in the different treatments were evaluated for the two agricultural seasons. Results showed that NeemAzal was a significant oviposition deterrent for female moths of A. segetum. During both agricultural seasons, the highest and lowest larvicidal effects were observed in Decis and Bt (EC) treatments, respectively. Ten DAT, 40, 60, 13 and 73% reductions of pest population larvae were observed were observed in NeemAzal, Bt (WP), Bt (EC) and Decis treatments, respectively. Sugar beet yield in all treatments was significantly higher than control. Total yields in NeemAzal, Bt (WP), BT (EC) and Decis treatments were 17.5, 25.6, 12.9 and 43.7% more than control in 2015 and 8.7, 19.7, 4.8 and 37.1% respectively in 2016. But sugar content in the different treatments was not significantly different. Totally, the most adverse effects on carabid beetles were recorded in Decis® treatment