EFFICACY OF THREE SYNTHETIC INSECTICIDES AGAINST SUCKING INSECTS OF CHILLI AND THEIR IMPACT ON COCCINELLID BEETLE

Abstract

The experiment was conducted in the Entomology research field of Hajee Mohammad Danesh Science and Technology University, Dinajpur during January to May, 2017 to assess the efficacy of three synthetic insecticides of different groups (imidacloprid, chlorpyrifos + cypermethrin and cypermethrin) against aphid (Aphis gossypii Glover), thrips (Scirtothrips dorsalis Hood) infesting chilli (Mohona-2) and their impact on prevalence of ladybird beetles. Treatments effectiveness was evaluated by three consecutive sprays following randomized complete block design (RCBD) with three replications. Data were recorded at 1, 3, 5, 7 and 14 days after spray (DAS) in each case. After three round spray, among three isecticides imidacloprid reduced the highest aphid population infested on leaf (96.70%) followed by chlorpyrifos + cypermethrin (92.54%) and cypermethrin (91.21%). In case of flower infestation by aphid, the highest reduction percentage were 97.02% (imidacloprid) followed by 94.54% (chlorpyrifos + cypermethrin) and 88.91% (cypermethrin) compared to untreated control. Imidacloprid checked thrips population by 92.50%, chlorpyrifos + cypermethrin by 87.00% and cypermethrin by 91.25% in terms of shoot infestation by thrips. Considering flower infestation by thrips, the reduction over untreated control was 97.59, 92.27 and 93.30% by imidacloprid, chlorpyrifos + cypermethrin and cypermethrin, respectively. The imidacloprid, chlorpyrifos + cypermethrin and cypermethrin provided the reduction percentages over untreated control were 88.72, 96.72 and 98.50% on ladybird beetle abundance, respectively. Thus, imidacloprid, chlorpyrifos + cypermethrin and cypermethrin were found effective against aphid and thrips but imidacloprid was the most effective amongst them in checking these sucking insects with limited impact on ladybird beetle in comparison with chlorpyrifos + cypermethrin and cypermethrin.