EFFICACY OF BIO-RATIONAL INSECTICIDES IN CONTROLLING THRIPS IN SUMMER COUNTRY BEAN

Abstract

The experiment was conducted at the central farm of Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka, Bangladesh to study the efficacy of biorational insecticides in controlling thrips country bean in summer. The experiment consists of the following management practices: T 1 =Spraying Neem oil @3 ml/L of water at 7 days interval, T 2 =Spraying Neem leaf extract @200mg/L of water at 7 days interval, T 3 = Mehgoni leaf extract@200mg/L of water at 7 days interval, T 4 =Tobacco leaf powder@30mg/L of water at 7 days interval, T 5 = Spraying Spinosad @0.4ml/L of water at 7 days interval, T 6 =Spraying Biotrin@1.4ml/L of water at 7 days interval and T 7 = Untreated control. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Data on number of thrips as insect pest, plant, leaf, inflorescence and pod infestation, different yield contributing characters and yield of summer country bean were observed. Among the seven (7) treatments the lowest number of thrips (2.50 plant ii -1 ) was observed in T 5 (Spraying Spinosad @0.4ml/L of water at 7 days interval), while highest number of thrips (16.67 plant -1 ) was observed in T 7 (Untreated control). The highest percentage of thrips reduction over control (85.50%) was observed in T 5 (Spraying Spinosad @0.4ml/L of water at 7 days interval) treatment. The present study revealed that the lowest number of thrips as insect pest and increased plant, leaf, inflorescence and pod infestation, different yield contributing characters and yield of country bean might be obtained by using the treatment T 5 (Spraying Spinosad @0.4ml/L of water at 7 days interval) besides T 6 (Spraying Biotrin@1.4ml/L of water at 7 days interval) performed as second best treatment whereas, T 7 (Control) and T 3 (Mehgoni leaf extract@200mg/L of water at 7 days interval) may protect the country bean at lowest rate in summer. The highest (3.08) benefit cost ratio was obtained due to application of T 5 (Spraying Spinosad @ 0.4ml/L of water at 7 days interval) while the lowest (2.26) in T 7 (control).