Efficacy of four selected plant extracts against bean bug, Riptortus pedestris Fabricius (Hemiptera: Alydidae) under laboratory condition

ABSTRACT: The topical spraying and residual methods were used to measure the toxicity and repellency effect of four plant leaf (neem, crown flower, water peeper and marigold) extracts against bean bug, R. pedestris. The plant extracts were prepared in one solvent and applied at three doses viz., 500, 600 and 700 mg L-1 of water with 50% ethanol. Results revealed that the maximum mortality (100%) of adults was recorded by topical spraying of Neem and Crown flower @ 700 mg L-1 at 48 hours after treatment. These were followed by water pepper and marigold at 54 and 60 hours after treatment @ 700 mg/L of water. At residual method, the maximum mortality (100%) of adults was also recorded while Neem sprayed at 48 hours after treatment @ 700 mg L-1. The result of repellency test showed that all the applied doses of leaf extracts had repellency and direct toxicity effects but Neem showed the best response and it possess the repellency class III followed by water pepper and marigold. Therefore, Neem and Crown flower extracts showed potential to control of bean bug, R. pedestris and can be used as alternative of synthetic pesticides.

Keywords: Bean bug, R. pedestris, topical spraying, residual application, repellency.