Resistance of Spodoptera exigua Population from Nganjuk against Methomyl, Chlorfenapyr, and Emamectin Benzoate

Abstract

Spodoptera exigua Hubner (Lepidoptera: Noctuidae) is the main pest of shallot causing significant economic losses. The continuous use of insecticides has resulted S. exigua to develop resistant against them. This study aims to determine the level of S. exigua resistance of Nganjuk and Bantul populations against methomyl, chlorfenapyr, and emamectin benzoate and temporal resistance of S. exigua of Nganjuk population to methomyl. Nganjuk population were sampled in June, September, and December. First instar larvae from the first generation were used tested using the leaf-dipping method. Temporal resistance test was carried out using the same concentrations. The resistance ratios of Nganjuk population to the insecticides methomyl, chlorfenapyr, and emamectin benzoate were 58.8; 8.8; and 2.5 fold respectively. The LC50 values of S. exigua of Nganjuk population collected in June, September, and December were 1127.44; 50.62; and 366.76 mg [AI] liter-1, respectively. The results of this study indicated that the S. exigua of Nganjuk population was highly resistant to methomyl and its level has changed over time. Resistance management by rotating the type of insecticide is not sufficient but should also consider its change of resistance pattern over time.

Keywords

• insecticide
• resistance
• spodoptera exigua
• temporal