Efficacy of the extract from pongam leaves (Pongamia pinnata L.) against Spodoptera exigua (Hübner) and Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

The beet armyworm Spodoptera exigua (Htibner) and the tobacco armyworm S. litura Fabricius (Lepidoptera: Noctuidae) are economically important insect pests of a variety of crops primarily in tropical and subtropical regions. Conventional control of these pests usually depends on synthetic chemical insecticides. Botanical pesticides have recently been paid considerable attention as an environmentally friendly measure to manage various insect pests. The present study was carried out to determine the efficacy of a leaf extract from pongam tree Progamia pinnata L. against the two armyworms. The results showed that the acute lethal toxicity of pongam leaf extract was high against the two armyworm species; the LC50 values were 1.94%, 1.52% and 1.1096 at 24, 48 and 72 hours, respectively for S. litura whereas the values for S. exigua larvae were 3.18%, 2.57% and 1.89% at 24,48 and 72 hours, respectively. Our study also indicated that low concentrations of pongam leaf extract caused significant reductions of vitality of the armyworms; they took more time to mature during the larval stage. Taken together, the treatment with a pongam leaf extract can negatively affect the armyworm populations directly and indirectly, and cause a reduction of overall pest numbers in the next generation. Thus, the pongam leaf extract is a recommendable bio-pesticide to control the armyworms.