Entomocidal activity of Azadirachta indica, Pongamia pinnata and Tridax procumbens leaf powder against the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae)

Abstract

Pests of stored grains cause significant quantitative and qualitative damage mainly in tropical regions. The rice weevil, Sitophilus oryzae L. is one of the most destructive species infesting stored rice and other cereal grains. In the present study entomocidal activity of Azadirachta indica (neem), Pongamia pinnata (karanj) and Tridax procumbens (coat buttons) leaf powder against adult S. oryzae under controlled laboratory conditions have been evaluated. Leaf powder obtained from different plant having concentrations of 5, 10, 15, 20, 25, and 30 mg were used to treat 50 g rice grain for each concentration while 50 g untreated grains used controls. Insect mortality recorded after 7, 14, 21, and 28 days after treatment. The results of A. indica exhibited the highest and fastest mortality achieving 100% with the concentrations of 25 mg and above within 14 days whereas P. pinnata resulted delay but 100% mortality with 25 and 30 mg by 28 days and T. procumbens showed mortality at 25 mg & 30 mg concentrations after 28 days. The overall efficacy ranking was A. indica > P. pinnata > T. procumbens. The findings highlight the strong potential of these botanicals, particularly neem, as safe, sustainable, and cost-effective alternatives to synthetic protectants for stored-grain pest.