Insecticidal, residual and sub-lethal effects of some plant essential oils on Callosobruchus analis (F.) infesting stored legumes

Stored legumes suffer both quality and quantity deterioration due to infestation by bruchids. Recently, plant essential oils (EOs) are recognized as safer substitutes to manage these pests by alleviating the concerns of residue and resistance problem of synthetic grain protectants. Insecticidal, sub-lethal and residual effects of Pogostemon cablin Benth, Mentha arvensis L., Cymbopogon martinii (Roxb.) Wats., Pelargonium graveolens L. and Acorus calamus L. EOs were investigated against Callosobruchus analis (F.) (Coleoptera: Chrysomelidae). In contact toxicity, LC 50 values ranged from 0.040 to 0.362 µl/cm 2 , being lowest for P. cablin. Cymbopogon martinii , P. graveolens and A. calamus EOs had strong repellent property (> 83%), while M. arvensis and P. cablin demonstrated moderate repellency (41–67%) at sub-lethal concentrations. Sub-lethal exposure reduced the oviposition (5.96–100%) and inhibited progeny emergence (21.22–100%) in dose-dependent manner. Acorus calamus EO showed potent oviposition deterrency and progeny emergence was totally abolished. EOs exhibited moderate to high residual activity, where M. arvensis and A. calamus treated seeds were completely protected (0% damage) for 70- and 84-days post-treatment. Results indicated the promising potential of five EOs to be used as bioactive ingredients for developing grain protectants to prevent post-harvest deterioration of legumes.