Efficacy of selected plant extracts against Tribolium castaneum Herbst in stored groundnut (Arachis hypogaea L.)

The efficacy of powders of plant parts from Azadirachta indica, Lawsonia inermis, Annona senegalensis and Hyptis suaveolens at 10, 15 and 20 g/250 g seeds was tested using Complete Randomized Design (CRD) against the storage pest Tribolium castaneum (Herbst) in groundnut in the laboratory. At 28 days after application, mean number of seeds damaged was 0.33±0.33 for A. indica and 2.33±0.33 for L. inermis at 20 g concentration when compared to untreated seeds (10.00±1.15). Aluminium phosphide gave complete control (0.00±0.00). Twenty grammes (20 g) at 28 days of A. indica was efficacious as aluminium phosphide in protecting seeds against damage by T. castaneum. All powders provided some control of T. castaneum. The percentage mortality of adult pest in 20 g of A. indica (53.33%), L. inermis (33.33%) is high compared to H. suaveolens (16.66%) and A. senegalensis (20.00%) as compared to untreated (0% mortality). At the end of 6 weeks of storage, the weight loss from original weight of 250 g was 40.89 g (16.36%) for untreated seeds, 1.88 g (0.75%) for A. indica and 5.05 g (2.02%) for seed treated with L. inermis at 20 g concentration each. Aluminium phosphide-treated seeds suffered minimal weight loss (0.16 g, 0.06%) at 20 g concentration. A. indica and L. inermis are recommended for post-harvest control of T. castaneum in stored groundnut for planting.   Key words: Plant extracts, biocidal activity, Tribolium castaneum, groundnut.