Control of Tribolium confusum J. du val by diatomaceous earth (Protect It™) on stored groundnut (Arachis hypogaea) and aspergillus flavus link spore dispersal
Environmental and human health problems associated with the use of synthetic pesticides have prompted the demand for non-polluting, biologically specific insecticides. The current study assessed the losses caused by Tribolium confusum and its control by diatomaceous earth and the effect on Aspergillus flavus spore dispersal during storage of groundnuts. When losses due to Tribolium confusum were assessed over a period of 60 days, it was found that an increase in insect population in stored groundnuts resulted in increased weight loss of stored groundnuts. The true weight loss due to insect feeding was 0.60 g per 400 g of stored groundnuts. When diatomaceous earth (DE) was applied to groundnuts followed by the introduction of insects in a compartment (A), increased mortality of insects with increased diatomaceous earth concentration was observed. For a concentration range of 0-2.5 g DE/kg groundnut, 2.5 g/kg treatment was the most effective (only 5 surviving T. confusum adults out of 50 were recovered in samples treated with 2.5 g/kg compared to 38 adults in the control samples). Larval emergence from groundnuts treated with DE also declined with increased diatomaceous earth concentration. When groundnuts were inoculated with A. flavus spores, followed by DE application and T. confusum introduction into compartment A, the transfer of spores between inoculated groundnut samples in compartment A and uninoculated samples in compartment B was reduced. The mean A. flavus spore concentration recovered from initially sterile compartment B was1.08x103; while it was 45 in the control and in samples treated with 2.5 g/kg dosage respectively. There was a significant difference in the mean numbers of spores recovered from groundnuts in different compartments (A, B) (H = 13.99, df = 4 and P = 0.007). Thus, from this study, losses due to T. confusum on groundnuts and fungal spore transfer in storage by this insect can be minimized by the application of diatomaceous earth (Protect-ItÔ) to stored groundnuts.
Key words: Groundnut, Tribolium confusum, Diatomaceous earth