Effect of grain type on the insecticidal efficacy of Paya® against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

The objective of the current study was to determine the insecticidal effectiveness of diatomaceous earth formulation (DE) Paya®. The effects of grain commodity (wheat, barley, maize and rice), exposure times and dose rates were evaluated. The efficacy of diatomaceous earth (DE) against 1–7 days old adults of Tribolium castaneum (Herbst) was evaluated on wheat, rice, maize and barley at 26±1 °C and 60±5% RH in darkness. The mortality of adults was tested at five concentrations: 0.125, 0.25, 0.5, 1 and 1.5 g/kg of grain and different exposure times (24, 48 h, 7 and 14 d). To evaluate the progeny production, dead and alive adults were removed from containers after 14 days and these containers were kept at above-mentioned conditions for 45 days. The results obtained indicated that the highest adult mortality was observed after the longest exposure period on barley and wheat so that the two highest DE dosages caused 100% mortality of T. castaneum. The efficacy of Paya® on maize and rice was not satisfactory, given that after a 14 days exposure at the highest dose rate the mortality did not exceed 37% and 66% in the case of maize and rice, respectively. The results demonstrated that the mortality increased with rises in concentration and exposure time and also highly affected by grain type