Toxicity of selected chemical insecticides against different life stages of the black carpet beetle, Attagenus unicolor, and the variegated carpet beetle, Anthrenus verbasci

Abstract

Carpet beetles, particularly Attagenus unicolor and Anthrenus verbasci, can damage stored wheat, with larvae representing the principal destructive stage. This study evaluated the toxicity of selected chemical insecticides against different life stages of these species under direct spray, residual exposure, and treated-grain conditions. Mortality was assessed at 24, 48, and 72 h after treatment. Ultracide consistently showed the highest efficacy across exposure methods and insect stages. Under direct treatment, Ultracide caused up to 90% and 100% mortality of A. unicolor larvae and A. verbasci larvae, respectively, at 72 h, while adult A. unicolor and A. verbasci mortality reached 100%. Residual exposure produced 100% mortality of larvae and adults of both species within 72 h in several treatments. Grain treatment with Ultracide resulted in 100% mortality of larvae of both species by 72 h and similarly high mortality in adults. Malathion generally showed the second-highest efficacy, whereas Deltamax was comparatively less effective under residual exposure. Mortality generally increased with exposure duration, and A. verbasci was more susceptible than A. unicolor across most treatments. Adults were generally more susceptible than immature stages under residual exposure, although susceptibility varied with insecticide and exposure method. Significant differences were observed among insecticides and the untreated control. Overall, Ultracide demonstrated strong contact, residual, and grain-treatment activity against both carpet beetle species and may provide effective chemical control; however, further studies on formulation, residue persistence, grain safety, and application rates are warranted before practical adoption.