Growth and Development of the Khapra Beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), on Different Food Substrates

The population dynamics of insect pests in stored products are fundamentally governed by the nutritional quality of their diet. This study quantitatively demonstrates how variations in food substrate directly regulate key life-history parameters, ultimately determining infestation potential and outbreak risk. In this study, we investigated the effect of different food substrates on the development, survival, and reproduction of Trogoderma granarium under controlled laboratory conditions. As results indicated, the significant variation in larval weight was observed across diets, with the highest weight attained on wheat flour and the lowest on barley flour. Pupal weight did not differ significantly among diets, indicating limited dietary influence on pupal mass. Larval and pupal developmental periods were significantly influenced by diet, with larvae showing the shortest development (15.00 ± 0.31 d) on cracked wheat and the longest (19.00 ± 0.63 d) on barley flour, whereas pupae developed fastest (5.00 ± 0.70 d) on wheat flour and slowest (8.00 ± 0.63d) on whole maize. Pupation success was highest on cracked wheat and lowest on cracked barley. Diet significantly influenced adult emergence and longevity, with maximum emergence on wheat flour and minimum emergence on barley flour, whereas adults exhibited the longest lifespan on cracked wheat and the shortest on barley flour. Diet significantly affected F₁ progeny production, with cracked wheat supporting the highest offspring numbers (92.10 ± 1.39%) and whole maize the lowest (20.20 ± 0.91%). Overall, the findings demonstrate that wheat-based substrates—especially cracked wheat—strongly promote the population growth of T. granarium , highlighting their importance in pest risk assessment and management strategies. Our research establishes that the nutritional matrix of a food substrate is a critical determinant, defining the carrying capacity and growth trajectory of insect pest populations within a commodity.