Preference and progeny development of stored product insects in response to grain characteristics of millets

Considering millets as climate-resilient crops and recognizing the greater need for nutritional security, cultivation and consumption of millets are being encouraged globally. Studies were conducted to understand the vulnerability of stored millets to different grain insects such as lesser grain borer Rhyzopertha dominica (Fab.), red flour beetle Tribolium castaneum (Herbst), and Angoumois grain moth Sitotroga cerealella (Oliv.) under free-choice as well as no-choice conditions at Post Harvest Technology Centre, Bapatla, Andhra Pradesh, India. Red flour beetles could multiply in significantly higher numbers in pearl millet flour in both free-choice and no-choice conditions (413.33 and 340.67 adults, respectively) followed by foxtail millet (276.0 adults) and sorghum (299.33 adults), respectively. Pearl millet was the most preferred by lesser grain borer with as many as 133.67 insects moving into the grain followed by sorghum (95.33 adults) under free-choice conditions. A mean total of 316.67 grain moths emerged from proso millet under free-choice conditions. On the other hand, finger millet and little millet were not preferred and resulted in emergence of very few moths (0.33 and 3.67 moths, respectively). Little millet and finger millet grains were less susceptible to both coleopteran and lepidopteran insects. Millet grains were analyzed for the physical parameters such as grain moisture, 1000-grain weight, grain volume, hardness, porosity, and the biochemical constituents such as protein, carbohydrates, total phenols, and tannins to understand their influence on insect preferences. Though significant correlations could not be drawn between the progeny development of insects and the physicochemical characteristics of grains, little millet and foxtail millet were found to be less preferred particularly by the internal feeders due to their smaller grain size. Pearl millet possessed higher amounts of sugars and proteins compared to other millets which might have contributed to insect preference.