Maize Weevil

Sitophilus zeamais, commonly known as the maize weevil, is a destructive pest of stored grain, closely related to the granary weevil, belonging to the family Curculionidae, order Coleoptera. Adults are dark reddish-brown to black, 2.5-4.5 mm in length, with distinctive, often reddish-orange, irregular spots on the hind wings (elytra). They possess a prominent, slender snout and are capable of flight. Larvae are legless, white, C-shaped grubs, developing entirely within the grain kernel. Pupae are also found within the kernel. Eggs are minute and white. The life cycle usually spans 30-45 days at optimal conditions (27-310C, 70-80% RH), but can be significantly prolonged by cooler temperatures, allowing for multiple overlapping generations annually.

Maize weevils are primary internal feeders, with all immature stages developing concealed within a single grain. The female weevil drills a small hole in a grain kernel, deposits an egg, and then seals the hole. Larvae consume the endosperm, hollowing out the kernel. Adults also feed on grain, creating small, irregular holes. Unlike the granary weevil, adults are strong fliers and exhibit positive phototaxis, often being found on the surface of grain or attracted to light. This flight capability aids in dispersal between storage facilities and fields. They can infest grain both in storage and in the field prior to harvest.