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Granary Weevils

Considered one of the primary stored product pests, granary weevils infest only whole kernels of grain.  Adult granary weevils are approximately 1/8 to ¼ inch in length with a head that elongates into a narrow snout.  Reddish-brown to black in color, unlike rice weevils, granary weevils lack the four light-colored spots on their wing covers.  Female granary weevils bore holes into the surface of grain kernels in order to deposit an egg inside.  The hole is then covered with a gel-like material.  An individual female is capable of laying more than 200 eggs into any of the commonly stored whole grains.  Eggs hatch within a few days of being laid, but remain within the grain kernel for a period of 19 to 34 days.  Small, white, legless grubs, larvae have a flat underside and a rounded upper portion of the body. Larvae feed on the kernel during which time they complete four molts.  Pupation also occurs in the kernel with adults emerging roughly five to sixteen days later.  Four generations per year is common.

Adults do not fly as they do not have use of their second pair of wings; however, they tend to wander and may be found far from the source of the infestation.  Due to this fact, it is important to locate and destroy or dispose of all sources of infestation.  All whole grains, including items such as popcorn, seeds, Indian corn and stored products should be considered potential sources.  Food attractant traps are available for this species and may be used to determine areas of activity and monitor activity.  A pest control professional can apply a residual insecticide to cabinets, closets and shelves where infested items have been identified in order to control adults.