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Rice Weevil

General Facts

The rice weevil is a small snout beetle which varies in size, but it averages about three thirty-seconds inch in length. It varies from a dull red-brown to black, and is usually marked on the back with four light red to yellow spots. The rice weevil has fully developed wings beneath its wing covers and can fly readily. The thorax is densely pitted with somewhat irregularly shaped punctures, except for a smooth narrow strip extending down the middle of the back. The larval stage of this insect is a soft, white, legless, fleshy grub which feeds on the interior of the grain kernel. When mature, the grub changes to a naked white pupa and later emerges as an adult beetle.

Adult rice weevils live for four to five months and each female lays 300 to 400 eggs during this period. The female uses her strong mandibles to chew a hole in the grain kernel where she deposits a single egg and seals the hole with a gelatinous fluid. During hot weather, the development period for egg to adult may be as few as twenty-six days. This period is greatly prolonged during cool or cold weather. Rice weevils are capable of flight, and infestations may develop in the field prior to harvest.

 

Damage

These weevils are very destructive grain pests. Of the three, the rice weevil is probably the most insidious, owing largely to the ability of flight. All three weevils develop as larvae within the grain kernels. They frequently cause almost complete destruction of grain in elevators or bins, where conditions are favorable and the grain is undisturbed for some length of time. Infested grain will usually be found heating at the surface, and it may be damp, sometimes to such an extent that sprouting occurs. Wheat, corn, macaroni, oats, barley, sorghum, Kaffir seed, and buckwheat are just some of the grains and products on which these weevils feed.

 

Control

Homeowners might not notice weevils when they are gathered on the outside of the home. But if the weevils manage to find an opening and invade the home, the homeowner often finds hundreds of insects crawling on the walls and windowsills. A vacuum cleaner is a quick way to remove weevils from the walls and furniture. Be sure to take the vacuum outside to empty it so the weevils don’t reinfest the home.

If weevils haven’t invaded, there is time for some prevention. Check outside for any openings that weevils could use to get inside. Look around doors and windows for missing caulk and damaged weather stripping. Check attic vents and crawl space vents for torn screens.

Most likely, homeowners seeing weevils are dealing with the stored product species. The most important control methods are to find the infested material and eliminate it. Careful inspection of items before purchasing can help prevent getting a new infestation. Products with holes or signs of damage on the packaging should not be purchased.