If moths are present in the top of the bin or other signs of insect damage are observed, then entry into the bin to inspect the surface of the grain mass will be necessary. The most common insect pest found infesting the surface of stored corn is the Indian meal moth. Moths generally enter grain bins through vents and open spaces around the top of bins. Once inside, they lay eggs on the grain surface. Larvae feed in the upper few inches of the grain mass and produce a thick webbing.
Grain damaged by Indian meal moth is often moist to the touch and gives off a very pungent odor.
Insect infestations in stored grains are best controlled by timely feeding of the infested grain to livestock. If this is not possible, then an insecticide application may be necessary. If an infestation of Indian meal moth is found, the producer should remove the webbing from the grain surface and treat the surface with an insecticide to destroy remaining larvae. Moths should be controlled by placing insecticide vapor strips in the air space above the grain surface. Generally malathion is not used for control of Indian meal moth because most populations of this insect are resistant to malathion.