Surface topdressing or cap-off application of an insecticide is an option for insect control in stored corn.

If the grain mass has not been treated, this type of application of a protectant insecticide is effective against insects that feed at the grain surface. Actellic, Bacillus thuringiensis (Bt), Diacon II, and diatomaceous earth may be applied to corn and incorporated into the top 4 to 6 inches of the grain mass by raking.

Actellic, Diacon II, and diatomaceous earth are labeled for use against all of the insects that infest stored grain. Bt products are effective against Indianmeal moth larvae (worm stage). Dichlorvos resin strips may be hung in the bin headspace as a further deterrent to Indianmeal moth infestation.

Diacon II contains an insect-growth regulator and it prevents the normal growth and maturation of immature insects. However, it does not kill adult insects and, therefore, may not be as effective as needed in many situations.

Diatomaceous earth is an abrasive and slightly sorptive dust that damages an insect's body covering. Death is caused by dehydration.

Annual rotation of stored corn, shipping out old corn and replacing it with the new crop each year, helps avoid buildup of insect infestations. Where annual rotation is practiced, topdress application of Bt (for Indianmeal moth) or Actellic applied in April or May usually provides adequate control without treating the entire grain mass.

Further information on insect pest management for stored grain can be found in the 2007 Illinois Agricultural Pest Management Handbook. Local University of Illinois Extension offices can facilitate you getting a copy.