Seedcorn Beetle and Slender Seedcorn Beetle
Stenolophus lecontei Chaudoir and Clivinia impressifrons LeConte
Appearance and Life History
Two ground beetles that occasionally attack corn seeds are the seedcorn beetle and slender seedcorn beetle. The seedcorn beetle is a yellowish-brown beetle about 5/16" (8 mm) long with a patch of black in the middle of each wing cover. The slender seedcorn beetle is a shiny reddish-brown beetle about 1/4" (6 mm) long, with a noticeable restriction between the thorax and the abdomen. The larvae, like the adults of both species, live in the soil foraging for food. It is not known for certain, but both species probably have two generations per year.
Seedcorn beetles are mostly beneficial by feeding on the eggs and small larva of many pest species (eg., rootworm) in the soil. Occasionally, when cold, wet weather delays corn emergence, these beetles will feed on and destroy the seed's germ, resulting in poor or non-emergence. Damaged seed will be hollowed-out. They may also feed on the mesocotyl of emerging plants, causing stunting.
Examine soil by digging in areas where seedlings are stunted or plants have failed to emerge. Check ungerminated seed for injury and presence of seedcorn beetles. Dig up 2 linear row feet (0.6 m) in each of 5 areas. Examine seeds for damage. Record the number of plants, good ungerminated seeds, and hollowed-out or otherwise damaged seeds in each area sampled.
Corn Insect Control Recommendations: E-series 219-W (PDF)
Since there are no rescue treatments for control of seedcorn beetles, replanting is the only available option. The decision to replant should be based on the remaining healthy plant population, the date, yield expectation, etc. If replanting before June, a seed treatment and/or soil insecticide labeled for seedcorn beetles may be advisable. The chart, Expected Grain Yield Due to Various Planting Dates and Population Rates, found in the "Seedcorn Maggot" management guidelines may help in replant decision making.
If control is necessary, contact your state Cooperative Extension Service or click here for control materials and rates.