Grape Colaspis in Corn

• Grape colaspis (Colaspis brunnea) is an insect pest that can feed on both corn and soybean, as well as numerous other host species.
• Economically significant damage to crops is rare, but possible.
• Larvae can cause significant damage to root systems, most commonly in corn, by eating root hairs and mining channels on the root surface. This limits water and nutrient uptake.
• Adults feed on leaves and corn silks but rarely cause economic levels of damage.
• Grape colaspis completes one generation per year in the Corn Belt.
• Seed treatments may help reduce larvae damage to roots.

Larvae

• Slightly curved, small white body with a tan head.
• Approximately 1/8-1/6 inch (3-4 mm) in length.
• Resembles a very small white grub.
• Has 3 pairs of short legs and hair bunches on bumps at the underside of the abdomen.

Adults

• Oval-shaped beetle of yellow-brown color.
• Approximately 1/6-1/5 inch (4-5 mm) long.
• Wings have rowed, shallow indentions which give the beetle a striped appearance.

• The grape colaspis completes only one generation per year in the Corn Belt.
• It overwinters as a small larva in the soil at a depth of 8 to 10 inches (20-25 cm). Larvae become active early in the spring, feed on the roots of host plants.
• Root feeding occurs in late May and early June.
• Adults typically emerge between middle to late June and lay eggs from July through early September.
• Adults feed on leaves and silks, as well as soybean leaves, but do not typically cause economic damage.
• Newly hatched larvae will feed on roots during the fall before moving deeper in the soil profile to overwinter.

• Larvae feed on the root hairs which can cause:
  • Stunting and wilting.
  • Purpling (from phosphorus deficiency).
  • Yellowing or browning on the edges of leaves.
  • In extreme cases, plant death and reduced populations.
• Injury is more likely to appear early in the season on seedlings, especially if seedling growth is slow due to unfavorable weather or other conditions.

Favorable Conditions

• Adequate soil moisture during late summer and fall appears to promote higher grape colaspis populations the following season.

Cultural Practices

• Manage the crop to promote early, rapid, and uniform seedling emergence to the extent possible.
• Promote strong root development through fertilization and proper drainage or irrigation.

Chemical Practices

• Seed treatments may help reduce damage.
• Insecticide application in July to control adults has been suggested as a method to reduce populations and limit larvae damage in the subsequent spring, but would likely not be practical due to a short application window and population movement.

• Steffey, K., S. Ratcliffe. 2001. Grape Colaspis: A Quick Review. The Bulletin. University of Illinois Extension.
• Montgomery, M. 2003. Grape Colaspis: Some Background. The Bulletin. University of Illinois Extension.
• Kaeb, B. 2006. Management of grape colaspis, Colaspis brunnea, in seed corn production. Thesis. Iowa State University.