Grape Colaspis in Corn
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Crop Focus from Pioneer Agronomy Sciences.
Pest Facts and Impact on Crop
- 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.
Pest Identification
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.
Grape colaspis larva.
Grape colaspis larvae size in comparison to a penny.
Grape colaspis pupa.
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.
Grape colaspis adult feeding on soybean leaf.
Adult grape colaspis
Pest Lifecycle
- 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.
Annual Life Cycle of Grape Colaspis in Corn
Pest Symptoms in Corn
- 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.
Seedling showing the symptoms of wilting and deficiencies from grape colaspis.
Feeding damage on corn leaf from grape colaspis beetles.
Integrated Pest Management
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.
References
- 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.
The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.