Insects that live in the soil, including wireworms, white grubs, rootworms, seedcorn maggots, whitefringed beetle larvae, lesser cornstalk borer and others, can damage corn seeds and seedlings. These insects cannot be controlled once corn seed has been planted. Rotated, conventionally tilled corn with good weed control generally has the least risk of serious early season insect damage, although insect damage can still occur under these conditions.
Several factors increase the risk of damage by soil insects and the need for an at-planting insecticide to prevent damage:
• Planting continuous corn in the same field.
• Planting in no-till or minimum-till situations (such as strip-till) where residue of the previous crop remains on the soil surface.
• Planting behind small grains, winter cover crops or sod of any type, especially in reduced tillage situations.
• Late planting (more than one month after the recommended planting time).
• Planting on light soils following periods of drought (lesser cornstalk borer).
• Planting on heavier soils following extended wet periods.
• Planting in fields with certain weeds. Southern corn billbug damage often is associated with nutsedge infestations, and sugarcane beetle can build up on bahiagrass. Leafhoppers and aphids can serve as vectors of corn viruses from Johnsongrass to field corn.
Historically low commodity prices for corn made routine preventive use of insecticides in Georgia a questionable practice. However, recent robust grain prices and availability of low-cost seed treatments make active pest management with insecticides more beneficial.
David Buntin is a Professor of Entomology at the University of Georgia (UGA). To view all of his comments on insect control in field corn, consult the 2010 UGA Corn Production Guide. Contact Buntin at (770) 412-4713 or email@example.com.