Seedling Soil Insect Pest Complex
This complex includes wireworm (e.g., Melanotus communis and others), seed corn maggot (Delia platura), southern corn rootworm (Diabrotica undecimpunctata howardi), white grubs (Phyllophaga spp.), and others. These insect pests cannot be managed after corn seed has been planted. Thus, their occurrence must be anticipated and preventative measures taken, if considered necessary. Accurately predicting whether any or all of these insects will occur in damaging numbers, on a field by field basis, is an impossible task. However, certain soil, crop, and cultural conditions may make the occurrence of these pests more likely and information about these factors can be used to make predictions. Poorly drained mineral soils and all organic soils typically have a higher risk of damage due to soil insects (as well as cutworms and billbugs). Weedy conditions in the previous crop (weed residue) and/or heavy growth of winter annual weeds tend to increase cutworms. Also, corn following corn, sod, or set-aside land is much more likely to be infested. No-tillage culture allows greater survival of some pests and may reduce corn seedling growth rate (due to cooler soil conditions), making the crop more susceptible to loss from soil insects. Thus, no-tillage represents a higher risk situation, especially when heavy plant residue is encountered. Historical information on crop loss to soil insects in areas or specific fields can also be used (e.g. fields that seem to have chronic wireworm problems). When a combination of these factors exist an effective insecticidal seed treatment or an at-planting soil insecticide may be beneficial. Five-year average test results from the late 1980’s, in the northeastern Coastal Plain, showed a 5.7 bushel per acre increase with the use of an at-planting soil insecticide in conventional tillage and on poorly drained soils of average pest conditions. Under no-tillage situations this increase was approximately 12 bushels per acre. See scouting guidelines for seedling pests.