Wireworms
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Wireworms (Melanotus sp.) can be especially destructive to sweet corn, particularly following certain rotations or in some fields that have a history of problems. Most wireworm larvae are hard, chestnut brown, smooth, and varying from ½ to 1½ inches in length when grown. Some species are soft and white or yellowish in color. There are many different species of wireworms that attack cultivated crops, but their biologies are similar. They overwinter in the ground as larval and adult stages. In the early spring the adults, called click beetles, become active. Many wireworm species have extended life cycles lasting two or more years, so past problems can be a measure of future problems. Wireworms attacking sweet corn reduce plant populations, since they feed on the seeds prior to germination or just after germination. The plant stand may continue to deteriorate, as wireworms can bore into the side of the crown and kill the growing point after emergence. They continue to feed upon the small roots of many plants throughout the season.
Wireworm attacking a corn seedling.
(Photo: UK Vegetable IPM Team, University of Kentucky)
Management:
- Wireworms are most often a problem in fields that have been in sod for many years, particularly bluegrass sod. Soil insecticides and/or seed treatments are recommended at planting for corn where the risk of wireworm damage is high.
- In fields with a history of problems, wait to plant until soil temperatures are sufficient to promote quick germination and growth, as this will limit wireworm losses.
- Certain species of wireworms are abundant only in poorly drained soils. The proper draining of such soils will prevent damage by these species.
- With wireworms, there is no effective rescue treatment once symptoms of damage are observed.
