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Wireworm Pressures High (05/26/16)

Numerous calls/emails on crops (winter wheat, hard red spring wheat, field pea, and sugar beets) damaged by wireworms have been received over the past weeks, especially in crops in no-till systems.

Wireworm Pressures High

Numerous calls/emails on crops (winter wheat, hard red spring wheat, field pea, and sugar beets) damaged by wireworms have been received over the past weeks, especially in crops in no-till systems. Wireworms are a difficult insect to scout for since the larva (worm) is hidden in the soil. Growers and field consultants have reported that the current rate of neonicotinoid insecticide seed treatments do not appear to be providing adequate control of wireworms.

Wireworm larvae are the damaging stage and they feed on the seeds or seedlings below ground. Growers often observed bare, patchy areas in a field, poor emergence or thin plant stand. The sub­terranean tunneling in seeds, roots or stems may cause the seedlings to wither and die. Crops are most susceptible in the early growth stages.

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Wireworms usually take three to four years to develop from the egg to an adult beetle. Most of this time is spent as a larva in the soil. Generations overlap, so larvae of all ages may be in the soil at the same time. Larvae move up and down in the soil profile in response to temperature and moisture. After soil temperatures warm to 50 F, larvae feed within 6 inches of the soil surface. When soil temperatures become too hot (>80 F) or dry, larvae will move deeper into the soil to seek more favorable conditions. Wireworms inflict most of their damage in the early spring when they are near the soil surface. During the summer months the larvae move deeper into the soil. Later, as soils cool, larvae may resume feeding nearer the surface, but the amount of injury varies with the crop. Wireworm larvae and adults overwinter at least 9 to 24 inches deep in the soil.

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Janet J. Knodel

Extension Entomologist

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