Cool, wet weather forces the wireworms closer to the surface. Dry, hot weather forces them deeper into the soil. Cool weather also restricts adult activity and lengthens the egg-laying period. Eggs laid near the soil surface or in compact soil are subject to high mortality when rapid fluctuations in moisture and temperature occur. Damage is higher in silt, medium textured, well-drained soils and in soils cultivated for at least 12 years.
Damage is usually light in heavy or very light soils.
Crops grown in newly-broken sod can suffer great losses for 1 or 2 years. After that period, the damage decreases rapidly only to gradually increase in succeeding years if no wireworm control measures are applied. Wireworms can be destructive to corn, potatoes, wheat, barley and onions in Manitoba. The larvae feed on germinating seeds or young seedlings, shredding the stems but seldom cutting them off. The central leaves die but outer plant leaves often remain green for some time.