Wireworms are difficult to manage
By Tom J. Bechman
You may go your entire farming career and never see a wireworm. But if they show up just once, you won’t forget them. And you will likely have them again.
The Indiana Certified Crop Advisers panel illustrates problems dealing with this insect this month.
Question: Wireworms are working on a couple patches in a 100-acre corn field. Should I tear them up and replant? If I do should I use an insecticide? We’re probably talking 20 acres.
Andy Like, Daylight Farm Supply, Evansville: Deciding to tear up a spot in the field depends on many factors, including time of year, growth stage of corn and percent stand loss. If you replant use a soil-applied insecticide the second time around. Soil-applied insecticides are typically more effective than insecticide seed treatments on wireworms because they kill the pest before it takes a bite out of the seed or seedling. Unfortunately, there are no rescue or post planting treatments.
Jesse Grogan, agronomist, LG Seeds, Lafayette: Wireworm damage and injury is prevalent in early season when soils are cool and wet, usually where grass weeds grew before. Replanting is expensive and spotting in areas can be difficult. You may cause damage with field equipment to good places. Evaluate stand loss in affected areas. If it’s less than 18,000 plants, the crop is in the early vegetative stage and good weather lies ahead, replant might be warranted. Patching in with seed in spots where existing plants have more than two leaves or if it’s wet usually doesn’t recover loss.
A seed-applied insecticide is usually effective unless wireworm populations are severe, then a soil insecticide should be used. If you have 18,000 plants or more at the two-leaf growth stage I wouldn’t replant. Wireworms burrow deep as soils warm up. The insect is much less of a threat in mid and late season.
Traci Bultemeier, DuPont Pioneer accounts manager, Ft. Wayne: If your seed was treated with an insecticide seed treatment, contact your seed rep. He or she may contact an insecticide rep for a field visit. Most corn insecticide seed treatments carry a label for control or suppression of wireworms. Consult your seed dealer.
From a 30,000 foot view, it would be unusual to tear up a whole field or even patches due to wireworms. They’re generally found in heavier populations in manured fields, or moist areas of any field.
They damage corn seedlings from April through June, but are multi-year pests, so seed treatment and scouting in following years is important. According to the Purdue University Corn and Soybean Field app, wireworm damage occurs mainly in early stages of corn growth. Make the replant decision after doing stand counts. Even if the stand only averages 25,000 per acre in May-planted corn, estimates are still 92 to 100% of estimated yield, which would make me think hard about tearing up patches or replanting affected areas. If you decide to replant, an insecticide seed treatment is a necessity.