Wireworms Have a Multi-year Impact

A pest that can persist in your soil for years and affect several different crops is wireworm. Soybean growers need to be aware that wireworms can stress the early-season crop through their below-ground feeding habits.

“Wireworms will feed through the cotelydons and the damage can be devastating to soybean stands,” says Brett Graham, Seedcare specialist with Syngenta based in Manitoba.

Wireworms are the larvae of click beetles. While the adults don’t damage crops, their presence is a strong indicator of a wireworm problem. Adult click beetles overwinter in the soil and emerge in the early spring, laying hundreds of eggs that are deposited throughout the soil down to a depth of 15 cm. The larvae hatch within three to seven weeks and spend the next three to five years feeding on roots and germinating seeds and moving up and down in the soil profile.

Wireworm baits

Although wireworms never come out of the ground, it is possible to scout for them using a baiting technique shown here. While baits can be a good resource, Graham cautions to be aware of the possibility of the false negative. “These pests love to sit where the moisture is, so they will go down in the soil until they find it. If you don’t have enough moisture in the top layer of the soil, your bait trap might give a false negative result. Also keep in mind that wireworms may not come to the bait trap if other food sources are present, such as volunteer plants, from the previous season.”

For this reason, Graham says it’s best to keep your seed protected from the pest.

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Images: Wireworms. The tan or copper-coloured worms are cylindrical and hard-bodied. They vary in size from 1 to 3 cm in length (½ to 1½ inches) and have three pairs of legs near the head end.

Management tips

• Scout fields to identify wilted plants or gaps where there are areas of dead plants. Dig around the plant to look for feeding damage and insect larvae, to confirm the cause of the damage.
• Wireworms can be monitored in the fall (or in the early spring for later-planted crops) using bait stations. A count of 0.5 to 1 wireworm per bait station indicates a potential problem.
• Use a seed treatment registered for wireworm control such as Cruiser Maxx® Vibrance® Beans to help protect seeds and seedlings from below-ground feeding

Always read and follow label directions. Cruiser Maxx Vibrance Beans is an on-seed application of Cruiser Maxx Beans Seed Treatment insecticide/fungicide and Vibrance 500 FS Seed Treatment fungicide. Cruiser Maxx® and Vibrance® are trademarks of a Syngenta Group Company. © 2019 Syngenta.