Scouting for wireworms starts with looking for bare or thinned patches — after the crop has emerged. Areas where maybe the seedling didn’t come up at all, or if they did, they’ve yellowed at the centre of the plant
“If you see that, there could be a couple different reasons why your crop has thinned in that area, like for example a frost patch,” says Dr. Haley Catton, research scientist in field crop entomology at Agriculture and Agri-Food Canada (AAFC), Lethbridge. “So, if you want to know if it’s wireworms, you have to go to that patch, go to those sick looking plants, and dig them up and see if you find the wireworms in the act of eating your plant’s roots.”
Wireworms can kill young plants at the seed or seedling stage, which impacts yield long-term, but also has other agronomic impacts, says Catton, like opening up space for weeds to grow. Wireworms can continue feeding on plants as the crop progresses, but after a certain point, the crop can withstand the feeding. (Story continues below video.)
When scouting, its important to remember that wireworms aren’t actually worms, they’re the larval stage of the click beetle and there are multiple species of them. In general, Catton says to look for a long-bodied, yellow, kind of hard-shelled worm-like creature.
It’s hard to study the beneficial insects that attack wireworms, says Catton, but there is hope, as her research team has just received a report from an agronomist in Saskatchewan that found the larval stage of a beneficial ground beetle feeding on the wireworm.
“We wish there was a threshold; right now the most effective control is chemical seed treatment, which you have to decide obviously before you seed,” says Catton. It’s important to look for the pest now though, as it can help in decision-making for next year’s seed treatment. Catton says they’re hoping to establish a threshold in the future, through overhead imagery research in commercial farm fields.
Wireworms have multi-year life cycles and are only adults above ground in the spring for one season of their life. The adults will lay eggs mid-spring which will hatch in summer and will grow into wireworms that can feed for multiple years.
The bonus to scouting for wireworms is that you can catch any cutworm issues you may be having at the same time. “You definitely want to know if you have a wireworm problem, or a cutworm problem, or both, because there are different treatments for the different types of insects,” says Catton. Cutworms are also a moth species, and there are in-season rescue treatments for cutworms, but not for wireworms.
More information — including high resolution photos — will be available in June or July of this year through AAFC’s guide to prairie wireworms, co-authored by Catton.