Published 10:00 am Tuesday, June 9, 2020
Wireworms this year are popping up in areas where wheat growers previously didn’t find them, Washington researchers and farmers say.
The pests are more active this year than recent years, said Aaron Esser, agronomist for Washington State University Extension in Adams and Lincoln counties.
“I have areas where I can go out and find wireworms quite easily that I’ve never been able to find them in the past…,” he said.
That’s because it’s been cold and wet, Esser said. Cool weather keeps wireworms feeding longer.
“We’ve got wireworm in areas where we haven’t seen it before,” said Gary Bailey, a St. John, Wash., wheat farmer and Washington Grain Commission chairman. “And the typical areas where we do have wireworms, they seem to be quite robust.”
Wireworms are the immature larval stage of click beetles. They can spend several years in the larval stage, feeding on germinating seeds and seedlings. This results in thinner crop stands and lower yields.
Wireworm scouting prior to planting is essential, according to Esser’s research project.
Wireworms like lower, wetter ground and tend to follow soil moisture, Bailey said.
The worst damage is in spring wheat, Bailey said. Winter wheat can also be affected.
He estimates one small, 65-acre field near St. John will see a 15% to 20% yield reduction.
“Depending on the year, sometimes the wheat can outrun it,” he said. “This particular year, I think all the environmental factors were perfect for it.”
Wireworms also like canola. A female click beetle, the adult form of wireworms, might leave a wheat field to find a grassy field to lay eggs. That could create wireworm pressure for years, Esser said.
Esser estimates one field on WSU’s Wilke Research Farm in Davenport, which usually produces 70 to 80 bushels per acre of spring wheat, will produce closer to 50 bushels per acre because of wireworms.
In some areas, wireworms can wipe out fields, he said.
Pesticide efficiency depends on the species of wireworm, Esser said. Farmers in Adams and Lincoln counties have increased pesticide application rates to keep wireworms in check in the last five years.
“They’re just hanging on longer this year,” Esser said. “And there seems to be more of them.”
No chemicals are labeled for wheat that will kill wireworms, Bailey said. Some are available for pulse crops, so a pulse rotation can be a good way to “thin the herd,” he said.
Esser hopes to see new, improved chemistry available in the next one to five years. But the COVID-19 quarantine has delayed the EPA approval process, he said.
“There needs to be some new products out there that will kill wireworms,” Bailey said. “Right now the only products we have kind of discourage wireworms from attacking the plant. This year, everything was just right, so the wireworms got the best of us.”
