ABERDEEN, Idaho — Researchers involved in an ongoing University of Idaho wireworm study have found populations of the pest tend to be lower in cereal fields with more compact soil.

The UI Extension scientists — entomologist Arash Rashed and barley agronomist Chris Rogers — have also seen evidence in greenhouse testing that wireworms hit wheat harder than barley.

“It could be differences in the amount of root exudates and respiration between wheat and barley,” Rogers said. “We don’t have any data on that yet.”

Rashed and Rogers are analyzing data from the second year of a three-year wireworm study, funded annually with $35,000 from the Idaho Wheat Commission, $15,000 from the Idaho Barley Commission and additional revenue from Regional Approaches to Climate Change, a partnership involving UI, Oregon State University, Washington State University and USDA.

Rashed said the study started in 2014, monitoring 10 fields for wireworms. The researchers solicited additional growers to participate at cereal schools and monitored 75 fields, spanning from Twin Falls to Ashton, in their project’s second year. Upon confirming the presence of wireworms in a field, they’ve continued routinely checking traps at different soil depths. They’ve also ask growers for crop rotation and tillage practice histories.

They’ve confirmed sugar beet wireworm is the predominant species in Idaho. UI is working to sequence the genome of the sugar beet wireworm and recently completed a project it initiated to sequence the mitochondrial genome of the species. Mitochondria are responsible for cellular energy production.

Rashed said the project has also confirmed wireworms are evenly distributed in Idaho counties, though they may appear in patches in the individual fields they infest.

In his soil analysis, Rogers said wireworm numbers seemed to drop as bulk density of soil increased — in both field and greenhouse testing. Rogers suspects wireworms have a tougher time moving through compact soil to feed on plant roots, He emphasized none of the soils in the study were too compact to effectively produce crops.

Based on the soil compaction observation, Rogers said, seed bed preparation could help limit wireworm pressure. Furthermore, no-till farming and planting alfalfa, which tends to compact soil, may also help. They plan to do further studies to test those theories, and to continue recruiting growers for the study’s third year. Additional greenhouse testing will also focus on differences in how wheat and barley plants respond to wireworms.

Rashed said there are no effective chemical controls for wireworms.

The researchers have produced a bulletin to help growers identify different wireworm species.

Cathy Wilson, director of research collaboration with the Idaho Wheat Commission, suspects that wireworm pressure has increased in recent years in the state because traces of chemicals that were banned a few years ago for wireworms have finally worn off in soil. She said growers have also become more aware of wireworms as they’ve addressed above-ground crop threats, but still noticed low yields.

“It’s one of the most intractable pest issues for cereals that we are dealing with,” Wilson said.

In the long term, Wilson hopes a regional group of researchers from various entities will collaborate on a federal grant-funded project to develop a “pathway toward a successful control system.”

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