East Idaho seed potato growers track aphid migrations with help of UI Extension pest trapping program

University of Idaho Extension educator David Callister’s Monday morning routine from mid-June through mid-September entails visiting four area seed potato fields and transferring bugs from rudimentary insect traps into vials.

Callister is part of a labor-intensive but crucial Extension aphid monitoring network that provides surety to southeast Idaho seed potato farmers in Butte, Caribou, Fremont, Lincoln, Minidoka and Teton counties. Extension seed potato pathologist Kasia Duellman, who is based at the U of I’s Idaho Falls Research and Extension Center, oversees the program, which posted weekly aphid tallies from 23 monitoring sites throughout the growing season.

Monitoring sites are selected based on input from cooperating growers who have agreed to have traps placed by their seed fields. The data is emailed directly to about 100 interested stakeholders.

Aphids spread an economically important disease of potatoes, called potato virus Y (PVY). Tracking aphid migrations can help growers recognize seasons in which the risk of disease transmission may be elevated and justify costly management decisions, such as applying mineral oil and insecticides to keep the tiny, winged insects at bay.

It takes Callister about two hours to make his rounds throughout a 10-mile radius near Arco. At the edge of each of the fields he monitors, he leaves a yellow bucket filled with water and a squirt of soap to break the surface tension and cause insects to sink upon landing. Yellow objects attract several aphid species.

Callister pours insect-laden water from the traps through a nylon mesh cloth, which he rolls and inserts into a plastic tube. Duellman’s lab sends staff and graduate students to pick up the tubes at the UI Extension office in Arco, and aphids are identified under a microscope and tallied. The aphids are then sent to entomologist Andy Jensen, the retired manager of the Northwest Potato Research Consortium, who identifies the specimens by species.

“When there was one count that was high, I got a call immediately from the farmer asking which bucket it was,” Callister said. “Watching aphid counts is important to potato producers.”

UI Extension educator Justin Hatch, Caribou County, oversees monitoring of the half dozen aphid traps in the Grace area, with the help of a grower cooperator.

“Really what it’s helping us do is identify patterns that develop throughout the season and hopefully pick up on those over time,” Hatch said.

Duellman’s team checks the aphid traps in Fremont and Teton counties, along with traps at two commercial sites near Rexburg and Aberdeen. Funding for the program comes from U of I, the Idaho Potato Commission and a small portion of a federal grant.

From 1987 through 2003, University of Idaho used tall suction traps made with PVC pipe to capture and monitor aphids statewide. Idaho Crop Improvement Association acquired four of the traps and resumed the program on a limited basis in 2011, focusing on seed growing areas in eastern Idaho.

UI Extension took over the program in 2019, adding yellow bucket traps to the network. Over the years, grower cooperators and interns with companies such as Simplot Grower Solutions have also helped service various sites, but logistical challenges hampered efforts to get samples to the Idaho Falls lab. Side-by-side comparisons of bucket trap and suction trap captures demonstrate to Duellman that both trapping methods show similar peaks and valleys in the timing of aphid migrations.

Based on the 2025 aphid counts, Duellman is concerned PVY levels could be elevated in the current seed potato crop compared with the prior year. The number of aphids captured in 2025 was unusually high and sustained throughout July. Based on her own data and other research, Duellman hypothesizes that heavy aphid exposure from June through July poses a greater risk of PVY transmission than exposure from August through harvest, as potatoes appear to develop some late-season resistance to the disease.

During the 2024 season, the aphid trapping network showed regional fields experienced a slight spike in aphid pressure prior to potato emergence, low pressure during June and July, and peak pressure during August. PVY infections in the subsequent crop proved to be relatively low compared to other recent years.

“Aphid monitoring gives the grower a better picture of risk. For example, if we have a peak flight of aphids in June right after emergence, we can tell growers this may be a high-risk year for PVY, and they can be more prepared to start applying a mineral oil plus insecticide program,” Duellman said. “It takes a lot of manhours to implement this monitoring program, but it’s really valuable information.”