Albert Adjesiwor of the University of Idaho shows Palmer amaranth in a Bruneau potato field. (Courtesy University of Idaho)

Weed pressure that has been significant so far this year will be the focus of research-focused field days in southern Idaho and southeastern Oregon.

Oregon State University, the University of Idaho and Amalgamated Sugar Co. plan the free events, slated to offer research updates and pesticide education credits. Researchers from each host organization are working together.

“It has been an early, fast and warm spring,” said Clarke Alder, senior weed scientist with grower-owned Amalgamated, based in Boise. “Conditions have been just right nearly everywhere in the state to get an early, fast and solid stand of sugar beets. But with that comes an early, fast and solid population of weeds.”

Sugar beet growers thus have been aggressively patrolling for and working to control weeds, including Palmer amaranth and kochia, he said.

Mild temperatures combined with a bit of moisture so far this spring means “plants are just happy, and they come full force,” Alder said. In beets, “we’ve had hardly any emergence issues. Weeds act the same way.”

Growing-degree days, or heat units, are well ahead of 2024 and 2023 totals to date, resulting in the yellow nutsedge weed emerging in onions and corn substantially earlier, said OSU weed scientist Joel Felix, who is based in Ontario

Palmer amaranth, a pigweed that UI weed scientist Albert Adjesiwor discovered in summer 2022 in southern Idaho, will be discussed on all three organizations’ field tours.

Distribution of Palmer amaranth so far seems to be wider in Idaho than in Oregon — where it has been found in a few fields in Malheur County — “and therefore, we continue the monitoring,” Felix said. The researchers drive the region, looking for the weed and talking to farmers.

Adjesiwor, who is based in Kimberly, Idaho, said he drove by a field near Glenns Ferry in mid-April and saw Palmer amaranth emerging earlier than expected, “partly because it’s warm enough for it to come up.”

Last year, most of these weeds emerged after beets were planted, he said. This year, Palmer emergence and beet planting were much closer together in some areas – meaning when beets emerge, the hard-to-control weed is already up and growing.

OSU’s weed management tour is slated from 9 a.m. to noon June 12 at the Malheur Experiment Station, 595 Onion Ave., Ontario. Topics include Palmer amaranth and its control, and studies on using cover crops and bio-fumigation to manage weeds. Refreshments will be provided.

For OSU weed tour information and registration, contact Jan Jones at janet.jones@oregonstate.edu.

UI plans weed management tours from 9 a.m. to noon June 24 at the Aberdeen Research and Extension Center, 1693 S 2700 W, Aberdeen, Idaho, and from 9 a.m. to noon June 25 at the Kimberly Research and Extension Center, 3806 N 3600 E, Kimberly, both followed by lunch.

Topics are to include Palmer amaranth and waterhemp updates; herbicide drift; weed control in corn, dry beans, beets, potatoes and quinoa; and updates on production of various crops.

For UI Kimberly weed tour information, contact Albert Adjesiwor at aadjesiwor@uidaho.edu or Angela Jackson at amjackson@uidaho.edu.  For UI Aberdeen weed tour information, contact Brent Buetler at brentb@uidaho.edu.

Amalgamated Sugar plans research field days, where weeds will be discussed, July 8 near Nyssa, Ore., and July 10 near Declo, Idaho. At each, registration starts at 4:30 p.m. and the program will run from 5 to 8:30 p.m. Dinner is provided.

For details on the Amalgamated field days, send an email to Clarke Alder at: calder@amalsugar.com.