By Jamie Martin
An herbicide-resistant pigweed called Palmer amaranth has rapidly spread across Southern Idaho, impacting over 7,000 acres of cropland.
Identified in 2022, this aggressive weed has been linked to significant yield losses, with some fields experiencing up to 47% reduction in production.
Palmer amaranth, first detected by University of Idaho Extension weed scientist Albert Adjesiwor, is known for its rapid growth, smooth stems, and egg-shaped leaves. It spreads easily through farm equipment, bird feed, and cottonseed meal.
By 2024, researchers found that the infestation had more than doubled, affecting major agricultural areas from Paul to Parma.
"It was clear that everywhere we had it in 2023, we had it in 2024," Adjesiwor said. "The farmers use the same equipment to harvest and till, and they move it around in their fields."
This weed is particularly problematic for sugarbeet, corn, and potato farmers. Testing has shown that Palmer amaranth is resistant to multiple herbicides, including glyphosate, with some plants surviving up to 16 times the normal dosage. This makes weed management increasingly difficult for growers.
Farmers are advised to report sightings of Palmer amaranth and rotate crops to small grains, which offer better herbicide control. In cereal fields, regrowth has been observed after harvest, requiring additional tilling or herbicide applications.
Meanwhile, researchers from the University of Idaho, Oregon State University, and Washington State University are working together to monitor and manage the spread of this weed.
Despite discussions, Palmer amaranth has not been listed as a noxious weed in Idaho due to concerns over management costs. However, Adjesiwor and his team continue their efforts, including seeking grants for additional research and herbicide-resistance testing.
Looking ahead, farmers must stay vigilant and adopt integrated weed management strategies to protect their crops from Palmer amaranth’s rapid spread and damaging impact.
Photo Credit: gettyimages-zoomtravels
Categories: National