An emerging pest problem may pose a threat to the supply of grass seed crops coming out of Oregon, where there is a large market for growers. Winter cutworms are moth larvae that move in packs and can damage grass by clipping off blades at ground level. Sometimes hundreds of them can be found together, eating their way across fields.

With spring around the corner, the worms’ population could be set to boom. Entomology experts from Oregon State University are urging growers and lawn care professionals to use insecticides to kill the worms, and tilling to expose them to birds and other predators so their population goes down.

The first winter cutworm damage reported in Oregon was to grass seed fields, golf course greens and lawns last fall. The pests were first identified as the cause of damage to lawns in the United States in 2007, when large numbers were found in hayfields and on lawns in Michigan. They are an invasive species and may have arrived in North America with plant shipments or other trade items from Europe and Asia.