Better Field Management Can Reduce Weed Spread

By Scout Nelson

Weed management is an important part of successful crop production. Unmanaged field edges and weed patches can produce seeds that spread into crop fields, making weed control more difficult in future growing seasons.

Jeff Stachler, Ph. D., North Dakota State University Extension Cropping Systems Specialist, recently highlighted the importance of managing weeds around fields and inside problem areas. Regular scouting, timely mowing, and careful weed control can help reduce seed production and protect crops.

Field data showed how quickly weed problems can increase. In Griggs County, only 4% of hard red spring wheat fields had Canada thistle within the field at harvest in 2021. By 2025, the figure increased to 25%. Wind-blown seeds from unmanaged field edges are one reason for the increase.

Canada thistle, perennial sowthistle, absinth wormwood, horseweed, and prickly lettuce can spread through wind. In Eddy County, 33% of hard red spring wheat fields had absinth wormwood within the field at harvest in 2025.

Herbicide use along field edges also requires care. Spraying glyphosate beyond the final crop row can remove perennial grass and allow annual weeds to grow. Reduced herbicide rates can also increase the risk of resistant weeds.

Kochia, waterhemp, wild oat, green foxtail, horseweed, and common ragweed can become serious problems when they remain near fields until harvest. Combine equipment can cut these weeds and spread their seeds across fields.

Farmers can use mowing to manage field edges. Problem weeds should be mowed when they first begin flowering. A 12-inch mowing height can help reduce seed production. If mowing starts late, weeds should be cut as low as possible.

Field margins should be checked regularly. Areas with annual weeds can be mowed about five feet from the field edge. Areas with perennial wind-dispersed weeds can be mowed up to 15 feet. Leaving land beyond 15 feet can provide habitat for beneficial insects and wildlife.

Foxtail barley in saline areas should also be managed before seedheads develop. Mowing is preferred over tilling because tillage can move salts into crop areas.

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