Today there is a growing demand for nonchemical weed controls to aid growers in the battle against herbicide-resistant weeds. Some are now turning to chaff carts, impact mills and other harvest-time practices to remove or destroy weed seeds instead of leaving them on the field to sprout.  

For these seed-focused controls to work, though, two conditions must be met. Weeds must retain large numbers of seeds at harvest time, and the plants must be tall enough for the seeds to be captured.

Scientists from Oregon State and Washington State universities recently explored whether harvest-time controls would be effective against downy brome, Italian ryegrass, feral rye and rattail fescue – four weeds that compete with winter wheat in the Pacific Northwest.

In an article featured in the journal Weed Science, the researchers say the efficacy of harvest-time weed seed controls varied by weed species and was influenced by the environment and growing conditions. Feral rye exhibited the greatest potential for harvest-time control due to slower seed shattering rates and higher seed retention (54 percent on average). The remaining weeds in the study had an average seed retention at harvest of less than 50 percent. Rattail fescue proved to be a poor candidate for harvest-time weed seed controls because of its low height.

Another important takeaway: For the best outcome from harvest-time controls, the team recommends harvesting as soon as possible after crop maturity so you can capture as many weed seeds as possible.

Want to learn more? You can read the article “Seed Retention of Grass Weeds at Wheat Harvest in the Pacific Northwest”, free for a month, online at Weed Science.