What is in this article?:
To lower the risk of developing herbicide-resistant weeds:
1. Identify main target weeds in each field
2. Deploy multiple, effective sites of action (SOA) against target weeds
3. Rotate herbicides with different SOA groups by year
4. Layer residual herbicides, if needed
5. Include SOA groups that have a low risk for developing resistant weeds
6. Control weeds when they are small
7. Don’t let weeds escape to produce seeds
Ryan Britt of Salisbury, Mo., discusses weed issues seen during soybean harvest with his dad, Randy. The farm battles ALS- and glyphosate-resistant waterhemp and marestail, which is especially challenging in a few continuous soybeans fields that limit the ability to rotate herbicide sites of action. With planning, they have created a program with four sites of action: groups 9, 4, 2 and 14.
Cover crops, rotation part of grower’s integrated plan
It’s the first week of September, and Ryan Britt is seeding a cover crop of annual ryegrass, tillage radish and crimson clover into wheat stubble. Britt raises corn, soybeans, winter wheat and cattle in north-central Missouri. He is battling herbicide-resistant waterhemp and marestail in his continuous no-till operation. He plants cover crops “primarily for weed management.”
Annual ryegrass helps suppress waterhemp, Britt says. And the residue shades the ground, inhibiting waterhemp germination during the growing season, says his agronomist, Jason Young of AgriVision, Salisbury, Mo. University of Arkansas 2009 and 2010 research found that a fall cereal rye cover crop significantly reduced glyphosate-resistant Palmer amaranth emergence in soybeans the next season. Palmer amaranth is a close cousin to waterhemp.
The cover crop doesn’t eliminate the need for herbicides, Britt says, but it does cut weed pressure. He also plants soybeans in 15-inch rows to help manage weeds. Two other rotation crops, wheat and alfalfa, also aid weed management.