“We have the strong potential to see carryover of many (soil-) residual herbicides this year,” said Aaron Hager, U of I weed specialist.
“A lot of residual herbicides were put on in the spring, and we didn’t get the control we wanted this year,” Hager said.
“A lot of what (herbicides) we used this year is attached to clay (particles) and we needed more in soil (and water) solutions,” he continued.
The amount of carryover varies depending on the herbicide characteristics, soil type, and weather conditions. This year’s lack of rain slowed the microbial and chemical processes that break down the herbicides.
Matt Montgomery, U of I Extension educator, described herbicide types and their potential for carryover. Carryover of ALS inhibitors, such as Pursuit and Accent, is more likely if the soil environment fails to break down the product, when soil pH is high, or if too much product is applied.
Other herbicide types that may carryover in dry soil environments are the triazines, such as atrazine, and those that inhibit pigments, according to Montgomery.
Hager said farmers can do little to prevent carryover injury in fields with crop rotation. Planting fields with the same crop next year would eliminate the potential injury, but he acknowledged that may not be possible in every field.
If a crop rotation is required, Hager advised farmers to delay planting as long as possible to allow more time for the herbicide to degrade.
Additional information is available on the U of I Pest Bulletin