Experts Recommend Residuals in Resistance Management Programs


WALNUT CREEK, Calif. — As more growers face resistance issues in their fields, researchers are recommending the addition of residual herbicides for a comprehensive herbicide program. These glyphosate-tolerant or even glyphosate-resistant weeds showed a strong presence across the country last year and will be sure to show their yield-robbing faces again this spring.

Researchers are suggesting that for optimal resistance management, growers should include a residual herbicide in their weed programs—especially early in the season, either before or at planting, before weeds are emerged and easier to control. 

Purdue University Weed Scientist Dr. Bill Johnson warns growers against relying exclusively on postemerge strategies, “By applying a residual herbicide, we can extend the window for putting on a postemergence herbicide to reduce yield loss and also reduce the exposure of our worst weed problems to glyphosate. I think that’s the key to resistance management—simply not exposing weed species to the same mode of action numerous times.”

Key findings from Johnson:

  • Weeds can start robbing crops of yield when the weeds reach approximately six inches in height.
  • In postemerge only situations, a one-day delay in weed management strategies can result in:
  • 1.2 bushel per acre/per day yield loss in corn
  • One-third of a bushel per acre/per day yield loss in soybeans

Experts Recommend Residuals in Resistance Management Programs, Page 2 of 2

There are many residual products on the market today, but Valent Product Development Manager John Pawlak encourages growers to look for a residual with long-lasting and broad spectrum weed control.

“With four to six weeks of control, Valor and Valor XLT will fit well into a grower’s resistance management program and can fight tough weeds, such as Palmer pigweed, ragweeds, waterhemp and marestail well into the season.”