Field experiments were conducted in the primary North American production areas of sweet corn grown for processing to determine how reduced applications of atrazine would affect weed control and crop yield. One of the newest herbicides available for use in sweet corn, tembotrione, was applied postemergence at a low dose with a range of atrazine doses from 0 to 1 pound per acre. Also, the authors conducted this work in two hybrids differing in canopy architecture and competitive ability with weeds.

Atrazine reduced the risk of poor performance of tembotrione. Atrazine doses up to 1 pound per acre with tembotrione improved grass control and broadleaf weed control in 5 of 8 and 7 of 8 environments, respectively.

"We saw a risk-reducing benefit, in terms of weed control and yield stability, of using some atrazine in most conditions," Williams said. "Of the three environments that had particularly low broadleaf weed control with tembotrione alone, sweet corn yield was improved with low doses of atrazine."

The bottom line, Williams said, is that a small amount of atrazine applied postemergence reduces the risk of herbicide failure. "When atrazine use is reduced, the typical hybrids having poor competitive ability disproportionately release grass and broadleaf weeds and suffer higher crop losses."

Atrazine wasn't needed when other aspects of weed management worked well in reducing weed pressure. For instance, a hybrid with more competitive growth characteristics performed better in systems using less atrazine. "The research also demonstrates room for improvement in non-chemical components of weed management, such as with cultural tactics," Williams said. "Because atrazine is inexpensive, its use enables growers to reduce the risk of variable weed control and potential crop losses at minimal cost, which means there is little economic incentive for alternatives unless, of course, the herbicide is restricted further or no longer available."

Although weed management systems in corn are dominated by herbicides, a simple replacement herbicide for atrazine doesn't exist in sweet corn.

"I believe overcoming such a challenge would be possible", he said. "But knowing how to make the transition will require an investment in sound research."