Growing concerns about weed resistance were on the minds of many no-tillers, speakers and sponsors during the recent 21st annual National No-Tillage Conference in Indianapolis, Ind. The consensus is that weed resistance is becoming a more alarming issue each year and that these concerns can no longer be ignored.

Advice From Australia

Those conversations reminded me of a comment made by Australian weed scientist Stephen Powles at one of the earlier National No-Tillage Conferences: “When you are on to a good thing with weed control, don’t stick to it.”

Since the introduction of glyphosate-resistant crops in 1996, no new herbicide modes of action have been commercialized. The most recent class of HPPD herbicide inhibitors to reach the market were first commercialized nearly 30 years ago. And while we’ve seen plenty of new herbicides in recent years, they’re either new premixes, formulations of existing active ingredients or new active ingredients added to existing herbicide classes.

For years, growers didn’t worry about weed resistance, counting on chemical companies to introduce new herbicide chemistries. But there is no new breakthrough chemistry coming.

“This reliance places us in a position where resistance to many herbicide groups could spread rapidly across the region,” says Iowa State University weed scientist Bob Hartzler. “To reduce the impact of resistance, steps must be made to diversify the types of herbicides used, incorporate other management tactics where feasible and use cultural practices that enhance the competitiveness of the crop.”

While 24 weed species are resistance to glyphosate, there are…