With Australian no-tillers dealing with some of the worst weed resistance issues in the world, the country’s growers are adopting a “zero tolerance policy” or a “take no prisoners” approach to weed control.
It’s an idea that may spread to North America as herbicide resistance continues to be a serious concern for many U.S. no-tillers. In fact, results from last winter’s annual No-Till Farmer Benchmark Study indicates 70% of no-tillers suspected or confirmed herbicide resistant marestail (horseweed) in their fields during 2018.
Avoid Weed Seed Buildup
Drew Lyon recently summarized the latest developments and trends in herbicide resistance management from scientists at the Australian Herbicide Resistance Initiative located at the University of Western Australia. The Washington State University weed scientist says the most significant Australian ideas for managing herbicide resistance focus on reducing and maintaining seed bank levels:
1. Renewed efforts needed in herbicide discovery. Herbicide resistance, particularly with glyphosate, has encouraged several ag chemical companies to recently invest more heavily in product discovery than they have over the past several decades.
2. Trait stacking in herbicide-resistant crops. This would include releasing varieties with resistance to two or three different herbicide modes of action. Even though the idea has potential, few weed scientists believe it’s a long-term solution since it could eventually lead to weeds that are resistant to multiple modes of action.
3. Increased use of pre-emergence herbicides. Pre-emergence herbicides can provide more effective early season weed control. By reducing early-season weeds, these herbicides lessen the potential for resistance in post-emergence herbicide treatments.
4. Plant breeders now considering weed competitiveness. While weed scientists have long advocated for the use of weed-suppressive varieties, only recently have plant breeders begun researching and developing germplasm with enhanced weed competitiveness.
5. Destroying weed seeds behind the combine. Several widely adapted weed management tools that are being used in Australia are starting to gain more attention in the U.S. and Canada.
6. More site-specific weed management. While this idea is mostly used in high-value, irrigated crops, recent investments by several suppliers may further develop this technology. Pacific Northwest research has shown targeted spraying systems such as Weed-It and WeedSeeker can greatly reduce herbicide costs, particularly during the later stages of summer fallow, Lyon says.
New Approaches Needed
With no easy weed resistance solutions in sight, North American no-tillers may soon see the day when they’ll be forced to adopt a similar “take no prisoners” policy when it comes to weed control.
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