Weed resistance in cereals is a growing problem. Commonly used ALS and ACCase inhibitors, synthetic auxins and other modes of action are becoming less effective against weeds like Italian ryegrass, wild oat, green foxtail, Redroot pigweed and kochia. That means fewer effective herbicide options are available to wheat and barley growers.
It can be easy for growers to choose a quick fix to control weeds now in an effort to save money. But the cheapest solution could increase the potential spread of weed resistance. You can help growers understand the need for long-term weed control strategies and how being proactive can help maximize yield and profit potential for years to come.
Don’t Just Control, Manage
When evaluating weed control, be sure your wheat and barley growers understand the difference between weed control
and weed management
. All growers work to control weeds
in an effort to eliminate an existing weed population and prevent yield loss. Using effective herbicide, tillage and other weed control methods work, but growers shouldn’t rely only on one method. Repeating strategies may be cost- and time-effective, but they allow weeds to become comfortable in the field and develop resistance to once reliable chemistries, causing more problems each year.
Weed management goes beyond weed control, focusing on “reducing weed invasion and emergence, preventing weed reproduction and minimizing weed competition with crops" to help growers fight weeds over several years. Keep herbicide tools effective, and minimize the development of resistance.
The Bottom Line: Controlling weeds costs…but it also pays
Kirk Howatt, associate professor at North Dakota State University, encourages growers to look at a long-term strategy for greater returns over several years. “Preventive management solutions cost more in the short-term," he said, “but they set up for a long-term gain and guard against expensive problems before they occur."
If weeds are allowed to flourish, populations increase. The weed seed bank explodes, which is a key principal in evolution of weed resistance. Weed resistance is simply a numbers game teamed up with overuse of a single herbicide.
Encourage growers to weigh their weed control options as they would when determining whether or not to use certified seed. The up-front cost may be greater and there may be risk associated with added investments, but weeds are managed before
a resistance problem occurs. When working with growers to develop a weed management plan, there are several cultural options
you can suggest that help control weeds long-term while benefiting them now.
1. Implement a crop rotation system
Rotating crops may be difficult in your area, but there are options. Rotating smother crops with wheat and barley can help prevent weeds from adapting to a particular environment, and control options are more flexible. Buckwheat, Sudan grass, rye, clovers, hairy vetch, alfalfa, barley and oats are smother crops that choke out weeds and release natural weed-killing chemicals. They also help improve soil structure, prevent erosion and provide crop nutrients.
2. Understand the impact of tillage
Help your growers understand how their tillage affects their wheat and barley crop and weed growth.
· No-till systems – Help improve soil health, benefit the environment and save times and money, but perennial weeds can flourish, as nothing beneath the soil is intentionally disturbed.
· Shallow tillage systems – Will disturb weed seeds, making it difficult for them to remain viable in the soil the next year, but some weeds like foxtails and kochia will thrive, as they prefer more compact and high-nitrogen soils, have deep roots and an invasive nature.
· Deep tillage - An effective way to disturb weed seeds in the soil, but it can also push seeds down further, where they may lay dormant for several years.
3. Keep the soil loose
Growers often consider how their soil quality contributes to weed growth and the development of resistance. By adopting some of the strategies above, growers can keep soil loose and friable, helping rain water to soak in. With healthier plants and larger crop root systems, soil quality improves and weeds like foxtail have a much harder time competing.
4. Stop weeds before they spread
Weeds disperse thousands of seed each year, which is why it’s crucial growers control weeds effectively. Help your growers avoid additions to the seedbank by recommending the use of a burndown like Touchdown®
herbicide in addition to an in-season application of a postemergence herbicide like Axial® XL