Eight ways to boost your herbicide resistance prevention strategy

It’s a dire situation that the number of herbicide groups various weeds are resistant to continues to grow across the Prairies; however, farmers should take heart as there are many actions they can take to protect their fields this year and for years to come.

It’s about managing weeds to reduce reliance on, and enhance the efficacy of, herbicides as much as possible, says Tammy Jones, weed specialist at Manitoba Agriculture. “There isn’t any new strategy, but just using the latest ideas for improving old systems — and really working the tried-and-true (ones).”

However, Jones wants to stress the seriousness of the situation. While hope springs eternal for new commercialized herbicide modes of action, she reminds farmers that even a broad, new mode of action may not work on many of the weeds that Prairie farmers contend with. Growers must therefore continue to use every weed control option, making sure all of the pieces of the herbicide resistance management puzzle are in place. Here is a roundup of most of them, with Jones’ newest pieces of advice.

1. Ensure your seed spacing and row spacing favour the crop and not the weeds. Some crops lend themselves to this better than others, however, keep on top of favourable seed and row spacing to stay ahead of weeds.

2. Use cover crops. For weed control, cover crops can work like a mulch that prevents weed seed germination, says Jones. “Fall rye has a great ability to cover the soil, to be competitive and produce high amounts of biomass. It seems like we’ll have good soil moisture this spring, so the crop can get a good start. In a dry spring, the fall rye can use valuable soil moisture. Fall-seeded oats can also produce good biomass accumulation and are winter-killed, so there’s no need for termination (a herbicide pass) in the spring.”

3. Significantly change your crop rotation. While many farmers have made some changes in rotation to address herbicide resistance, Jones encourages them to try for even greater diversity. “It’s tough because shortening a rotation may bring more profit this year, but you really need to keep the long-term view in mind,” she says. “There are many aspects to rotation and you may think you can apply a different herbicide because the crop is different, but the weeds in the new crop might be resistant to that herbicide too.”

4. Change things up. By using different seeding dates, different crop maturities for varying harvest dates, or a deep-rooted perennial crop that doesn’t favour a more shallow-rooted weed population can make a significant impact. Jones points to studies in the 1980s and 1990s that showed a certain crop or tillage pattern favours the success of specific weeds, such as winter wheat favouring downy brome grass. Avoiding these patterns helps to keep the weeds from establishing a foothold.

5. Become an expert patch manager. What works best can differ among patches, but Jones notes that mowing or hand-pulling before seed set provides a lot more benefit than growers realize.

6. Clean your equipment as needed. Also, leave weedy fields until last.

7. Look at newer tillage equipment. Inter-row tillage is becoming a more reasonable option, even with narrow rows, since cameras can help make adjustments to stay between the rows or even provide shank control to prevent crop damage. There are costs associated with this, but Jones says the investment may be worthwhile.

8. Use the time you have. This spring will be challenging in terms of getting ruts smoothed out after last fall’s wet weather. “Getting rid of ruts has to happen, and most growers will be in a hurry to get into the fields to seed, but I’m worried about weed control,” says Jones. “The time needed to get rid of ruts means a narrower window to control those weeds earlier. Mark green patches when you are out there smoothing the fields. Do another tillage pass later before planting to disturb weeds when they are small, if you have adequate soil moisture and have the time before seeding. We don’t always have the flexibility we want and there are hard decisions to make.”

Overall, Jones says growers need to subject these herbicide-resistant weeds to death by a thousand cuts. “Farmers are good at this for the most part and it’s complex and there is only so much time in the day,” she says. “All you can do is your best.”