Resistance and In-Crop Herbicides in Pulses

“It is difficult to find a chemistry that is safe on the crop, controls multiple weeds, is fairly easy to make, (and is) relatively inexpensive to make.” - Dr. Brian Jenks

Creating, trialing and gaining an EPA approved label for herbicides with new mechanisms of action is an expensive, difficult process. It is unlikely we will see any new chemistries in the next year or two. Pulse growers are already limited on what is available so waiting for a new product will not help them in the near future. So how can pulse growers manage their weed populations without a new product? Farmer Ryan Ellis and North Dakota State University Weed Scientist Dr. Brian Jenks return in this episode to help explain what weed management practices can and need to be applied to pulse crops. The difficulty with limiting weeds in pulse crops are the extreme limitations of in-crop additives that can be used without damaging the crop. The weed that many pulse growers are most concerned about is the emerging issue of Palmer Amaranth. There are very few if any chemical options for managing its spread.

Crop diversity is one tactic to managing weed populations. Ryan shares that his pulse crop rotation is “always sort of changing.” On top of spreading pulse crops out by 3 to 4 years he also now rotates which pulse crops he produces on that rotation. There is also evidence of weed resistance to certain herbicides which further limits their use. 

“Group one resistance is certainly going to be a problem. It is a problem, but it's going to continue to be a problem.” - Ryan Ellis

On top of having very limited post-emergence options, the crops themselves are very susceptible to the weeds. “Lentils and chickpeas aren’t that competitive” according to Dr. Brian Jenks. Killing a broadleaf weed in a broadleaf crop requires planning, timing and extreme care. Dr. Jenks highlights the significance of timing in applying post emergent sprays. 

“In general we have to spray the weeds when they’re small in order to get decent control because if we wait until the weeds are four to six inches tall, we’re going to miss them.” - Dr. Brian Jenks

Another factor Dr. Jenks explains is the timing of spring rains. While the farmer cannot control the weather, the spring rains are required to “activate (the) soil applied herbicides.” To avoid dependence on this rainfall for activation of the herbicide, Dr. Jenks recommends focusing most weed management practices in the fall.

“If we can take out 70 to 90% of the weeds in the fall, then we’re not so dependent on the rain to help us start clean.” - Dr. Brian Jenks

This Week on Growing Pulse Crops:

• Learn more from Ryan Ellis and Dr. Brian Jenks
• Explore weed resistance issues in pulse crops
• Hear about what practices can augment weed control in pulse crops where chemical control may be limited

Growing Pulse Crops Podcast is hosted by Tim Hammerich of the Future of Agriculture Podcast.