This week, I’m sharing information I learned at last week’s weed science school. One thing that was new to me, perhaps I should’ve known it but never really thought about it, waterhemp is a shade tolerant plant! We talk about palmer being so incredibly efficient with sunlight that I never thought about waterhemp being so efficient in the shade.

Dr. Kevin Bradley, weed scientist at the University of Missouri gave a great presentation. He had three main points which I share below.

1-More complex herbicide labels: get used to new labels for the future. Those who read the new Enlist® label would be more familiar with them. The labels are based on hydrologic soil groups (determined by soil texture which influences water infiltration and holding capacity). Depending on those hydrologic soil groups, the land manager/applicator needs to meet a minimum number of credits specified by complying with various management practices. This is similar to requirements EPA was proposing in their review of atrazine. Kevin shared this appears to be the way new labels will be formulated for the future.

2-Integrated approaches for weed control: ones he mentioned included cover crops, robots, releasing sterile weed pollen, electrocution, flaming, tillage practices, crop rotation, and chemicals. He did some work with Weed Zapper™ on electrocution of weeds. It has a copper boom attached to the front of the tractor which electrocutes any plant it contacts with up to 15,000 volts. It does this with a 110,000 watt generator attached to the back of the tractor. He shared that it had the best application on weed escapes later in the season that were at flowering or beyond (as a seed control mechanism) vs. trying to control smaller weeds. It provided decent control of marestail, giant ragweed, and waterhemp but not palmer and grasses. His team looked at any impacts to seed viability later in the season. On waterhemp with viable seed, the electrocution reduced that seed viability by 67%.

He also shared on combine seed destroyers where companies are hoping to provide this technology as an add-on feature to kill weed seed. He shared Redekop™ has a deal with Deere in Canada while Seed Terminator™ is planning to work with all brands right now. In the south where there’s typically green palmer at harvest, he said there’s an issue with clogging when using seed destroyers but didn’t see that issue as much in Missouri. His team put cameras on the ground and on the combine to show how it worked and they also collected seed during harvesting. The video from the cameras showed around 30% of weed seed shatters prior to entering the combine header…so there’s a portion that will never have a chance to be destroyed. However, it did an incredible job of separating weed seeds and funneling them into the seed destroyer where damaged waterhemp seed exiting the combine ranged from 66-83%. Across the 7 locations over two years, fuel consumption was 3 gal/hour greater, engine load was 5.6% higher, and speed was 0.24 mph slower when the Seed Terminator™ was on. They saw a significant reduction of waterhemp in the soil. It just depended on if it took 1 or 2 years to achieve it.

3-Zero tolerance for resistant weeds was an interesting topic to discuss with the audience. Ultimately, he was sharing that we’re in a new era of resistant weeds in which plants are able to break down the herbicide at increased rates using ‘metabolic resistance’. I need to dig into this to better understand these mechanisms, but he talked about ‘target site resistance’ where weeds in the 1990’s-early 2000’s conferred resistance by overcoming a specific site of action so the herbicide couldn’t bind. Since 2010 through today, weeds are able to use ‘metabolic resistance’ in which they can confer resistance to other herbicides in same group and possibly to herbicides in other groups. No one had good answers on how to get to a ‘zero tolerance for resistant weeds’ but one thing we all agreed upon was that it would take integrated approaches in order to do so.