FIGHT Todays Resistant Weeds and PREVENT Those of Tomorrow
An Integrated Weed Management Program is Critical to Fight Resistance
Each year, the number of cases of herbicide resistance increases and shows no sign of slowing down. Palmer amaranth and Common waterhemp have shown resistance to 9 different herbicide groups. See Figure 1.
University and industry experts agree that an integrated system of multiple modes and sites of action with overlapping soil residuals, is essential to an effective weed management strategy. In addition, incorporating different chemical and cultural management practices improves the ability to control tough and resistant weeds and protect existing herbicide technologies.
Dr. Pat Tranel, University of Illinois stated in a program executed by Beck Ag; “You can go from one seed to a hundred thousand or more. When you think about weed management, you really need two perspectives: short-term where the goal is to prevent yield loss this year, but also long-term to get that seed bank under control and strive to be smaller every year. When you are dealing with an enemy weed that’s able to produce thousands upon thousands of seed, 95% control is nowhere near close enough. You have to be above 99% control in order to have a sustainable year after year system.”
TOUGH® 5EC came to the corn market in the 2021 season. The active ingredient in TOUGH® 5EC is pyridate, which is an underutilized chemistry in the Unites States. TOUGH® 5EC provides a unique tool for growers to control some of the most challenging weeds, especially resistant weeds such as Palmer amaranth, Common waterhemp, and Kochia. Clint Einsphar – now at Aurora Coop in Bertrand, Nebraska put TOUGH 5EC to the test in 2021. “We have a pretty severe case of kochia in our area and dicamba-based products or a secondary mode of action haven’t been working very well, and in the last few years is just getting worse. We tried TOUGH on a couple of severe fields and got excellent control of the kochia. Kochia was our main target and we got really good results; it was quick burn down there. Some of the kochia died in three days so it was awesome. It was an excellent secondary opportunity for us to try to use something different and we got good results. We just went full bore with it the rest of the spring season.” Figure 2 shows one area Clint treated with 8 oz/acre of TOUGH 5EC, 10 oz of Banvel® and .25 quarts of atrazine. 10 days later the Kochia was dead.
TOUGH® 5EC works by blocking a weed’s photosystem II process, triggering the release of toxic forms of oxygen, and causing rapid cell wall degradation. Research, field trials and grower use in 2021 have shown very positive results in control, when TOUGH® 5EC is added to an existing weed management program.
- Pyridate is applied after emergence of the weed.
- Pyridate is quickly absorbed by the leaves (rain-fast within 60 minutes).
- Pyridate blocks photosystem II of the weed by irreversibly binding to the D1 protein and inhibiting the transport of electrons. High energy electrons then interact with oxygen, producing toxic forms of oxygen.
- The toxic forms of oxygen interact and degrade the cell’s membranes resulting in necrosis (browning) and ultimate death to the weed.
TOUGH 5EC Synergizes HPPD Herbicides and Enhances Atrazine
A synergetic effect has been observed when Pyridate is combined with HPPD inhibitor herbicides, such as mesotrione. When combined, the amount of toxic oxygen produced is increased, reducing the plants ability to detoxify these oxygen molecules. This in turn increases the speed of kill and reduces the competitive effect of growing weeds in crops. Dr. Prashant Jha, Iowa State University conducted a number of university trials with TOUGH® 5EC over the past few years. Dr. Jha states; “TOUGH is definitely going to be an effective strategy paired in a tank mix with HPPD inhibitors or Group 27 herbicides. When they are mixed together, like Callisto and TOUGH, we are achieving that 90 to 95% control with rapid necrosis and kill of plants within seven days after application.”
Dr. Jha evaluated the effect of a combination of three effective modes of action – atrazine, HPPD inhibitor herbicides, and TOUGH® 5EC on resistant weeds in Iowa. The results were impressive. It has been observed, when only atrazine and HPPD inhibitors are combined, the metabolic pathway in HPPD resistant weeds also degrades atrazine, therefore the plant metabolizes atrazine before it can assist the HPPDs. (See Figure 3) However, TOUGH® 5EC moves into the leaf quickly along with the HPPD herbicide to reach the target sites before they can be degraded. Dr. Jha continues “Now we have three multiple modes of action, which is one of the best management practices. Pyridate is available faster to assist that HPPD ahead of the metabolic degradation process in HPPD resistant weeds, and that’s how it is a game changer.”
Dr. Bill Johnson of Purdue University was one of our cooperators in the summer of 2020 who conducted a trial to evaluate TOUGH® 5EC as part of a post emergent program for enhancing control of glyphosate-resistant Common Waterhemp in Corn. The trial evaluated the multiple mode of action program mentioned above. Click on link to watch the results. https://www.youtube.com/watch?v=EmOVYwfpSAw
Adding TOUGH 5EC to your integrated weed management program is a great way to increase control of resistant weeds and reduce the seedbank!