Control Resistant Weeds and Invest In Future Crops, Not the Weed Seed Bank!
The Weed SEED Bank
Globally, weed scientists have focused efforts on ways to manage the weed seed bank. We know that resistant weeds such as Common Waterhemp and Palmer Amaranth can produce 100,000 to 400,000 seeds even when competing with a crop. These seeds are small (1-2mm) and are easily dispersed by wind, animals, livestock feed and equipment. Depending on the tillage systems in place, seeds are buried in the soil near the surface to six inches below. While the fate of the seeds is dependent on several factors such as soil type, environmental conditions, and predation (Figure 1), researchers have found that seeds buried six inches deep can still germinate and be viable 20% one year later, 10% two years later, and 5% three years later.
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 (Figure 2).
University and industry experts agree that an integrated system of multiple modes 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.
Iowa State University Extension weed specialist Bob Hartzler stated in a recent article; “We like to talk about redundant weed control. So you have one herbicide that’s providing 95% control and then you use a second herbicide that also provides 95% weed control. And that goes against common sense,” Hartzler says. “Most growers are going to say, ‘Well, this herbicide is providing 95% control, why should I pay the extra money for a second herbicide?’ But if we want to protect these herbicides, that is the approach that’s needed.”1
Belchim Crop Protection introduced TOUGH® 5EC 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.
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 and field trials have shown very positive results – a 5 to 29% increase – when TOUGH® 5EC is added to an existing weed management program utilizing HPPD’s.
- 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 synergistic effect has been observed when Pyridate is combined with HPPD inhibitor herbicides. When combined, TOUGH rapidly enters the plant and increases the amount of toxic oxygen produced while the HPPD reduces the plant’s natural ability to detoxify them; a one-two punch. This in turn increases the speed of kill and reduces the competitive effect of growing weeds in crops. Dr. Prashant Jha, Iowa State University has 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. 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.”
Results (Figure 3) from a trial conducted at the University of Illinois this year, confirm the results of past years demonstrating TOUGH 5EC’s synergistic effect with HPPD herbicides. While the weeds treated in this trial were up to 9 inches tall (recommend weed size should be 3-5 inches at time of application), adding TOUGH 5EEC in the mix dramatically increased control of Tall waterhemp significantly reducing the number of seeds that will be deposited into the weed seedbank!
Adding TOUGH 5EC to your integrated weed management program is a great way to increase control of resistant weeds and decrease deposits to the weed seedbank!