The consistent increase in the number of herbicide-resistant weeds globally has been a major thorn in the side of the agriculture sector for decades. Currently, there are 509 unique weed-resistant cases globally (www.weedscience.org), with weed resistance instances steadily increasing across many crops including corn, soybean, rice, and cotton.
A common strategy to mitigate against this risk has been to alternate or combine modes of action (MOA’s) and sites of action, as part of an integrated weed management program. Even so, more must be done as the focus turns to improve the control of weeds to ensure farmers maximize their crops, especially in this volatile economy.
Pyridate Reawakening
Resistance management led Belchim Crop Protection to re-register TOUGH® 5EC. The active ingredient pyridate, when added to the POST tank mix, is highly effective in controlling HPPD-resistant weeds. TOUGH® 5EC Herbicide, a fast-acting, selective, contact herbicide, was approved by the EPA in 2020 for post-emergence broadleaf weed control in corn, mint, and chickpeas.
Prior to full registration, mint growers had already been using TOUGH® 5EC under FIFRA Section 18 for Emergency Use. Researchers such as Dr. Ian Burke, a J. Cook Endowed Chair of Wheat Research and Professor at the Department of Crop and Soil Science at Washington State University, had also been testing it in the chickpea market given the lack of registered post-emergence herbicide alternatives available.
Expanding into row crops, 150 plus university research trial results conducted in 2017 - 2021 across the corn belt have shown a significant increase in weed control when TOUGH® 5EC is included in the tank mix. Dr. Prashant Jha of Iowa State University even stated that specifically with regards to corn, with glyphosate, mesotrione, atrazine, plus TOUGH® 5EC in the tank mix, he sees 95-100% control.
Making Complete Control Possible
Keeping the focus on corn for a moment. Considering that one common waterhemp plant produces upwards of 400,000 seeds when competing with a crop, even just 5% escapes quickly become a significant number for farmers to manage. Research (Steckel 2007) has found that just eight waterhemp per 11 square feet can reduce corn yield by 74%. This is simply not a risk worth taking. With a solution like TOUGH® 5EC, even if the typical post-product provides 95% control of weeds, adding TOUGH® 5EC can help achieve 100% control.
There is no silver bullet to control resistant weeds but using multiple MOAs as part of an integrated weed management program, and specifically within the post-emergence tank mix has produced positive results. Showing up to 100% control when included in the tank mix, TOUGH® 5EC, with active ingredient pyridate, is quickly becoming an integral component of any best management practice when it comes to combating weed resistance. This MOA enables farmers to focus both on protecting their current crop and reducing the number of weed seeds going into the soil seed bank. By optimizing the tank mix with the addition of TOUGH® 5EC, farmers continue sharpening control against the most troublesome and tough-to-kill weeds, like waterhemp, palmer amaranth, and kochia and helps to prevent the selection of herbicide resistant weeds in the future.
Strengthening HPPDs
With HPPD-resistance growing, it made sense for Belchim USA to look deeper into the chemistry to see how products could work together to provide increased control. While HPPDs are still effective against many weeds, in practice, farmers saw that several weeds were becoming increasingly resistant to HPPDs. Enter TOUGH® 5EC. Belchim USA understands the value of the HPPD chemistries and has shown addition of TOUGH® 5EC will help to preserve them for years to come.
TOUGH® 5EC’s active ingredient, pyridate, increases production of free radicals (single oxygen molecules that disrupt cell membranes causing cell collapse), while HPPDs reduce the plant’s ability to detoxify these naturally occurring free radicals. This synergy between these MOAs attacks weeds from two directions, leading to a faster speed of kill and increasing control of HPPD resistant weeds.
TOUGH® 5EC also enhances atrazine, which is often added to the tank to work in concert with HPPDs. HPPD resistant pigweeds have also been found to be resistant to atrazine. The resistance is metabolic and the plant breaks both chemistries down very fast. Atrazine moves into foliage slowly, as it is mainly absorbed through the plant roots, and some HPPD resistant weeds metabolize it too quickly preventing its rapid assistance to the HPPDs. Pyridate, with its fast foliar absorption properties, enhances Atrazine by hitting the D1 protein at a different site thus enhancing the overall action there to trigger the production of the free radicals and gives faster speed of kill.
Ultimately, TOUGH® 5EC synergizes HPPDs and enhances atrazine, with a one-two punch that results in a significantly faster kill rate and can provide up to 100% control of tough-to-kill broadleaf weeds.
More Integrated Program = Better Control
“The benefit of adding TOUGH® 5EC to a traditional weed control program in Roundup Ready corn was that TOUGH® 5EC helped tighten up the efficacy on velvetleaf and waterhemp. The addition of atrazine helped residual control of late-emerging weeds such as morningglory, giant ragweed, and other broadleaf weeds species,” said Dr. Bill Johnson, Extension Weed Scientist at Purdue University.
There are multiple combinations for the use of TOUGH® 5EC, whether increasing control when tank mixed with HPPDs and atrazine in corn or as a desperately needed post-emergent solution in mint and chickpeas. Field trials and grower use has shown that pyridate’s MOA increases weed control in herbicide-resistant weed populations by up to 30%, often achieving the goal of 100% control, and making this a vital tool for growers now and into the future.
