The commonly used expression ‘driver weeds’ is a reference to highly problematic weed species which dictate or drive growers’ herbicide selection and management decisions annually. Key weeds that are top of mind and most frequently called out by growers as being on their driver weed list are Palmer amaranth, giant ragweed and common lambsquarters.

Profiling the Problem

“Driver weeds continue to have a significant impact on bottom lines by impacting yield. And as driver weeds affect more acres, growers are seeking new solutions that are more aggressive in controlling these tough-to-manage weeds,” says Brock Waggoneer, Midwest Sales Agronomist with HELM Agro US. “Taking a zero-tolerance approach to reduce weed seed production that add to the weed seed bank is key. Fewer weeds germinating each year reduces resistant weeds and spreading driver weed populations.”

According to Waggoner, finding a solution starts with weed control strategies that no longer rely on a single herbicide mode of action (MOA). It also requires having a deeper understanding of the biology of hard-to-control weeds like Palmer amaranth, giant ragweed and common lambsquarters.

“Each weed species has had millions of acres of selection pressure for resistance to multiple MOA,” he says. “And with that, we are seeing a lot more weeds no longer responding to certain chemistry as effective measures of control.”

“Each weed species has had millions of acres of selection pressure for resistance to multiple MOA,” he says. “And with that, we are seeing a lot more weeds no longer responding to certain chemistry as effective measures of control.”

Take Palmer Amaranth, for example – a summer annual broadleaf cited as the most concerning driver weed across the South and making inroads into the Midwest. Palmer amaranth has male and female plants that are open pollinated which leads to genetic outcrossing that helps herbicide resistance to propagate.

In an article published by the University of Illinois, research has demonstrated that Palmer amaranth is more competitive than other pigweed species with growth rates as high as three inches per day and yield loss potential as high as 78 percent in soybean and 91 percent in corn.

“A single female Palmer amaranth plant left untreated has the potential to produce hundreds of thousands of seeds,” says Waggoner. “These seeds are like interest on a credit card and can quickly eliminate gains made toward paying the balance. These seeds also take a ride in the combine which aids in spreading the ‘wealth’ in short period of time across a grower’s operation.”

Giant Ragweed is a summer annual broadleaf and one of the first to emerge in early spring. Having separate male and female flowers on the same plant allows for cross-pollination that leads to variations in genetic diversity and greater potential for resistance. Giant ragweed can grow as tall as 16 feet in nutrient rich soils with a single untreated plant producing as many as 5,100 seeds season.

In an article published by Michigan State University, researchers recorded that competition from just two giant ragweed plants per 11 square feet can reduce corn yields by as much as 37 percent. And one plant per 11 square feet has shown to reduce soybean yields by 52 percent.

Common Lambsquarters, is one of the most widely distributed weeds across the U.S. soybean belt. A cool season annual, common lambsquarters germination period is from mid-April through June. Control challenges come from ALS and triazine-resistant biotypes which are becoming more geographically wide spread.

Waggoner says continued reports of reduced control to glyphosate applications is also becoming more prevalent across the soybean belt. Due to common lambsquarters early emergence and rapid growth, it is extremely competitive with soybeans.

As cited on the Take Action Pesticide Resistance Management website, one common lambsquarters plant per foot of row can reduce soybean yield by as much as 25 percent. Capable of growing in excess of six feet tall, lambsquarters can readily adapt and survive in almost any environmental condition. Adding to its wide spread havoc - a single plant produces on average 72,000 seeds with escaped lambsquarters weeds regularly reappearing in the same fields the following year.

Reviton to the Rescue

To gain control over dreaded driver weeds, Waggoner says a critical first step for grower evaluation is their preplant burndown application.

“For growers who want to turn the odds in their favor when battling tough driver weeds like Palmer amaranth, giant ragweed and common lambsquarters, a new herbicide called Reviton® is now available,” say Waggoner.    

A new weed control tool from HELM Agro US, Reviton is a non-selective herbicide for broad-spectrum burndown control of emerged weeds ahead of planting in corn (field), cotton, soybeans or wheat.

Reviton’s novel performance comes from an active ingredient never before registered in the U.S. Preparing fields for a clean start ahead of planting, Reviton targets broadleaf along with grass weeds while protecting emerging crops from the threat of resistance.

Reviton has demonstrated consistently high-performance ratings in burndown efficacy of more than 50 broadleaf and grass weeds, including Palmer amaranth, giant ragweed and common lambsquarters, which are known candidates for ALS, triazine and glyphosate-resistance issues.

“With a new active ingredient, Reviton helps growers take selection pressure off auxins herbicides being used for burndown like 2,4-D and dicamba, and saves them for in-season use,” says Waggoner. “A best-in-class new control tool for both broadleaves and grasses, Reviton strengthens existing weed control programs while providing better resistance management.”

A Cleaner, Weed-Free Start

Key performance benefits of new Reviton include a low use rate formulation, broad tank mix compatibility, crop rotation flexibility, greater options in plant-back, and fast-acting results. Extending its versatility, Reviton can also be used as a desiccant on cotton for quick and reliable crop drydown prior to harvest.

“Reviton’s active ingredient, called Tergeo®, is classified as a Group 14 PPO-inhibiting herbicide,” says Waggoner. “Once absorbed by foliage of susceptible weeds, Tergeo starts shutting down chlorophyll production and photosynthesis. By disrupting this critical growth process, weeds begin to wither and die within 24 hours.”

Formulated as a suspension concentrate (SC), Reviton contains 2.83 pounds of active ingredient per gallon of formulated product with an application rate range of one to three fluid ounces per acre. Whenever using Reviton, the addition of a methylated seed oil (MSO) is recommended for consistent control. HELM Agro US recommends that growers talk directly to their retailor partner about premium MSO adjuvants best suited for use with Reviton.

For enhanced performance in controlling resistant or otherwise difficult-to-manage emerged weeds like Palmer amaranth, giant ragweed and common lambsquarters, Waggoner says tank mixing Reviton at one fluid ounce per acre with either glyphosate or glufosinate is highly recommended.

“As a highly-effective early-season weed management tool, Reviton has broad compatibility with acetochlor, metolachlor, and sulfentrazone-based products for residual control that keeps new weeds from emerging.” he adds.

Safe and Flexible Choice

In regards to crop safety, Waggoner says Reviton’s active ingredient has shown no signs of crop injury or phytotoxicity when used according to label guidelines. Reviton’s crop safety profile also allows greater options when it comes to setting up crop rotation plans and plant-back scenarios.

“Because Reviton doesn’t have residual activity like many herbicides in the same class, growers have greater flexibility in regards to customizing burndown applications, or whenever they need a favorable plant back window,” he adds.

Following a Reviton application, the plant-back interval for corn and wheat is immediate, while soybeans require 0-7 days depending on your soil type and rate and cotton requires 7-14 days interval for planting.

“As a next-generation herbicide, Reviton’s performance features easily translate into maximized yield potential, increased return on investment, plus grower peace of mind when the goal is zero-tolerance for tough driver weeds like Palmer amaranth, giant ragweed and common lambsquarters,” he concludes.

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