Farmers can manage weed resistance at the bank

VERMONT, Ill. — The weed seed bank is one place where nobody wants to see their accounts grow.

“Unlike your bank account, you can’t withdraw the weed seed bank deposits that are made. You can’t change that. A net-zero deposit would be great,” said Blake Miller, a Syngenta agronomic service representative in central Illinois, whose territory extends from Danville to Burlington and Pittsfield to Paris.

Growers can manage and control the weed seed bank by careful planning, field practices and utilizing an appropriate and timely herbicide program.

“Once that deposit of weed seed is made, then you are going to be challenged with that into the future. It’s a cycle that’s hard to stop when you continue to increase that seed bank. Likely today it contains multiple resistant biotypes of these weeds,” Miller said.

Boots — and tires — on the ground in fields represent two of the top ways to control the weed seed bank.

“The first thing is scouting. Growers need to be — and they typically are — familiar with their fields. Growers and their retail service providers need to be familiar with the problem areas, and they need to understand the types of weeds that are in their fields,” Miller said.

Making timely and accurate applications of herbicides to the labeled rates can help stop the deposit before it starts.

“Use full, labeled rates of herbicides,” Miller said.

How and when applications are made plays another vital role.

“It’s really important that application equipment is calibrated and you get a uniform application. We need to make our post-emergence applications in a timely manner from our residual application, no more than 28 days,” Miller said.

Regular scouting and knowledge of a field’s problem spots also helps with awareness of weed growth.

“The tallest weed in the field should not be over 4 inches. That’s not the average of the weed height, but the height of the tallest weed. That is a mindset change. Smaller weeds are easier to kill or overwhelm,” Miller said.

Another practice that can be time-consuming but that can help stop the spread of problem weeds is making sure weed seeds are not spread mechanically.

“If they know they have problems in a certain field, clean the equipment off before you leave that field. Don’t transfer soil that may have those weed seed deposits,” Miller said.

Getting growers to vary their herbicide programs can be a challenge.

“We’ve got some new solutions out here, more in the soybean space, but don’t treat those as a silver bullet. Keep deploying a comprehensive weed management solution with a residual, followed by an effective post-emergence herbicide that contains another overlapping residual,” Miller said.

One product that fits that bill is Acuron® corn herbicide.

Acuron has four active ingredients and three effective sites of action. A 2015 study from the University of Illinois College of College of Agricultural, Consumer and Environmental Sciences showed that fields are 83 times less likely to develop weed resistance if they receive more than 2.5 sites of action per herbicide application.

The flexibility and durability offered by Acuron are key to managing the weed seed bank and stopping resistant weeds from overwhelming fields — and yields.

“Innovation has been slow in the herbicide space across the industry. It’s important that we create durable herbicide programs and use products like Acuron that have built-in resistance management, because of the multiple sites of action, and use those in a way that optimizes and creates durability until we get to the next innovation,” Miller said.

© 2021 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all state or counties. Please check with your local extension service to ensure registration status. Acuron is a Restricted Use Pesticide. Acuron® is a registered trademark of a Syngenta Group Company. All other trademarks are the property of their respective owners.

This column was contributed by Illinois AgriNews for Syngenta.