Years ago, the primary weed control activity in the fall consisted of going after Canada thistle and other tough perennials such as dandelion, especially in no-till situations. Fall is still an excellent time to work on those weeds, says Bill Bradford. But today, many more growers are opting for fall herbicide applications on entire fields. The goal is to get a jump on 2019 weeds before they get the upper hand, he notes.
Bradford is a sales representative for the North Central Division of Helena, based in Markle, Ind. “We will be busy this fall spraying lots of fields,” he says. Many of those acres will be after corn, going to no-till soybeans next spring.
“Marestail is one of the biggest targets,” Bradford notes. Dandelion is a perennial that many people still go after with fall applications, too.
“We often use a mix of 2,4-D and dicamba, but we can sometimes use glyphosate, too,” he says. “We’ll use various modes of action, and we’ll adjust depending upon which weeds are in the field.”
According to labels, applications can’t be made on frozen ground. So the application season typically ends sometime around Thanksgiving.
“You still need to add a residual with your burndown herbicide in the spring,” Bradford says. “The advantage is you typically start with a clean field in the spring.”
Bradford was recognized by his peers and named Indiana’s Certified Crop Adviser of the Year at the annual CCA convention last December.
More fall application tips
The biggest secret to success with fall herbicide applications is selecting the right herbicide for the job, says Bill Johnson, Purdue University Extension weed control specialist. “Some people opt for just a foliar application to kill marestail, henbit, chickweed and other weeds which are emerged,” he says. “Others add a residual herbicide to help on marestail control. It adds cost, but it can result in cleaner fields next spring.”
Like Bradford, Johnson says a common fall mix is 2,4-D plus dicamba. If grasses are present, you can add glyphosate. The beauty of the fall application, he notes, is that it can knock out marestail that germinate in the fall.
“Most labels allow you to spray as long as the ground isn’t frozen,” he says. “However, we look at it the same way we approach it when temperatures are warming up in the spring. Applications will be more effective if plants are actively growing. We like to see a couple days with highs in the 50s and hopefully nighttime lows that stay out of the 30s when you spray.”
Several residual herbicides can be effective in fall applications, Johnson notes. Just make sure the residual herbicide you choose fits with the crop intended for that field in 2019.
Fall herbicide applications don’t rule out cover crops, especially if you’re using cereal rye or wheat, Johnson says. In fact, you can use 2,4-D and dicamba with most grass cover crops as long as you aren’t planning to harvest them for grain the next year. If you include brassicas or clovers and other legumes, you eliminate spraying, he notes, since broadleaf herbicides kill legumes and brassicas.