Perhaps the two best ways to assess weed control success or failure in soybean fields is through drone images taken during late-season scouting trips and from the combine as you harvest. Steve Gauck advises taking advantage of both methods to size up how well your weed control program performed in 2024, and how you can make improvements for next year.

“Looking at aerial images before the season is over certainly helps you zero in on any weedy patches in your fields,” says Gauck, a regional agronomy manager for Beck’s, based near Greensburg, Ind. Beck’s sponsors Soybean Watch ’24.

“It’s important to walk fields too, checking for weeds as you go,” he notes. “And even if you scout by air, you may need to do some ground-truthing, walking to those spots to make sure exactly which weeds were present.”

With today’s drone and camera technology, it is often possible to identify weeds from aerial photos, especially if the drone flew at a low altitude. You will also get another opportunity to make a positive identification when you harvest the field.

Toward better weed control

One reason to fly fields and identify weed escapes or to note them at harvest is so you can plan for better weed control next season, Gauck says. “If you missed weeds, they came up later, or you didn’t get complete control and they grew back, try to figure out why,” he advises.

Related:View soybeans from air to get ‘big picture’

Perhaps weeds were too big when they were sprayed, already taller than the recommended height on the label. Or maybe you shaved rates to save dollars on weed control. Then again, maybe the herbicides you applied aren’t the strongest choices for the weeds you are finding in your fields later in the season.

WEED PATCHES: The best way to assess weed control across the field is with an aerial image from a drone, agronomist Steve Gauck says. Note where patches of weeds have appeared in this late-summer photo. (Steve Gauck)

“Knowing which weeds are out there at harvest gives you an opportunity to figure out why you didn’t get better control,” Gauck says. “It is too late for this year, but it gives you great feedback for tweaking weed control for next year.”

Gauck firmly believes in starting off next season with concrete weed control plans. “Many growers don’t realize how much even early weed competition can impact soybean yields,” he says. “One thing I do every year while scouting is pull up soybean plants growing by weeds and plants growing without weeds nearby.

“The difference is always striking. Soybean plants growing with competition from weeds are spindly, with more distance between nodes and fewer nodes overall. That is a recipe for lower yield.”

Treat volunteer corn as a weed too, Gauck says. “Soybean plants growing near a volunteer cornstalk look just like plants growing near a weed. Plus, volunteer corn attracts insects and can harbor disease. Make sure your weed control plans for ’25 include how to remove volunteer corn.”

From the field:
Continue scouting those soybeans

Here is what Beck’s field agronomists across the Midwest are saying about the soybean crop this week.

In Wisconsin. “We got a nice rain shower across most of the state over the past week, and we will likely be looking for more rain before too long. White mold is starting to show up in many areas, with most fields at the R4 to R5 growth stage.

“It will hurt yields in many areas, as seed development will essentially cease on those plants which are infected. Most pods will not fill out. I’ve heard of a few areas hitting aphid thresholds for spraying, but they are not very widespread.” — Joey Heneghan

In Kansas. “We received favorable rainfall across most of eastern Kansas last week between a couple different rainstorms that led to many areas achieving 2 inches or more in a week! This helped raise some optimism on the soybean crop. It helps with pod development and hopefully helps with late-season pod retention.

“Over the last couple of weeks, areas with sudden death syndrome are noticeable from the road. Pressure from SDS still seems lower overall than this same time last year. Insect pressure from either pod worm or stinkbug remains low at this point.” — Brian Green

In South Dakota. “We have had sporadic rains across the territory in the last two weeks. We are seeing some good pod set with this, as we continue spraying for aphids. A little bit of white mold is showing up. There is some gall midge on edges of fields that will be damaging in sporadic fields near grass waterways. Overall, if we keep getting a few rains, we will have a good crop. We are hoping the drowned-out spots aren’t too big and don’t lower field averages too much.” — Jerry Mathis