The first thing Steve Gauck notices when he walks into a soybean field in late summer are volunteer corn plants or weeds sticking above the canopy. Both are unsightly in his eyes, and both are unwelcome guests.

“We recommend taking volunteer corn plants out early in the season because they compete with soybeans growing near them,” says Gauck, a regional agronomy manager for Beck’s, based near Greensburg, Ind. Beck’s sponsors Soybean Watch ’24.

“If you check individual soybean plants withing a few feet of a volunteer corn plant, they are usually more spindly and taller after competing with corn plants. Large weeds can produce the same effect. In either case, nodes on the soybean plant are usually spaced farther apart, meaning fewer total nodes and fewer pods per plant,” Gauck explains.

Adding a grass herbicide to eliminate volunteer corn on a postemergence herbicide pass usually takes care of the issue, Gauck notes. In the Soybean Watch ’24 field, the grower didn’t add a herbicide for volunteer corn because last year’s corn crop wasn’t tolerant to glufosinate, the active ingredient in Liberty, and he sprayed glufosinate on this year’s soybeans, which are tolerant to Liberty. However, scattered volunteer corn plants came through later.

“Note that these volunteer corn plants are covered with aphids,” Gauck says. “That’s the other primary reason for not letting volunteer corn survive late into the season. They can attract pests, particularly insects, which could wind up feeding on the soybean crop, too.”

Related:Should you apply fungicide on $10 soybeans?

Stinkbug watch

Scouting just before the calendar flipped to August, Gauck found a few green stinkbugs feeding on plants. At the time, numbers were very low, well below the threshold level established by entomologists as the point at which it would pay economically to treat them.

“The point is that if you find them during summer scouting, you know they are present,” Gauck says. “You want to keep scouting and monitoring them. If environmental conditions shift and favor them, they can build up to economically damaging levels in some areas in some years.

“The problem with stinkbugs is that they can utilize their sucking mouth parts to penetrate pods once they form and suck out nutrients. In years where they become severe, they can destroy individual seeds within pods, doing it all the way until harvest.”

ENEMY NO. 1: Green stinkbugs can be a formidable foe if they gain numbers late in the season. Agronomist Steve Gauck suggests scouting for them all the way to harvest.

The other problem with stinkbugs and similar insects is that they open pods up for potential disease infections. Soybean quality issues can develop if diseases set up shop inside pods. It is often insects like green stinkbugs that open the door for these diseases.

According to the Purdue Corn and Soybean Field Guide, treatment is warranted if you find 40 stinkbugs per 100 sweeps with a sweep net, which is just under half a stinkbug per sweep, and pods are still green. In seed fields, pull the trigger faster. Insecticide application is recommended in seed fields if scouts find 20 stinkbugs per 100 sweeps and pods are still green.

From the field:
Cautious optimism for reproductive stages

Here is what agronomists are seeing in soybeans around the Midwest. These comments are provided by Beck’s field agronomists.

In Illinois. “Timely rainfall the last three weeks in July have benefited soybean growth by adding vegetative growth, which means more nodes, in the top of the plant. Isolated areas that received too much rain are showing plant stress and death. Phytophthora root rot and death of rhizobia nodules have been noticed in poorly drained soils, and in areas with prolonged saturated soils.” — Chad Kalaher

In Iowa. “Soybean fields are moving past flowering and into pod formation and development. Bean plants have ramped up N fixation. Many are a beautiful deep-green. Nearly all fields have closed the rows. We are getting nice rains this week that are helping to moderate temperature and spur more N fixation and vegetative growth. Hopefully, this will add a few more nodes to help produce more beans.” — Greg Shepherd

In Indiana. “Fields with low areas that were hit with large amounts of rain showed yellowing in some cases. Growers who are applying fungicides may opt to add in nutrient packs to help get these areas going again.” — Steve Gauck