If you don’t like surprise parties, keep scouting soybean fields until harvest. Otherwise, Steve Gauck says you could be the guest at your own unwanted surprise party. You could discover damaged pods and soybeans with seed quality issues when you pull the combine into the field.

“If I am monitoring a field, like the Soybean Watch ’24 field, I want to keep returning and walking until the crop is ready for harvest,” explains Steve Gauck, a regional agronomy manager for Beck’s. Gauck is based near Greensburg, Ind. Beck’s sponsors the Soybean Watch ’24 field.

“Stinkbugs are a key pest we worry about late in the season,” Gauck notes. “They can continue feeding, even late in the season. With their piercing mouth parts, they can suck material out of individual beans with pods. Too much of that can lead to yield loss.”

The initial damage from the insect is not the only concern, Gauck says. By penetrating the pod and leaving a wound, stinkbugs open pods up to infection by diseases. Often, when stinkbug pressure is high, seed quality issues accompany a loss in yield. But seed quality issues are usually linked to diseases that invaded after the insect opened the pod for infection.

Two main types of stinkbugs can cause damage: the green stinkbug and the brown marmorated stinkbug. According to the Purdue Corn and Soybean Field Guide, brown marmorated stinkbugs generally stay close to field borders where they enter a field. You can find green stinkbugs anywhere in the field.

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Adult green stinkbugs are typically green and shield-shaped, but they can vary somewhat in color. If you find 40 stinkbugs per 100 sweeps with a sweep net, or 0.4 stinkbug per sweep, and pods are still green, Purdue recommends spraying. If it is a seed field, where quality is an even greater concern, treat if you find 20 stinkbugs per 100 sweeps, or just 0.2 stinkbug per sweep.

Identify the insect

Just because you see obvious feeding on pods doesn’t mean stinkbugs are the culprit. “Grasshoppers will feed on pods too, late in the season when leaves aren’t as attractive an option,” Gauck says. “The difference is that without sucking mouthparts, grasshoppers don’t penetrate the pods. Unless a pod is chewed all the way through, soybeans inside remain intact. They are also not subject to invasion by diseases.

“When I walked the Soybean Watch ’24 field recently, I found feeding on pods here and there. However, when I looked closer, pods were still intact. So, grasshoppers fed on these pods, not stinkbugs.

“We really didn’t see signs of stinkbug damage. So, there was no need to consider an insecticide application. However, I will return before harvest to make sure stinkbugs don’t invade the field late. We don’t want the grower to find that kind of surprise when he harvests the field.”

From the field:
Dry weather could affect soybean yield

Rainfall, which was too abundant at times during the season, disappeared across most of the Midwest over the past few weeks. That’s when soybeans needed a drink the most. Here is what agronomists saw across the Midwest over the past couple of weeks:

In Minnesota. “Many soybean fields within southern Minnesota are beginning to turn towards maturity. Early-planted fields are coming on fast, with some that could be harvested in the next 10 to 14 days, weather pending. A fair amount of white mold and sudden death syndrome can be found throughout the territory, hampering yields in some fields. 

“Looking at pod counts year over year, we are looking solid. The downside is the middle of the plant is showing a fair amount of two-bean pods, a function from stressful periods we encountered earlier. The top third of plants shows that weather straightened out. We see mostly three- and four-bean pods towards the top of the canopy.” — Dale Viktora, Beck’s field agronomist

In Missouri. “Soybeans have really started to turn in the past two weeks. There have been some earlier-planted and early-maturity beans harvested already. We are hearing yield reports of 60 to 70 bushels per acre so far.

“Longer-season beans and later-planted beans could still benefit from a rain, but that is not looking favorable. We are seeing quite a few flat pods towards the top of the canopy where we have been drier. Hopefully, the faucet will turn back on soon!” — Celena Kipping, Beck’s field agronomist

In Iowa. “Most soybean fields are beginning to turn now. Disease continues to progress. More SDS and more septoria brown spot are showing up. The severity in southeast Iowa is moderate to low. I do not believe they will have a major influence on yields.

“A cornfield or two has been harvested in the past few days with temps in the high 80s. I have not seen a combine in a soybean field. Based on pod counts and plant health, soybean fields planted in April will have a yield advantage. We will find out soon enough, as widespread harvest will no doubt begin within the next week.” — Greg Shepherd, Beck’s field agronomist

In Nebraska. “Things are beginning to turn here in southeast Nebraska, and some of it is premature. The most premature are dryland acres. We have not had much substantial rain during August and these first two weeks of September. Irrigated acres look like they will produce a good crop and probably will be better than last year. There have been low instances of SDS on those acres. So, with no big hurdles, we should see good yields there. 

“Dectes stem borer is the primary insect concern, and fields that have been heavily impacted will need to be prioritized first during harvest. There have been subtle cases of brown stem rot, which will need to be harvested first as well.” — Trey Shepherd, Beck’s field agronomist

In South Dakota. “Soybeans look good with pods filling well. Most are in the R5 or R6 stage. Some of the earliest-planted beans could be harvested in the next two weeks. Without rainfall in most areas for the last two weeks and with temps that have reached into the ’90s, some beans are moving along faster than expected.

“We see mostly two- and three-bean pods being set. I can see the value of late vegetative foliar applications, where there is heavier pod set on lower nodes. We still have some later waterhemp coming through the canopy.” — Jerry Mathis, Beck’s field agronomist

In Michigan. In Isabella County, located in the middle of Michigan, about an hour-and-a-half north of Lansing, about a third of Roger McCarthy’s acreage is irrigated. He says he’s looking at boom or bust.

Parts of Michigan had ample rain all season with plenty of heat and growing degree days. “But unless you had moisture, crops are either poor or nearly dead,” he says. “We’ve got some really good soybeans, but it’s a different story just 5 miles down the road.”

McCarthy farms 750 acres in the Blanchard area. “With the dry weather in this area, guys that got their beans in late are looking at small beans,” he adds. — compiled by Jennifer Kiel, editor of Michigan Farmer