Research HighlightsControlling Insects in Ultra-Late Soybeans
Highlights:
- Ultra-late soybeans in the southeastern Coastal Plain can experience heavy insect pressure during their compressed growing season.
- University of Georgia research is finding that farmers should plan to make at least one insecticide application for their most serious pressure to protect soybean yield and quality.
- While more data is needed for confirmation, current recommendations follow insect thresholds for full-season and double-crop soybeans.
By Laura Temple
Coastal Plain farmers can raise two crops in one year with the ultra-late soybean production system.
In this system, they plant soybeans in late July or early August, after harvesting full-season corn or vegetable crops grown under irrigation. These ultra-late soybeans in the Southeastern U.S. mature in about 90 to 100 days and provide better weed control than leaving the field fallow. They produce about 20 to 25 bushels per acre, a bonus as a second crop.
However, at that time of year, insects have reached much different lifecycle and population stages than when most soybeans are planted in April, May or June. When ultra-late soybeans are flowering and setting pods around mid-September, stink bugs, caterpillars and more eagerly feed on the crop.
David Buntin, entomology professor at the University of Georgia, started research in 2023 to develop recommendations for insect control in ultra-late soybeans, with funding from the Georgia Soybean Commodity Commission.
“We want to understand insect pressure in this unique system,” he says. “Then, farmers need to know when and how to economically protect both soybean yield and seed quality.”
Monitoring and Fighting Late-Season Insects
Buntin’s doctoral entomology student Susanne Deeb conducted scouting and field trials. The first year of the project, they used two locations. They held trials at three locations in 2024 and 2025.
Deeb noted that ultra-late soybeans typically miss kudzu bug pressure, an issue for early and full-season soybeans. However, caterpillars like cabbage looper and green clover worms cause problems during flowering and early pod development. Stink bugs feed on developing soybeans in the pod, causing discoloration and shriveling that can lead to dockage at the elevator.
She also reported heavy silverleaf whitefly pressure near Tifton in south-central Georgia, a region with year-round vegetable production. Whiteflies feed on soybean leaves during early vegetative growth stages.
Buntin and Deeb designed trial treatments to address this insect pressure.
- Control plots received no insecticides.
- An early season application of a butanolide, Sivanto Prime, targeted whitefly.
- Applying chlorantraniliprole aimed to control caterpillars.
- A pyrethroid application handled stink bug pressure.
- A combined application of chlorantraniliprole and a pyrethroid managed both caterpillars and stink bugs.
- For complete insect control, they applied insecticide every two weeks starting at the V2 or V3 growth stage.
Plots received their designated treatments at all locations, regardless of insect mix and pressure levels. Deeb also monitored insect populations weekly throughout ultra-late soybean production, using the shake cloth method.
“Insect pressure varied by year and location,” she reports. “But we saw yield differences of 7 to 10 bushels per acre in all locations when controlling the main insect problems, which also varied by location.”
That’s a significant yield boost for a system aiming to yield at least 20 to 25 bushels per acre.
Ultra-Late Insect Management Recommendations
Based on initial data, Buntin and Deeb believe insect pressure in ultra-late soybeans is similar to pressure in double-crop soybeans.
Farmers should scout ultra-late soybeans weekly for insects. Timeliness is critical in the compressed growing system.
“Defoliation happens fast,” Buntin says. “Insects typically are developing quickly at this time. As the insects grow, they eat more. So, a lot can change in this crop in just one week.”
He says farmers should plan to make at least one insecticide application for their biggest insect problem, whatever that may be. However, they may need a second application for another pest, depending on the season and pest pressure.
“We currently encourage farmers to follow insect thresholds for full-season and double-crop soybeans when determining when to spray ultra-late soybeans,” he explains. “We need more data to confirm that current thresholds make sense for this system, but we tentatively advise using established thresholds.”
In Georgia, those thresholds allow for up to 30% defoliation of soybeans prior to flowering. After flowering, once soybeans reach the R2 or R3 growth stage, the treatment threshold is 15% defoliation or 8 larvae per row-foot.
As ultra-late soybean acres slowly increase in the region, information like this helps farmers successfully implement the system.
“We appreciate the Soy Checkoff support from the Georgia Soybean Commodity Commission to investigate practical issues like this,” Buntin says.
Additional Resources
Testing Varieties for Ultra-Late Soybean Production on the Coastal Plain – SRIN article
Long Juvenile Genetics Offer Potential Solution for Ultra-Late Soybeans – SRIN article
2023 Soybean Production Guide – University of Georgia publication
Meet the Researcher: David Buntin University profile
Published: Oct 6, 2025
The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.
