Research Highlights

Research Highlights
Can Aggressive Pest Management Protect Seed Quality?

The prevalence of purple seed stain and standard soybean seed damage in early maturing soybeans can cause North Carolina farmers to receive docked payments from their local elevators. Photos: North Carolina State University

By Laura Temple

When North Carolina farmers deliver their early maturing soybeans to local elevators, they sometimes receive docked payments due to seed degradation. This trend has them looking for solutions.

“Farmers asked if more aggressive mid-season management of insects and diseases might ease some of the seed quality issues encountered with August and September harvest that have historically been contributed largely to weather,” says Rachel Vann, assistant professor and soybean extension specialist with North Carolina State University. “Our goal is to answer common production questions, so we conducted trials to find out.”

The North Carolina Soybean Producers Association funded her collaborative research with Dominic Reisig, professor and row crop entomologist with North Carolina State University. Graduate student Kelley O’Reilly led the study, which was conducted over two seasons. Annual trials at three locations included research station and on-farm plots. They used three soybean maturity groups between MG 3 and MG 5, and they chose three early planting dates in an effort to create microenvironments where seed quality issues would likely emerge. 

Depending on crop rotation, soil type, location and many other factors, Vann explains that farmers in the state raise soybeans from MG 2 through MG 8. However, seed damage, including standard damage and purple seed stain, most commonly appears in the earlier maturing varieties less than MG 5. Those earlier varieties often produce higher yields and can bring a premium for early delivery.

“We don’t fully understand the drivers behind the decline in soybean quality, especially in earlier maturing varieties,” she says. “We think that weather is a primary driver, but disease and insect management also needed to be studied. We had seen some interesting differences in seed quality issues on field edges that had not been aerially sprayed for mid-season pests, and we wanted to investigate more.”

When combined across all locations, maturity groups and planting dates, mid-season soybean pest management had no impact on seed damage or purple seed stain, or PSS. Source: North Carolina State University

Trial treatments included fungicide and insecticide applications alone at the R3 reproductive growth stage, consecutive fungicide applications and consecutive combined fungicide and insecticide applications at R3 and R5.  

“In general, foliar fungicides increased yield, but they didn’t have much impact on seed damage or purple seed stain,” Vann reports. “In one plot, insecticides controlled a late-season stink bug outbreak, which can be a problem. In this case, stink bug management resulted in a 1 to 2% decrease in purple seed stain, which was an interesting finding.”

She notes that the reduction in seed damage may not be worth the treatment investment, but that this observation deserves further investigation. She also recommends additional research into factors that impact seed damage and purple seed stain to develop potential solutions. 

“Aggressive mid- and late-season pest management can benefit soybean yields, but we did not see a significant impact on seed damage,” she says. “This research confirms that environmental conditions are the driving factor. The combination of extreme heat and rainfall while the seeds fill out and mature in the pods intensifies the damage and purple seed stain that leads to price dockages at delivery, and aggressive pest management cannot overcome this.”

Published: Dec 11, 2023