Fungicide seed treatments may give soybeans a boost when used under the right conditions, according to research at the Arkansas Agricultural Experiment Station.

“Fungicide treatments haven't typically been used on soybeans because they give inconsistent results,” said University of Arkansas plant pathologist Craig Rothrock. “We want to determine the situations in which it pays to use them and which treatments will work best.”

“Our goal is to give producers the information they need to get a healthy stand,” said UA plant pathologist John Rupe. “For starters, we wanted to know which fungal pathogens are most important.”

Rupe and Rothrock are testing three important plant stresses farmers face — soil temperature at planting, flooding and seed quality — at five locations in Arkansas. They are testing four popular fungicides to determine their effectiveness under these varying conditions. They are in the second year of the study, which is supported in part by the Arkansas Soybean Promotion Board.

“We're trying to find out what pathogens are associated with each of these stresses, how important they are to stand quality and what treatments are most helpful,” Rupe said. “We've found, for instance, that pythium is the most important pathogen associated with flooding.”

Pythium, though often grouped with and treated like fungus, is related to blue-green algae. Four species of it are found in Arkansas, Rupe said.

“Seed quality is important,” Rothrock said, “because seed from two varieties or just different sources may have different susceptibility to fungal pathogens, but better-quality seed may give a better stand, despite a pathogen, because it's more vigorous. Poor seed may exude sugars or other nutrients that can trigger growth for fungi.”

They're using two soybean varieties: Hutcheson, because it's a commonly used Group V bean grown in Arkansas; and Archer, a Group I variety not adapted to Arkansas, but which has potentially valuable resistance to pythium.

“This resistance is a long-term aspect of this project,” Rothrock said. “Archer's resistance to pythium is expressed in both high- and low-quality seed and in different areas, so we feel confident the resistance is real. If we can characterize this resistance, we may be able to cross it into a soybean that's adapted to Arkansas.”

UA soybean breeder Pengyin Chen is investigating the heritability of Archer's pythium resistance, Rupe said.

At this point in the project, Rupe and Rothrock are seeing better stands of soybeans with treated seed in the absence of flood, but those results are specific to certain test sites. “We're trying to characterize those sites, to find out what makes the difference in how effective the treatments are, so producers can tell if treating seed for their fields will help them or be a waste of money.”

By determining which seed treatments are effective for certain field conditions, Rothrock and Rupe hope to make a seldom-used tool a profitable option for Arkansas soybean producers.

“One of the advantages of fungicides is that you're putting them right at the location where they're needed,” Rupe said. “It's a precision tool that can make a difference when used at the right time, at the right place.”


Fred Miller is science editor for the Arkansas Agricultural Experiment Station. e-mail: fmiller@uark.edu.