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Frogeye leaf spot continues spread

A plant pathologist at the University of Kentucky Extension says frogeye leaf spot is continuing to spread across the Midwest.

Carl Bradley tells Brownfield the fungus that attacks soybean leaves was once thought to only be a southern issue.

“I guess I would say kind of the mid-South, but it’s all the way up in North Dakota now.”  He says, “So it’s a lot bigger geographical footprint than it used to have.”

Bradley says the spread is likely weather related.

“A little more humidity; weather that just keeps those leaves wet for an extended period of time.”  He says, “I think some of the rising temperatures that have been noticed in some of those further northern states has been probably part of it.”

He says the disease can reduce yields up to thirty percent if untreated, but farmers can protect their crop with a properly timed fungicide application.

“It’s right around that R3 growth stage when those soybean pods are just starting to develop.”  He says, “Primarily the triazoles are probably doing the heavy lifting for control of frogeye leaf spot.”

However, Bradley says there’s widespread evidence of the disease developing fungicide resistance.

“We found strains of this fungus that were resistant to those strobilurin fungicides. We now know that those strains are present in over 20 states.”  He says, “When fungi develop resistance to the triazole chemistry class, it’s something that you start to see sort of a slow erosion of efficacy over time. And we’ve got some data maybe showing that we’re heading in that direction.”

He says farmers should also work with their seed supplier to select frogeye leaf spot resistant varieties. 

AUDIO: Carl Bradley – University of Kentucky