Fungicide-resistant soybean disease found in Ark.
A fungicide-resistant pathogen that causes a soybean disease called frogeye leaf spot has been found Arkansas, confirmed in fields in St. Francis and Phillips counties, said Travis Faske, Extension plant pathologist for the University of Arkansas System Division of Agriculture.
The disease is caused by the fungus Cercosproa sojina. Strains resistant to the range of strobilurin fungicides have been found in Tennessee, Louisiana and Missouri, but until now, not in Arkansas. Infected soybean leaves have small leaf spots with a tan/brown center and reddish or purple margin. The pathogen overwinters in soybean residue and is dispersed by splashing rain or wind onto soybean plants.
The initial symptoms show on the leaves. Left untreated, the fungus can also infect the stem and soybean pods.
"Strobilurin fungicides are one of the most common fungicide classes used to manage soybean leaf diseases," raising the risk for the development of resistance, Faske said. "It's very likely that other locations within the state have populations of strobilurin-resistant frogeye leaf spot."
The disease is more of a problem for soybeans planted in May or June, including edamame.
Faske said this "will change the way we manage this disease for many years to come."
"This is eventually going to cut in half our fungicide arsenal," Rick Cartwright, associate director of agriculture and natural resources for the University of Arkansas System Division of Agriculture said on Friday. "If this fungus is resistant to one of the strobilurin products, it will be resistant to all of them. This only leaves the triazoles."
Arkansas farmers were expected to plant more than 3 million acres of soybeans this year.
For more information on crop production, visit www.arkansascrops.com, uaex.edu, or contact your county Extension office.