MSU conducting survey to find resistant fungus
Allen said continued monitoring for the presence of strobilurin resistance in frogeye leaf spot will provide soybean producers with valuable information to help them manage the disease and reduce the likelihood of yield loss or crop failure.
Maria Tomaso-Peterson, a MAFES researcher and Standish’s major advisor, said the purpose of this research is to get ahead of fungicide resistance in this disease before it develops.
“We’re being proactive in identifying whether or not we have strains of this fungus that are resistant to the strobilurin fungicides, and if so, to what extent,” Tomaso-Peterson said. “The fungal population progressively develops resistance, allowing the resistant spores to increase in numbers throughout a soybean field. This is called practical resistance.”
The next step will be to develop a fungicide program that helps slow down the development of practical resistance to the fungicide.
Fungi have a higher likelihood of becoming resistant to strobilurin fungicides because this class of chemicals has what is known as a “single-site mode of action,” which means it has only one way of attacking disease-causing organisms.
“Strobilurin fungicides target fungal respiration, so we will use a rotation of fungicides and tank mixes that include different classes of fungicides,” Tomaso-Peterson said. “We also will suggest planting resistant varieties, and where practical, using crop rotation, so soybeans are not planted on the same land each year.”
Tomaso-Peterson said strobilurin resistance in turf grass pathogens took only a few years to develop, but specialty crops such as turf grass require many more fungicide applications each year than do row crops. So far, it has taken more than 15 years for fungicide resistance to manifest in soybean diseases.
“We suspect there is probably practical resistance to this fungicide, and Jeff is doing this research to give us a better idea of the scope of the problem,” she said.
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