APS Homepage

POSTERS: Fungicide and antibiotic resistance

Survey for quinone outside inhibitor fungicide-resistant Cercospora sojina in Kentucky
Danilo Neves - University of Kentucky. Carl Bradley- University of Kentucky, Kelsey Mehl- University of Kentucky

Quinone outside inhibitor (QoI) fungicides can have a high level of efficacy in controlling diseases. However, this class of fungicide has a high risk of selecting for resistant individuals within a fungal population. QoI fungicides have been used to control frogeye leaf spot (FLS) in soybean, caused by the fungus Cercospora sojina. Resistance to QoI fungicides in C. sojina isolates was first reported in 2010. Since these initial findings, C. sojina isolates resistant to QoI have been detected in 15 states, including Kentucky. The objective of this survey was to estimate the frequency of QoI-resistant in C. sojina populations collected in different soybean growing regions in Kentucky in 2018. A total of 131 single-spore isolates were obtained from soybean leaves with FLS symptoms collected in 9 counties. A discriminatory dose of 0.1 µg/ml technical grade azoxystrobin, or a molecular assay was used to distinguish QoI-resistant and –sensitive isolates. The frequency of QoI-resistant C. sojina isolates was 70%. This survey reports the presence of C. sojina isolates resistant to QoI fungicides in all counties, where samples were collected. To avoid widespread occurrence of QoI-resistant C. sojina isolates and economic losses, farmers should adopt integrated pest management strategies such as planting resistant cultivars, rotating to non-host crops, and applying different or mixed modes of action fungicides.