Resistance to Azoxystrobin in the Gummy Stem Blight Pathogen Documented in Georgia

Fig. 5. Examples of 3 different categories of dose-response curves observed in in vitro spore germination assays to determine sensitivity of Didymella bryoniae to azoxystrobin. The red curve shows a typical S-shaped dose-response relationship, with an EC50 value less than 10 µg/ml; isolates with this type of dose response were considered sensitive (S) to the fungicide. The blue curve shows some dose response, and the EC50 value is greater than 10 µg/ml, but could not be accurately estimated because germination was not inhibited by more than 50%, even on the highest fungicide concentration tested (10 µg/ml); isolates with this type of dose-response were considered resistant (R). The green curve shows no dose response to the fungicide and germination was not significantly inhibited by the fungicide, even at the highest concentration tested; isolates with this type of dose response were considered highly resistant (HR).



Image from Plant Health Progress article:
Resistance to Azoxystrobin in the Gummy Stem Blight Pathogen Documented in Georgia