Guide for managing target spot & fungicide resistance in SA
Spiral gradient plates demonstrating the empirical methods used to test the efficacy of different fungicides on Target spot (Alternaria solani). Left: Non amended control. Right: MIRAVIS Prime (Group 7 + 12 Premix (Pydiflumetofen + Fludioxonil)) amended media
Image credits: Dr. Phillip Wharton
Target spot (early blight), caused by the fungal pathogen Alternaria solani, is a significant threat to potato crops across South Australia and Victoria. Historically target spot has been controlled using single-site systemic fungicides. However, recent target spot isolate screens from the 2025 growing season have revealed high levels of insensitivity to commonly used fungicides in A. solani populations.
This guide walks growers through how to tackle the challenge of Target spot resistance and includes:
List of fungicides and their Target spot insensitivity levels
Description of the pathogen’s life cycle & epidemiology, including what is and makes a crop more susceptible to it
A walk-through of the methodology behind the insensitivity tests
A recommended action plan for sustainable field resistance management
This guide was developed by Dr. Phillip Wharton, and Dr. Nigel Crump.
