Symptoms
Small circular brown-to-grey spots with darker margins, sometimes with a yellow halo, scattered across older leaves. Spots merge in severe cases, causing leaves to yellow and drop early.
Prevention
Space plants for airflow and avoid wetting foliage when watering. Remove fallen leaves and rotate crops to reduce inoculum.
Treatment
Organic
Spray neem oil or a copper-based fungicide at first sign. Pick off and destroy spotted leaves to slow spread.
Chemical (last resort)
Apply mancozeb or chlorothalonil on a 10-14 day schedule during wet weather. Rotate with a systemic fungicide if pressure is high and observe PHI.
Affects 3 crops
Sources
MARDI Crop Protection Guide; DOA IPM Manual