Leaf spot: identify, prevent, control

Worst in warm, wet weather through summer and autumn, December to May.

Leaf spot covers several fungal and bacterial diseases that mark leaves with spots and blotches, common on silverbeet, tomatoes, capsicum and many greens. It spreads in wet weather through splashing water, and while light cases are cosmetic, heavy spotting strips leaves and weakens plants.

How to identify it

• Round or angular brown spots, sometimes with a yellow halo or pale centre
• Spots merging into larger dead patches as it spreads
• Lower, older leaves affected first then moving up the plant
• Leaves yellowing and dropping under heavy infection

How to prevent it

• Water at the base in the morning and avoid wetting the foliage
• Space plants and remove lower leaves for good airflow
• Mulch the soil to stop spores splashing up onto leaves
• Rotate crops and use clean seed

Organic control, step by step

• Pick off and bin affected leaves at the first sign
• Avoid handling and harvesting when plants are wet
• Spray a copper-based fungicide as a protectant in wet spells, following label rates
• Repeat copper sprays after rain through the risk period
• Remove badly infected plants to protect the rest of the bed
• Clear all infected debris at the end of the season

Plants it attacks