Pest of the Month - Powdery Mildew

What's it look like?

A powdery grey coating appears on the underside of leaves and eventually spreads to upper side and stems of the plant. The older leaves may turn yellow and die. Sunburn on leaves can happen in hot weather.

What it attacks

Melons, cucumbers, pumpkins, zucchini, marrow and squash, especially in warm and humid weather.

What to do before it arrives

• Install a drip system irrigation. Fungal spores are spread by irrigation water falling on unaffected leaves.
• Choose disease resistant varieties - read your plant labels and seed packets carefully.
• Make sure there's good air circulation around plants.
• Spray a preventative spray of diluted milk (1 part to 9 parts water) or chamomile at least every fortnight.
• Check the underside of leaves for first evidence of fungus growing.

Source: University of Minnesota

What to do if you already have problems

• Remove any infected leaves as soon as you see it occur. Do not compost.
• Remove plants if they're overcrowded. Poor air circulation can increase the problem.
• Use milk or chamomile spray and apply it every couple of days until it's under control. Then keep up a preventative spray every 10 to 14 days. Reapply after rain.
• Practise crop rotation.