We’ve had very mild weather in the last few weeks. Some parts of Melbourne have had double their monthly average rainfall. This has been ideal conditions for fungal infestations in the veggie patch. Powdery mildew and other fungal infections are quite common and almost inevitable towards the end of the growing season. You might notice it particularly on zucchinis, pumpkins and other cucurbit crops. This year it has presented particularly early. Our zucchinis turned white in a matter of days recently. Even our basil has some black spot on it (so we quickly harvested as much as we could and turned it into basil pesto). So far our tomatoes are looking very healthy and strong and are not showing any sign of fungal infection. Hopefully the warm, dry week ahead will help to slow the progress in diseased plants.
I don’t normally treat veggie with these sort of diseases. It’s often better to just remove any diseased parts. When the plant has become overwhelmed, remove it completely.
It is fine to put affected leaves into the compost or worm farm. The fungus is a naturally occurring pathogen in the garden. So you wont be adding to the fungal load in any significance.
Like most things, prevention is better than cure. Reduce humidity in the garden by encouraging airflow. Avoid watering the leaves of susceptible plants. Instead, concentrate the water onto the soil underneath them.