How to deal with mildew on courgette plants
Organic gardener Sally Smith answers your questions about what to do if you have mildew on your courgette leaves and how preparation is key to avoiding it in the first place. If you have a similar problem with your courgettes, share your experiences in the comment section below.
Wendy Abbott asks: My courgettes have suddenly developed mildew. Will this damage the plant and affect the production of courgettes? How can I treat it organically?
Answer: Powdery mildew very commonly affects courgette plants at this time of year and later in the season. Cool night temperatures following warm dry days and dry soil conditions all favour development of this fungus; they are big leafy plants and pull lots of moisture from the soil. From an organic perspective as well dealing with the problem now try and make a note of any growing conditions that may have contributed to the problem this year and aim to rectify those in the future. First of all look to your soil conditions, is your soil free draining and not very moisture retentive? Is your veg plot enclosed without free air movement? Are plants growing too close together? Do you have a crop rotation plan? Soil preparation before planting is key to avoiding this problem in the future, dig in plenty of organic matter in spring and ensure plants are well watered in dry weather.
For now though, remove the worst affected leaves and compost them (this is fine as the fungus is not going to survive composting). Really drench the soil and keep up watering especially in dry spells. Mulch the soil with grass clippings or compost to retain moisture and especially if you are going away. Spraying weekly with a proprietary potassium bicarbonate spray (available from the Organic Gardening catalogue) may help to combat the fungus too, it isn't cheap to buy but may be worth it if the plants continue cropping for some time. But don't expect miracles, once cooler nights set in towards the end of August and September, the fungus may well return and then it is time to dig them out and consign them to the compost heap.