How do I stop powdery mildew spreading to other plants?


Hello Tui, last summer I had white mildew on my zucchini plants which also transferred to other plants in the garden. How do I stop this from happening?

Marilyn Griffiths


Hi Marilyn,

Unfortunately zucchini (courgette) plants are susceptible to powdery mildew, it is hard to stop the spread to other plants, some are more susceptible than others to this common fungal disease. There are a few things that can be done to try and reduce the incidence of powdery mildew in your zucchini crop such as making sure your plants are well spaced and have good air circulation so the conditions surrounding the plants are not ideal for the fungus to multiply. There are organic fungicide sprays to help reduce the incidence of mildew that can be sprayed throughout the season, look for natural potassium bicarbonate (not bicarbonate of soda). Remove and destroy infected plant material by placing in the rubbish or burning, do not compost infected plant material as this helps the spread. Avoid overhead watering, water around the base of the plants and not the leaves. Plant disease resistant varieties, check out seed supplier catalogues for varieties that are resistant to powdery mildew. Once the plants get mildew they are good for another couple of weeks and are then best removed, plant a late crop of fresh plants if it isn't too late in the season. 

The Tui Team 

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