Sometimes a disease is more of a visual inconvenience than a functional inconvenience, and such is the case of powdery mildew. Easily identified as the powdery-looking blotches on your plants’ leaves, it tends to affect the Cucurbita family – squash, zucchini (courgettes), pumpkin (winter squash) and cucumber – and is caused by poor airflow and humid conditions.

While it can affect plants in the early stages, it is more common (almost inevitable) in the latter stages of a cucurbita plant’s life. When removing these plants from the patch in late summer and early autumn, it would be unusual not to have some powdery mildew affecting the leaves.

Although not commonly terminal to the plant in question, it can affect its ability to photosynthesise and therefore produce fruit, and is embarrassing for the plant when at public functions and dinner parties.

Optimal Conditions

Late spring, with its warm weather and humid conditions.


Circular, powdery-looking blotches on the tops of the leaves. It mostly affects the gourd family, as well as peas and beans.


Adequate spacing of plants and using drip irrigation, as surface water connecting with the leaf increases the probability of infection.


Cutting off affected leaves and culling overcrowded plants.


Apply a milk spray of 1 part full-cream (whole) milk to 10 parts water.

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