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The leaves on my zucchini plants are turning white and dying

Mildew-eating Ladybird Powdery mildew is caused by several species of microscopic fungi, some of which attack a wide range of plants and others are more specific. Symptoms begin with the appearance of small, isolated white spots on foliage which increase in size and coverage. Young leaves can become distorted, curled at the edges or puckered. Sometimes the entire leaf can be covered, such as with pumpkin, zucchini, cucumber and melon, killing the leaf. Infections can spread to fruit, flowers, soft stems and buds and sometimes develops into a felted coating.

Powdery mildew develops rapidly on plants during warm, humid weather. Once spores have germinated they continue to grow in very dry weather. Unchecked, this disease can spread rapidly and significantly reduce crops and spoil flowers.

 

Control:

  • Dilute one part organic cows milk with between five to ten parts water. Stronger solutions can encourage other fungi, like sooty mould, to develop. Spray the solution during the cool of the morning to reduce the risk of foliage being burned in intense sunshine before it dries. Wet both sides of leaves and stems until it begins to drip off. Reapply after rain or irrigation, which rinses this non-persistent solution off. It is most effective when applied in the early stages of infection;

milk:

  • is the nutrient fluid secreted by the mammary glands of female mammals;
  • is variable in its components, depending upon the species, but contains unsaturated fat, protein and calcium;
  • it is believed that the antibiotic qualities of pasteurised milk impede the germination of powdery mildew spores. This remedy was discovered by chance in Brazil. Initially cows milk was found to be very effective at preventing powdery mildew on the cucumber family (Cucurbitaceae) which includes gherkin, marrow and choko. Trials at the University of Adelaide have subsequently showed its efficacy on roses, zucchini, tomato and grape.

Supporting strategies

  • Grow mildew-resistant varieties of plant where available;
  • Water during the morning so foliage dries out quickly, reducing the risk of spores germinating;
  • Water potted plants and seedlings at the roots, keeping foliage dry, reducing the risk of spores germinating;
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