A Glass of Milk for your Garden
Some organic gardeners have been using milk as a fungal control for decades, but it has only been in recent years that it has been looked at seriously as an effective and safe control of powdery mildew on some garden plants.
University of Adelaide research is exploring its potency. Grape vines have been the main crop that Peter Crisp used as part of his trials during a three-year research project, but he has also used milk spray on roses, zucchinis and tomatoes where it has been very successful in combating powdery mildew. A dilution anywhere between 1:5 and 1:10 milk to water is adequate, but if it is much stronger than that it can cause problems like sooty mould. Low fat milk is less effective than full cream milk, but the difference is not really significant. There are various compounds that are active in milk including the fats. The natural antibiotics present in milk, as well as the production of other agents during exposure to sunlight both act to reduce fungal infection.
For it to work effectively it must be used regularly at seven to 10 days intervals, or every fortnight if it is hot. The most important thing is to get a good even coverage over all of the leaves. One of the great advantages of milk fungicide is that you don’t need any protective gear for spraying.