Powdery mildew affects squash plants, spreads rapidly, and will travel all over the garden. In addition to squash plants, it will afflict any number of veggies, including: artichokes, cucumbers, eggplant, lettuce, melons, parsnips, pumpkins, and gourds So if you discover powdery mildew on your squash, keep any eye on other plants in the same family, cucurbits, and start treating them straight away. Disinfect any tools after working around cucurbits. If you use a tool around summer squash, for instance, disinfect the tool before working around cucumbers. If the tool isn’t disinfected properly the powdery mildew spores will be passed from one plant to the other. Disinfect tools with full strength vinegar or a solution of one part bleach to nine parts water.
Powdery mildew thrives in moist conditions so allowing the leaves to remain damp overnight can increase the likelihood of powdery mildew. It is better to water the soil around the plants and avoid getting the leaves wet.
You will need to prune the leaves that are heavily infected and remove the debris from the garden. Please remember to bring your own bag or use one of the take home trash bags, ( found on the shed door or attached to one of the compost bins). Please do not place diseased vegetation in the compost bins.
To successfully kill powdery mildew on the leaves, you need to act at the earliest sign of infection. One of the best organic treatments is a solution of milk and water sprayed on the leaves.