Got Powdery Mildew? Get Milk!
Now is the time to be concerned with Powdery Mildew(PM) – a fungus that appears on the leaves of vines such as cucumbers, squash, zucchini , pumpkin, and watermelon. PM looks like white powdery splotches (see photo on the right) and typically shows up on the lower and inner leaves of plants.
By covering the surface of leaves, PM reduces the amount of photosynthesis that takes place, as well as infiltrating and damaging the leaf itself. It is rarely fatal for a plant, but can reduce the plants vigor – making it more prone to other pests and diseases – and can potentially impact the quality and quantity of your harvest. Different types of PM actually attack a wide range of landscape plants, but it only becomes problematic when the conditions are right.
PM can build up to damaging levels when your plants are not getting enough sun, air flow or humidity stays high for prolonged periods. Take note of which plants seem especially prone to PM and consider planting them in a different spot next year. But that doesn’t help you much right now, does it?
PM control is pretty simple. By removing and disposing of diseased foliage and thinning the vines to increase air circulation, you’re almost there. After that, a study published in Crop Science (Wagner 1999) showed that weekly applications of skim milk protected against PM as well as synthetic fungicides! Mix one part skim milk (make sure it’s skim milk to reduce the risk of damaging your plants) with 9 parts water, and cover the foliage once a week. PM is rarely harmful in the well-tended garden. Just make sure you keep a keen watch, and act as soon as you see symptoms.