Despite our best efforts to keep the leaves of our plants dry, the zucchini plant has developed powdery mildew.
Since we use an irrigation system to water our crops, the leaves of the plants do not get wet. But there’s been plenty of rain this spring and summer to drench the leaves and cause powdery mildew.
The fungal disease occurs in a variety of plants, and a powdery white mildew covers the surface of the leaves, causing the leaves to yellow and dry out.
Older leaves are infected first. The mildew competes with the plant for nutrients and reduces crop yields. According to the National Gardening Association, this fungal disease occurs across North America and can even cover fruits and pods of crops.
If the problem is advanced, it can kill crops because the mildew will interfere with plants’ ability to photosynthesize. The disease usually develops late in the season on mature plants, according to the NGA.
Powdery mildew can occur in both humid and dry weather; with the hot, humid summer we’ve had, it isn’t surprising to see the disease infect one of our crops.
The Organic Gardener recommends avoiding watering leaves when hand-watering to prevent the disease. If crops in your garden have been infected with powdery mildew, remove the badly infected leaves, and apply GreenCure as a root drench or a foliar spray as a preventative.