Powdery mildew is a common problem that affects a variety of crops, including pumpkins and winter squash. It causes a white powdery layer to appear on the plants’ leaves and stems, and can result in reduced yields, shorter growth times, and pumpkins that have little flavor. It does not usually kill mature pumpkin plants, though if left untreated, the disease can spread rapidly and weaken the plant to the point that it will not bear fruit.
Infected plants tend to produce a thick, powdery layer on the leaves and stems of cucurbits such as pumpkins and squash. The powdery mildew spores travel in the air and can infect neighboring plants.
Resistant varieties are available that can help prevent or minimize the effects of powdery mildew. They contain genes that suppress the fungus, making them more resistant to the disease.
Fungicides are also effective at controlling the disease. They have to be applied to both the foliage and the soil around the plant. If you decide to use a fungicide, choose one that is designed for edible crops and follows the manufacturer’s directions. Apply the fungicide in the early morning to make sure that all areas of the plant are protected.
Milk - This has been shown to be an effective mildew-fighting agent and can be used as a spray on infected pumpkin leaves. Mix equal parts water and milk in a spray bottle, and apply to the leaves once a week.
Water - Although it’s ironic that wet conditions are the most favorable for powdery mildew to form, water can wash away spores and prevent them from attaching to leaves. Be careful not to overwater, since this will only encourage the growth of the fungus.
Other ways to treat the disease include pruning off infected leaves, spacing plants far enough apart to ensure good air circulation and avoiding excess fertilization. If you are growing pumpkins in humid, warm zones, you should be extra vigilant with watering and avoiding over-fertilization.
Rotate your crops periodically to prevent the introduction of diseases and pests that may be difficult or impossible to control with conventional methods. For example, you should not grow the same crop for two years in a row, as cucurbits like pumpkins are highly susceptible to powdery mildew and can become infected from neighboring plants.
Alternatively, you can plant different cultivars of the same crop to prevent the risk of resistance developing. This method will also reduce the amount of time you spend managing this disease as the resistant cultivars are less likely to be infected.
In addition, if you do have resistant cultivars, you should monitor them carefully for signs of powdery mildew. This is especially true if you are using a fungicide.
If you are unable to manage the disease yourself, you can always consult a specialist for advice. Many garden centres and landscape companies offer expert help on tackling the disease. They will be able to recommend a fungicide for you, and can even supply it at your local garden centre.
