Keep an Eye out for Powdery Mildew

This time of year, you may notice a white, powdery looking growth on fruit, vegetable plants or ornamental plants in your garden. What is it? It could be powdery mildew.

Powdery mildew is caused by several different fungi that may attack plant leaf surfaces, shoots, fruits, and flowers. There are several species of powdery mildew; all are spread by wind and thrive in shady areas when temperatures are between 60-80 °F. The fungi attack both new and old foliage, and can be a problem on certain plants. The disease usually occurs first on new leaves, before spreading to older parts of the plant. This is why over fertilizing worsens powdery mildew. 

Ornamental Plants

Many woody and herbaceous plants are affected. Of special concern are rose, crape myrtle and sycamore, which can be seriously harmed by this disease. You can read in detail how to prevent and control this disease on ornamentals in the UC IPM publication Pest Notes: Powdery Mildew on Ornamentals.

Fruit and Berry Plants

Powdery mildew can be serious on woody plants like grapevines, caneberries and fruit trees. It can also affect strawberry plants. Read more about how it affects these plants in Pest Notes: Powdery Mildew on Fruits and Berries.

Vegetable Plants

A wide variety of vegetable crops are affected by powdery mildews, these include artichoke, beans, beets, carrot, cucumber, (cucurbits are very susceptible), eggplant, lettuce, melons, parsnips, peas, peppers, pumpkins, radicchio, radishes, squash, tomatillo, tomatoes, and turnips. Learn management techniques in Pest Notes: Powdery Mildew on Vegetables.