Powdery Mildew

Powdery mildew is a common disease on many types of plants. There are many different species of powdery mildew fungi (e.g., Erysiphe spp., Sphaerotheca spp.) and each species only attacks specific plants. A wide variety of vegetable crops are affected by powdery mildews, including artichoke, beans, beets, carrot, cucumber, eggplant, lettuce, melons, parsnips, peas, peppers, pumpkins, radicchio, radishes, squash, tomatillo, tomatoes, and turnips. Powdery mildews generally do not require moist conditions to establish and grow, and normally do well under warm conditions; thus they are more prevalent than many other leaf-infecting diseases under California’s dry summer conditions.