Powdery Mildew

Powdery mildew is a disease caused in tomatoes by several species of fungi. It most commonly causes a white, powdery coating, but it can also manifest as yellow spots and necrotic areas, and the coating may be sparse or visible mainly on the underside of the leaves. The disease reduces the photosynthetic surface area and stunts growth. Leaf wetting is not necessary for infection, and conditions favorable for development depend on the specific pathogen species. It is advisable to remove the first infected leaves while the plant is dry, improve air circulation, and avoid excess nitrogen; any pesticide should be applied strictly according to the label instructions for tomatoes.