What is Powdery mildew in tomato?
Yield and fruit quality can be reduced by powdery mildew because the disease can develop quickly, and severely affected leaves are killed. Powdery mildew causes white powder to form at base, the leaves, buds and blossoms on crops. This dust resembles talcum powder as well as causes distortion of leaves, yellowing of leaves and rapid leaf fall. Mildew can destroy the look of one’s plants, and may ultimately decay and destroy plants.
Causal organism: Leveillula taurica and Oidium lycopersicum
Initially it appears as light green to yellow blotches or spots that range from 1/8 to ½ inches in diameter on the upper surface of the leaf. The spots eventually turn brown as the leaf tissue dies. The entire leaf eventually turns brown and shrivels, but remains attached to the stem. A white, powdery growth of the fungal mycelium is found on the top of leaves
Removing old leaves from the bottom of plants reduces disease from both fungi, often to the extent that no other control measure is needed. If symptoms develop early, multiple, early applications of wet table sulfur or dusting sulfur will prevent new infections. Sulfur should be used with caution on young foliage at temperatures above 90°F; read and follow label directions.Applications of other contacts such as potassium bicarbonate products and oil sprays will kill the existing mycelium and spores on the leaf surface and are most effective when disease is in early stages.
Photo source : http/www.longislandhort.cornell.edu