Powdery Mildew
Erysiphe spp., Podosphaera spp., Sphaerotheca spp., Golovinomyces spp., Leveillula spp.
Overview
A widespread fungal disease that forms a white to grayish powdery coating on leaf surfaces, stems, and sometimes flowers and fruit. Caused by various species of obligate parasitic fungi in the order Erysiphales.
Symptoms
White to gray powdery patches on upper leaf surfaces, stems, buds, and flowers. Leaves may yellow, curl, and drop prematurely. Severe infections cause stunted growth and reduced yields.
Environmental Conditions
Humid
Prevention
Plant resistant varieties. Ensure adequate air circulation and spacing. Avoid overhead irrigation. Prune to improve airflow. Apply preventive sulfur or potassium bicarbonate sprays.
Management
Apply neem oil, sulfur-based fungicides, or potassium bicarbonate at first signs. Remove and destroy infected plant material. Milk sprays (1:9 ratio) can be effective. Biological controls include Bacillus subtilis products.