Powdery mildew, caused by the fungus *Erysiphae polygoni* (also classified under the subphylum Erysiphe of the Ascomycota phylum), is a widespread plant disease affecting over 60 species across 13 different plant families. This pathogen is an obligate parasite, meaning it cannot survive outside its host, and it exhibits physiological differentiation, which allows it to adapt to various environmental conditions. The infection primarily occurs during the anamorphic phase, where the fungus produces conidia that lead to visible symptoms on the plant.
In the field, the most noticeable signs of the disease are white, powdery spots on the leaves, formed by spores, conidiophores, and mycelium. These spots spread rapidly, covering large areas of the foliage. In severe cases, a thick layer of white powder can be seen on the leaves. As the disease progresses, the infected leaves begin to yellow, wither, and eventually fall off, weakening the plant and reducing its productivity.
The pathogen survives the winter in cold regions within closed, protective structures called chasmothecia, which remain on the ground. In the following spring, these structures release ascospores that are carried by wind to new hosts. Once infected, the fungus produces conidia, which further spread through air currents, continuing the cycle of infection. The disease thrives in shaded, warm, and humid environments, but in arid conditions or when plants are weak due to poor growth, the infection can become more severe.
To manage powdery mildew, several fungicides are recommended. These include 25% triadimefon diluted at 2,000 times, 45% Dakein WP at 800–1,000 times, 47% Garnett WP at 800 times, 70% thiophanate-methyl wettable powder at 1,000 times, and 50% sulfur suspension at 200–300 times. Applications should be made every 7–10 days, with a total of 2–3 treatments typically required for effective control. Early detection and consistent spraying are key to preventing the spread of the disease.
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