Powdery mildew

The causative agents of this disease are ascomycete fungi belonging to the genus Podosphaera, responsible for one of the most common plant diseases worldwide. These are obligate parasites that grow on the surface of plant tissues, feeding by inserting haustoria into the epidermal cells, which weakens the plant significantly.

These fungi have a wide host range, primarily infecting pome and stone fruits, such as apples and cherries, as well as berry bushes like gooseberries and black currants. The pathogen targets young leaves, shoots, buds, and fruits, often leading to severe stunting and distortion of affected plant organs.

Symptoms initially manifest as small patches of white, powdery mycelium that eventually cover entire leaf surfaces and shoots. As the Podosphaera infection progresses, the leaves may curl, turn yellow, and drop prematurely, while fruit set is often severely hampered, leading to total loss of quality in sensitive cultivars.

The disease thrives in moderate temperatures and high relative humidity. Unlike many other fungal pathogens, powdery mildew does not require free water or high rainfall for spore germination, allowing it to spread rapidly during warm, dry weather through wind-dispersed conidia.

Effective management strategies include the use of resistant crop varieties, pruning to improve airflow, and the application of fungicides. Preventive treatments with sulfur, triazoles, or strobilurins are essential for controlling the disease, particularly in high-density orchards where the climate promotes rapid secondary infections.