Cobweb mold

Cladobotryum mycophilum is a fungal pathogen responsible for the disease known as cobweb mold in mushroom farming. It is a specialized mycoparasite that exclusively attacks cultivated mushrooms, causing rapid tissue degradation and significant economic losses by covering the mycelium and fruiting bodies with a dense fungal mat.

The primary host for this pathogen is the white button mushroom (Agaricus bisporus). The disease affects all stages of mushroom development, starting from the small pinheads to fully grown mushrooms, and also spreads across the casing layer, effectively choking the growth of the mushroom mycelium beneath it.

Early symptoms appear as a delicate, white, cobweb-like growth spreading across the casing soil. As the infection progresses, this growth becomes thicker and turns greyish, pink, or brownish. The infected mushrooms become soft, deformed, and eventually undergo a wet rot, which often produces an unpleasant, earthy smell.

The development of the mold is highly dependent on environmental conditions, particularly high humidity (over 90%) and poor air circulation. Spores of the fungus are easily dispersed by air currents, splashing water during irrigation, contaminated tools, clothing of workers, and common mushroom flies, making it difficult to contain once established.

Management and prevention focus on maintaining high standards of farm hygiene. This includes the effective pasteurization of casing materials, regular ventilation, and moisture control to prevent stagnant air. In case of an outbreak, affected areas should be immediately isolated and treated with selective fungicides, or physically removed with the surrounding casing material to prevent further sporulation.