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Which fungal disease is especially harmful to pine trees?

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Stone pine trees with rounded canopies stand amid low shrubs and flowering yellow bushes in Donana National Park, Huelva province, Andalusia, Spain. — Pine A stand of stone pines (*Pinus pinea*) in Doñana National Park near Seville, Spain.

A particularly harmful fungal disease for pine trees is blister rust, which is caused by rust fungi belonging to the genus Cronartium.1

This disease affects pine trees of all sizes and ages, causing the development of external blisters on the trunk from which fungal spores are released. As the infection spreads, it weakens the tree's stems and retards growth; while it can be lethal on its own, it also leaves surviving trees highly vulnerable to secondary attacks by bark beetles.1

A notably virulent form is white pine blister rust, caused by the fungus C. ribicola, which has significantly depleted populations of five-needled (white) pines across North America since its introduction around 1900. Because these fungi require an alternative host to complete their life cycle, they cannot spread directly from one pine tree to another. Management strategies to combat the disease include the use of fungicides, strict sanitation measures, and the cultivation of resistant tree varieties.1