Alder disease

Caused by fungus – alder phytophthora (Phytophthora alni)

The alder phytophthora fungus (Phytophthora alni) is common throughout Europe, but it had not spread in Latvia and Lithuania until 2016. It mainly affects black alders, less often white alders. Phytophthora-infected trees have smaller leaves than healthy trees, black spots form on the bark near the base of the trunk up to 3 m high. Sometimes the leaves turn yellow and the crown of the tree becomes thinner. As the disease progresses, trees usually die. If black alder trees grow in flooded areas, fungal spores enter the water and spread the disease.