Alder phytophthora in Poland: occurrence and plants colonization.

Common alder (Alnus glutinosa) decline has been observed in Poland during the last 6 years. Alder Phytophthora was recorded, however, only from one sampling area in the middle of the country. Species of Armillaria, Fusarium, Mucor, Penicillium and Trichoderma were also isolated from diseased trees. Inoculation of alder stem parts, leaves and seedlings with Phytophthora isolates resulted in the development and spread of necrosis. Studies will be continued in the nearest years.