Abstract
A description is provided for Heterobasidion annosum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On coniferous trees, particularly Picea, Larix, Thuja, Tsuga; also less commonly on numerous dicotyledonous hosts (Koenigs, 1960). DISEASE: Butt-rot. Causing decay to roots and heart wood of living trees. A tissue-paper-like layer of mycelial felt, forming between the bark and wood, is lilac, pink or purple at first, but later turns red, red-brown or purple-brown. White pockets are formed in the red region of the wood, sometimes preceded by black specks. GEOGRAPHICAL DISTRIBUTION: World-wide in temperate regions (CMI Map 271, ed. 2, 1968). TRANSMISSION: Disseminated by wind-blown spores produced at all times of the year. Viable spores have been found airborne 70 miles from the nearest source (47, 3604), and in surface soil after 8 months (46, 13g). Also found in seed germination tests of Abies by Batko (38: 711). Spores may be introduced on nursery seedlings into disease-free areas (41: 260).