Causes of incipient rot and rot in regrowthEucalyptus diversicolor(karri) trees

Abstract

Eucalyptus diversicolor(karri) is the second most important commercial timber tree in Western Australia. Sawlogs from regrowth trees often have a discoloration in the heartwood that is more abundant than in sawlogs from mature trees. Other symptoms in regrowth logs include white rot, white pocket rot and brown rot. Fungal isolations and pathogenicity tests were conducted to determine whether this discoloration was incipient rot, and if so, what caused it and which rot(s) would eventually develop. A combined sample of 329 discs from recently felled trees and freshly cut scantling had discoloration in 48%, white rot in 14%, white pocket rot in 12% and brown rot in 4% of pieces of wood.Hymenochaete semistupposawas isolated from 22% of discoloured wood and 39% of white pocket rot samples.Stereum hirsutumwas isolated from 4% of discoloured wood and 13% of white rot samples. Koch's postulates in regrowth karri trees showed thatH. semistupposacaused extensive discoloration, with white pocket rot developing in the heartwood within 4 years, whileS. hirsutumcaused extensive discoloration, with white rot developing in both the heartwood and sapwood within 2 years. It was concluded that the discoloration was incipient rot, which would eventually develop into either white rot or white pocket rot.