Discoloration of pressure impregnated wood caused by Amorphotheca resinae
F Rune, A P Koch
Amorphotheca resinae Parbery with the anamorph Cladosporium resinae (Lindau) von Arx & de Vries is a cosmopolitan fungus known from aviation kerosene, hydrocarbon contaminated soil and creosoted timbers. In Denmark it causes heavy discoloration on wood treated with waterborne chromate-containing preservatives e.g. CCA-oxide type. The teleomorph produces small spherical fruitbodies widespread on the wood surface causing a more or less black discoloration, while the numerous, dense, conidial heaps of the anamorph appear as irregular greyish-brownish blotches. A survey has shown that both stages appear on freshly CCA-impregnated wood during outdoor storage on all surfaces except on the ends. Stacking with e.g. 15 mm sticks restrains, but does not prevent the problem, and planed as well as sawn surfaces are attacked. On account of its extreme pH-tolerance (from pH 2-9) and its exceptional tolerance towards copper-chromate fungicides, the spores may germinate and the infection take place shortly after the impregnation, and even before fixation of the preservative is completed. The high capacity to grow on impregnated timber mostly increases the spore-count and hence the infection potential on the storage site. Attempts to use different types of additives or surface treatment with mould specific fungicides have not been entirely successful.