Choice tests and neighbor effects during fungal brown rot of copper- and non-treated wood

In previous work, a 'choice' test was used to test wood durability in mixtures of wood types. Results demonstrated that a filamentous fungus (Gloeophyllum trabeum) made a 'choice,' degrading white pine significantly less when less-durable woods were readily available. For this experiment, we substituted white pine with copper-treated pine and used three fungi (G. trabeum, Serpula himantioides, and Wolfiporia cocos) representing a range of copper tolerances. Southern pine blocks treated commercially with micronized copper azole or treated in-house using copper ethanolamine were used as treated wood substrates. Trials were soil-block tests, using two-block combinations to include non-treated, non-durable pine or as single-block treatments. After 12 weeks of decay, copper tolerance by S. himantioides and W. cocos was evident while G. trabeum was not copper tolerant. Availability of non-durable pine blocks, however, had no effect on decay in copper-treated wood. This contrasts with our past results using white pine. The reason for the discrepancy may relate to fungal mechanisms of copper tolerance (e.g., constitutive oxalic acid secretion) which may differ from mechanisms to overcome extractives in white pine. More fungal research using choice trials to assess these 'neighbor effects' is logical, given increased use of mixed, composite, and hybrid materials.