Publisher Summary Decaying wood presents unique opportunities for those interested in growth and interaction of fungi with one another to form populations and communities in natural substrata. This is because decaying wood is a spatially defined, bulky resource in which many of the fungi—especially those causing decay—frequently occur as single colonies, each occupying considerable volumes. Wood becomes decayed under a wide range of circumstances—namely, within the living tree, after felling or pruning in dead trunks, logs, stumps, and branches, and at almost any stage during its conversion and subsequent varied use by man. The process and rate of decay is generally influenced by innumerable factors—including the type of wood, its moisture content, its nitrogen content, treatment with preservatives, and temperature. This chapter explores the usage of decaying wood as a vehicle for understanding natural fungal populations and communities. The chapter focuses on the decay in dead or moribund natural woody substrata such as stumps, logs, trunks, and branches rather than in living trees or with timber converted for use by man and which have been variously treated or preserved.

Population and Community Structure and Dynamics of Fungi in Decaying Wood

Biological control of wood decay against fungal infection

Mould inhabitants of creosoted wood were tested for volatile activity against Lentinus lepideus and other basidiomycetes. Only Trichoderma spp. were shown to release volatiles which produced fungistatic effects on Fomes annosus and both fungistatic and fungicidal effects on two strains of Lentinus lepideus. Other basidiomycetes were largely unaffected by volatile production. The implications of these results with regard to the biological control of decay in creosoted transmission poles using Trichoderma spp. are discussed.

Control of growth of Lentinus lepideus by volatiles from Trichoderma

A total of 27 marine fungi was screened for evidence of interference competition and an index of antagonisra was calculated for each one. All of these fungi were grown in liquid culture and extracts were tested for antifungal activity. Extracts from four fungi, Leptosphaeria oraemaris, Arenariomyces trifurcatus, Monodictys pelagica and Remispora species showed antifungal activity. The biochemical basis for this activity was investigated leading to the identification of an antifungal sesquiterpene, culmorin, from L. oraemaris. The triglyceride fraction from both L. oraemaris and A. trifurcatus had antifungal activity.

The Biochemical Basis for Interference Competition among Some Lignicolous Marine Fungi

The antagonism of Trichoderma harzianum, Scytalidium album and an unidentified fungus (isolated from Monotropa hypopitys) against the root rot fungus Fomes annosus was studied in vitro and in vivo. Antibiosis was demonstrated on malt extract agar and on powdered wood. Competition between F. annosus and its antagonists was studied in stem discs and in living stems of Norway spruce. Effective antibiotics on agar and sawdust did not always bring about effective antagonism against F. annosus in stem discs or living trees. Factors such as growth rate of the antagonists in wood and their ability to invade the substrate during competition may influence the effectiveness of F. annosus suppression. The results from studies on antagonism in stem discs agreed with the results from tests in living trees. The frequency of penetrations through the wood cell walls was drastically lowered by the presence of the antagonists but was not closely correlated with the abundance of F. annosus.

Antagonism against fomes annosus. Comparison between different test methods in vitro and in vivo

In a survey of the fungi in heartwood of Douglas-fir poles, three conditions were observed: no fungi, unifungal cultures of Poria carbonica Overh. or related basidiomycetes, and a mixed microbial population. From some apparently sound wood cores, a species of Scytalidium was isolated, usually as a unifungal culture. This organism was distinguished by release of a water-soluble yellow pigment into the agar and production of dark spores as the colony aged. Strong antagonism of Scytalidium sp. to P. carbonica on malt extract agar was attributed at least partly to the production of an antibiotic substance by Scytalidium. There was no evidence of change in the mechanical properties of the wood or of injury to the wood cells as a result of Scytalidium growth. The xylan moiety in the hemicellulose was the preferred energy source observed. Wood chips permeated with this organism and then steamed were not damaged by an actively growing colony of P. carbonica.

Jacques L. Ricard

Papers

Inhibition of Poria carbonica by Scytalidium sp., an imperfect fungus isolated from Douglas-fir poles

Wood protection process