Biological control of internal decay in creosoted distribution poles
The use of biological agents both in the form of the pure cultures of Trichoderms plysporul, T. harzianum and Scytalidium FY strain and a commercial product in which all three are included (Binab FYT pellets) to control Lentinus lepideus both in the laboratory and in the field was investigated. Autecological studies with the three control organisms show that L. lepideus (identified as a primary decay fungus in creosoted poles from the literature and from studies of poles in Scotland) was overgrown and lysed or lysed from a distance by all control fungi when grown on the same agar plates. Other organisms resident in poles produced either a similar result or produced a stalemate/neutral reaction. When grown in situation which prohibited soluble metabolite contact, or when control organisms in wood blocks were killed and the blocks thoroughly leached, volatiles produced by Trichoderma spp. caused lysis of L. lepideus and residues of both Trichoderma spp. and Scytalidium FY strain were shown to inhibit growth and decay by L. lepideus. Both Trichoderma spp. and Scytalidium FY strain produced water soluble antibiotics effective against L. lepideus. Volatiles of Trichoderma were shown to be more effective against L. lepideus and Fomes annosus but not against other decay fungi which were tested. Field studies undertaken over a three year period on more than 200 poles showed that Trichoderma was easily established in poles and that this was not limited by pole moisture contents. Nutrient transfer was not found to take place from soils to poles. Pole age, decay status and presence of previous remedial treatment did not seem to prohibit Trichoderma establishment which was shown to be present in over 90% of poles inoculated with FYT pellets. Scytalidium was never isolated from either pellets or poles. Extensive sectioning of poles showed that the spread of Trichoderma within poles was variable and was linked to the quantity o other organisms resident in the poles. The incidence of L. lepideus in poles was reduced by 45% by either prior or subsequent inoculation with Binab FYT pellets. Microbiological and storage conditions of the commercial product were monitored during the project and the potential use of biological control as one other form of preservation which may protect creosoted wood in service as distribution poles is discussed.
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