The effect of treatment duration with Trichoderma harzianum fungus on the biopreservation efficacy of beech wood against white rot

Biological protection is one of the rather new and environmentally friendly methods of wood protection, in which living microorganisms have replaced chemical substances. This research was carried out with the aim of investigating the biological protection of beech wood against the white rot fungus (Trametes versicolor) using Trichoderma harzianum. For this purpose, the antagonistic ability of Trichoderma against wood rotting fungus was evaluated in dual culture medium as well as on wood. Trichoderma was incubated on wood samples in two time periods of four and eight weeks, and then samples were exposed to white rot for 16 weeks. The dual culture test proved the antagonism of Trichoderma against wood-destroying fungi, in a way that after 14 days, Trichoderma had not only prevented the spread of T. versicolor hyphae, but also overgrew on its mycelia. Cellulase enzyme assay showed that this isolate of Trichoderma had little ability to secrete this enzyme, and for that reason, sample weight loss due to fungal treatment was neglectable; a result that was also confirmed by infrared spectroscopy. The duration of wood incubation with Trichoderma was an important factor in the efficiency of treatment: increasing the time by one month significantly reduced weight loss of treated samples from 15% to below 1%, while the weight loss of the control samples was more than 30%. It can be concluded that the long-term treatment of beech wood with Trichoderma does not have a destructive effect on the wood and protects it against the white rot. Therefore, it is suggested to use this type of biological agent as a pretreatment of beech wood or to combine it with other preservative materials.