Evaluation of Trichoderma spp. as a biocontrol agent against wood decay fungi in urban trees

Laboratory and field tests were performed to establish the potential of Trichoderma spp. as a wound treatment for biological control of wood decay fungi in urban trees. A selection of Trichoderma species were tested in dual culture and interaction tests in wood against four basidomycetes Ganoderma adspersum, Ganoderma lipsiense, Inonotus hispidus, Polyporus squamosus and one acomycete Kretzschmaria deusta. Hyphal interactions were observed by scanning electron microscopy (SEM). The effect of Trichoderma spp. on wood colonization and degradation of wood decay fungi were quantitatively measured by dry weight loss of wood and qualitatively by histological studies. Trichoderma atroviride (T-15603.1) was consistently and highly competitive against most wood decay fungi with the exception of Polyporus squamosus which showed resistance towards antagonism in laboratory tests. Field experiments with T-15603.1 were carried out at different locations and hosts. A total of 159 angiosperm trees and 1431 wounds from six different species (Platanus × hispanica, Acer pseudoplatanus, Tilia platyphyllos, Populus nigra, Quercus rubra, Robinia pseudoacacia) were treated with different conidial suspensions. In comparison to control wounds, T-15603.1 induced a highly significant (P < 0.001) preventive effect (82.3%) against the selected wood decay fungi. Monitoring results with RAPD-PCR showed that the conidial formulation of 0.1% urea and 0.2% glucose combined with a humidity storing gel as a carrier substance enhanced significantly (P < 0.001) the germination rate, conidial viability and therefore the establishment of T-15603.1 in the wood substrate. The results demonstrate that T-15603.1 can be successful following application as biological wound treatment against wood decay fungi on urban sites.