Abstract
Trichoderma species previously isolated from fumigated Douglas-fir stumps were tested for the ability to control wood-staining fungi. Ponderosa pine wafers were inoculated first with spore suspensions of one of 146 Trichoderma isolates, then with a mixture of two wood-staining fungi (Ophiostoma piceae and Alternaria alternata). After 4 weeks the wafers were visually rated for discoloration caused by the biocontrol isolate or the stain fungi. - Many of the potential biocontrol isolates reduced or eliminated discoloration caused by the stain fungi, but some of these same isolates also discolored the wood. More than one-third of the biocontrol isolates reduced total discoloration to below 15 % of the wood surface. Most of these effective isolates were T. viride or T. virens. - Further screening of effective biocontrol isolates that cause the least discoloration is recommended, as is the use of these isolates in combination.