Ash leachates from recently burned litter in a ponderosa pine forest in central Oregon were tested for their effects on growth and development of Armillaria mellea in culture. Two isolates were used: one from an infected western hemlock and the other from an infected ponderosa pine tree. Colonies developing from agar discs containing mycelia of the hemlock isolate and grown on a solid agar-base medium supplemented with leachates extracted from 1, 5, 10, or 20 grams of ash per liter of media had significantly lower dry weights than colonies grown on nonsupplemented medium. There were no significant differences among leachate concentration in dry weight colonies developing from aerial rhizomorph tips of the hemlock isolate, although these colonies had significantly greater dry weights at each concentration than did those developing from mycelia. Some colonies started with aerial rhizomorph tips of the hemlock isolate developed mycelial fans similar to those found in trees infected with A. mellia. Colonies started with mycelia of the pine isolate and grown on media supplemented with 5 grams of ash leachate had significantly less growth than control or cultures grown on media with 10 grams of ash leachate.
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