Penetration and colonization of oak roots by Armillaria mellea in Wisconsin

Abstract

The level of Armillaria mellea activity on root systems of living and herbicide-killed oâks was assessed. Epiphytic rhizomorphs were almost always present on living and dead oak roots. After an oak was killed or completely defoliated, A. mellea usually penetrated directly through the root-collar bark and spread rapidly in the cambium. Sapwood in the root collar and main lateral roots was colonized within 2 years. The production of thizomorphs from this region was assessed on trees that had been killed by herbicide sprays 2 to 14 years before sampling.