Forest fires influence the abundance of Armillaria root disease in ponderosa pine. J. T. Blodgett (1) and J. E. LUNDQUIST (2). (1) USDA-Forest Service, 1730 Samco Rd., Rapid City, SD; (2) USDA - Forest Service, 240 West Prospect, Fort Collins, CO. Phytopathology 94:S8. Publication no. P-2004-0051-AMA.
Forest tree diseases influence forest fires by changing stand structure and generating fuels, but little is known about how fires influence fuel-generating diseases. This field study was designed to examine the effects of fire on the abundance and potential spread of Armillaria root disease in ponderosa pine (Pinus ponderosa) forests. Five plots were established in an area of the Black Hills National Forest, SD that burned 3 years previous to this study. Each plot consisted of four subplots that varied in fire intensity (i.e., low, medium, and high fire intensity, and unburned). The abundance of Armillaria rhizomorphs on root collars increased (P < 0.001) as fire intensity increased. Pair-wise comparisons were significant among fire intensities except between unburned and low intensity subplots. Our results show that Armillaria can survive intense fires and can readily colonize roots of trees killed by fire.