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Edaphic Factors Associated with the Incidence and Severity of Disease Caused by Fomes annosus in Loblolly Pine Plantations in Virginia. S. A. Alexander, Former Graduate Research Assistant, presently Post Doctoral Fellow, The Pennsylvania State University Fruit Research Laboratory, University Park, Blacksburg, 24061; J. M. Skelly(2), and C. L. Morris(3). (2)(3)Associate Professors of Plant Pathology and Physiology, respectively, Departments of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061, and Chief of Forest Insect and Disease Investigations, Virginia Division of Forestry, Charlottesville, Virginia. Phytopathology 65:585-591. Accepted for publication 23 December 1974. DOI: 10.1094/Phyto-65-585.

Twenty circular 0.08-hectare (ha) plots were established in thinned loblolly pine, Pinus taeda, plantations with ten trees on high- and low-hazard disease (Fomes annosus) sites. The incidence of F. annosus was determined by aseptically removing six chips from each of two roots per tree and incubating the chips on ortho-phenyl-phenol medium at 23 C for two weeks in the dark. Average disease incidence for high-hazard plots (138 trees) and low-hazard plots (129 trees) was 32.6 and 7.8%, respectively. The difference in diameter between infected and noninfected trees was significant (P = 0.05) on all plots and at P = 0.01 on low-hazard plots. Fourteen soil parameters were measured at depths of 10 to 20 cm. Sand, noncapillary pores, and bulk density were positively correlated with disease incidence; clay, capillary pores, field capacity, permanent wilting percentage, and organic matter were negatively correlated. Of the soil parameters measured, sand, porosity, organic matter, and field capacity had the highest correlation when compared with disease incidence. In undisturbed loamy-sand and sandy-clay-loam soil cores, conidiospores were washed to a depth of 9.5 cm and 0.5 cm, respectively. Percent root infection tended to increase with soil depth in high-hazard soils, indicating the possible association between porosity, spore movement, and root infections in sandy soils.

Additional keywords: root rot, losses, spread.