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Disease Detection and Losses

Incidence, Severity, and Growth Effects of Heterobasidion annosum in Unthinned Loblolly Pine Plantations. R. S. Webb, Former graduate research assistant, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061; S. A. Alexander(2), and J. M. Skelly(3). (2)(3)Assistant professor, and professor, respectively, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061. Phytopathology 71:661-662. Accepted for publication 23 November 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-661.

The root systems of 648 loblolly pines in high and low hazard unthinned plantations in Virginia were mechanically excavated and examined for the incidence and severity of Heterobasidion annosum root rot. Radial increment growth at diameter breast height (1.4 m) was determined for the 10-yr period prior to excavation for each tree. Of the 348 trees observed in high hazard plantations, 8.3% were infected by this pathogen, while 3.3% of the 300 trees observed in low hazard plantations were infected. Overall disease incidence and severity were minor among trees from either plantation hazard type. Duncanís multiple range analysis detected no significant differences (P = 0.05) in radial increment growth between trees infected and uninfected with H. annosum (P = 0.5). Implications for management strategies are discussed.