Root Disease, Longleaf Pine Mortality, and Prescribed Burning

A study was initiated at the Savannah River Site, New Ellenton, SC, to determine factors involved in decline of longleaf pine associated with prescribed burning. Pretreatment and post-treatment surveys were conducted on all treatment plots. Symptomatic trees were recorded by means of a crown rating system based upon symptom severity. Three years after prescribed burning treatments were initiated, mortality and numbers of symptomatic trees increased in the hot burn plots. Crown symptoms corresponded to tree physiological status determined by cambial sucrose synthase activity. Root pathogenic fungi such as Leptographium terebrantis, L. procerum, and Heterobasidion annosum were widespread throughout the study site, regardless of treatment. The Leptographium species were found to be pathogenic based upon inoculation experiments and H. annosum was observed to be involved in root infections and mortality. Histological studies indicated a high fine root mortality rate in the hot burn treatment. The decline syndrome on these sites is a complex of interacting factors and involves root pathogens, soil factors, root damage, and physiological