Incidence of Heterobasidion annosum and Other Root-Infecting Fungi in Residual Stumps and Roots in Thinned Slash Pine Plantations in Florida. E. L. Barnard, Forest Pathologist, Insect & Disease Section, Bureau of Forest Management, Florida Division of Forestry, FDACS, Gainesville 32602. S. P. Gilly, and W. N. Dixon. Former Biologist, and Forest Entomologist, respectively, Insect & Disease Section, Bureau of Forest Management, Florida Division of Forestry, FDACS, Gainesville 32602. Plant Dis. 75:823-828. Accepted for publication 16 February 1991. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1991. DOI: 10.1094/PD-75-0823.

Heterobasidion annosum was confirmed to be present in 17 of 30 thinned slash pine (Pinus elliottii) plantations in north and north central Florida. Symptoms of possible root disease were detected on only 8% of 1,840 live trees, 14% of 2,204 stumps, and 13% of 811 dead trees examined. Although H. annosum was isolated from 47% of root and wood samples with white stringy rot, this symptom was observed in only 0.6, 5, and 4% of the live trees, stumps, and dead trees, respectively. Resin-soaking and/or staining was observed in 6, 2, and 7%, respectively, of the live trees, stumps, and dead trees, and H. annosum was isolated from only 10% of root and wood samples exhibiting this symptom. Inonotus circinatus was isolated from 9% of root and wood samples displaying resin-soaking and/or staining. Other root and stump infecting fungi detected were Armillariella tabescens, Phaeolus schweinitzii, Leptographium procerum, Fomitopsis palustris, Monascus floridanus, and a Ganoderma sp. A. tabescens was a predominant root and stump colonizer in four of the 30 plantations and sometimes occurred in the same roots as H. annosum. H. annosum was confirmed present in only two of 11 plantations surveyed with the “annosus sampling procedure,” whereas the presence of the pathogen was confirmed in six of the same 11 plantations via a 20-unit plantation-row plot method. In one plantation, H. annosum was undetected using the annosus sampling procedure, despite the fact that the fungus was isolated, respectively, from 33, 83, and 60% of the live trees, stumps, and dead trees sampled via the plantation-row plot method.