Residual Naval Stores Stumps as Reservoirs of Inoculum for Infection of Slash Pines byPhaeolus schweinitzii

Abstract

BLAKESLEE, G. M., and S. W. OAK. 1980. Residual naval stores stumps as reservoirs of inoculum for infection of slash pines by Phaeolus schweinitzii. Plant Disease 64:167. Signs and symptoms of Phaeolus schweinitzii infection, including root and butt rot, wind-thrown living trees, and dead standing trees, were observed in plantations of 10- to 22-yr-old slash pines in north-central Florida. The likely source of the pathogen is believed to be resin-impregnated (lightered) stumps remaining from naval stores operations. Phaeolus schweinitzii (Fr.) Pat. (formerly Polyporus schweinitzii Fr.) has long been recognized as a cause of brown cubical root and butt rot in numerous species of conifers. In general, the disease has been a problem only on mature or overmature trees, especially those with basal wounds such as fire scars (1,2,5,6). Damage has been reported, however, on young (20- to 25-yr-old) eastern white pines (Pinus strobus) on unfavorable sites (3,8), on 28-yr-old Douglas-firs (Pseudotsuga menziesii) in the eastern United States (4), and on intermediateaged (40- to 45-yr-old) eastern white pines in stands subjected to multiple thinnings (7). This paper reports the occurrence of root rot centers in unthinned, unwounded 10- to 22-yr-old plantations of slash pine (P. elliottii var. elliottii) in north-central Florida. Resin-impregnated stumps from past naval stores operations are considered the likely source of the pathogen. During the past several years, we have frequently observed sporocarps of P. schweinitzii in young (10- to 15-yr-old) and pole-sized (20- to 22-yr-old) plantations of slash pines in the flatwoods region of north-central Florida. These sites formerly supported low-density stands of large, old-growth longleaf (P. palustris) and slash pines that had been worked for naval stores. When these