First Report of Fusarium subglutinans as a Cause of Late-Season Mortality in Longleaf Pine Nurseries. W. A. Carey, School of Forestry, Auburn University, AL 36849-5418. W. D. Kelley, School of Forestry, Auburn University, AL 36849-5418. Plant Dis. 78:754 . Accepted for publication 10 March 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0754C.
Fusarium subglutinans (Wollenweb. & Reinking) P.E. Nelson, T.A. Tousson, & Marasas was isolated consistently from diseased longleaf pine (Pinus palustris Miller) seedlings from two nurseries with extensive seedling mortality. Diseased seedlings came from 10-mo-old bare-root seedlings in Alabama (26% mortality, February 1991) and 7-mo-old containerized seedlings in North Carolina (47% mortality, November 1993). Pitch-soaked tissues characteristic of F. subglutinans infections (pitch canker) both in mature pines and in loblolly pine (P. taeda L.) seedlings were generally absent in longleaf pine seedlings. Infected tissues first appeared water-soaked without discoloration and then darkened as necrosis progressed. Symptomatic tissues were usually restricted to the interior of the bud (aboveground stem) and occasionally extended from there into the large primary root. Mycelium, polyphialids, and microcon-idia typical of F. subglutinans grew abundantly on the symptomatic tissues of dissected seedlings after 3 to 5 days in moist chambers. Wound inoculations with hyphae and spores of isolates from longleaf pine seedlings produced symptoms in longleaf seedlings similar to those observed in the nurseries and typical pitch-soaked tissues in loblolly seedlings. The distribution of infected seedlings within nurseries and observations of dissected seedlings in the laboratory suggest that infections require wounding and (hat insects are important wounding agents. Previously F. subglutinans was reported on seeds and younger seedlings of longleaf pine (I); this is the first report of damage to older seedlings.Reference: (I) G. B. Runion and R. I. Brack. Plant Dis. 72:872. 1988.