VIEW ARTICLE

Fusarium oxysporum f. sp. perniciosum on Fusarium-Wilted Mimosa Trees. R. J. Stipes, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061; P. M. Phipps, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061, Present address of junior author Department of Plant Pathology, North Carolina State University, Raleigh, N. C. 27607. Phytopathology 65:188-190. Accepted for publication 30 August 1974. DOI: 10.1094/Phyto-65-188.

The presence of Fusarium oxysporum f. sp. perniciosum was determined in 1,200 lenticels of 20 Fusarium-wilted mimosa trees (Albizia julibrissin) that became symptomatic either 1-2 years before, or during the observation period. F. oxysporum was isolated and identified in culture from 38, 83, and 79% of lenticellar tissues from trees that exhibited symptoms at the time of sampling, and 1 or 2 years previously, respectively. About 90, 85, and 96% of these cultures, respectively, produced typical foliar symptoms of Fusarium wilt on root-dip-inoculated greenhouse seedlings, thereby confirming the identity of the fungus as F. oxysporum f. sp. perniciosum. Two of 240 lenticels from asymptomatic trees yielded the pathogen. Many lenticels in which sporodochia of a Fusarium sp. were observed were located on the underside of branches. The high incidence of the pathogen in lenticels of these diseased trees constitutes a new report. These findings suggest that lenticellar sporodochia may function as major sources of inoculum from which epiphytotics may occur, especially after periods of warm, humid weather that stimulates sporulation. Accordingly, we emphasize the importance in disease control of prompt destruction of symptomatic trees.