Disease Note.

First Report of Fusarium decemcellulare as a Pathogen of Mango in the United States. Randy Ploetz, University of Florida, 18905 SW 280th Street, Homestead 33031-3314. Aime' Vazquez, and David Benscher, University of Florida, 18905 SW 280th Street, Homestead 33031-3314. Plant Dis. 80:1207. Accepted for publication 22 July 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1207C.

For about 20 years, large galls have been observed on trees of mango, Mangifera indica L., in the USDA-ARS germ plasm collection in Miami, FL. They range to 45 cm in diameter, have rough, scaly exteriors, and are usually found on the main trunk or scaffold limbs. Cracks may penetrate the phloem and become necrotic, but the branch death associated with galls in Mexico and India has not been observed in Miami. Internal tissue from galls on the cv. Langra were surface disinfested in 70% ethanol (10 s) and 0.5% NaCIO (2 min), and submerged in molten potato dextrose agar (PDA) amended with streptomycin sulfate (100 mg L-1). Fusarium decemcellulare C. Brick was isolated from 5% of the tissue pieces. Salient features of the fungus included dark carmine-red pigmentation on the underside of PDA cultures, microconidia borne in false heads or chains, very large macroconidia (mean: 74.2 x 6.2 µm, range: 92 to 55 x 7 to 5.5 µm), branched and nonbranched monophialides, and slimy yellow sporodochia, ca. 1 mm in diameter. The fungus's teleomorph, Nectria rigidius-cula Berk. & Broome, was observed neither on mango tissue nor in culture. A monoconidial isolate was grown on PDA + yeast extract, and conidial suspensions and pieces of mycelium from the cultures were each used to inoculate 20 stems on potted plants of the cv. Tommy Atkins. Inoculation sites were cut to the cambium with a scalpel and covered with Parafilm for I week after inoculation. After 3 months, areas inoculated with conidia and mycelium both exhibited cracked and peeling bark. Most sites had a corky appearance and were hypertrophied, swelling up to 1.5 times the diameter of the subtending branch. Internally, the cambium was discolored 5 to 50 mm above and below the point of inoculation. F. decemcellulare was consistently isolated -from symptomatic cambial tissue distal to the wound site. In contrast, eight wounded, noninoculated sites on the same plants developed no external symptoms and minor vascular discoloration (mean total <2mm), and did not yield the fungus. Although F. decemcellulare has been previously reported to cause galls on mango in Mexico (1) and Venezuela (2), this is the first report of its pathogenicity on mango in the United Slates.