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Etiology

Early Sugar Maple Stem Discoloration and Microorganism Invasion in Simulated Wounds of Felling and Fire Scars. J. T. Basham, Forest Pathologist, Department of the Environment, Canadian Forestry Service, Great Lakes Forest Research Centre, Sault Ste. Marie, Ontario, Canada P6A 5M7; Phytopathology 68:1693-1699. Accepted for publication 5 June 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1693.

A total of 427 stem wounds were inflicted on 172 Acer saccharum trees, the majority by means of drawknives inserted at varying depths to simulate blazes and mild-to-severe felling scars. Heat applied from a propane torch simulated fire wounds. The wounds were of two basic sizes, and were inflicted in spring, summer, and autumn. The nature and rate of development of discolored wood that appeared beneath the wounds varied with the age, type, size, and severity of the wound, and the season in which they were inflicted. The most obvious histological features of discolored wood were assessed. The wound discoloration frequently was separated from clear wood by a pronounced dark greenish-brown zone. The most intense discoloration generally was associated with the most severe wound types. Few Hymenomycetes were isolated from the discolored wood in the 8 yr following wounding; however, non-hymenomycetes were frequently isolated, particularly Phomopsis sp. B and Alternaria tenuis. The identity and frequency of isolation of microorganisms varied widely with wound type, size, and severity, the time since infliction, and the season of infliction. All of these factors may be relevant in assessing potential quality reductions in sugar maple crop and amenity trees by the subsequent activity of decay-causing Hymenomycetes.