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Infection of Defoliated Sugar Maple Trees by Armillaria mellea. Philip M. Wargo, Plant Pathologist, Northeastern Forest Experiment Station, U.S. Dept. of Agriculture, Forest Service, Hamden, Connecticut 06514; David R. Houston, Plant Pathologist, Northeastern Forest Experiment Station, U.S. Dept. of Agriculture, Forest Service, Hamden, Connecticut 06514. Phytopathology 64:817-822. Accepted for publication 4 January 1974. DOI: 10.1094/Phyto-64-817.

Manually-defoliated and insect-defoliated trees were inoculated with Armillaria mellea to determine the influence of time of season and frequency of defoliation on root invasion by the fungus. Insect populations collapsed and caused only light defoliation. This resulted in a low incidence of infection of trees by A. mellea and low tree mortality. Manual defoliation in June or July for 1 or 2 yr resulted in more infections and higher mortality than did manual defoliation in August. The incidence of infection was higher when trees were defoliated for two consecutive years than when they were defoliated once. Not all dead trees were infected by A. mellea. There was evidence that Stegonosporium ovatum may hasten death of stem tissues severely stressed by defoliation.