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Cankers and Decay in Red Oaks caused by Fomes robustus. D. W. French, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55101; Frank W. Perpich, High School Teacher, Department of Plant Pathology, University of Minnesota, St. Paul 55101. Phytopathology 64:1148-1149. DOI: 10.1094/Phyto-64-1148.

Cankers caused by Fomes robustus were found in 0.4 – 33% of the red oaks in 80 locations in Crow Wing and Clearwater Counties, Minnesota. The average incidence was 4.3%. The cankers were associated with branch stubs and mechanical wounds in the main stem, from 0.3 – 5.2 m aboveground. The ages of infected trees averaged 47 yr (range 20-84 yr). Average age at time of infection was 29 yr and the youngest tree was 7 yr old when infected. The decay was essentially limited to the sapwood and heartwood behind the canker. In 32 trees, the average length of decayed wood was 92.7 cm and volume averaged 448.5 cm³. Five trees without sporocarps had an average volume of decay of 51.6 cm³ and those with sporocarps, 521.9 cm³.