Disease Note.

Diplodia Canker (Sphaeropsis sapinea) of Abies concolor in Iowa. C. J. Luley, Department of Plant Pathology, Iowa State University, Ames 50011-1020. M. L. Gleason, Department of Plant Pathology, Iowa State University, Ames 50011-1020.. Plant Dis. 72:79. Accepted for publication 14 September 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0079E.

A canker disease of Abies concolor (Gord. & Glend.) Lindl. was found on branches in several windbreaks in Iowa during 1984-1986. Symptoms included resin flow, sunken elliptical cankers, and branch dieback. Sphaeropsis sapinea (Fr.) Dyko & Sutton (syn. Diplodia pinea (Desm.) Kickx) was identified as the apparent cause of the disease on the basis of isolations from canker margins and fruiting bodies present in cankers. A host range study in the greenhouse confirmed pathogenicity of S. sapinea on seedlings of A. concolor. Pinus nigra Arnold, P. resinosa Ait., and Picea pungens Engelm. Nine seedlings per treatment were either injected by syringe or sprayed with a myceliumspore suspension. Controls were injected or sprayed with water. Resin flow and collapse of stem tissues near injection sites developed most rapidly on P. resinosa and P. nigra. Symptoms developed more slowly and were less severe on Picea pungens and A. concolor. On A. concolor, lesions similar to those observed in the field developed within 4 wk after inoculation. After 9 wk, S. sapinea was reisolated from 70% of Picea pungens, 66% of P. resinosa, 55% of P. nigra, and 33% of A. concolor seedlings injected with inoculum and 22% of Picea pungens seedlings sprayed with inoculum. The fungus was not isolated from any control seedlings. These findings suggest that S. sapinea is the cause of a previously unreported canker of A. concolor.