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Scanning Electron Microscopy of Pinus monticola Bark Infected with Cronartium ribicola. Bruce L. Welch, Biological Laboratory Technician, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401; Neil E. Martin, Research Plant Pathologist, USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, Utah 84401. Phytopathology 63:1420-1422. DOI: 10.1094/Phyto-63-1420.

This paper demonstrates the usefulness of scanning electron microscopy to help elucidate the physical association of Cronartium ribicola to its host Pinus monticola. Mycelia had smooth to slightly roughened surfaces and were of various diameters. Mycelia either bridged intercellular spaces or were appressed to the host’s cell walls. Mycelial projections into host cells or haustoria were not found. The sheathing material of the mycelia appeared to be intimately involved with the contiguous surfaces of pathogen and host cells. Host cell walls contiguous to the pathogen showed no evidence of lysis.