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Correlation of Isolability of the Oak Wilt Pathogen with Leaf Wilt and Vascular Water Flow Resistance. Garold F. Gregory, Plant Pathologist, Forest Insect and Disease Laboratory, Northeastern Forest Experiment Station, Forest Service, USDA, Delaware, Ohio 43015; Phytopathology 61:1003-1005. Accepted for publication 22 March 1971. DOI: 10.1094/Phyto-61-1003.

Isolations and water flow-rate measurements made on short stem sections of young red oak seedlings inoculated with the oak wilt pathogen, Ceratocystis fagacearum, about 1 to 2 inches above the soil line, revealed that the oak wilt pathogen was isolable first near the inoculation site. As time after inoculation increased, the pathogen was isolated progressively farther up the stem until, when leaf symptoms became visible, it was present throughout the stem. At the onset of leaf symptoms, many but not all petioles contained the pathogen. The pathogen was never isolated from leaf blade homogenates or vessel washings from stem sections. The resistance to water flow through the vessels of the short stem sections was progressively less at greater distances up the stem from the inoculation site.