Isolations of Verticillium albo-atrum from olive trees in Tulare County indicated that the T-l strain was most often associated with severe verticillium wilt in Manzaniilo and Sevillano varieties. T-l was also associated with severe wilt in Acala cotton in Tulare and several adjacent counties. The SS-4 strain, which causes only mild symptoms in Acala cotton varieties, was isolated from olive trees and was a relatively mild pathogen in the Manzanillo olive variety. These results indicate that the T-l strain is a major factor in the severe wilt problem in both cotton and olives in Tulare County.

Lecturer and Associate in the Experiment Station, Department of Plant Pathology, University of California, Davis

Diana Fogle gave technical assistance, and Jeff Hall provided photographic assistance. John Whisler provided Manzanillo olive plants for greenhouse tests. One isolate of V. albo-atrum from olives was provided by A. V. Ravenscroft.