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Quantitative Assessment of the Effect of the Olive Knot Disease on Olive Yield and Quality. M. N. Schroth, Professor of Plant Pathology, Department of Plant Pathology, University of California, Berkeley 94720; J. W. Osgood(2), and T. D. Miller(3). (2)(3)Agricultural Extension Service Farm Advisor, and Assistant Research Plant Pathologist, respectively, Department of Plant Pathology, University of California, Berkeley 94720, (3)Present address: Assistant Professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 63:1064-1065. Accepted for publication 1 March 1973. DOI: 10.1094/Phyto-63-1064.

The incidence of olive knot disease caused by Pseudomonas savastanoi was related to a striking reduction in yield. The yield of olives from trees with 0.1 - 0.3 knots/0.3 m of fruit wood (light infection) and from those with 0.51 - 1.0 knot/0.3 m (moderate infection) averaged 121.3 kg (267.5 lb) and 94.6 kg (208.5 lb)/tree, respectively. The reduction in yield was also associated with a substantial decrease in the sizes of olives. The difference in average income/tree considering both yield and quality was $36.77 for lightly infected trees and $27.30 for moderately infected trees. On an acre basis, this comes to a loss of $403.38. The data indicated that it would be economically advantageous to develop a control for the disease.

Additional keywords: disease appraisal, Pseudomonas savastanoi.