VIEW ARTICLE

Early Botrytis Rot of Grapes: Time of Infection and Latency of Botrytis cinerea Pers. in Vitis vinifera L.. W. D. McClellan, Farm Advisor, University of California Agricultural Extension Service, Tulare County, Visalia 93277; William B. Hewitt, Plant Pathologist, Department of Plant Pathology, University of California, Davis: 9240 So. Riverbend Ave., Parlier, California 93648. Phytopathology 63:1151-1157. Accepted for publication 5 March 1973. DOI: 10.1094/Phyto-63-1151.

Early Botrytis rot of grapes is a new development in an old disease caused by Botrytis cinerea. A brown rot of grapes starts in midseason and may continue to develop until harvest in the absence of rain. The disease may affect only a few grapes or most all the grapes in a cluster. Infection takes place during bloom. The fungus invades the stigma and style and then becomes latent in the necrotic stigma and style tissue at the stylar end of the grape. At véraison or later the fungus resumes growth and rots the grape. The presence of pollen on the grape stigmatic surface increases the germination and germ tube growth of conidia of the pathogen. Experiments with conidia exposed to grape extracts representing different stages of maturity indicated that in extracts of immature grapes, the conidia germinated and grew very poorly. These factors may be involved in the infection process and the latency phenomenon.