The fruit defect, sunken mottle, is a major problem facing Honey Dew growers in the Central Valley. It is an insect-borne malady, apparently caused by watermelon mosaic virus, type 2, according to this study. In recent years it has caused losses of about one-third of the Honey Dew acreage in Stanislaus County. It has been especially severe on late-planted fields. Control of the virus requires knowledge and control of the insect vector and any host plants. The best long-term solution to the problem maybe a breeding program for mosaic-resistant line of Honey Dew melons.

Davis. R. E. Webb, U. S. Department of Agriculture, Beltsville, identified the virus type in the cage experiments; K. A. Kimble, Department of Plant Pathology, Davis, isolated strains of mosaic viruses from field plantings; J. W. Perdue, Department of Vegetable Crops, Davis, prepared the photos.