Virus and virus-like diseases have an enormous impact on strawberry production throughout the United States. They influence and may limit the choice of parental lines for plant breeders. They are responsible for many of the special management methods used by nurseries to provide growers with certified planting stock from virus-tested sources. They are a major source of yield loss in fruiting fields. In this review, two main questions will be addressed: 1) What progress has been made recently in detecting and determining the cause of the noninfectious disease called June yellows and in detecting and characterizing the virus and virus-like agents that cause eight major infectious diseases of cultivated strawberry on the U.S. Pacific Coast?, and 2) How well are these diseases currently being controlled, and what of the future? Pacific Coast strawberry virus and virus-like disease analysis and detection The eight most economically important virus and virus-like diseases of strawberry on the Pacific Coast are June yellows, strawberry mottle, strawberry vein banding, strawberry crinkle, strawberry mild yellow-edge, tomato ringspot, tobacco streak (also known in strawberry as necrotic shock disease), and pallidosis. They are grouped here by their method of natural spread in the. field, although all eight occur in daughter plants that are vegetatively propagated from runners (stolons) of diseased strawberry plants. These diseases and their causal agents have been the subjects of two recent reviews (Converse, 1987; Converse et al., 1988). The first reference contains numerous color illustrations of symptoms of the major strawberry viruses on diagnostic hosts. Except where specifically noted, the reader may consult these two references for the relevant original literature in this field. June yellows (Jy). This is a nonpathogenic disorder, probably of genetic origin, that spreads naturally only through runners, pollen, or seed from a JY-infected plant. No pathogen nor unique nucleic acid has been consistently associated with JY. Double-stranded RNA (dsRNA), not found in healthy plants, has been found in JY plants, but erratically and in varying sizes. Transmission of JY between two plants not of the same vegetative clone occurs only sexually, and the appearance of symptoms in resulting seedlings may be delayed for several seasons. A strawberry cultivar with symptoms of JY usually has lower plant vigor. Bringhurst and Voth (1989) documented a 43% yield loss in the California cultivar Tufts with JY compared to symptomless 'Tufts'. To avoid the development of JY in their selections, plant breeders try to select parents with ancestries as free from JY as possible. Since no bioassay or biochemical test has yet been devised for reliable detection of JY in strawberry plants in which JY may be latent, plant breeders may evaluate their parental lines by crossing them to cultivars such as 'Tufts', or 'Tardive de Leopold', as suggested by Wills (1962)-genotypes that favor the expression of JY symptoms in their offspring. Obviously, th...
