A comparison made at the East Mailing Research Station of the strawberry viruses known in California with those of England indicated that the curly-dwarf mottle, mottle, mild yellow-edge, latent-A, and crinkle viruses occurred in both England and California; the rusty-leaf mottle, lesion-B, vein chlorosis, green petal, mosaic, raspberry yellow dwarf, and raspberry ring spot viruses were not known in California; the vein banding, yellow vein banding, latent-B, lesion-A, and western aster yellows viruses were not found in England; while the leaf-curl virus was known only in plants in the East Mailing Research Station glasshouse.

The viruses studied could be provisionally grouped according to their symptoms and vector-host relationships, but the evidence obtained did not clearly define the level of relationships among the viruses within the groups.

Comparative tests suggested that the incubation period for development of symptoms in the plant and the rate of virus loss by vectors are useful characters in distinguishing between strawberry viruses, but the acquisition threshold period and rate of virus acquisition appeared to be less useful.

Rusty-leaf mottle, curly-dwarf mottle, yellow vein banding, lesion-A, and lesion-B are newly described viruses with aphid vectors.

Pentatrichopus thomasi and P. thomasi ssp. jacobi are reported to be vectors of strawberry viruses while Amphorophora rubi was demonstrated to be a vector of the leaf-curl virus.

Duchesnea indica and Nicotiana bigelovii are newly determined experimental and natural hosts respectively of the western aster yellows virus.