Strawberry pallidosis-associated virus (SPaV) was found closely associated with pallidosis disease. The modes of transmission of the virus were studied, including pollen, seed (achene), and whitefly transmission. Three whitefly species were tested for their ability to transmit SPaV, but only the greenhouse whitefly, Trialeurodes vaporariorum, was identified as a vector of the virus. Testing strawberries for SPaV and Beet pseudo yellows virus (BPYV), a second crinivirus associated with pallidosis disease, in strawberry-producing areas in North America confirmed a high incidence of both viruses in areas where high populations of whiteflies were present. Infection rates as high as 90% for SPaV and 60% for BPYV were observed when plants exhibiting decline symptoms were tested. Lower rates of infection were found in regions where whiteflies were absent or found in low numbers. The role of these criniviruses in the strawberry decline observed over the past few years along the western coast of North America was examined.