A survey for sweet potato (Ipomoea

batatas L.) viruses was conducted in five commercial fields in

Costa Rica from February to May 2002. High percentage of

plants showing virus-like symptoms were observed in three

of the five commercial fields. Graft-inoculations of fieldcollected

samples to the virus indicator plant Ipomoea setosa

were conducted. Foliar samples from inoculated plants were

tested serologically for Sweet potato feathery mottle virus

(SPFMV) and Cucumber mosaic virus (CMV), by reverse

transcription polymerase chain reaction (RT-PCR) for Sweet

potato chlorotic stunt virus (SPCSV), and by molecular

hybridization for Sweet potato leaf curl virus (SPLCV). The

aphid-transmitted SPFMV was the most common virus

detected. Other viruses detected included SPCSV and

SPLCV. CMV was not detected in any of the samples tested.

Mixed infections of SPFMV and SPCSV were detected in the

3 commercial fields with a high percentage of plants showing

virus-like symptoms. The identity of SPCSV was confirmed

by whitefly (Bemisia tabaci) transmissions and RNA analysis

of selected RT-PCR positive samples.