The aim of this research was to determine the causal organisms of yellowing and vein clearing type of symptoms of melon and cucumber plants growing under greenhouse conditions, and which Bemisia tabaci biotypes are involved in transmission of viruses in Adana, Mersin and Antalya provinces. For this purposes, the diseases surveys were periodically made in 2010 and 2011, and whitefly vectors collected on the young leaves of the hosts from different district of cucurbits growing area. The virus infected plants were tested against to cucurbit viruses by PCR. The result of work suggested that CVYV and CYSDV are responsible for the disorders of the yellowing type of symptoms. The infected plants showed mainly interveinal chlorosis and yellowing type of nutrition deficiency symptoms on the leaves. Among the collected 134 melon samples, 63 and 24 plants were found to be infected by CYSDV and CVYV. In the case of cucumber samples, CYSDV and CYVV were detected on the 82 and 12 plants out of 110 cucumber plants. The collected whitefly-vector from the infected cucumber and melon plants were tested by PCR. The assay showed that B. tabaci Biotype B (92%) efficiently transmits the viruses but Q biotype (8%) poorly transmitted the viruses. The study of PCR clearly pointed out that individual whitefly is a harbour of viruses and transmits the viruses. DNA fragments were directly sequenced and compared with CYSDV and CVYV isolates with that of Israel, USA and Spain isolates. It was concluded that 96% of CYSDV (AY580985, FJ492808) and 95% of CYVV isolates nucleotide identity with the coat protein gene with Israel, USA and Spanish isolates.