Seasonal and spatial variation in the prevalence of viral diseases and associated aphid-borne viruses in cucurbits in Cote d'Ivoire

Viral diseases are a major constraint to cucurbit production worldwide. In 2014 rainy and dry cropping seasons, cross-sectional surveys were conducted in farmers' cucurbits fields in six agro-ecological zones (AEZs) of Côte d'Ivoire to assess prevalence and distribution of viral diseases. A total of 757 leaf samples were collected from melon, squash, cucumber, watermelon, gourd calabash, and pumpkin plants showing various virus-like symptoms. Enzyme linked immunosorbent assay (ELISA) using antisera against cucumber mosaic virus (CMV), zucchini yellow mosaic virus (ZYMV), papaya ringspot virus (PRSV), watermelon mosaic virus (WMV) and Moroccan watermelon mosaic virus (MWMV) were performed to detect viruses in the samples collected. Results revealed that viral diseases were prevalent in all the agro-ecological zones, with significantly higher mean prevalence in the dry season (53.6%) than in the rainy season (29.35%). The overall mean disease severity index was also significantly higher in the dry season (47.58%) than in the rainy season (28.17%). CMV, ZYMV and PRSV were found in all AEZs at varying rates between the rainy and dry seasons, whereas WMV and MWMV were not detected. CMV was more prevalent in the dry season (32%) whereas ZYMV was more prevalent in the rainy season (34%). This study has revealed that viruses infecting cucurbits are widespread and occurred in mixed infection which poses a potential threat to cucurbit crops production in Cote d'Ivoire.