Epidemiology of zucchini viruses in Flanders in support of a sustainable management strategy

In temperate regions, cucumber mosaic virus (CMV), watermelon mosaic virus (WMV), zucchini yellow mosaic virus (ZYMV) and papaya ringspot virus (PRSV) cause major losses in zucchini. A seven-year (2007-2013) survey was organized in the two main zucchini growing areas, Antwerp and West Flanders, to assess virus status and epidemiology. A clear evolution in importance of the distinct viruses represented in the viral populations was observed. In Antwerp, WMV was found throughout the survey period and gradually evolved to become the most dominant virus, while CMV occurrence declined over the years. In contrast, in West Flanders, CMV was consistently the most commonly detected virus. In both regions, ZYMV incidence strongly decreased during the survey, while PRSV was a minor problem, only observed from 2008 to 2010 and in 2013. Mixed infections of CMV with either WMV or ZYMV occurred frequently throughout the survey. The importance of prevalent weed species as natural virus reservoirs was also assessed and confirmed for CMV and WMV, with CMV clearly having the broadest host range. The survey results supported the development of a sustainable management strategy.