Main symptoms

The courgette ( mosaic virus Zucchini yellow mosaic virus , ZYMV), due to the many strains reported from the first description of this virus, causes quite different symptoms. In addition, these can vary in intensity depending on the season (they are usually more severe in summer), the species or variety infected. It should be noted that more accentuated symptoms may be observed in the event of co-infection with other viruses (synergy), and in particular with the cucumber mosaic virus (CMV). ZYMV probably causes the most dramatic symptoms in zucchini (Figures 1 and 7), and it is often in this host that this virus has been initially reported in many countries.

The first symptoms on foliage are thinning of the veins (figure 2) and yellowing (figure 3) which quickly develop into a mosaic (figures 4 and 11). The symptoms quickly become much more severe with significant deformities: dark green blisters and blisters (figure 5), "shoe lace" leaves (filiformism) (figures 6 and 7). These latter symptoms can now be confused with those produced by severe strains of WMV.

The symptoms on fruits are also very spectacular: discoloration particularly marked on varieties with yellow fruits, and above all significant blisters which completely deform courgettes (figures 8 to 10) and squash (figures 12 and 13). The fruits are of course not salable, and crop loss can be complete with early infection.