Main symptoms

The symptoms caused by the virus of cucumber mosaic ( Cucumber mosaic virus , CMV) on melon usually appear 1-2 weeks after inoculation by aphids. Significant differences in symptoms are observed depending on the strain, stage of infection and varietal susceptibility.

The first symptoms are expressed in the melon in the form of one or a few chlorotic spots on the leaf inoculated , they become generalized then develop into a mosaic (figures 1 to 8). The intensity of symptoms varies a lot from variety to variety and are usually more severe in summer. In France, on Charentais type melons, a classic mosaic is observed on the foliage and sometimes on the fruits and a general reduction in plant vigor (figure 2). With early infection, production can be severely compromised. In other varieties of melon, the mosaic can be much more severe and the plant gets stuck.

The fruits also present more or less marked mosaics (figure 9)

In cucumber: Symptoms of strong mosaic are observed on the foliage and on the fruits. In varieties with long fruits grown in glasshouses, we can note a sudden wilting of the plant a few days after inoculation, even before the appearance of mosaic symptoms.

In zucchini: Symptoms begin with chlorotic spots on the inoculated leaves. As the mosaic grows, the leaves curl up on themselves, warp, the plant hangs up and takes on a yellowing appearance. The first fruits produced show small, more or less pronounced "pin-prick" depressions, then all the flowers sink and fruiting stops. In zucchini, CMV is more common in cool periods (spring, autumn). In addition, we note a greater sensitivity of young plants (we speak of resistance or less sensitivity at the "adult" stage).

In watermelon: Watermelon is very rarely infected with CMV which most often causes black necrotic spots.