Main symptoms

Sclerotinia sclerotiorum mainly attacks the stems and fruits of the melon.

It causes elongated lesions on the stem starting from senescent or injured tissues (aborted fruits, tendrils, floral parts, senescent leaves, etc.). These can be located near the crown or higher up on the plant, especially when the melons are trained. They have a damp and dark appearance (Figures 1 to 5), and they end up girdling it several centimeters. Of exudates sometimes brown gummy bead (figures 2 to 4). Note that on the distal part of the girdled branch, the leaves can turn yellow, wilt and dry out.

A moist, dark rot develops on the fruit , at the stylar scar (Figure 6) or in contact with the soil (Figures 7 and 8). It spreads rapidly and gradually spreads; the fruits eventually shrivel and / or collapse more or less completely (Figures 10 and 11).

The mycelium more or less fluffy and white is formed on all the affected tissues (Figures 2, 5, and 7), as well as large black irregular structures, rather elongate, measuring 2-20 mm x 3-7 mm of sclerotia (figures 5 and 8 to 11).

The teleomorph of these fungi is sometimes visible on the soil surface. Small "trumpets", apothecia (Figure 12), form on the larger sclerotia. They produce ascospores , the source of airborne contamination.