Main symptoms

Botrytis cinerea can attack virtually all aerial organs of many Cucurbits: leaves, stems and especially fruits.

On the leaves , it is responsible for spots that frequently start at the edge of the blade. These are rather circular, at least at the beginning of the evolution, humid, and gradually necrosis. They can present concentric zonations (figure 1) and be haloed with a chlorotic halo. These spots can also be initiated from contaminated floral parts that have fallen on the leaf blade.

Moist cankers may gradually surround the stem , most often starting from pruning or plucking wounds, or from senescent tissue. In this case, the distal part of the plant may wilt and waste away.

The fruits of Cucurbitaceae, like those of many other plant species, have natural entry points liable to be colonized by Botrytis cinerea , and in particular nutritive bases (senescent tissues such as flowers, or dried petals) or wounds. This is particularly the case at the level of the stylar scar where the faded petals remain attached (Figures 2 and 3) for a longer or shorter period of time depending on the ambient humidity.

The latter are ideal nutritional bases which allow this opportunistic fungus to settle and subsequently contaminate the fruits (figure 4).

It is also in this stylar zone that physiological bursts (or growth slits ) take place, gaping wounds favorable to contamination by B. cinerea . Thus, a moist, dark rot develops at the tips of the fruits (Figure 5).

The stalk scar, and the stalk area are also vulnerable, but to a lesser degree. The wound produced when picking a melon, or the more or less marked natural bursts forming when the fruits are ripe, also allow contamination.

Fruit lesions can occur when they come into contact with other contaminated fruits or organs, such as flower parts colonized by B. cinerea falling on wet fruits (Figure 3).

On all the organs attacked, B. cinerea produces, if conditions permit, a more or less dense gray mold (figures 2, 3 and 6).