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Main symptoms

Sclerotinia sclerotiorum mainly attacks the stems and fruits of zucchini and other squash.

It causes elongated lesions on the stem starting from senescent or injured tissues (aborted fruits, tendrils, floral parts, senescent leaves, various injuries, etc.). These can be located near the collar or along the length of the stems. They have a damp and dark appearance (Figure 1), and they end up girdling them several centimeters. Of exudates gummy brown bead sometimes. 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 or in contact with the soil. It spreads rapidly and gradually spreads; the fruits end up shrinking and / or collapsing more or less completely.

The mycelium more or less fluffy and white is formed on all the affected tissues (Figure 2), as well as large black irregular structures, rather elongate, measuring 2-20 mm x 3-7 mm of sclerotia (Figures 3 and 4 ).

The teleomorph of these fungi is sometimes visible on the soil surface. Small "trumpets", apothecia (Figure 5), form on the larger sclerotia. They produce ascospores , the source of airborne contamination.

Last change : 04/16/21
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Figure 5