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Main symptoms

All aerial organs of cucurbits can show symptoms of gray cloudy caused by Cladosporium cucumerinum , even at a juvenile stage in the nursery. The symptoms observed on species of this botanical family are often quite comparable, and one could attribute to them the following generic descriptions:

Small moist lesions appear on leaves often the youngest . These lesions gradually spread to form more or less circular spots, turning brown and necrotizing with age. They can sometimes take a grayish tint and be haloed with a more or less wide yellow halo. Affected tissue may loosen and fall, giving the inner part of the spots a more or less starry appearance, and the leaves a riddled appearance. Note that wet lesions sometimes start from veins that turn brown locally.
leaves Zucchini and squash (Figures 1-5) are dotted with small greasy spots, quickly turning brown, and surrounded by a yellow halo. The damaged core tissues tear and may partially fall out.

on the stems and petioles Elongated lesions develop . They are also damp at first and gradually turn brown. Their size fluctuates depending on the species and climatic conditions. Note that a viscous substance sometimes beads infected tissue (figure).
Under very favorable conditions, the apices of plants can be more or less destroyed and wither away.
On zucchini , many greasy and necrotic spots can be observed on the petioles (Figures 6 to 8).

on fruits Cladosporiosis is most damaging . Small canker, greasy and concave spots, often going unnoticed, initially develop on young fruits which are particularly sensitive. They then spread, sometimes confluence, and take a circular to elongated shape and a rather light shade. Gradually browning gummy exudates locally bead. Note that these spots are initially harmless on the young fruits of Cucurbitaceae; as development progresses, they have very important repercussions on their shape in particular. Indeed, their extension and the local establishment of corky scar tissue in relief sometimes lead to bursts and significant deformations, making the fruits unmarketable.
As for the fruits of zucchini and squash , they show small greasy, canker and brown spots when they are young (Figures 9 to 13). Once well developed, they are sometimes corky and strongly deformed (Figures 14 and 15).

A gray to dark green conidial felting and more or less dense covers the diseased tissues of all the organs attacked. Is it particularly visible on lesions on stems and fruits?

Last change : 04/16/21
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