Pseudomonas syringae pv. aptata mainly attacks the aerial organs of the melon.

The spots on the leaves (Figures 1 to 6) are initially oily, dark green and small in size. They are more easily distinguished by observing the limbus by transparency. These spots evolve quite quickly; affected tissues turn yellow and necrotize, eventually appearing brown to brown in color. Whole sectors of the leaf blade can be affected especially when several spots come together, they also quickly turn brown and dry out.

Canker damage is also visible on the stems and petioles (Figures 7-9). They are elongated and more or less extensive. Initially wet to oily, the fabrics soon gradually turn brown and crumble slightly. These organs are sometimes entirely surrounded, which ultimately leads to the drying out of entire leaves, and of the end of certain branches.

Spots also appear on the fruits (figures 10 to 15); these are relatively discrete at the start of development. At this stage, the epidermis very locally takes on an oily appearance. Translucent spots, rather circular and slightly depressed, soon spread. Their development in spurts sometimes gives them a concentric appearance (Figures 11 and 12). The tissues located in their center gradually turn brown to completely black (Figure 13).
A longitudinal section in the fruits shows that the underlying tissues are also translucent, even suberized and / or collapsed, in their place sometimes remaining a cavity (figures 14 and 15). The tissues surrounding the seeds are also affected.

Leaf mortality and damage to fruit can greatly reduce production and lead to significant economic losses.