Main symptoms

 

Symptoms caused by Fusarium spp. on the different plants belonging to the genus Cucurbita seem diversified, fluctuating according to the species of Fusarium raging and the species of Cucurbita affected; They have in particular been well characterized on Cucurbita pepo . In this species, two main types of symptoms have been described:

Type 1, observed on immature fruits, has dry, hard, circular to oval lesions, with a rather limited diameter of 0.5 to 2 cm, with a corky, hollow center, with or without a green halo. Orange sporodochia often form in their center ( F. acuminatum , F. graminearum , F. equiseti );

Type 2 is observed more on the fruits after harvest, and involves less well-defined lesions, starting from type 1 lesions, or associated with the presence of mycelial development, and characterized by tissues soft, rotten and collapsed ( F. graminearum , F. equiseti , F. avenaceum ... ).

In France, we have also observed the presence of courgette and various squash Fusarium on on:

- parts of rotten fruit in contact with the ground (figure 1);

- fruits already affected by apical necrosis or coulure (figures 2);

- lesions initiating via the peduncle (figure 3) or the end of the fruits (figure 4);

The lesions were often wet, or dry and spongy (Figure 5), leading to rotting, the affected tissues covering either with white (Figure 6) to pinkish (Figure 7) mycelium (Figure 7) or orange sporodochia (Figure 8). .

Note that rotten tissues invaded by certain species Fusarium can take on a reddish to purple tint (figure 9). Other Fusarium can cause brownish internal lesions.