Main symptoms

Fusarium solani f. sp. cucurbitae parasitizes seedlings, plants and fruits at all stages of their development.

Diseased plants wilt more or less at the hottest times of the day (Figures 1 and 2); these wilts are sometimes reversible. In the most severe cases, the plants eventually dry out entirely (Figure 3).

The cause of this wilting can be found in the neck of the feet of zucchini and other sensitive cucurbits. A wet lesion has developed here, a rot that has progressively gained the lower part of the stem and the taproot, but also the upper part of the root system (figure 1). At the neck , the altered tissues are moist and show a dark to brownish tint (Figure 4). This lesion ends up encircling the rod for several centimeters. Note that comparable lesions may develop more authoritatively on the stem, from wounds or remnants of senescent leaves (Figure 5). The vessels in the altered area eventually turn brown (Figure 4). The roots located in the same stratum of the soil are also affected. Their cortex turns yellow, brown and decomposes.

The portion of the stem near the soil surface is covered by a mycelium white to pinkish (Figure 5) on which the sporodochia and macroconidia of this Fusarium are formed .

The fruits are also attacked: a wet and soft rot develops on the part in contact with the ground. The altered tissue also takes on a dark tint.

Note that other species of Fusarium spp. are also reported to be responsible for fruit rots.