Main symptoms

On cucumber and melon, heavily affected plants are not very growing and / or end up wilting quite suddenly at the hottest times of the day, or even drying out over time. On zucchini and squash, the symptoms of Phomopsis sclerotioides on the roots often go unnoticed, often not leading to reduced plant growth, or even wilting and drying out.

After having pulled up and carefully washed the root systems of a few diseased plants, we see that they are more or less altered (figures 1 to 4), rotten, locally suberized. Some roots have disappeared and those which remain show more or less extensive reddish-brown necrotic lesions (figures 5 and 6), some are more or less corky (figures 3, 4 and 7). The root tissues end up rotting and decomposing, which ultimately means that the root systems are very reduced.

On the root lesions, black lines are observed locally ( pseudo-stromas ) (figure 8), more or less thick and with irregular contours surrounding areas of tissue. In certain portions, it is sometimes more difficult to discern numerous greyish-black to brown pits distributed in a “mosaic” in place in the cells of the cortex. These are the pseudo-microsclerotia (figures 9 and 10) of this fungus.