Verticillium dalhiae is one of the fungi responsible for verticillium ( wilt Verticillium wilt ) on several vegetables, including tomatoes. This disease is reported in many production areas around the world and can cause severe damage. It affects both field crops and under cover. As with Fusarium wilt, there are now many resistant varieties. In France, this disease is only rife in amateur gardens where non-resistant old varieties are cultivated, especially in spring and autumn. Indeed, its development in plants seems to be slowed down or even inhibited when temperatures rise above 30 ° C, which sometimes explains the reversible nature of the disease. It should be noted that we were able to observe its rapid resurgence a few years ago when certain seed companies considered that they could ignore this resistance in soil-less tomato cultivation. Damage manifested itself fairly quickly on the new varieties lacking the “ gene Ve ” , reminding us that this fungus is still very present in a good number of farms, and in particular in the substrates of soilless crops. Let us add that race 2 is starting to appear on tomato rootstocks (intra- or interspecific) and more occasionally on a few resistant tomato varieties grown in soil.
 

Like many other vascular diseases, verticillium wilt attacks on tomatoes cause plants to wilt at the hottest times of the day. It does not take long for the leaflets to show an interveinal yellowing of the lamina, which takes the shape of a “V” (Figures 1 and 2). Gradually, the leaf tissues necrotize and dry out in the central part of the discolorations (figure 3). As the disease progresses, several leaflets and leaves show comparable symptoms.
  

A longitudinal cut in the stem shows that the vessels are more or less brown (figures 4 and 5), the vascular browning observed is however less marked than that caused by F. oxysporum f. sp. lycopersici . The outside of the stem does not show any particular symptoms.
 

As in the case of Fusarium wilt, consult a specialized laboratory if you have the slightest doubt, as many diagnostic confusions are possible.

For additional information on this fungus, you can consult the sheet Verticillium dalhiae .