Verticillium dalhiae

(Verticillium wilt)
 

Verticillium dalhiae (Verticillium wilt) is a soil fungus that has been observed in several tobacco production regions in France, particularly in the north and in the Landes region. It occurs mainly at the end of the season, just before and during the harvest. It seems that it rather affects Virginia type tobacco. It causes sectorial foliar lesions that depreciate the quality of harvested tobacco (see Curing barn diseases).
 
Verticillium wilt is a vascular disease which starts with partial wilting of lower leaves (figures 1 and 2). Vascular tissues are affected, but unlike other vascular diseases, such as Fusarium wilt and bacterial wilt, the staining of vessels is quite discreet. The vessels turn yellow to light brown (figures 3-5).
 
Only isolates made from vessels allow the  confirmation of the presence of this fungus in diseased plants. If you have any doubts about your diagnosis, do not hesitate to send a sample of a diseased plant to a specialized laboratory that will perform the appropriate tests.

For more information on this pathogen, we recommend you to consult the fact sheet of Verticillium dalhiae.