Main Symptoms

Sclerotinia sclerotiorum has a behaviour on tobacco rather similar to Botrytis cinerea. It is also a coloniser of nutrient sources and senescent tissues present on the seedlings in nurseries and on senescent tissues of tobacco plants in the fields.

On seedlings the stem cankers are particularly harmful (figure 1). The fungus invades the stem after having colonized the cotyledons or one of the first senescent leaves. The cankers, located at the base of the stem are moist and light brown and tend to be covered with a dense white mycelium and very characteristic large black sclerotia. Some lesions may develop after transplanting if infected plants were not detected during the pre-transplant sampling and sorting.

In the field some stem cankers are observed (figures 2 to 5) originating from defoliation wounds, pith invasion, and various forms of leaf rot (figure 5).  This fungus also causes damage occurs during curing, in particular on dark and Burley tobacco (figure 6).

Some of the information on the worldwide distribution of the disease is obtained from surveys conducted by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). The reliability of the information is not confirmed in all countries.