Main Symptoms

Thielaviopsis basicola is a soilborne fungus, which grows both in nursery and in the field (figure 1 and 2). It causes significant damage to the underground part of plants. It gradually colonises the plant roots, causing many brown to black lesions along the entire root length destroying most of the feeder rootlets (figure 3). Finally a large proportion of the root system has a typical black rot (figure 4). Large roots, which are rather less susceptible than the feeder rootlets, may have superficially suberous sleeves of dark brown to black (figures 5 to 6).
 
Affected plants are often poorly developed and chlorotic. Sometimes they wilt when the weather becomes hot. 
 
 
Some of the information on the disease distribution worldwide 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.