Thielaviopsis basicola

(Berk. & Broome) Ferraris (1912)
 
Black root rot

Thielaviopsis basicola occurs in many countries around the world but it is most severe on tobacco grown in cool climates. This is certainly the reason why it has not much been reported on tobacco in Asia, Oceania and Africa. On the American continent it is observed mainly in Canada and USA where the losses from this disease are important in several states, especially in Kentucky. It affects tobacco in almost every European country. Severe outbreaks have been reported in Italy, Poland and Germany. 
 
With the development of bright type of tobacco growing in France Thielaviopsis basicola quickly became a major limiting factor of the production. Fortunately the development and use of resistant varieties has favourably improved the situation which was particularly critical during the 80's.