Coniothyrium minitans, un agent de lutte biologique au service de la protection intégrée

Abstract

Sclerotinia stem rot is a major disease on winter oilseed rape which causes severe yield losses twice a decade. Chemical control is usually applied at the beginning of flowering stage, every year. Because of a reduced use of chemicals expected, a biological control agent as Coniothyrium minitans could be usefull for controlling the disease. Experiments have mainly been carried out with Contans<sup>®<sup/> WG, a ready-for-use formulation of C. minitans. Firstly effectiveness of C. minitans against sclerotia of Sclerotinia sclerotiorum was demonstrated. Then, its use on oilseed rape crops has been studied for several years in large size experimental plots. When it is incorporated into soil, C. minitans reduced the soil infestation by destroying sclerotia. By decreasing the soil infestation, C. minitans also reduced the primary inoculum pressure. Thus it allowed to reduce the sclerotinia risk and the disease incidence. The results are discussed according to the decision support system CETIOM in progress. Thus, a reduction of sclerotinia risk underneath a decision threshold in treated field plots could prevent any further spray of fungicides. However, it can be needed to apply fungicides which are more efficient when the disease pressure is reduced. These results contribute to integrate the use of Contans<sup>®<sup/> WG in the disease management of sclerotinia stem rot of oilseed rape.