Impact of cabbage root fly (Delia radicum) on infections of oilseed rape with Verticillium longisporum and Phoma lingam

Oilseed rape is an economically important crop in German agriculture. As a result of intensive cultivation, an increasing incidence of some brassica- related fungal diseases and pests has been observed recently. Verticillium longisporum and Phoma lingam are causal agents of Verticillium wilt and Phoma stem canker respectively. Verticillium longisporum is a soilborne vascular pathogen, which infects the plant roots by direct penetration or through open wounds. The pathogen enters the vascular system and then moves upwards in the xylem vessels. Resulting from infection, premature ripening of the seed may occur. Phoma lingam (Leptosphaeria maculans)- infections are initiated in autumn, when leaves get infected by airborne ascospores. The fungus grows from the lesions down the petiole to the stem base, where it causes canker and subsequent yield loss. The cabbage root fly is thought to be a relatively new pest of oilseed rape, which can cause severe root damages resulting from feeding larvae. Since July 2005, an interdisciplinary PhD- project has been investigating possible interactions between the cabbage root fly and the incidence/severity of fungal diseases in oilseed rape. The study aims at determining the influence of root damages, caused by the cabbage root fly, on fungal infections, disease development and yield of oilseed rape. It is assumed, that root damages facilitate infection and disease process. If confirmed, a further objective is to develop strategies to prevent oilseed rape from serious losses caused by this pest/disease- complex.

Harald Keunecke (PhD)
Supervisors: Prof. Andreas von Tiedemann, Dr. Bernd Ulber (Entomology Section)