The system management approach of biological weed control: Some theoretical considerations and aspects of application

Theoretical considerations behind the system management approach of biologi cal weed control are presented. These include, a part describing and explai ning the effects of parasitic fungi on crop - weed competition, a part desc ribing and explaining the epidemic spread of parasitic fungi on weeds, and a part relating crop - weed competition at the population level to epidemic s. The theoretical framework developed may also provide a basis for the use of other natural enemies, like insects, for biological weed control follow ing the system management approach. Aspects of application are discussed us ing data of the interaction between the annual weed Senecio vulgaris and th e rust fungus Puccinia lagenophorae.