Plant Virus Diseases: Epidemiology

Abstract The epidemiology of plant virus diseases concerns the cyclical development of virus diseases within plant populations in time and space. It also deals with how and why a virus is spread by vectors in an ecosystem. The main factors that influence the epidemiology of plant virus diseases involve the viruses, the plant hosts and the vectors. The interactions between these factors are complex and depend on the species, strain and isolate of the virus, its host range and the ability of the vector to disseminate the virus. All components of the epidemiological process of a plant virus are influenced by the environmental conditions, both biotic and abiotic, which can determine the successful development of an epidemic. Knowledge of these factors is fundamental to the choice and improvement of control methods to prevent or eliminate plant virus diseases. Key Concepts Plant viruses are a concern for agriculture as virus diseases can cause qualitative and/or quantitative losses of yield. Modern agriculture has caused the dissemination of exotic plant species, viruses and vectors into foreign environments. The emergence of novel virus species and strains has been increasing worldwide in the past two decades. Most plant viruses are transmitted by vectors, mainly insects. A noticeable number of plant viruses have been found to pass from one generation to the next through seed. Weeds and other wild plants play a key role as alternative virus reservoirs and as a source of novel viruses which can potentially infect crops. Environmental factors, both physical and biotic, may affect the infection cycle at different grades. Understanding of epidemiological processes is fundamental to the choice and improvement of control methods to eliminate the diseases that viruses cause. Control strategies basically focus on the elimination of virus sources and the avoidance of spatio–temporal coincidences between viruses, vectors and crops.