Plant Disease Epidemiology: The challenges to managing economically important pathogens in Australian cotton

Abstract

Since the beginning of agriculture, generations of farmers have been developing practices for battling the various diseases suffered by their crops. Following the discovery of the causes of plant diseases in the early nineteenth century, our growing understanding of the interactions of pathogen and host has enabled the development of a wide range of methods for the management of specific plant diseases. In basic terms, to manage a disease, we need to reduce its progress and keep disease development below an acceptable level. This can be achieved through reduction of the initial inoculum, reducing the rate of infection, and by reducing the duration of the epidemic. These three major tactics for managing plant disease epidemics can be incorporated into our plant disease management strategy. In developing disease management strategies however, we also need to take into consideration the dynamics of plant disease, that is, the changes in the incidence and severity of disease in time and space. This is complicated by the fact that different diseases differ in their dynamics. Therefore, for each pathogen, we have to fit these tactics into an appropriate overall strategy based on epidemiological principles.

Three important economic pathogens/pest occurring in Australian cotton include Fusarium oxysporum f.sp. vasinfectum (Fov), the cause of Fusarium wilt; Verticillium dahliae (Vd), the cause of Verticillium wilt, and Rotylenchulus reniformis (Rr), also known as Reniform nematode. For all three organisms, the higher the inoculum level pre-plant, the greater the impact on cotton (and other susceptible hosts). However, epidemiology differs for each of these organisms. Therefore, aspects within the overall strategy required to manage each disease differs and needs to be specifically targeted. The challenges of each pathogen/pest, success of management strategies and possible