Optimizing Fungicide Applications for Plant Disease Management: Case Studies on Strawberry and Grape

Fungicides are important tools for management of plant diseases caused by fungal and oomycete pathogens. Without use of fungicides, major crop losses are inevitable, and food supply networks as we know today are most likely not able to sustain itself. As a result, fungicides are applied in regular basis in many parts of the world; however, their applications need to be optimized in order to obtain the best result in disease management due to multiple factors such as fungicide efficacy, the risk of resistance development, environmental concerns, pesticide residue in harvest, impact on beneficial organisms, etc. The ultimate goal is to keep the losses from diseases to a level that does not represent a threat to the crop production and to the economy of the grower while reducing the number of applications as much as possible. In order to achieve this goal, growers commonly employ integrated pest management (IPM) approaches where multiple management options are used together to achieve best efficacy with minimum chemical usage. Especially in environmentally challenging growing areas, use of fungicides is an important component of the IPM approach. Abusive uses of fungicides can cost not only growers’ budget, but also cost society and environment. Therefore, fungicide usages need to be carefully planned with a good understanding of plant disease epidemics, their components (host, environment and pathogen), fungicide mode of action (biochemical, biological, physical), risk of resistance development, and host physiology, among other aspects. In this chapter, we will review these components that are involved in decision-making process to optimize fungicide application. The main focus of discussion is on management of diseases of strawberry and grape, because both are high value, intensively managed crops where application of fungicides are conducted on a regular basis.