The Use of Mathematical Models to Guide Fungicide Resistance Management Decisions

Abstract

Historically, models have had little influence on decision-making in fungicide resistance management. The reasons are found in the level of abstraction of these models making it difficult for stakeholders to interpret them and inadequate connection between modelling and experimentation. Recently, however, the authors of this chapter have developed models in close collaboration with stakeholders and experimenters. These models range from simple functions representing governing principles of resistance evolution to complex models for quantitative studies. In this chapter we discuss the development and testing of these models. A governing principle is discussed predicting whether a change in a fungicide application programme will increase or decrease the rate of selection for fungicide resistance. Complex models are discussed that reflect sufficient biological detail to study specific plant-pathogen-fungicide combinations. Ultimately we describe the combined experimental and modelling work that is currently undertaken to informing resistance management methods.

List of Terms Used in the Chapter

Fungicide resistance:

We use method rather than strategy so that we can use themanagement methods words strategy and tactic in their exact and specific meaning in the chapter.

Principle:

A general rule that has a range of applications across a wide field. A principle of fungicide resistance management is a rule that applies to a wide range of specific resistance management methods.

Strategy:

The “what” aspect of resistance management. What do we want to achieve with resistance management?

Tactics:

The “how” aspects of resistance management. How do we achieve our strategy of resistance management?

Emergence:

When a new fungicide mode of action is introduced and the population is uniformly sensitive, resistance has to arise through mutations in sensitive strain(s). Emergence occurs when the resistant population increases so that it is large enough not to die out because of demographic stochasticity.

Selection:

The process that determines the relative contribution of a genotype to the next generation. When a fungicide is used and a resistant genotype is present in the population, its proportional contribution to the next pathogen generation is larger relative to that of the fungicide-sensitive strain(s) in the population.

Effective disease control:

The disease control of a sufficient level to keep yield losses below a required level.

Fungicide effective life:

The time from introduction of the fungicide to the point at which effective control can no longer be obtained.