Epidemiology of Botrytis cinerea in Orchard and Vine Crops

Substantial economic crop losses occur worldwide in tree fruits, nut crops, vines and small fruits as a result of infection by Botrytis cinerea. Fungicide-based management, once an accepted practice, is becoming increasingly restricted, a trend likely to continue in the future. Greater emphasis on alternative, non-chemical control will require improved knowledge of B. cinerea ecology and epidemiology in affected crops. Epidemics are often initiated in the spring from conidial inoculum produced on over-wintering structures on a very wide range of plant species. From floral infection in the spring, several infection pathways to fruit infection and crop loss at harvest are described. The majority of these pathways include a degree of symptomless latency, or quiescence, in the host tissue. In some crops (e.g. grapes) multiple pathways are described, each one dependant upon many complex host, pathogen and environmental factors. In other crops (e.g. berry fruits), a single dominant pathway is described. Latency, once poorly understood, has become the focus of research in the last decade. Several host defence mechanisms are described which may account for this period of enforced dormancy. Once pathogenic growth resumes and typical B. cinerea symptoms appear, many factors affect the subsequent rate of B. cinerea epidemics and we describe some of these in detail. The growth of organic production in the last decade has high-lighted the need for a greater understanding of the complexities of epidemic development in order to develop durable and sustainable disease control strategies.