The overwintering chasraothecia of Podosphaera aphanis and the initiation of the subsequent epidemic

摘要

Commercial strawberry production in the UK has used polythene (Spanish) tunnels since 1993. This protection was introduced to give a harvest period of five months rather than the six weeks from unprotected strawberries. The covering protects the plants from rain damage which was the main agent for the spread of grey mould fungus, Botrytis cinerea. Polythene tunnels have thus improved the conditions for strawberry production and controlled grey mould. The environment created in the polythene tunnels is, however, favourable for the growth and development of powdery mildew of strawberries, caused by Podosphaera aphanis. Epidemics of P. aphanis are now the main threat to strawberry production in the UK. Strawberry breeders in the UK concentrate on fruitquality and appearance. As a consequence only a narrow range of varieties is grown, most of which are disease susceptible (Dodgson et al., 2005). Growers could manipulate the tunnel environment to control P. aphanis but in practice the conditions required to produce high quality fruit correspond to the conditions that enhance epidemics of P. aphanis. Disease control in commercial crops is, therefore, dependant on regular applications of fungicides.