Survival of the inoculum of powdery mildew of strawberries andit's importance in integrated contol

摘要

Powdery mildew of strawberries (Podospheara aphanis) has become a major threat to strawberry production since the extensive use of polythene tunnels in the last 15 years. The micro-climate created in the polythene tunnels is ideal not only for production of fruit but also for the epidemic build up of P aphanis. In the spring and summer the epidemics are driven by the extensive production of asexual condidiospores in this favourable environment for the disease. Growers control the disease by fungicide use throughout the summer. Previous work has produced a risk prediction programme for this phase of the disease. However strawberries are perennial crops that overwinter in the field and harvest is taken for 3 to 4 years. In the winter months the tunnels are uncovered and the plants and P aphanis are exposed to ambient temperatures. In these months the disease survives as both mycelium and as chasmothecia (ascocarps containing asci and ascospores).The work reported here will focus on the production and maturation of the chasmothecia and the effect that one or two winter fungicide sprays have on the development of the chasmonthecia. This knowledge can then be used to contribute to the development of an integrated control strategy which can then cover the full annual cycle of strawberry production.