Improved management of strawberry powdery mildew through development and deployment of forecasting systems

Strawberry is a major fruit crop in Norway, and in the USA. Powdery mildew, caused by Spaherotheca macularis, is a major cause of potential loss in commercial strawberry production worldwide. Research on the pathogen ecology and epidemiology of S. macu laris has largely stagnated over the last 40 years, with little advancement in our knowledge of pathogen biology and ecology; perhaps because effective chemical control during this interval has provided an unprecedented degree of disease suppression. How ever, powdery mildews are historically among the most troublesome pathogens with respect to fungicide resistance. Failures of demethylation inhibiting and strobilurin fungicides to control several other powdery mildews have recently been reported. To be tter manage strawberry powdery mildew with a dwindling arsenal of fungicides will require a more complete understanding of the disease than we presently possess. Such fundamental questions as (i) how does the pathogen survive winter, (ii) when does infec tion occur, (iii) how do host and environmental factors affect disease development, and (iv) how can we best manage the disease with the remaining tools, remain largely unanswered. A thorough and critical examination of the biology, ecology, and epidemio logy of this disease under Norwegian conditions is therefore warranted. A paucity of accurate and reliable information on pathogen biology and ecology, and how these relate to crop development, has been the greatest impediment to more-efficient and effec tive management of strawberry powdery mildew. Our overall goal is to reduce loss due to strawberry powdery mildew through the development of practical forecasting models based upon a comprehensive investigation of pathogen biology, ecology, and epidemiol ogy. Our five specific sub-goals address all of the above basic questions, and their application to improved disease management.