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Tittel: Evaluation of a disease forecast model in relation to airborne inoculum of Bremia lactucae
Forfattere:Nordskog, B., Gadoury, D., Seem, R. & Hermansen, A.
Navn på utgivelse: NJF Report
Publikasjonstype: Proceeding fra int. konf. m. ISBN-nr
Volum (nr): 3 (2)
Side(r): 422-423
Utgivelsesår: 2007
Avdeling: Bioforsk Plantehelse - Ås
Fagområde: Plantehelse og plantevern
Sammendrag: The prediction of infection periods for lettuce downy mildew (Bremia lactucae) is based on the assumption that spores are produced at night and released in the early morning. The divergent light conditions at Nordic latitudes might affect both sporulation and spore release. Therefore, we monitored release of B. lactucae spores in relation to the climatic conditions in lettuce fields to evaluate the performance of existing forecasting models in timing of fungicide applications for management of lettuce downy mildew in Norway.  In 2005, epidemics were created at two field locations that had no previous lettuce production, and a total of 59 days of spore trapping permitted the study of spore release under natural conditions. Sporulation events were compared to predicted spore production events in Modell-Analys (MA). At the two locations, 76 % and 74 % of the spores were trapped between 08.00 and 16.00, respectively. Spore concentration icreased with decreasing relative humidity (RH), ofting coinciding with increasing solar radiation and temperature. Spore production events predicted by MA were correct at 66 % of the days. However, when the criteria for spore production were adjusted, 78 % of the days were correctly predicted.