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Tittel: Evaluation of Disease Forecast Models in Relation to Airborne Inoculum and Fungicide Control of Bremia lactucae in Lettuce
Forfattere:Nordskog, B., Gadoury, D., Seem, R. & Hermansen, A.
Navn på utgivelse: Advances in Downy Mildew Research, Vol 3
Publikasjonstype: Proceeding fra int. konf. m. ISBN-nr
Side(r): 257-262
Utgivelsesår: 2007
Avdeling: Bioforsk Plantehelse - Ås
Fagområde: Plantehelse og plantevern
Sammendrag: Several models for prediction of infection periods for lettuce downy mildew (Bremia lactucae) are 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, during the period 2001 to 2005 a total of 13 field trials were established in late season lettuce fields to evaluate efficacy of fungicide applications made according to the models PlantPlus (PP) and Modell-Analys (MA) in Norway. Disease severity varied from 0 to 89.4 % in unsprayed control plots at harvest. Fungicide treatments had a significant effect compared to untreated control in all but two of the field trials with disease incidence over 1 % at harvest. Fungicide applications at 10-day intervals and according to PP and MA resulted in an average of 3, 2.5 and 3.3 applications, respectively. There were no significant differences in disease severity at harvest between treatments according to 10-day interval, PP and MA for any of the field trials. 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. Spore production events predicted by MA were correct at 66 % of the days. However, when adjusting the criteria for spore production, 78 % of the days were correctly predicted.