Articles
Is DOWNCAST an effective model for predicting onion downy mildew in Ontario, Canada?
Article number
1398_14
Pages
105 – 108
Language
English
Abstract
Onion downy mildew, caused by the Oomycete Peronospora destructor, is a highly destructive foliar disease of onion.
The disease, however, does not occur every year in the Holland Marsh, Ontario, Canada.
Symptoms develop 10-14 days after infection and proper fungicides must be applied prior to infection to be effective.
Disease forecasting is used to indicate when no fungicides are needed and to properly time protective fungicide applications when there is disease risk.
The integrated pest management (IPM) program uses the forecasting model DOWNCAST to predict the risk of sporulation and infection based on daily air temperature, relative humidity, and leaf wetness duration and also temperature in the days after infection.
Fungicide sprays are also recommended if downy mildew is found in the region.
Spore trapping was added to the IPM forecasting program to detect sporangia of P. destructor in the air.
Rotorod spore traps are assessed three times a week throughout the growing season.
From 2012 to 2021, the forecasting program was accurate in eight of the 10 years, including two years where there was no disease risk, and no disease was found in the Holland Marsh.
In most years, onion downy mildew developed 14-17 days after sporangia were found.
While the model alone is mostly effective, DOWNCAST can be improved with trapping and rapid identification of sporangia to confirm disease risk.
DOWNCAST continues to be a useful tool for onion growers in the Holland Marsh and other regions in Ontario.
The disease, however, does not occur every year in the Holland Marsh, Ontario, Canada.
Symptoms develop 10-14 days after infection and proper fungicides must be applied prior to infection to be effective.
Disease forecasting is used to indicate when no fungicides are needed and to properly time protective fungicide applications when there is disease risk.
The integrated pest management (IPM) program uses the forecasting model DOWNCAST to predict the risk of sporulation and infection based on daily air temperature, relative humidity, and leaf wetness duration and also temperature in the days after infection.
Fungicide sprays are also recommended if downy mildew is found in the region.
Spore trapping was added to the IPM forecasting program to detect sporangia of P. destructor in the air.
Rotorod spore traps are assessed three times a week throughout the growing season.
From 2012 to 2021, the forecasting program was accurate in eight of the 10 years, including two years where there was no disease risk, and no disease was found in the Holland Marsh.
In most years, onion downy mildew developed 14-17 days after sporangia were found.
While the model alone is mostly effective, DOWNCAST can be improved with trapping and rapid identification of sporangia to confirm disease risk.
DOWNCAST continues to be a useful tool for onion growers in the Holland Marsh and other regions in Ontario.
Publication
Authors
M.R. McDonald, K. Vander Kooi, T. Blauel
Keywords
Peronospora destructor, forecasting, IPM, spore trap, Rotorod
Groups involved
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