Sclerotinia Risk in Canola
This forecasting program has been developed by the North Dakota State University Canola Pathology program with support from the
Sclerotinia Initiative, the Northern Canola Growers Association, and the Minnesota Canola Council. While the information presented
by this program is based on data generated through extensive research, it is only intended to serve as a guide for growers.
This forecasting program has two components, a general risk map and a risk calculator. The general risk map uses weather information
to estimate risk of disease development throughout the canola growing areas of the state. This map is updated twice every week
starting in mid June and continuing during the canola flowering period. The risk calculator combines information on cultural
practices and the field past history of Sclerotinia with weather information retrieved from the nearest NDAWN weather station to
estimate the risk of disease development for a specific field. To access the risk calculator visitors are asked to set an account
and to provide information pertinent to the field of their interest.
News and Tips for You
July 31, 2013
Flowering period is ending
While the risk of infection by Sclerotinia remains high for many regions of North Dakota in response to cool temperatures and recent rains, most fields planted before June 10 should be ending the flowering period by now. Consequently, the window for infection by Sclerotinia is closing and fungicide applications at this time may not be necessary. Field trials have indicated that very little to no return is obtained when plants are sprayed during late flowering period or later. Further, examination of the number of hours per day in which dew formation is likely indicates that an average of less than 8 hours of dew have occurred in the last week. This should reduce the risk of Sclerotinia development too.
July 19 2013
Increased risk of Sclerotinia
The risk of infection by Sclerotinia has increased in the region in response to recent rains and cooler night temperatures that will increase
leaf wetness duration. Growers are encouraged to look for apothecia in their fields. Fungicide applications are suggested when the risk of infection
is high in a field where apothecia are present and the plants have not reached the 50% flowering stage. Illustrations of flowering stages can be found
in NDSU extension publication PP-1410.
June 16 2013
Reading Sclerotinia Risk Maps
Maps depicting the estimated risk of development of Sclerotinia stem rot on canola will be produced approximately every three days for the next six weeks. When reading the maps growers should be aware that the estimated risk applies only to canola crops that are entering the flowering period or are already flowering. This risk is calculated considering the effect of environmental factors. A risk calculator that combines the effect of weather variables, cultural practices, and history of Sclerotinia is also available. While this information is intended to advise growers when conditions may be favorable for disease development, the final decision on whether to spray a fungicide or not should include economic considerations such as the potential yield of the field and the potential market price for the commodity.
May 28 2013
New strains of blackleg, capable of infecting most currently planted commercial cultivars, are increasing in frequency throughout North Dakota.
The fungus that causes blackleg survives from one season to the next on canola residues and their spores can be spread by water splash and air currents.
Yield losses due to blackleg typically occur when plants are infected very early in the growing season (when plants have less than four to six true leaves).
To reduce the possibility of infections, growers should avoid planting canola next to fields that had severe blackleg in the 2012 growing season.
If that is not possible, then fungicide use should be considered. Fungicides azoxystrobin (Quadris), prothioconazole (Proline), and pyraclostrobin (Headline),
are registered in North Dakota for control of blackleg in canola. These products should be applied when canola plants have no more than four leaves.
Older plants are in general less prone to develop the stem cankers that are responsible for yield loss, and thus the economic return of a fungicide
application may be reduced.