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.
New blackleg label system for canola hybrids
Starting with the 2019 growing season, the canola seed industry in Canada will disclose the major blackleg-resistance genes present in their hybrids using a labeling system. This system is intended to help growers rotate major-resistance genes to improve blackleg management and extend the shelf-life of available resistance genes. Additional information is presented here.
June 16, 2017
Reading Sclerotinia Risk Maps
The risk map will be available this year starting on June 18th. Maps showing the estimated risk of development of Sclerotinia stem rot on canola will be produced daily for the duration of the flowering period. 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. Growers are encouraged to look for apothecia in their fields before making spraying decisions, especially if their fields are located in areas with intermediate or high risk.
Early detection is critical to avoid losses due to blackleg
Blackleg infections that take place when canola plants have less than four leaves are more likely to result in yield losses than those happening when plants are older. Growers should scout their fields for symptoms of early infection on cotyledon leaves starting two weeks after planting. These lesions may be irregular in shape and have a light brown color. Numerous pycnidia which look like tiny grain of black pepper may be produced in the dead tissues especially if humid conditions prevail for several days. The fungus will move from the cotyledon leaves into the stem but will do so without showing further symptoms of infection. In this way, infected plants that have already dropped their cotyledon leaves may look healthy.
As the plants continues developing, symptoms on true leaves may also appear. Usually these lesions are not produced by the same fungus that caused the cotyledon lesions but by spores that arrived at later time. Nevertheless, their presence in plants with less than four true leaves is an indication that blackleg may be a problem that requires fungicide applications. A list of fungicides registered for use in canola against blackleg can be found in NDSU extension publication 2016 Fungicide Guide (Canola-Rapeseed).