Sclerotinia Stem Rot Checklist

For each risk factor, select the risk points that apply to your field

Risk factor Possible answers Risk points
NUMBER OF YEARS SINCE LAST CANOLA CROP More than six years
Three to six years
One to two years


DISEASE INCIDENCE IN LAST HOST CROP None
Low (1 to 10%)
Moderate (11 to 30%)
High (31 to 100%)



CROP DENSITY Low
Normal
High


RAIN IN THE LAST TWO WEEKS Less than 10 mm (0.4")
10 to 30 mm (0.4 to 1.2")
More than 30 mm (1.2")


WEATHER FORECAST High pressure
Variable
Low pressure


PERCENT SCLEROTIA GERMINATION IN A LOCAL DEPOT 0 to 5%
6 to 25%
26 to 50%
51 to 100%



TOTAL RISK POINTS FOR ALL RISK FACTORS =

Sclerotinia incidence can vary greatly among fields and years, making scheduled spraying of fungicides unprofitable. However, when sclerotinia risk is high, preventative fungicide applications can effectively lower disease severity and improve yield. Assessment of disease risk within each field is essential to improve the odds that fungicides are only applied when it is economical to do so.

This checklist developed in Sweden can be useful in helping to assess disease risk in fields. Growers should fill out the checklist for each field shortly after first flower (when 75% of the canola plants have at least 3 open flowers). The greater the risk score for a field the higher the probability of a positive economic return. Results in Sweden have suggested that fields scoring 40 or higher will likely benefit from a fungicide, but this may vary a bit depending on fungicide cost and commodity price.

Something else that may affect the risk profile of a field is the genetics that have been chosen. Research has shown that there is a correlation between lodging and sclerotinia levels, and susceptibility to lodging can be related to genetics. As well, the introduction of varieties with some tolerance to sclerotinia into the marketplace offers an additional management tool that may reduce the risk in fields where they are grown.

Disclaimer
The decision whether to apply a fungicide for control of sclerotinia stem rot in canola is the sole responsibility of the grower. AAFC cannot guarantee the accuracy of sclerotia-depots and risk points assigned to sclerotia germination in the modified sclerotinia stem rot checklist.