NDSU launches a canola sclerotinia stem rot risk map online today.
The risk map uses weather variables to predict the threat of sclerotinia.
It is designed to help determine if a fungicide application may be warranted for management of the disease, says Sam Markall, NDSU Extension plant pathologist.
The sclerotinia life-cycle begins when the overwintering structure, sclerotia, germinates and forms small mushroom-like structures called apothecia, Markall explains. Apothecia release ascospores, which can utilize canola petals as a food source.
From those colonized petals, infection then progresses into branches and stems and can result in yield losses and lodging.
Because the infection begins on flower petals, canola is only at risk for sclerotinia stem rot during flowering.
In general, 1-2 inches of rain within a week or two of flowering will provide a favorable environment for sclerotia germination and subsequent spore formation. Moderate temperatures and long dew periods (or rain) during bloom will favor infection and disease development, Markall says.
The risk map is generated by analyzing weather variables from NDAWN weather stations throughout the state. When favorable environments exist for disease development, a "risk" will be reported on the risk map.
Use the map only as a guide, Markall says.
Disease development is driven by a combination of environmental conditions and availability of apothecia in the field. The risk could be higher or lower than estimated depending on prior history of sclerotinia problems and crop rotations used in the previous three years
Also, canola is only at risk in flowering so the risk map is only applicable to your field during (or possibly immediately prior) to bloom.
For the map, see www.ag.ndsu.edu/sclerotinia.
Source: NDSU Crop and Pest Report