As the season progresses and as conditions stay cool and damp the possibility for Blackleg to appear in canola is greater. Blackleg (Leptosphaeria maculans) is a fungus that can cause significant damage and yield reduction to a canola crop under the proper conditions. Blackleg is a fungus that can come from infected seed or from spores created by old infected canola stubble residue. There are two types of strains mildly virulent and highly virulent which can infect canola crops. The mildly virulent strain will cause minimal damage and minimal yield loss. The highly virulent strain can cause significant damage and yield loss. Blackleg can infect canola plants as early as the cotyledon stage up to the early maturing stage of the plant. While it is extremely difficult to spot at the early onset of infection, grayish white legions can appear on stems or leaves with tiny pepper like black spots or spores, called pycnidia which can be spread by wind or rain to neighboring plants and infect them as well. It is recommended that farmers use preventative maintenance to avoid blackleg infections in their canola crops. Some of the tools to prevent Blackleg infection in your crop would be to:
First: select Blackleg resistant varieties which will be the best way to prevent the disease in your fields.
Second: is rotation. Canola crops grown back to back or in very short rotations are more susceptible to infection.
Third: is to use fungicides to treat crops that may be susceptible to the disease.
On some of our scouting trip this summer we have found Blackleg spores growing on old canola stubble below the crop canopy. The cool wet conditions are ideal for the growth of the spores. Some spores can travel several kilometers in the wind so beware of neighboring fields that had canola in their rotation in previous years. It is important to scout fields around the time of swathing to identify if black leg has indeed infected your crop. By doing this it can help farmers make decisions to prevent the disease in future crop years. If you think you may have the potential to have blackleg infections in your canola crop, please speak to your chemical reps about possible fungicide applications. Some registered fungicides have staging and pre harvest restrictions as well as export restrictions on harvested grain treated with certain fungicides.
As the growing season progresses and the country side turns yellow we invite producers to keep scouting fields and look for possible disease issues or insect pressure. Stay tuned for more information on other diseases and insect information. Enjoy your summer and happy farming.
Ramblings from Dan.