Here’s a little tidbit for you: if you’re scouting canola at the 2- to 4-leaf stage and spot blackleg lesions it’s already likely too late to spray. What’s more, a fungicide application later in the season is also likely a waste of money and time, even if symptoms are severe, because the yield loss has already occurred. Have I inspired you to scout early yet? I’m guessing not, and you’re not alone. (Click here to see what you’re looking for.)
If you’re like many of the people who attended last week’s blackleg field day near Portage la Prairie, you’re probably wondering why in the heck you’d bother scouting seeing as you can’t really do much about it. But I think I’ve distilled down an answer that you CAN do something about: It’s all about next year, and the year after that.
You see, blackleg is actually a far larger tax on canola production than is realized. It’s under-reported and not scouted for like it should be. Why? In part because we’ve had really great resistance built in to high-performance genetics. What could possibly go wrong? Well, the pathogen, like all living things, adapts, and new races of blackleg are building in western Canadian fields. Not all our current canola variety resistance doesn’t work against these new “varieties” of blackleg.
Simply put, blackleg is nature’s kick in the pants for not observing a proper rotation.
Here’s the good news farmers need to remind themselves of: blackleg can only survive and spread if it has canola residue to live on. Canola residue breaks down relatively quickly, which is also good news. However, farmers who alternate between canola and a cereal, then back to canola are not allowing for enough time for residue to disappear. Simply put, blackleg is nature’s kick in the pants for not observing a proper rotation. Sorry, guys, but that’s the truth.
But back to early season scouting. Let’s say you get out there now and do find some early season infection. Let’s say after swathing and harvest you go back out and do a more complete assessment of infection levels and estimated losses. Now you know a key piece of the puzzle when determining risk for the NEXT time you grow canola on that field, not this time. NEXT time you grow canola you can think about rotating the variety (work is underway to determine if there’s an easy way to know which company’s lines have which source of resistance, but that’s another story). NEXT time you can wait two or three seasons before growing canola. NEXT time you may anticipate a fungicide application for the 2-leaf stage.
Because, unfortunately, for this year, it’s already too late.