The Fieldman’s Files – Scouting for Clubroot

I attended the International Clubroot Workshop in Edmonton Aug. 7th to 9th and found it to be a real eye opener. It truly was “International” with speakers and attendees from such countries as China, Japan, Korea, Germany, Sweden and the UK.

Clubroot is not an “Alberta Canola” issue, it is a worldwide problem of all brassica crops and we heard about the devastating effects on Bok-Choy and Chinese Cabbage, the management issues with Winter Oilseed Rape and the research on new testing methods, control & management and difficulties in breeding long-lasting resistance against so many virulent pathotypes. The final session was of a six member expert panel who answered questions from the audience. When they were asked if they could only give one recommendation to deal with clubroot 4 out of 6 said, “use longer rotations”, one “said keep it out” and the other said “scout your fields”. “Scout your fields” is a very timely idea.

M.D. Inspectors will be starting our clubroot/blackleg inspections shortly, but there is no way we will get out to properly inspect all 1600 or so fields of canola in the M.D. As producers you, or someone working for you will go over every acre of canola, either with a swather or while straight combining.

Identifying a problem like clubroot early is key to be able to manage it. Ignoring it and growing canola in short rotation can very quickly increase spore loads and cause massive wrecks in that field, and it can also be spread on equipment to other fields if you don’t know its there and aren’t taking any precautions. Having clubroot and growing resistant canola in short rotation can select for those pathotypes that the resistance does not work on.

Currently the resistant varieties work very well on only 5 of the 17 known pathotypes and a few canola varieties also offer Intermediate resistance to the 5x pathotype. Even resistant varieties are not completely resistant, even to the pathotypes they are supposed to be resistant to so it is possible to find galls expressed on Clubroot Resistant canola.

My recommendation is to have a garden trowel and secateurs (pruning shears) in all the swathers and combines. If you see some canola that doesn’t look “right” it might be time to stop and check it out. Not looking “right” could include yellowing, wilting, stunting, premature ripening and plant death.

There’s a very good likelihood it will appear in patches, and often near the field entrance or in wet areas. I realize this year in some fields there are many, many areas that drowned and will not look “right”. No one will stop to check them all out so pick a couple; concentrate on patches that perhaps aren’t as easily explained (doesn’t usually drown there). Use the garden trowel to dig out some plants and examine the roots. Keep in mind Clubroot at low spore levels may only have small galls which can easily be missed, Knock the dirt off and examine especially the lateral roots. If you don’t see anything on the roots use the shears to snip the plants at ground level and check for blackleg. The photo below shows canola stems with examples of the range of Virulent blackleg infections from left to right, 0 to 5. If you’re seeing a significant incidence of stems rating 2 or higher, it’s likely you experienced yield loss due to the blackleg.

Even if you aren’t seeing anything odd in your fields, it is still a very good idea to stop and check things out, take a body break and pull some plants every now and then. Especially at low infections levels there may be no above ground indication at all. Clubroot is definitely a disease you don’t want to find, but if you are going to find it then best scenario is finding it while spore levels are low, before you’re dealing with billions of spores per gram of soil and your whole farm is infected. If you find a spot with plants you believe may be Clubroot infected, I would highly recommend marking it in some way, or dropping a pin with your phone so you can find it again. I would be definitely willing to work with any producer who believes Clubroot was found on their land, to send in samples for lab confirmation and to help manage it. Best of luck with harvest, I hope we get some beautiful smoke-less drying days soon. Contact me at (780) 837-0043 or by email at asb@mdsmokyriver.com.

All photos courtesy of Normand Boulet.