The Fieldman’s Files – Clubroot Update, an opinion piece, Part 2

A canola root heavily infected by clubroot.

Normand Boulet, CCA
Agricultural Fieldman
M.D. of Smoky River No. 130

Note: The first part of this article is found in the December 12 edition of the Smoky River Express.

Last week I tried to establish that finding clubroot in the M.D. of Smoky River was not only inevitable, it was desirable because then we could move from denial to acceptance and management.

I certainly hope all you producers are actively scouting your fields and looking for clubroot because if it is on your farm, the sooner you find it the better chance you have of keeping the impact to a minimum.

Now then, you might be thinking, “clubroot, what’s the big deal, there are clubroot resistant varieties available, this is like blackleg, its business as usual.”

This is the issue I have with that mindset. Virulent blackleg is and was a devastating threat to canola production, but in the early ‘90’s when the resistant varieties came out, they took care of the problem, totally and forever (or so it seemed).

The resistant varieties still work well, and generally although we do find blackleg in every field, we look for it (except for one last year), it is for the most part at low infection levels and is at least in most fields, not affecting yield significantly.

The first Clubroot resistant varieties came out in 2009, and three years later there were already field scale infestations around Edmonton where resistance was broken and growing any kind of canola, resistant or not would have been a totally foolish thing to do because you were assured no crop.

It took a whole bunch of research and work to understand that the available resistant varieties worked against five clubroot pathotypes, and 17 pathotypes were discovered to exist. Even though pathotype three (as it was then called) was the most prevalent pathotype in Alberta and the resistant varieties worked well against it, there were other background levels of pathotypes which the resistance did not work against.

Once those other pathotypes “tasted” those resistant varieties a few times, spore levels increased quickly, and in a matter of three years the resistance was no longer effective in some fields. A shift in pathotype prevalence took place because pathotype 3 was being supressed, and other pathotypes were allowed to flourish. Only around Edmonton you say?

Pity, but no. Samples from the 20 fields found in Big Lakes County last year were sent for pathotyping and it was found that 5X was present (in low levels) in 88 per cent of the samples. 5X is what the first resistant breaking pathotype was called because it looked and acted like pathotype 5, but unlike the regular pathotype 5, 5X broke resistance.

There were other resistance breaking pathotypes found since then and researchers at the U of A and Agriculture Canada ended up developing a Canadian Clubroot Differential (CCD) because the previously used CCD’s could not differentiate all the pathotypes being found in Canada.

So the new CCD was used to differentiate the clubroot being found into 17 distinct pathotypes. Seventeen is scary enough, it appears there are 3 new pathotypes that have not been seen before in Big Lakes and while their resistance breaking potential is currently being evaluated, one thing is certain – the total number of pathotypes will continue to go up and not all these new pathotypes will be controlled through resistant varieties.

There is still much to be learned but one thing is certain. Resistant varieties are not a silver bullet, they are a tool which must be used in conjunction with a whole list of other tools including; rotating out of canola, controlling volunteer canola and mustard family weeds, minimizing soil disturbance and cleaning equipment. The Alberta Clubroot Management Plan is a good source to read up on those tools.

Why do I think clubroot is in the M.D.? First off, to be here it would have to get here, how would it get here?

It would get here with soil movement, consider this: It was discovered around Edmonton in Canola in 2003, but it was known to be in market gardens around Edmonton since the 1970’s, some of those market gardens were abandoned and just absorbed into the field, so Clubroot has been there, bidding it’s time since the ‘70’s or earlier.

In that nearly 50-year period, how many pieces of equipment were purchased from around Edmonton and brought here with no cleaning done? How many combines, seed drills, tractors or sprayers were demo’d there, in field after field and brought here? How many rigs moved from there or construction equipment with their hundreds of pounds of soil on them? How many hunters and ATV enthusiasts with their quads and side-by-sides came up north without cleaning them?

In that approximately 50-year period, is there any field in the M.D. you can definitely state did not get some soil either directly, or indirectly from what is now known to be a Clubroot infested area?

By indirectly I mean the neighbour bought a used combine from a farm near Leduc and clubroot was introduced to a field near you. Spores are increasing in number due to short canola rotation and “not the best” weed control in cereals.

The field is heavy harrowed and wind blows thousands of pounds of soil, or water erosion moves dirt onto your land, its topsoil so that’s OK! But if soil can move, so can clubroot.

The last question I want to try and address, which probably no one else has, is: “Why did it take so long to show itself around Edmonton?” Think about farming in the ‘70’s, canola was a rotation crop you put in when the field was clean enough because weed control choices were not great. Along comes herbicide tolerant canola in the mid-nineties and it suddenly goes from being a crop that requires very good management to being the easiest crop to grow.

Generally pretty decent prices compared to other crop choices, the loss of some rotation crops (we weren’t the only ones with dehy plants), a move away from mixed farms and increasing demand for canola oil all led to canola going from a once in five or more years to 1 in 2 and canola/snow “rotations”.

Clubroot was there, and with spores that last up to 20 years in the soil and can sleep until a host plant wakes them, it could remain at low levels not causing any problems until rotations were tightened to the point of breaking.

Assuming you have read my two latest articles, and somehow you still think we’re immune, consider this: clubroot prefers acidic soils (we have that), it thrives in wet conditions (yeah, that never happens here) and it infects a wide range of hosts including canola – this M.D. is in most summers, 50 per cent yellow.

It also will live on mustard family weeds like stinkweed, flixweed, Shepard’s purse (yup, we got all those) and of course volunteer canola.

Matter of fact, those plants only have to live for about six weeks for clubroot to go from spore in the soil to gall releasing spores back into the soil, with a massive multiplication ratio.

The question I have is; what management tools are you using to protect your farm? Are you actively scouting? Are you cleaning equipment coming onto your land from elsewhere?

Are you cleaning equipment between fields? Are you insisting that oil and gas exploration companies clean and disinfect their equipment before they leave their previous location?

Are you growing clubroot resistant canola with a minimum two years between canola crops? And the last question, if you found it and aren’t telling anyone, how are you managing it?

Managing clubroot is imperative to the success of farmers in this M.D. If you have questions, give me a call, if I don’t know I’ll try to find the answer.

In addition, if you have read the two articles in the series and now you want to call and ream me out, call me at (780) 837-0043.

A stickweed plant root, also heavily infected by clubroot. Photos courtesy of International Clubroot Workshop.


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