Nothing fancy about killing clubroot

Studies by Alberta Agriculture crop pathologist Michael Harding, which compared different disinfectants that can be used on farm equipment, showed a 50:50 concentration of common household bleach and water killed spores and is cheaper.
 | File photo

Household bleach works as well as specialized disinfectants, say experts — and it’s cheaper, too

A jug of household bleach is an important tool in the fight against clubroot.

Studies by Alberta Agriculture crop pathologist Michael Harding, which compared different disinfectants that can be used on farm equipment, showed a 50:50 concentration of common household bleach and water killed spores and is cheaper.

A few years ago, Virkon disinfectant was among those recommended for washing farm equipment to prevent spread of clubroot from field to field.

“Virkon is not as effective as originally thought,” said Canola Council of Canada agronomy specialist Autumn Barnes.

“Bleach is quite affordable and a really good option. We know it works and we know it works quickly, so that’s what our recommendations are. None of us agronomists use Virkon and are recommending that people do not use Virkon for equipment sanitation.”

The Alberta Agriculture study compared results from nine commercial disinfectants and three other unidentified products not on the market. Four of them achieved 95 percent kill on clubroot spores, but bleach is the lowest cost and the easiest to obtain.

Speaking at an Alberta Canola “powering your profits” event in Lethbridge Nov. 20, Barnes said a mist of the bleach solution is a good step toward controlling spore spread. However, it does lose effectiveness over time, once opened.

“If you’re not going to be using a lot of it, don’t go buy some discount vat of bleach,” she said.

Southern Alberta canola growers are on alert since clubroot was found in Rockyview County south of Calgary this summer. The crop disease has so far not been a huge factor in the province’s deeper south.

That doesn’t necessarily mean clubroot isn’t already present, Barnes said.

“Once we start looking for it, we’re going to find it. It is coming, whether it’s your next door neighbour or your own farm.”

Kevin Serfas, director with the Alberta Canola Producers Commission, praised the Rockyview County grower for coming forward when clubroot was confirmed in one of his fields.

“Good on him for coming forward and even letting everybody know,” said Serfas.

“He didn’t have to tell anybody, so if you want to know that there is clubroot in the area, we can’t be attaching a stigma to the people that are coming forward.”

Barnes said the grower did nothing wrong and was growing canola in a fairly common one in three-year rotation. However, analysis of spore load showed clubroot had likely been present for several years.

In addition to Rockyview, clubroot was also confirmed this year in the Municipal District of Greenview and Northern Sunrise County in Alberta’s northwest.

Agronomists speculate that clubroot has been slower to spread into southern Alberta because irrigation provides more crop rotation options and because of higher soil pH.

However, Barnes said the latter reason isn’t necessarily proving out. An infected field in Newell County, north of Brooks, has a pH of eight. Although clubroot seems to prefer pH of six to 6.5, higher numbers don’t provide protection.

“pH is not going to save you. If you have the spores, if you have the conditions for the disease, you are going to get clubroot,” she said.

In a later interview, she said small patches of the disease have been managed with lime applications, but that has other less favourable effects on the soil.

Crop rotation, with at least two years without a host crop, is one way to reduce risk. Hosts include not only canola but also volunteer canola, mustard, wild mustard, stinkweed, flixweed and shepherd’s purse, so weed control is important.

Soil movement between fields should be minimized, and if clubroot is anywhere near the area, farmers are encouraged to grow resistant canola varieties, Barnes said.

“It’s not free and it’s not easy to bring in resistance genes, and there’s not an indefinite number of them, so we need to be really respectful of the genetics that we’ve got.”

Proven, Invigor, BrettYoung, Cargill, Pioneer, DeKalb and Canterra all have resistant varieties on the market.

Soil can be tested for spores, but the best way to identify the disease is to scout fields during the growing season and examine the roots of canola plants. Barnes advised paying particular attention to field entrances and exits, areas near grain bins and bags, beehive site entrances, lower areas, weedy areas and patches of crop that are prematurely ripe.

If galls are found on plant roots, growers should first obtain lab confirmation and then figure out their next moves.

Reporting the finding can help manage spread and help in the allocation of resistant seed varieties.

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