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Cavalier County’s Clubroot Conundrum

Clubroot of canola has been an ongoing concern since 2013 when the pathogen was first found in Cavalier County. Since that initial identification, the pathogen has spread and is now being classified as an epidemic by Dr. Venkat Chapara, the pathology specialist at the Langdon Research Extension Center (LREC). As producers in the county look ahead to the 2019 growing season, both Dr. Chapara and NDSU Extension Agent Anitha Chirumamilla cannot stress enough the impact this pathogen could have on canola crops.

Posted 1/24/19

By Melissa Anderson

“This disease, if unchecked, can wipeout canola production from Cavalier County,” Chirumamilla cautioned.

Clubroot is a very different disease compared to all other diseases that producers deal with in agriculture for the following reasons:

1. The pathogen is very primitive and complex as it is neither a fungus nor a bacteria. This makes it difficult to control as to what chemical can be used.

2. It’s very hard to get rid of this pathogen. Once you get this into your field, the pathogen spores could survive up to 20 years

3. There is absolutely no chemical control available.

In canola growing counties, education on and prevention of spreading of the pathogen is a high priority for NDSU extension agents. Discussion amongst the research scientists, extension specialists and their partners including Northern Canola Council and NRCS is a constant.

“[We discuss] how to spread the message effectively into the grower communities so that we can minimize the spread of this disease,” Chirumamilla said.

Extension has been educating growers and communities extensively about the seriousness of this disease and measures needed to prevent the spread. However, being a soil-borne pathogen, the spores can be carried to new fields by equipment, water, wind, and even through muddy boots.

“It is really hard to contain this disease unless the producers practice thorough sanitation – thorough sanitation of the farm equipment including  boots worn in the field, longer crop rotations of at least three-four years, using a resistant variety if the grower has clubroot in his field,” Dr. Chapara explained are how producers can protect and limit the spread of clubroot.

The canola industry in Canada, where the pathogen was first discovered, has suffered greatly as a result. Chirumamilla stated that Alberta, Canada, has seen the worst of clubroot effects. The Alberta government has gone so far as to have their legislators track the clubroot-infected fields by having producers report to the legislature about canola rotations,and the clubroot resistant varieties that will be grown. Even with such a massive effort, the pathogen is still one step ahead of producers and the ag industry.

“The disease is spreading faster as the pathogen developed new strains/pathotypes that overcome the resistance genes,” Chirumamilla stated.

At the LREC. Dr. Chapara has been working extensively  for the last three years to reach out to producers to warn of the clubroot pathogen spread and the management practices that need to be adopted not only county wise, but at the state, national and even international levels.

“A well-executed clubroot survey program has been implemented in North Dakota with well-trained Langdon REC employees and the county agent for the past three years that determined the seriousness of this disease on canola in North Dakota and in United States,” Dr. Chapara said. “Research on canola varietal resistance, brassica hosts and soil amendments to control clubroot have been conducted by the Langdon Research Experiment Station for the past two years and will be continued as high priority research. This is the first research report on clubroot on canola management in the United States.”

Dr. Chapara and the team at LREC also request soil samples from growers who want to know whether they have clubroot in their soils. NDSU scientists in Fargo are also using a molecular-based assay to determine clubroot resting spore presence and count per gram of soil.

“This would be very helpful to the growers to decide their rotations,” Dr. Chapara shared.

Over the course of Dr. Chapara’s research and surveys, clubroot has been found in soils up to 6.4 pH. That is still below pH 7 and is considered acidic. If the pathogen develops a tolerance to basic soils and moves into soils higher than a pH 7, the concern for growers in Cavalier County would greatly increase.

“Growers who have above 7 pH need not to worry,” Dr. Chapara said. “But be aware that fields have variable pH spots. If you have low pH spots you are likely to get it. Then you can opt for soil amendments with beet lime or pellet lime.”

For those who like to employ cover crops for their fields, they, too, need to be aware of what they are putting in the ground as clubroot  infects all brassica crops such as cauliflower, cabbage, rutabaga, radish, turnip, brussel sprouts, kale etc. Among these, only radish is a commonly grown cover crop in North Dakota.

“If you have low pH soils and you opt for a cover crop of radish, you are inviting clubroot,” Dr. Chapara warned.

It isn’t just crops, either, that can play host to the pathogen as there are also common brassica weeds in North Dakota. Dr. Chapara provided the following examples: wild mustard, shepard’s purse, pennycress, volunteer canola, and stinkweed. If a grower has low pH soils and clubroot is in his fields, Dr. Chapara said that the grower cannot ignore these brassica weeds as they keep on adding clubroot spores to the soil which makes it very difficult to get rid of clubroot and grow canola.

“The disease clubroot of canola, its survey and awareness research, wouldn’t be possible without the unconditional support from producers, county agents, media such as Cavalier County Republican, Agweek and radio, and last, but not least, the grant funding from Northern Canola Growers Association, Crop Protection Harmonization Board and Northern Canola Research Program (USDA/NIFA) to conduct this research at Langdon,” Dr. Chapara said.

Dr. Chapara has  two years of varietal resistant research results on clubroot of canola published in 2018 – Annual Report of Langdon Research and Experiment Center.

“There are excellent clubroot resistant varieties of canola available in the market, which growers can choose for their next rotation,” Dr. Chapara stated.

Dr. Chapara advises growers to refer to the annual research report which is available online (www.ag.ndsu.edu/langdonrec/annual-research-reports1-1/2018-annual-research-report/view) or there are copies available at the Langdon Research Extension Center.