Howard: Evaluating Physical and Chemical Methods for Cleaning and Disinfecting Tools, Machinery, Equipment and Other Hard Surfaces Contaminated with Clubroot
Date: December 2012
Term: 3 years
Status: Completed
Researcher(s): Ron Howard, D. Burke, S. Lisowski and C. Pugh, CDC South, Alberta Agriculture and Forestry, Brooks AB
SaskCanola Investment: n/a
Total Project Cost: n/a
Funding Partners: n/a
Project Summary
Clubroot in canola is a destructive soilborne disease that spreads mainly via contaminated soil carried from field to field by equipment. This project evaluated the efficacy of various disinfectants and thermal treatments against the long-lived resting spores of the clubroot pathogen P. brassicae under laboratory, greenhouse conditions and commercial fields. The results showed that cleaning, pressure washing and disinfection of farm and industrial equipment was effective at limiting the spread of the clubroot pathogen. Improved sanitation is a rapid and cost-effective strategy to manage the spread of clubroot in canola and can be broadly applied by the agricultural, oil and gas and construction industries.
Clubroot in canola, caused by Plasmodiophora brassicae, is a destructive soilborne disease now confirmed in several counties in central Alberta, with the potential to spread to other traditional canola growing areas of western Canada. Once a field becomes infested, it is difficult, if not impossible, to get rid of the pathogen because it produces long-lived resting spores. Resting spores are mainly spread via contaminated soil carried from field to field by equipment. Farm, oil field and construction machinery represent the greatest risk of spreading the disease as soil is frequently carried on these types of equipment.
In 2007, clubroot was added as a declared pest to Alberta’s Agricultural Pest Act, followed by the development of the Alberta Clubroot Management Plan to direct farmers and others working in infested fields on ways to prevent the build up and spread of clubroot. Cleaning and sanitation of machinery and equipment was one of the key recommendations in the plan; however, very little was known about the relative efficiency of these methods.
Researchers in Alberta initiated a three-year project in 2009 to evaluate a wide variety of physical and chemical methods including the efficacy of various disinfectants and thermal treatments against the resting spores of the clubroot pathogen P. brassicae under laboratory and greenhouse conditions. Effective treatments were also evaluated in commercial operations.
In the first year, researchers developed in vitro methods and plant-bait assay protocols to treat suspensions of clubroot resting spores in the laboratory. The trials compared 10 commercial disinfectants at four concentrations (zero, one-half, one, two and five times manufacture’s label rate) for recommended exposure times. These treated resting spores were subsequently used to inoculate Brassica spp. seedlings, which were grown and monitored under greenhouse conditions for disease development and severity. Spore mortality was rated using the Evan’s blue staining analysis and two staining assays were evaluated with thermal treatments at 40.0°C and 60.0°C at various incubation times. In general, with few exceptions, most disinfectants appeared to be highly effective at one or more rates and the higher rates of thermal treatments appeared to be highly effective.
In 2010, a chisel plow and four-wheel-drive tractor and grain cart from a clubroot infested commercial field were cleaned, pressure washed and disinfected with various products and sampled with sterile cellulose sampling sponges. The sponge samples were subsequently processed and used for bright-field microscopy analysis and plant-bait assays of clubroot resting spores. In 2011, the same methods were used for sampling and testing a center pivot, chisel plow and four-wheel-drive tractor. In addition soil and crop residues were collected intermittently during the cleaning process. Soil collected from the four-wheel-drive tractor and chisel plow was quantified and used for plant-bait assays.
The results from the field trials showed that cleaning, pressure washing and disinfection of farm and industrial equipment was effective at limiting the spread of the clubroot pathogen. EcoClearTM Fast Acting Weed and Grass Killer, HyperOx® and Sodium Hypochlorite 10.8% were effective while Ag-Services Inc. General Storage Disinfectant, KleenGrowTM, SaniDate® Disinfectant, ThymoxTM and VirkonTM were marginally effective. All plant-bait assays were negative and all thermal treatments of 40°C to 100°C proved effective at various minimum incubation times.
The amount of soil recovered from the four-wheel-drive tractor was estimated at 300 kg, indicating that farm and industrial equipment has a great potential to spread soil from clubroot infested fields.
Overall, the results from the laboratory, greenhouse and commercial field trials showed that improved sanitation, including cleaning, pressure washing and disinfection of equipment, is a rapid and cost-effective strategy to manage clubroot in canola, and can be broadly applied by the agricultural, oil and gas and construction industries.
Other References to this Research Project
Canola Research Hub Blog: Reduce the spread of clubroot spores with effective sanitation
Canola Digest: Canola Digest Science Edition 2017