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Mechanical technology developed by AAFC researchers helps carrot growers control Sclerotinia Rot and increase profitability.

Across carrot growing regions of Canada, Sclerotinia rot of carrots is one of the most serious diseases affecting production. The disease is a major concern especially in the Atlantic regions where long periods of high humidity and wetness are common and where the majority of carrots are stored for long periods of time for winter sales.

“With no chemical control or other options available to growers, we were looking for effective alternative solutions to help growers protect carrot crops,” says Kevin Sanderson, Research Scientist with Agriculture and Agri-Food Canada (AAFC) at the Crops and Livestock Research Centre in Prince Edward Island (PEI). “My colleague Rick Peters, Research Scientist and myself initiated a project in 2006 to followup on some earlier research done at the University of Guelph that showed trimming carrot foliage could reduce the severity of disease. We designed and built a prototye carrot foliage trimmer (CFT) and conducted field trials in PEI.” The cost to build the prototype was about $4000.

The four-row prototype carrot foliage trimmer was designed to trim a portion of the canopy of carrot tops in-between the growing rows. By trimming back the foliage, the opening increases airflow and the sunlight helps to dry out the foliage. The cut carrot foliage trimmings fall between the rows and dry out, which causes any fungi on the leaves to die. The goal was to control the disease before it goes into storage, which is where the most significant losses occur. In PEI alone, the carrot industry can experience losses of up to $500,000 in any given season due to the disease, which translates to losses up to $1,600/hectare to the grower.

“In that first year, the incidence of Sclerotinia rot was very high and our research showed fantastic control of the disease by trimming,” explains Sanderson. “Overall the trimming did not have any impact on yields and growers had fewer losses in the field and in storage. Any small yield losses from trimming were compensated by improved harvestability and reduced harvest losses.”

The results from two field seasons showed that trimming the foliage with the prototype CFT reduced Sclerotinia rot up to 86% in the field and up to 77% in storage without affecting carrot yield. “The best timing was also at row closure, with the recommendation to remove between 45 to 50 cm of the foliage depending on the row width,” explains Sanderson. “Trimming two weeks earlier doesn’t provide the same level of disease control and two weeks later (after row closure) is too late because fungal infections have already occurred.”

Trimming Becomes Standard Production Practice
Based on the success of the research, Oxford Frozen Foods Inc. in Nova Scotia built a nine-row unit for use on their 2000 acres of carrot production in 2007, and today it has become part of their standard production practice for their operation. “The estimated cost of building the nine-row unit was about $10,000 and the company says they recovered their costs in the very first year,” says Sanderson. “Oxford can trim about 100 acres per day for a cost of about $5 per acre.”

As part of their technology transfer efforts, Sanderson and Peters have promoted CFTs at various events in every province and territory across Canada over the past few years. Several commercial trimmer units have been constructed in other parts of Canada (PEI, NS, ON), the US and internationally (United Kingdom, Scotland, France), all based on the original AAFC CFT technology. “Most growers are building their own units, based on information we provide them from our prototype and other units built around the world,” says Sanderson. “The interest keeps growing from both conventional and organic growers. Most recently we have had requests from Germany, Holland and Israel primarily for organic production.”

Growers using the technology have observed other benefits to canopy trimming including a reduction in foliar blights and bacterial soft rot with reduced need for sprays for these diseases. They also note that when making required pesticide applications after trimming, spray penetration is improved. Trimming also results in easier harvesting, improved quality of the marketable crop and increased returns.

“CFT has proven to be a very inexpensive management tool and units are now being built and used worldwide,” says Sanderson. “This is an environmentally friendly method for both conventional and organic growers to significantly reduce Sclerotinia rot and is another tool for reducing their environmental footprint. Many growers are benefiting by making carrot foliage trimming a standard production practice.”

“The development of the carrot foliage trimmer for mechanical control of Sclerotinia root rot, the only control option currently available to growers, has been a great example of agricultural research directly meeting farmer’s needs,” says Kevin Sanderson.

Kevin Sanderson
Ph: 902-566-6881

Rick Peters
Ph: 902-940-1379

Photo credit: “Kevin Sanderson and Rick Peters, AAFC”