Agriculture and Agri-Food Canada scientists in Charlottetown, Prince Edward Island, have developed a mechanical device to trim a portion of the canopy of carrot tops in-between the growing rows. The carrot foliage trimmer helps control Sclerotinia rot and provides a simple way to reduce chemical pesticide use in carrot production. The project is one of many funded through the Pesticide Risk Reduction Program of Agriculture and Agri-Food Canada's Pest Management Centre.
Each year carrot producers across Canada potentially lose a substantial amount of their harvest due to Sclerotinia rot caused by Sclerotinia sclerotiorum. This is a devastating disease destroying crop quality and making carrots unsuitable for human consumption. The disease is found in all carrot-growing areas in Canada but is more prevalent in Eastern Canada where conditions are more humid and wet. There are no known effective controls for this serious disease.
Although Sclerotinia rot becomes apparent in storage, the disease actually begins in the field. During the growing season, the canopy of one row of carrots will grow to the point where it meets that of the adjacent rows. As a result, air and sunlight cannot reach the soil, moisture levels increase, and fungal diseases can begin to form.
The Carrot Foliage Trimmer
AAFC scientists have developed a mechanical device to trim the carrot foliage. Trimming is most effective about the time of row closure, which is late July/early August in Prince Edward Island. Field trials have shown the trimmers usefulness in opening the canopy which allows sunlight penetration, reduces humidity, increases air flow and prevents the accumulation of moisture beneath the canopy. All these factors contribute to decreasing conditions that are favourable for diseases such as Sclerotinia rot to develop. There are both environmental and cost of production benefits by reducing need for fungicides. An added benefit is realised as trimming by reduces the amount of foliage the harvester has to cut thus making harvesting more efficient.
The four row trimmer is equipped with 8 carbide tip rotary saw blades that are 46 cm in diameter. The blades can be individually adjusted for row spacing and canopy width to define the severity of cut. The unit mounts on the back of a tractor and blades are powered by hydraulic motors. As the saw blades spin they lift the carrot foliage and trim it back at the same time. The unit also has a series of lifter bars which lift older foliage lying on the soil surface prior to cutting with the blades. This ensures the removal of older senescing tissues that are most susceptible to infection. The cut carrot foliage trimmings fall between the rows and dry out which causes any fungi on the leaves to die.
This prototype was designed and constructed by Charlottetown staff. The trimmer has been tested using a 40 horsepower tractor. It is proving to be versatile and could be easily adaptable to conventional and organic growing systems across Canada. Initial evaluation of the carrot foliage trimmer in 2006 indicated that mowing at row closure significantly reduced the incidence of Sclerotinia rot in foliage and harvested carrots in storage.
In the summer of 2007 Oxford Frozen Foods, a Nova Scotia fruit and vegetable processor started using a trimmer commercially in its operations. The company has modified the original design to meet their specific production requirements. In addition, a Wisconsin carrot grower has built a trimmer based on the AAFC prototype.
Carrot producers interested in building their own trimmer based on the original design should contact the author for detailed information.
Funding for this project was provided by the Pesticide Risk Reduction Program of the Pest Management Centre (PMC), Agriculture and Agri-Food Canada. The Pest Management Centre funds a number of alternative pest control projects to help Canadian producers develop an integrated approach to managing agricultural pests and reduce on-farm chemical pesticide use.
For more information contact: Rick Peters