Reduced-Risk Strategy for Integrated Weed Management in Field Vegetables
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For inquiries regarding this strategy, please contact:
Pesticide Risk Reduction Program
Pest Management Centre, AAFC
Pesticide risk reduction strategies are developed under the Pesticide Risk Reduction Program (PRRP), a joint program of Agriculture and Agri-Food Canada (AAFC) and the Pest Management Regulatory Agency (PMRA) of Health Canada. The key objective of the program is to reduce the risks to the environment and to human health from pesticide use in agriculture. To achieve this objective, the Program works with grower groups, industry, provinces, and researchers to identify gaps in pest management and opportunities for pesticide risk reduction, and to develop and implement strategies to address these.
A pesticide risk reduction strategy is a detailed plan developed through consultation with stakeholders aiming to address grower needs for reduced-risk management tools and practices for specific priority pest issues. The strategy document presented herein, is intended to update stakeholders on the activities supported by the Program in developing and implementing the strategy and new tools and practices made available through this process. The strategy also provides baseline information and enables tracking of advancements in pesticide risk reduction.
For more information on the activities and outcomes of the Program's strategy work to date, visit the Pest Management Centre website www.agr.gc.ca/prrmup
The Pesticide Risk Reduction Program acknowledges all participating stakeholders and organizations, specially, the members of the Integrated Weed Management Working Group including Kristen Callow of Ontario Ministry of Agriculture and Rural Affairs (OMAFRA), Clarence Swanton, Robert Grohs and Rene Van Acker of University of Guelph (ON), Danielle Bernier and Mario Leblanc of Ministère de l'Agriculture, des Pêcheries et de l'Alimentation (MAPAQ), Viliam Zvalo of Agra Point (NS), Nathan Boyd of Nova Scotia Agriculture College, Shauna Mellish and Stephanie Compton of Prince Edward Island Department of Agriculture, Gavin Graham of New Brunswick Department of Agriculture, Aquaculture and Fisheries, Luc Brodeur of Phytodata (QC), Connie Achtymichuk of Saskatchewan Ministry of Agriculture, Susan Smith of British Columbia Ministry of Agriculture and Land, and Rob Nurse, Diane-Lyse Benoit, Bonnie Ball Coelho, and Kevin Sanderson of Agriculture and Agri-Food Canada (AAFC) for their continued collaboration and contribution to the development and implementation of a pesticide risk reduction weed management strategy for field vegetables in Canada.
This report summarizes the collaborative efforts, activities and progress status of the Pesticide Risk Reduction Program since 2003 in supporting the development and implementation of a reduced-risk strategy to manage weeds in field vegetable crops in Canada. The objective of this strategy is to reduce risks to humans and to the environment from herbicides used in vegetable production, while helping growers to achieve viable weed management and farm profitability, and also minimize risk of herbicide resistance.
This strategy was developed through stakeholder consultations and collaborations with provincial weed specialists, public and private weed scientists, vegetable industry representatives and other, many of whom have actively participated in the Integrated Weed Management Working Group. Within this strategy, herbicide risks and key weed management issues are identified, reduced-risk solutions to address these issues are discussed and prioritized, and a strategic action plan to support development and implementation of these solutions is developed. This process provides a framework for the funding program delivered through AAFC's Pest Management Centre in support of implementing the reduced-risk weed management strategy for the vegetable sector.
Field vegetables are important crops grown annually in all regions of Canada. Overall, there are about 100,000 hectares of field vegetables grown across Canada, with Ontario and Quebec having the largest acreages and providing about 80% of Canadian vegetable production. Overall, field vegetable farm gate value in 2009 was $773 million. Vegetables are among the most intensive cropping systems with high input and maintenance operations to ensure maximum yields and quality produce to meet increasing demand for fresh and processing markets. Adequate weed management and herbicide use are an essential part of viable vegetable production.
The key issue identified for field vegetables through this strategy was the lack of a variety of control options and tools to enable sustainable weed management in a multiple crops. Repetitive use of the few herbicides available has led to resistance development within weed populations. For instance, resistance to linuron, one of most heavily used herbicides and one of the few weed control options in organic (muck) soils, has been reported in ragweed and pigweed species. Moreover, some herbicides, including linuron, are currently being examined under Health Canada's re-evaluation program. This program uses up-to-date scientific approaches to examine older (registered prior to 1995) active ingredients to ensure ongoing protection of human health and the environment. As a result of this process, some of the currently registered products that do not meet acceptable safety standards may be removed from the marketplace, potentially, leaving growers with fewer control options.
The need for lower risk herbicides and non-chemical alternative control options, suitable for inclusion in integrated management systems was thus identified as a priority gap to be addressed by this strategy. It is anticipated that bridging this gap will minimize full reliance on herbicides and mitigate the risk for development of weed resistance to herbicides.
The Reduced-risk Strategy
A number of herbicide screening projects have been funded through the Program since 2003 to help with the generation of efficacy data required to support submissions to Health Canada's PMRA for registration of new minor uses of reduced-risk herbicides.
An Integrated Weed Management Working Group (IWM WG) was established in summer 2009 to provide expert advice and help the Program in developing a strategic direction in achieving sustainable weed management for the field vegetable sector. The IWM WG consisted of provincial vegetable and weed specialists, University and government weed scientists, and extension experts of the vegetable industry. The WG is chaired by an AAFC Pest Management Centre employee and co-chaired by an external member representing the vegetable sector.
Since its inception, the IWM WG has been involved in a number of consultations and regular exchange of information and ideas through teleconferencing and emailing. On November 26, 2009, many members met in person at the Canadian Weed Science Society (CWSS) Annual meeting in Charlottetown, Prince Edward Island. Typically, updates on the achievements of the IWM WG and the status of the IWM strategy are provided at the CWSS annual meetings.
Discussions within the WG have led to the identification of key weed management issues and gaps which field vegetable growers are facing as well as recommendations for reduced-risk control options to address these issues. Below are some areas of concern identified over the past years in some key vegetable producing provinces in Canada:
- Lack of replacement products and practices to avoid full reliance on few herbicides (e.g. linuron) and allow reduction in herbicide use in vegetable production;
- Lack of tools and approaches to minimize unnecessary use of herbicides;
- Lack of effective programs for herbicide resistance management (e.g. addressing redroot pigweed and ragweed resistance to linuron which is used extensively in carrots and onion);
- Lack of adequate replacement products for atrazine; loss of atrazine in British Columbia has led growers to rely on Basagran only for weed control in sweet corn;
- Lack of grower knowledge on available cultural control methods and integrated practices;
- Lack of knowledge on herbicide residual effects in various rotation systems (e.g. tomato following sweet corn in rotation)
- No-till shown as an effective cultural weed management method but not being adopted;
- Lack of weed control approaches suitable for the organic vegetable sector.
A new round of consultations carried out in Fall 2010 validated the previously identified issues and provided a renewed look at potential new solutions as new research results emerge. Research and development areas identified through this process have been the basis of funding support provided by the Program targeting pesticide risk reduction in field vegetable production.
The strategy action plan table below summarizes the goals and specific solutions that the IWM WG has identified and proposed as well as the actions taken by the Program to address these solutions. To date, three main goals were targeted, eleven projects have been funded and additional activities have been undertaken through the support of AAFC's Pesticide Risk Reduction Program to advance the implementation of the reduced risk weed management strategy.
In essence, the plan is centered on obtaining lower risk control products and practices which:
- reduce the use and reliance on herbicides,
- minimize unnecessary herbicide applications, and
- allow integration of various control options.
In summary, the major outcomes expected from the implementation of the reduced-risk weed management strategy in field vegetables include:
Efficacy data for reduced-risk herbicides to fulfill regulatory requirements and contribute to submissions to PMRA for new minor use herbicide registrations;
- Recommendations on innovative herbicide application technologies leading to reduced use of herbicides;
- Recommendations on innovative cultural weed control practices, such as the use of cover crops;
- Recommendations on integrated weed management systems combining a variety of tools and practices;
- Extension publications, presentations and demonstrations to communicate and promote grower adoption of the new technologies made available through this strategy work.
It is anticipated that in combination, these outcomes will help field vegetable growers reduce reliance on herbicides and achieve sustainable management of weeds while maintaining viable vegetable production in Canada.
Through this strategy work, the Program is also providing collaboration opportunities and promoting new partnerships among various stakeholders, including growers groups, weed and crop experts, government research scientists, and the processing industry. Working together with these entities increases the likelihood that the tools and practices developed through this strategy will be adopted by growers and that the risk reduction goals in weed control will be achieved.
This report is a living document and will be updated periodically as new information becomes available.
Action plan to implement A reduced-risk strategy for weed management in vegetable Production in Canada: Progress status (April 2011)
Status legend: Project addressing a milestone is complete (Completed); Work/project underway (On-going); Areas recommended for further work or technologies to be promoted (Future)
Action plan to implement a reduced-risk strategy for weed management in vegetable production in Canada: Progress status (April 2011)
|Target||Milestone||Status||Strategy Implementation Activities|
(Hyperlinks: Project synopsis, summaries, factsheets available on Pest Management Centre website or elsewhere)
|GOAL 1. Establish base knowledge||Improve knowledge of weed biology, weed/crop interaction, herbicide resistance issues in vegetable crops||Greater understanding of weed response in various production systems (i.e. tillage, seed bank dynamics)|
|Assess the effect of critical weed free periods, crop density, crop spacing, fertility program, and cultural practices on weed/crop competition||Completed||Partially addressed by work conducted under AAFC project PRR07-260 - Determination of the critical weed-free period in carrots grown on muck and mineral soils. Maximum duration that carrot crops must be free of weeds, without compromising yield, is until the 12 leaf stage of crop growth. Based on this finding, carrot growers are recommended to scout fields for weeds until carrots are at the 12 leaf stage. This critical weed-free period may occur over a shorter duration when carrots are seeded later in the season and weed infestation is moderate to low.||March 2009|
|Future||Critical weed-free periods to be determined for other vegetable crops grown in muck and mineral soils|
|Assess the scope of the problem and determine cultural/chemical solutions to address the issue|
|Develop management decision support tools||Develop interactive weed identification and herbicide selection tools||Improper identification of weeds and lack of knowledge on available low risk control options may lead to unnecessary applications of herbicides and loss of product efficacy due to resistance development.
A need was put forward to develop a national web-based interactive tool (searchable database) to help vegetable growers and extension service personnel to accurately identify weeds and make informed decisions about choice of herbicide. A tool similar to Weedinfo.ca , which was developed previously for field crops (corn and soybean) with the partial support of Pesticide Risk Reduction Program, was suggested. ON's provincial version of this tool is WeedPro75 . WeedPro75 includes a functional database where researchers can upload or access weed related research data and results from various publications.Québec Ministry of Agriculture, Fisheries and Food (MAPAQ) has made available for use an interactive web-based pesticide selector tool called SAgE Pesticides. It helps selecting herbicide options based on toxicity and risk to human health and environment. Many horticultural and field crops are already included in this tool and inclusion of others is under way. MAPAQ has also made available a pesticide risk indicator called Pesticide Risk Indicator for Québec (IRPeQ) available in French and English. IRPeQ and SAgE Pesticides are linked.
|GOAL 2. Identify and develop new reduced-risk control solutions||Investigate means to reduce pesticide use||Develop integrated weed management systems including cultural and chemical control options||Completed||Partially addressed by AAFC project PRR06-700 - Reduced risk weed control strategies in carrot production in organic & mineral soils. Approaches integrating chemical treatments with cultural control techniques were devised as alternatives to full reliance on herbicides, such as linuron, for broadleaf (e.g. ragweed & redroot pigweed) weed control: 1) For carrot production in mineral soils and on raised beds, the most economical, effective and environmentally responsible alternative was using banded application of linuron combined with mechanical cultivation using side knives between the beds thus reducing herbicide use by 66%; 2) For carrot grown in organic soil the control program with the most potential was the one in which linuron is applied broadcast prior to carrot emergence, followed by a single cutting at 3 leaves stage of carrots, thus reducing herbicide use by 50%. Approach (1) can be transferred and recommended for grower adoption (see follow up under Goal 3); approach (2) is under further investigation.||March 2009|
|Evaluate efficacy of reduced risk herbicides||Completed||AAFC project MU03-WEED1 - Evaluation of low risk weed management options in sweet corn, tomatoes, sugar beets, peppers, cole crops and vine crops. Efficacy and crop tolerance data were generated to support 7 registrations (Dual II Magnum1,2 on squash, pumpkin and pepper; Callisto1,2 and Accent2 on sweet corn; Pinnacle2 and Prism on tomatoes) and 4 URMULE submissions (Impact2 on sweet corn; Command1 on peppers; Frontier1,2 on cabbage , and Goal1 on cole crops).1 Submitted through AAFC's Minor Use Pesticides Program; Registered.||March 2008|
|AAFC project MUR06-030 - Evaluation of low risk weed management options in snap beans, lima beans, carrots, red beets, pea, and dry bean. Efficacy and crop tolerance data were generated to support six new herbicide uses, including 1 registration (Upbeet1,2 in red beets) and 5 URMULE submissions (Dual II Magnum2 and Pursuit2 in peas; Dual II Magnum in red beets; Lontrel in red beets; Sencor1 in carrots; and Dual II Magnum1,2 in carrots). 1 Submitted through AAFC's Minor Use Pesticides Program; Registered.||March 2008|
|Completed||AAFC project MUR06-100 - Reduced risk herbicides for horticultural crops in organic soils: supplemental registration data and herbicide screening. Work undertaken in Ontario and Quebec on onions, lettuce, Chinese cabbage and celery. Results were inconclusive for Chinese cabbage and celery. Efficacy and crop tolerance data was generated to support submission of Prowl (pendiméthaline) for use in lettuce and label expansion for Chateau (flumioxazin) through AAFC's Minor Use Pesticides Program and also recommendations on using flumioxazin for post-emergence broad leaf control in onion grown in muck soils.||March 2008|
|Completed||AAFC project SCR07-002 - Processing peas herbicide screening trial. Efficacy and crop tolerance assessments confirmed that four of the herbicides evaluated in this study: Odyssey (imazamox+imazéthapyr) [registered], Chteau (flumioxazine), Outlook (diméthenamide-P) and Sandea (halosulfuron-méthyle) were considered effective and safe to be pursued for registration for broadleaf weed management in processing peas.||December 2007|
|On-going||AAFC(Minor Use Pesticides) project AAFC09-059 investigated herbicide candidates for cleaver (Galium aparine) control in carrots. The field efficacy trial portion of the project is now complete and Nortron Flowable Herbicide (ethofumesate) was selected as the best candidate among control options tested. Following this result, Nortron was chosen as a 2011 solution priority at the Minor Use Priority Setting Meeting in March 2010.|
|Future||Identify potential bioherbicides suitable for use in both organic and conventional vegetable production in Canada.|
|On-going||The Pest Management Centre works closely with the Pest Management Regulatory Agency, the biocontrol industry, grower representatives, and international experts, providing necessary regulatory support to facilitate the registration and the adoption of biological control products. Support includes advice on regulatory and scientific questions related to biopesticides registration/commercialisation, literature surveys and writing scientific rationales for registration submissions, supplementary efficacy trials, assisting in assembling and submitting the registration packages. Since March 2010, the Pest Management Centre established an annual Biopesticide Priority Selection Workshop to facilitate stakeholder participation in identifying priority biopesticide uses to be supported by the Centre through the regulatory path. To date, 16 priority uses have been selected (8 in 2010 and 8 in 2011), none of which include bio-herbicides for field vegetables.|
|Investigate cultural weed control options||Potential use of cover crops in combination with other cultivation techniques||Completed||AAFC project PRR07-040 - Evaluation of reduced-risk weed management approaches for annual grass control in sweet corn. Study evaluated the efficacy as well as environmental and economic benefits of using various cover crops (e.g. adzuki beans, radishes and fall rye) as living-mulches between the rows to manage weeds in sweet corn. Although weed control achieved with living mulches alone was lower, yields did not differ from the industry standard, meaning that using living mulches alone may be a viable pesticide-free weed management option in sweet corn. Using living mulches in combination with herbicides provided an added benefit of better season long weed control.||March 2010|
|Completed||AAFC project PRR10-010 - Literature review on applications of cover crops as part of integrated weed management systems in vegetable production in Canada. The review identified 4 approaches suited to sustainable weed management that can be recommended for adoption by Canadian vegetable growers: A) fall seeded cereal rye + hairy vetch cover crop mixture, chemically killed before no-till tomato; B) fall seeded rye chemically killed before zone-till cucurbits; C) aerial overseeded rye into late harvested crops such as potato or carrot; and D) summer seeded sorghum or Sudan grass before or after short season vegetables such as fresh market cole crops or pea.||June 2010|
|Future||Investigate combinations of cultural control approaches such as reduced (zone/deep) tillage and cover crops for weed management (especially cleavers) in field vegetables (e.g. cucurbits, broccoli, cauliflower, rhubarb, etc.).|
|Future||Investigate cultivation techniques such as using cover crops in rotation or in between the crop rows, tillage, banding applications with bioherbicide products for weed management in organic production.|
|Future||Investigate sustainable weed management approaches (e.g. using herbicides in combination with cover crops) in vegetable production under plastic (e.g. eggplant, tomato, pepper, cucumber).|
|Future||Evaluate equipment available for the destruction of cover crops (kill efficacy, cover crop re-growth, speed of destruction, cost of equipment, cost of operation, facility of use and adjustments).|
|Future||Demonstrate incorporation of cover crops for weed management in field and processing tomato|
|Investigate mechanical weeding methods||Future||Evaluate crop tolerance and weeding efficacy of different mechanical weeders used in vegetable crops (e.g. onions, cucurbits, tomatoes, sweet pepper, cabbage, broccoli, snap beans, red beets and sweet corn).|
|GOAL 3. Promote and facilitate adoption of reduced risk solutions||Communicate to growers results from the strategy work||Develop and distribute extension material featuring new tools and practices made available||Completed||Critical weed-free period established for carrots PRR07-260 - Determination of the critical weed-free period in carrots grown on muck and mineral soils and relevant recommendations on this window for essential weed control in carrots is incorporated into ON Crop Production Guide. Also a factsheet titled Weed Management in Carrots is published on OMAFRA's website.||August 2009|
|Completed||Two factsheets were published on the results of PRR06-700 - Reduced risk weed control strategies in carrot production in organic & mineral soils about weed management in carrot crops:
Carrot Production on Raised Beds-Reduced risk weed control strategies
Banded Herbicide Application in Carrot Production
Two factsheets on banded herbicide technology in FR were translated in EN and published:
Banded Herbicide Application in Potatoes
Banded Herbicide Application
|On-going||Efforts are underway to develop extension publications to disseminate information and demonstrate practices identified through the cover crops project (PRR10-010). A factsheet and a poster were published on the results and recommendations coming out of literature review and disseminated at growers events held in winter 2011.|
|Hold grower oriented workshops and field tours||Future||Identify venues to disseminate information and promote sustainable weed management practices recommended by the literature review on cover crops and other projects.|
|Demonstrate to growers the economical and environmental benefits of commercial adoption of new tools and practices made available||On-going||AAFC Project PRR10-080- Demonstration of reduced use of herbicides in carrot crops through chemical banding and mechanical cultivation in Prince Edward Island||March 2012|
|On-going||AAFC Project PRR10-090 - Demonstration of reduced use of broadleaf herbicides in carrot crops through chemical banding and mechanical cultivation in Nova Scotia||March 2012|
|On-going||AAFC Project PRR10-120 - Demonstration of reduced use of broadleaf herbicides in potato crops through chemical banding and mechanical cultivation in Quebec, Prince Edward Island, and New Brunswick||March 2012|
|Future||Demonstration of reduced use of herbicides in carrot crops through chemical banding and mechanical cultivation in QC|