Reduced-Risk Strategy for Integrated Weed Management in Field Vegetables

Preface

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

Acknowledgement

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.

Introduction

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:

1. reduce the use and reliance on herbicides,
2. minimize unnecessary herbicide applications, and
3. allow integration of various control options.

Strategy Outcomes

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.