Pesticide Risk Reduction Strategy for Root Insect Pests of Carrot, Parsnip and Onion

For inquiries please contact:
Pest Management Centre, Agriculture and Agri-Food Canada

October 2017


Pesticide risk reduction strategies are developed under Pesticide Risk Reduction (PRR) of Agriculture and Agri-Food Canada's (AAFC) Pest Management Centre. To reduce undesirable impact of the use of pesticides in agriculture, PRR works with grower groups, industry, provinces, researchers and regulators to identify gaps in pest management and opportunities to develop and implement strategies to address these.

A pesticide risk reduction strategy is a detailed plan developed through consultations with stakeholders aiming to address grower needs for reduced-risk management tools and practices for a specific pest issues. The strategy document presented herein is intended to update participating stakeholders and the public at large on the activities supported by PRR in developing and implementing the strategy and the new tools and practices made available through this process.

For more information, please visit the Pest Management Centre.


Pesticide Risk Reduction acknowledges all participating stakeholders and organizations for their continued collaboration and contribution to the development and implementation of a pesticide risk reduction strategy for root vegetables in Canada, especially the members of the Root Insect Pests of Carrot, Parsnip and Onion Working Group, including:

  • Heather Meberg – E.S. Cropconsult, British Columbia;
  • Tracy Shinners-Carnelley – Peak of the Market, Manitoba;
  • Anne-Marie Fortier – Phytodata, Quebec;
  • Rachael Cheverie – Perennia, Nova Scotia;
  • Susanna Acheampongo, Tracy Hueppelsheuser and Susan Smith – Ministry of Agriculture and Food,British Columbia;
  • Connie Achtymichuk – Saskatchewan Ministry of Agriculture;
  • Dennis Van Dyk and Travis Cranmer – Ontario Ministry of Agriculture and Rural Affairs;
  • Mario Leblanc – Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec;
  • Chris Maund – Government of New Brunswick, Agriculture;
  • Sebastian Ibarra – Prince Edward Island Department of Agriculture and Forestry;
  • Mary Ruth McDonald and Cynthia Scott-Dupree – University of Guelph;
  • Gaétan Bourgeois and Robert Vernon – Agriculture and Agri-Food Canada;
  • Health Canada Pest Management Regulatory Agency.


Insect pests attacking the roots of carrot, parsnip, and onion were identified as a high priority issue for strategy development through stakeholder consultation and a systematic assessment of pesticide risk reduction potential. These pests are primarily managed through the application of insecticide products, some of which are under re-evaluation or scheduled for regulatory phase-out by Health Canada's Pest Management Regulatory Agency (PMRA). Specifically, carrot rust fly (Psila rosae F.), carrot weevil (Listronotus oregonensis L.) and a complex of root maggots (Delia spp. (species) on onion lack effective alternative control approaches.

This report summarizes the collaborative efforts, activities and progress of the Pesticide Risk Reduction (PRR) in supporting the development and implementation of a reduced-risk strategy to manage key root insect pests of carrot, parsnip and onion in Canada. The objective of this strategy is to make available to growers non-chemical control solutions which reduce risks to humans and to the environment from insecticides used in vegetable production, while enabling effective and economical pest management. This work was complementary to PMRA's Diazinon Transition Strategy Working Group for root and bulb vegetables, which coordinated efforts to secure conventional chemical alternatives to pesticides being removed due to re-evaluation.

A working group comprised of provincial vegetable crop specialists, entomologists, extension experts and vegetable industry stakeholders was established by the PRR to discuss issues related to the management of these pests. Key issues identified by the working group include: gaps in knowledge regarding the behavior and presence of these pests in the affected crops; lack of validated models for prediction of pest populations; lack of effective alternative tools, both conventional and non-conventional; and a need to communicate results to the growers.

This strategy identifies main goals and provides information about supported projects. It is anticipated that additional projects will be taken on as some goals are met and different work is required to continue implementation of the strategy. Projects currently underway are investigating the prevalence and behavior of the indicated pests and potential alternative controls for these (see Table 1). This document is updated periodically as new information becomes available.

Pest management and pesticide risk reduction issues

In Canada, carrots, parsnips and onions are important annual crops primarily grown in Quebec and Ontario, but with some production in the Atlantic and Prairie provinces and in British Columbia. In 2016, these crops were planted on over 14,400 hectares and contributed a farm gate value of $219 million to the Canadian economy.

Insect pests with a subterranean larval stage can lead to particularly severe economic losses to these crops, as the pests directly damage the marketable product though feeding, and cause further injury by providing an entry point for soil pathogens. In addition, the underground and consequently hidden activity of these pests complicates the development and implementation of monitoring protocols and thresholds. Carrot rust fly and carrot weevil are important pests of carrot and parsnip across many growing regions in Canada. Onion maggot (Delia antiqua) is often considered one of the most important root pests of onion, although recent research indicates overall damage may be caused by a complex of root maggots that also include seedcorn maggot (Delia platura) and bean seed fly (Delia florilega).

Current management options for these pests include neonicotinoids, pyrethroid, pyrethrin, benzoylurea and organophosphate products. Although most uses of diazinon were phased out in 2016 by PMRA's regulatory re-evaluation, diazinon is still currently registered for the control of onion maggot larvae in onions. However, since the initiation of this Strategy, a number of other chemical insecticides re-evaluations have been initiated by PMRA: clothianidin and imidacloprid (carrot rust fly, onion maggot and seedcorn maggot), cypermethrin (carrot rust fly, onion maggot flies), lambda-cyhalothrin (carrot rust fly and carrot weevil), phosmet (carrot weevil), and chlorpyrifos (onion maggot larvae). Thus, there is an urgent need for the development of robust, reduced risk management options for these pests.

Strategy development

This strategy focuses on carrot, parsnip, and onion due to a high potential for pesticide risk reduction in these crops. The specific root insect pests targeted in this strategy – carrot rust fly, carrot weevil and onion maggot – were prioritized through working group discussions. These pests were also identified within PMRA's Diazinon Transition Strategy and are ranked as top provincial priorities at AAFC's 2017 Annual Minor Use Pesticide Priority Setting Workshop. See the Minor Use Crop and Pest Problems list. Cabbage root maggot is not addressed through this strategy. For more information on PRR work related to this pest please see: Reduced-Risk Strategy for Cabbage Maggot Management in Brassica Crops.

Some priority pest management gaps were identified through earlier consultations held by PRR in 2005 and 2006. In response to those discussions, PRR supported one project relevant to this strategy, PRR07-090 Development of bioclimatic models to forecast the dynamics of two insect pests: carrot weevil and carrot fly.

Working group consultations

An expert working group (WG) was established in the spring of 2013 to provide advice to guide the development of a strategy for sustainable management of the targeted pests. The WG consisting of provincial vegetable specialists, University and government scientists and extension experts of the vegetable industry continues to meet to discuss progress and implementation of the strategy. Consultations and regular exchange of information and ideas are conducted through teleconferences, email and personal communications. New membership to the group is welcome; interested individuals and organizations are encouraged to contact the PRR for more information.

Priority issues and gaps

Discussions within the WG have led to the identification of gaps in knowledge and tools restricting the development of integrated management strategies for the targeted pests. Below are issues of concern identified by the WG for the target pests in carrot, parsnip and onion.

  • Lack of knowledge on the biology and behavior of carrot weevil, including overwintering habits as well as spatial and temporal movement patterns into the field, which may contribute to inappropriately timed treatment recommendations
  • Lack of effective monitoring tools for an emerging 2nd generation of carrot weevil and limited knowledge as to the effect of this new generation on carrot production
  • Limited knowledge on external factors influencing carrot rust fly populations and a need to validate currently established bioclimatic models in the diverse carrot growing regions of Canada
  • Lack of knowledge on the densities, distribution and actual damage caused by different species of the Delia root maggot in onion crops
  • Lack of replacement products for diazinon, and a need for a diverse set of solutions to reduce the potential for resistance development to alternative chemical solutions in pest populations
  • Insufficient information on the effect of climate (in particular high temperature) on pesticide efficacy on carrot rust fly
  • Lack of management approaches and products suitable for the organic vegetable sector

Action plan

Potential actions to address these issues are discussed by the WG and an action plan is developed. The following action plan table outlines the goals of the strategy, identifies milestones, and indicates the activities that are taking place. The initial focus of the strategy is on improving the current knowledge on the distribution, occurrence and impact of the targeted pests. This knowledge will help to determine the optimum timing and application of alternative tools and products to be pursued as the strategy progresses.

The goals identified in this Pesticide Risk Reduction Strategy for root pests of carrot, parsnip and onions are to:

  1. Establish base knowledge on biology and behavior of targeted pests
  2. Identify and develop new reduced-risk control solutions and tools
  3. Promote and facilitate adoption of reduced risk solutions

Table 1 – Action plan to implement a reduced-risk strategy for root insect pest management in carrot, parsnip and onion production in Canada

Strategy goal #1: Establish base knowledge on biology and behavior of targeted pests
Milestones Status Implementation Activities Completion Date
Determine spatial pattern and timing of migration into the crop by carrot rust fly and carrot weevil Completed PRR14-020 - Develop spatial modelling and forecasting tools for the management of carrot rust fly and carrot weevil in carrot producing regions of Eastern Canada. This project showed that carrot rust fly and carrot weevil were both readily found within the carrot field early in the season and that the Degree Day models developed in Quebec 30 years ago did not accurately predict emergence of these species in the provinces studied. 2017
Refine emergence prediction models and evaluate efficacy of entomopathogenic nematode products On-going Work is underway through project PRR17-020 - Applying updated bioclimatic information to validate and refine Integrated Pest Management program recommendations for carrot rust fly and carrot weevil management. This project aims to add several field-years data to the previously collected data obtained through PRR14-020. Several commercially available entomopathogenic nematode products are also being evaluated for their efficacy against carrot weevil and carrot rust fly. Not applicable
Determine distribution, timing and level of damage caused by key Delia species attacking onion Completed PRR14-040 - Investigate factors that determine the occurrence of and level of damage from seed corn maggot in key onion production regions of Ontario and Quebec. This study showed that emergence data of the Delia spp. did not correlate well with the prediction model and there was not a strong correlation between trap captures and onion plant damage. 2016
Determine distribution, timing and level of damage caused by key Delia species attacking onion On-going Work is underway through project PRR17-010 - Survey of Delia species of maggots affecting onion in Quebec, Ontario and Eastern Provinces. In this project, data on the presence of Delia spp. within onion fields is being collected and damage to onion plants in the field and in the laboratory is examined and correlated to Delia spp. Not applicable
Strategy goal #2: Identify and develop new reduced-risk control solutions
Milestones Status Implementation Activities Completion Date
Develop decision support tools Completed PRR07-090 - Development of bioclimatic models to forecast the dynamics of two insect pests: carrot weevil and carrot rust fly. The results of this project conducted in Québec and Ontario were incorporated into the AAFC modelling software CIPRA - Computer Centre for Agricultural Pest Forecasting, which has since been incorporated into AgWeather Quebec. This website provides bioclimatic models for several crops and decision making tools for crop producers in Eastern Canadian provinces. 2010
Develop decision support tools On-going Bioclimatic models need to be validated for use in other regions, and refined in some cases to take account of multiple generations of pest emergence. Work underway through projects PRR17-010 and PRR17-020 aims to collect more emergence data on onion and carrot pests, respectively, in Eastern provinces, thus contributing to the development of bioclimatic models or to the refinement of existing ones. Not applicable
Investigate the use of cultural approaches Future It is anticipated that data generated from projects in Goal 1 will identify potential cultural control alternatives for carrot and onion pests. Not applicable
Investigate bio-pesticides and non-conventional products Completed PRR15-030 - Investigation of GF-120 Fruit Fly Bait to suppress carrot rust fly populations in Eastern Canada and British Columbia. This study showed that GF-120™ was not as effective at reducing damage to carrot plants as was Matador 120EC and that GF-120™ was not an economical viable alternative when used as a spray. 2016
New conventional products available for adoption On-going Through the Pest Management Centre's Minor Use Pesticides, the following active ingredient has been submitted for registration: spinosad (onion maggot) and work is currently underway on spinetoram (carrot rust fly and onion maggot). See Minor Use Pesticides - Project Status by Crop report. Not applicable
Strategy goal #3: Promote and facilitate adoption of reduced risk solutions
Milestones Status Implementation Activities Completion Date
Communicate results from the strategy work to growers Future As projects mature, information generated from the work will be transferred to growers and other vegetable stakeholder through factsheets, presentations at industry meetings and participatory research approaches where applicable. Not applicable
Communicate results from the strategy work to growers Future Mechanisms to facilitate the uptake of reduced risk solutions by growers will be discussed by the WG as the strategy matures. Not applicable
Status legend:
  • Completed: Project addressing a milestone is complete
  • On-going: Work/project is currently underway
  • Future: Priority identified for future work