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Archived - RMD-08-03: Review of the pest status of the swede midge (Contarinia nasturtii) in Canada

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Date Issued: 2009-02-24


This Risk Management Document (RMD) includes a summary of the findings of a pest risk assessment and records the pest risk management process for the identified issue. It is consistent with the principles, terminology and guidelines provided in the IPPC standards for pest risk analysis.

1.0 Purpose

The purpose of this document is to record a risk management decision.

2.0 Scope

This risk management decision document summarizes the Canadian Food Inspection Agency's (CFIA) decision to deregulate swede midge, Contarinia nasturtii, in Canada.

3.0 Background

The swede midge, Contarinia nasturtii, was first detected in Southern Ontario in 2000. Significant losses, which were at first attributed to nutrient deficiencies, had been observed in broccoli fields in the province since 1996. When swede midge was confirmed in Ontario, it became clear that these losses were due to swede midge damage.

After the completion of a Pest Risk Assessment in 2002, CFIA declared swede midge as a regulated quarantine pest for Canada. The phytosanitary requirements related to swede midge, covered in the policy directive D-02-06 (Interim Phytosanitary Requirements to Prevent the Entry and Spread of Swede Midge (Contarinia nasturtii)), target measures to prevent the entry and spread of swede midge from infested areas to non-infested areas of Canada and the United States. Commodities that have been identified as potential pathways for the dispersion of the insect and are therefore targeted by the requirements for swede midge are transplants and seedlings of the host plant species (Brassicaceae), used farm equipment and soil. Seeds of the host plant species are not considered a high risk pathway of dispersal of swede midge, therefore the canola industry is not impacted by the Swede midge requirements as the crop is propagated by seeds rather than by transplants.

The CFIA first initiated visual surveys in Ontario and Quebec in 2002. In the ensuing years, the CFIA has identified swede midge in most counties/municipalities in Southern Ontario and Quebec where cole crops are grown. The availability of a pheromone trap in 2005 contributed to the rapid increase in the number of areas where the insect was detected.

As a result of the CFIA's 2007 and 2008 field surveys, swede midge was identified for the first time in Manitoba, Saskatchewan, Prince Edward Island and Nova Scotia.

Review of the pest status of swede midge was initiated during the summer 2007 after the USDA contacted the CFIA regarding an harmonized approach on this pest. The deregulation initiative in the U.S. was precipitated by observing Canada's rapid and wide detection of the insect since its first identification Ontario in 2000. This was despite the implementation of phytosanitary requirements to prevent the human assisted dispersal. The United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) determined that the insect was not a threat to the cole crop industry and the implementation of phytosanitary requirements similar to those implemented in Canada, would not suffice to slow its spread. In addition, a high percentage of the growers located in infested areas consider swede midge a quality pest, rather than a pest of quarantine significance, and include it in their regular pest management program. In light of this information, the CFIA has initiated the process for the deregulation of this pest in Canada.

4.0 Pest Risk Assessment Summary

A Pest Risk Assessment was conducted in 2002 to evaluate the potential risks related to the introduction and establishment of swede midge. An update of this document was completed later in 2002 to incorporate additional facts and data acquired following in-depth literature review and consultations with European experts on the plant health risk of Contarinia nasturtii (Kieffer) (Diptera: Cecidomyiidae), the swede midge, a European gall midge that feeds on Brassicaceae and allied cruciferous plants. The objective of the update was to assist the Canadian Food Inspection Agency (CFIA) to:

Another Pest Risk Assessment, a joint Canada-U.S. initiative, was completed in June 2008 to determine the probability of introduction and spread of swede midge on canola pods and seeds, as well as the potential impacts of this pest on canola in Canada and the U.S. The Plant Health Risk Assessment Unit of the Science Advice Division, CFIA, and the Plant Epidemiology and Risk Analysis Laboratory of the Center for Plant Health Science and Technology, PPQ, APHIS, USDA, jointly prepared this document, to assist CFIA and USDA in determining whether regulatory action is required to protect canola industry and canola producers in both countries.

The 2008 Pest Risk Assessment provides specific information pertinent to this pest for different host plants. The phytosanitary risks associated with this insect have been characterized and estimated. Major points determining the risk are summarized below.

Pest Biology - Swede midge is an invasive species native to Europe and Asia where, in some areas, it is considered a considerable pest of cole crops - cabbage, cauliflower, rape, etc. It was reported for the first time in North America, in Ontario, in 2000. The adult is a small and delicate fly with a life span of one to four days. Larvae live inside the stems, leaves, and in the florets of cruciferous plants, feeding on growing vegetative and generative tissues. A complete life cycle lasts, on average, about 26 days. This fly overwinters in the larval stage in cocoons in the soil. In Ontario, swede midge can have up to five generations per year depending on climatic conditions.

Damage - On cole crops (other than canola), the following symptoms and damages have been recorded: leaf and flower gall formation, closed and swollen flower buds, crinkled and puckered heart leaves, brown scarring of petioles and stems, crumpled and twisted or distorted central leaves, swollen petioles, absence of head in cabbage, destruction of inflorescence in broccoli and cauliflower, and absence of a central shoot with formation of many lateral or secondary shoots. Rotting is often observed following swede midge attacks.

In Ontario, swede midge was reported to have caused damage to field-planted canola plants for the first time in 2005. Damage was observed in spring canola, especially during the seedling and early rosette stages, but became more severe during stem elongation and pod formation stages. Injured plants were unable to complete stem elongation, as well as the formation of flowers and pods. Damage was reported to be significantly higher when spring canola was planted late in the season. There is no report yet of swede midge damage to canola in the Canadian prairies or anywhere else in Canada. One potential explanation is that chemical treatments, which are part of the regular pest management regime against various other insect pests of canola, also indirectly control swede midge populations.

Distribution - In North America, established populations of the swede midge have been reported on plants belonging to the family Brassicaceae in the Canadian provinces of Saskatchewan, Manitoba, Ontario, Quebec, Nova Scotia and Prince Edward Island, and in the U.S. States of New York, Connecticut, Massachusetts, New Jersey, and Vermont.

Likelihood of Introduction

Entry potential - For Brassica vegetable crops, transplants and soil are the pathways that present the highest risks for introduction of swede midge from infested to non-infested areas. Produce presents only a low risk of vectoring midge life stages. Canola provides no pathway for the movement of this pest because it is direct-seeded in Canada and the U.S. Planting equipment that is contaminated with soil may, however, serve as a means of movement of larvae and pupae. Swede midge can also be spread naturally by wind. This fly can travel short distances by "floating" in the air, and thus can move to adjacent non-infested fields if suitable host plants are available or it can disperse and survive on many species of weedy cruciferous plants as alternate hosts.

Extent of Potential Distribution - Bioclimatic modeling has revealed that swede midge could potentially become established in all Canadian provinces, with the risk being greatest in south-western British Columbia, southern Ontario and Quebec, New Brunswick, Nova Scotia, and Prince Edward Island. Population growth is forecasted to be high in western Canada especially in years with above average precipitation. Factoring in climate change, it has been predicted that a warmer climate regime will extend the favorable range of swede midge across North America.


Economic - Economic losses due to swede midge have been reported by growers in Ontario and Quebec. In canola, losses will depend on the synchrony in phenology between the insect and the host plant. Winter and early spring canola, in areas where the planting is possible, will have a better chance to escape the damages due to swede midge because their vulnerable stage, bud formation, is completed when the populations of the insect are at their highest.

Sociological - No sociological impact is envisaged as a result of swede midge damage to cole crops.

Environmental - There is no direct impact of swede midge on the environment. There may be indirect impact however, as a result of increased insecticide applications to manage infestations and meet the phytosanitary requirements related to the insect, which may affect populations of non-target organism. Pesticide use may also contaminate soil and water ecosystems.

Conclusion - In 2002, the overall phytosanitary risk of swede midge on Brassica vegetable crops was rated medium, indicating that specific phytosanitary measures were needed to mitigate the risks of this pest. The Pest Risk Assessment for swede midge on canola, that was completed in 2008, concluded that the overall phytosanitary risk for the insect on canola was low and that the negative economic impact of this insect can be prevented if phenological asynchrony can be created and maintained between the insect and the host plant, and current control practices for other canola pests may also be effective against the swede midge.

5.0 Risk Management Considerations

5.1 Potential Market Access

Canola seed (end use propagation) and canola grain (end use consumption or processing) are not considered to be pathways for the movement of swede midge, therefore, they are not targeted by the CFIA's regulation for swede midge (D-02-06). The establishment of swede midge in canola producing areas of western Canada would therefore not have an impact on canola seed or grain marketing, either domestically or internationally.

The domestic movement and export of Canadian vegetable and ornamental cole crop transplants, considered by the CFIA to be pathways for the movement of swede midge, are currently targeted by the CFIA's regulation for swede midge. In order to allow the movement of transplants and seedlings of the regulated host species from infested areas of Canada to non-regulated areas of Canada or the U.S., Canadian growers currently have to comply with the requirements specified in the Swede Midge Certification Program developed by the CFIA.

In 2007, the CFIA was notified by the USDA/APHIS that they would be interested in considering the deregulation of swede midge. As a result of these discussions, the CFIA and USDA created a working group to evaluate this option. USDA/APHIS has recently indicated they are ready to move forward with the deregulation of swede midge. If the CFIA was to proceed with the deregulation of swede midge, both countries would have a harmonized swede midge policy and therefore, regulated commodities would be able to move between the two countries without any restriction related to swede midge.

A consequence of deregulation, achieved by both countries, would be the fluid movement of material that was formerly regulated with respect to swede midge. These include transplants and seedlings of host species, used farm equipment and soil. In addition, the CFIA would remove the requirements related to the mandatory participation to the Swede Midge Certification Program, for growers involved in the movement of regulated host plants from regulated areas to non-regulated areas of Canada. This would greatly reduce the costs for the affected growers. Additional requirements pertaining to other pests would still apply, but the deregulation of swede midge would result in the elimination of all the phytosanitary requirements related to swede midge.

5.2 Introduction of swede midge into non-regulated areas within Canada and the impact on vegetable cole crops and canola

Since swede midge was first reported in Ontario in 2000, surveys have detected established populations of swede midge throughout most of the cole crop growing areas of southern Ontario and Quebec. The CFIA's 2007 and 2008 field surveys confirmed the presence of swede midge in several areas within Saskatchewan, Manitoba, Prince Edward Island and Nova Scotia. The rapid expansion to new areas since the first detection may be attributed to: the biological characteristics of the insect, which allows for natural spread and establishment in most of the Canadian areas where Brassicaceae plants are grown; expanded scope of surveys within Canada, improved survey protocols; the availability of efficacious pheromone traps; and the movement of cole crop transplants, soil and used agricultural equipment.

The deregulation of swede midge within Canada could potentially contribute to its introduction into areas where swede midge has not yet been reported. The most likely human mediated pathways would be the movement of cole crop transplants, used agricultural equipment and soil (alone or associated with plants) from presently regulated to non-regulated areas. However, considering the distribution of swede midge in the other countries where it is established, the climatic modeling of the potential geographical range of this pest, and based on its rapid dispersion despite the implementation of phytosanitary requirements to prevent its spread, it is generally accepted that the insect would eventually disperse naturally to areas where it currently does not occur.

The Pest Risk Assessment on swede midge on canola indicates that the insect may have an economic impact on canola yields if the insect and plant obtained phenological synchrony (ie if sufficient numbers of the adult swede midge attacked the plant at an early stage when it is vulnerable). Limited information exists within Canada on what degree of impact swede midge could have on Western Canadian canola yields under phenological synchrony. Canola fields where swede midge populations have been identified through CFIA surveys in Saskatchewan and Manitoba have not shown visual damage associated with swede midge infestations. In addition, regular pest management regimes, implemented to control various other pests of canola, may also indirectly be effective in reducing swede midge populations and their potential impacts.

Swede midge produced significant damage on vegetable cole crops in Ontario and Quebec in the late 1990s. However, since the first findings, growers, in collaboration with extension specialists and researchers, have developed cultural and integrated pest management strategies to minimize the damage associated with swede midge. In particular, the use of crop rotation, greenhouse and field sanitation and insecticide spray timing, are recommended as good agricultural practices that can contribute to decreasing the damages caused by swede midge.

5.3 Removal of Domestic Movement and Export Restrictions on Canadian Cole Crop Transplant Retailers and Wholesalers

Deregulation of swede midge in Canada would remove the domestic movement and export requirements that currently restrict the movement of cole crop transplants from regulated to non regulated areas within Canada and to the U.S. The only option currently allowing the movement of transplants and seedlings of plant species host of swede midge from regulated to non-regulated areas is participation in the Swede Midge Certification Program (SMCP), for which requirements are summarized in D-03-01. The deregulation of swede midge and associated cancellation of D-03-01, would result in reduced costs to those participating in the SMCP. In addition, the deregulation of swede midge would allow the free movement of vegetable cole crop transplants not only within Canada but also to and from the U.S.

6.0 Pest Risk Management Decision

Since surveys were initiated in 2002, the geographic distribution of swede midge has been confirmed and continues to expand each year. The labour intensive nature of the swede midge survey and the very large acreage to be surveyed makes it difficult to fully assess the distribution of swede midge in the canola production areas of Alberta, Saskatchewan, and Manitoba. However, based on a limited number of survey sites, and the positive survey findings, it appears that swede midge may occur extensively within these provinces.

Because of the expanding distribution of swede midge within Canada, despite the stringent requirements in place, the CFIA postulates that continued export and domestic restrictions will have limited success in stopping the continued spread of the insect into areas of Canada where it does not currently occur, while incurring serious costs and challenges to Canadian industries. It is likely that the actual distribution of swede midge is much wider than currently documented.

In addition, based on the recent discussions with the USDA, the harmonized approach in the deregulation of swede midge in both countries would result in the free movement of all swede midge regulated material between both countries. Additional requirements pertaining to other pests would still apply, but the deregulation of swede midge would result in the elimination of all the phytosanitary requirements related to swede midge.

Stakeholder comments received back following the circulation of the CFIA's swede midge Risk Management Document (RMD-08-03) in November 2008, were mostly in favor of the CFIA's proposal to deregulate the insect in Canada. Further discussions with concerned stakeholders were held in February 2009 to address concerns that were raised by these stakeholders.

7.0 Next Steps

By the publication of this Risk Management Decision Document, the CFIA is announcing its intent to proceed with the deregulation of swede midge in Canada. As of March 31, 2009, the CFIA will stop enforcing the regulations currently in place for swede midge, with respect to the export, import and domestic movement of commodities regulated for swede midge. In addition, the CFIA directives D-02-06 and D-03-01 will be revoked. The CFIA will notify Canadian stakeholders and trading partners potentially impacted, that the phytosanitary requirements targeting swede midge will no longer be implemented.

8.0 References

Canadian Food Inspection Agency. 2008 (1st revision). D-02-06 Phytosanitary Requirements to Prevent the Entry and Spread of the Swede Midge (Contarinia nasturtii).

Canadian Food Inspection Agency. 2008 (2nd revision). D-03-01 Swede Midge Certification Program (SMCP).

Dumouchel, Louise. 2002. PRA 02-04 Contarinia nasturtii (Kieffer) - The swede midge (update). Plant Health Risk Assessment Unit, Canadian Food Inspection Agency, Ottawa.

Smith, J.W., L. Dumouchel & A. Ameen. 2008. Joint Canada-U.S. PRA Contarinia nasturtii (Kieffer) (swede midge) on canola. Plant Epidemiology and Risk Analysis Laboratory, United States Department of Agriculture - Animal and Plant Health Inspection Service, North Carolina & Plant Health Risk Assessment Unit, Canadian Food Inspection Agency, Ottawa.

9.0 List of Stakeholders

Insect Pest Management, Alberta

10.0 Communications Plan

Following the official adoption of a revised policy regarding the deregulation of swede midge in Canada, the CFIA will notify its trading partners and the Canadian industry of the changes that will result from the deregulation of swede midge in Canada.

11.0 Endorsement

Approved by:

Chief Plant Health Officer

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