Cabbage maggot management and research around the world: a status report and development for IPM strategies for Canada

Project Code PRR06-690

Project Lead

Peggy Dixon   Agriculture and Agri-Food Canada

Objective

To conduct a literature review and compile information on IPM from countries where cabbage maggot (CM) is a major pest as well as where it occurs but is not a pest issue

Summary of Results

Root maggots [Delia spp. (Diptera: Anthomyiidae)] are a serious pest problem for growers worldwide. Feeding damage on the roots can severely reduce yields and potentially destroy the plant. For root vegetable crops, injury can render the product unmarketable. In Canada, the cabbage maggot (Delia radicum) is a primary pest of Brassicacea crops including canola and brassicaceous vegetables such as cabbage, rutabaga, cauliflower and broccoli. Other important species include the turnip maggot (Delia floralis) and to a lesser extent, the seed corn maggot (Delia platura).

Current control methods for cabbage maggot in vegetables rely on a few old chemistries (e.g. organophosphates) some of which are currently under review by Health Canada's Pest Management Regulatory Agency (PMRA). These products, also have limited efficacy as they cannot directly contact the maggots which are buried under the soil. The product efficacy issue is further complicated by the short growing period of the crops and the changing patterns of insect emergence. For canola, there are no registered insecticides to control cabbage maggot. Alternative, reduced risk control options are, therefore, needed to manage this pest in an effective and sustainable manner.

Due to the cosmopolitan distribution of root maggots and worldwide scope of these pest issues, there is a considerable research effort internationally in developing alternative management strategies. The present study aimed at reviewing the scientific literature and current strategies used for cabbage maggot control around the world. The goal was to identify management tools and practices with immediate relevance to Canadian growers and which could be adopted in Canadian production. The findings from an intensive review of the published literature, surveys and interviews with research and IPM experts from a number of European countries, Canada and USA were compiled in a report featuring international status of IPM in cabbage maggot management. The study highlights research and development advancements in a number of control approaches and strategies with potential for application in Canadian agriculture.

The review revealed that there are national and regional differences in the approach to Delia management which varies with the type of crop (canola/vegetables), type of damage (direct vs. indirect), scale (farm/field size) and production system (organic vs. conventional). Furthermore, the results of this review suggest that there is no one single method available that will provide full control of cabbage maggot. The development of a true integrated systems approach based on a combination of several management tools appropriate to each specific situation will be necessary to control infestations in a sustainable manner.

Some recommended approaches which may be applicable for cabbage maggot management for vegetable brassicas in Canada include cultural methods (such as crop/row mesh covers, exclusion fences, relay cropping), and lower risk control products such as biopesticides (e.g. Metarhizium anisopliae), classical biological control (e.g. European beetle Aleochara bipustulata), and novel insecticides (e.g. garlic extracts). Canola specifically will require further investigation into methods to control cabbage maggot. As there are no available insecticides for use in canola, cultural practices are the primary means of limiting the economic impact of cabbage maggot. This study suggests that more research is needed on Delia-weed-disease-natural enemy interactions in canola to develop an effective, integrated pest management approach.

The compilation of this information is an important first step to the development of an integrated strategy for management of cabbage maggots on a variety of Brassicacea crops in Canada. Risks to human health and the environment can be reduced through this approach, which will at the same time protect the economic investment of the farm.

For more information about this project, please contact Dr. Peggy Dixon.

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