Relay Cropping: A Management Tool For The Cabbage Maggot

Carolyn Parsons^1,2* Peggy Dixon¹ and Murray Colbo ²

The cabbage maggot (Delia radicum L.) (Diptera: Anthomyiidae) is a serious pest of brassica crops. It presents challenges to the organic vegetable grower and is currently managed through the use of crop rotations and row covers.

A considerable amount of research has demonstrated that crop diversification often results in reductions in egg-laying by the cabbage maggot. Relay cropping is one way that growers can increase plant diversity within a field and involves the growing of two or more crops on the same land with the two crops overlapping in space and time for a short period.

Relay cropping experiments were conducted in the summers of 2003 and 2004 in St. John's, Newfoundland. An open field experiment investigated relay cropping cauliflower and lettuce to reduce first generation cabbage maggot egg numbers while minimizing competition between the two crops.

Results showed that lettuce planted between cauliflower rows significantly reduced the numbers of eggs laid by D. radicum. Having the lettuce and cauliflower in the field together for only four weeks minimized competition and cauliflower yields between treatments were comparable. Relay cropping provided an acceptable level of cabbage maggot control and produced a second marketable crop off of the same land.

Although further research into other crop combinations and potential effects on other pests and predators and parasitoids is needed, relay cropping could provide the organic grower with a feasible method of managing the cabbage maggot.

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Source
2nd OACC Organic Research Workshop, Presented in association with the Organic Connections: Prairie Wide Organic Conference and Trade Show, November 14-16th, 2004


Author Locations & Affiliations
(1) Agriculture & Agri-Food Canada, St. John's, Nfld
(2) Memorial University of Newfoundland
* Corresponding author, E-mail parsonsc@agr.gc.ca


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