Canola, Mustard Pest Spreading

REGINA - Mar 16/04 - SNS -- Areas of Saskatchewan reporting cabbage seedpod weevil (CSPW) infestations are spreading into the main canola and mustard seed producing areas of the province, although not in economically significant numbers.

"The CSPW does not appear to thrive in dry conditions so, while it was first confirmed in southern Alberta in 1995 and rapidly increased in numbers, populations have been reduced substantially in the last couple of years. In Saskatchewan, the 2003 survey indicated populations of economic significance in a limited area south and west of Swift Current, a non-traditional canola-growing area," says Scott Hartley, the insect pest control specialist with Saskatchewan Agriculture, Food and Rural Revitalization (SAFRR).

The CSPW is sometimes described as a "crucifer specialist," because it feeds only on plants in the mustard family, including cabbage, flixweed, brown and wild mustard, and both Polish and Argentine canola. Yellow mustard, Sinapis alba, is currently the only cruciferous crop that is highly resistant to CSPW. Non-cruciferous crops, such as wheat, barley and potatoes, are also resistant to this pest.

Hartley says producers who plan to grow canola in the southwest should monitor for the CSPW. Details on management may be found in the SAFRR publication "Cabbage Seedpod Weevil," available on the SAFRR Web site.

Hartley thinks that the CSPW eventually will inhabit all the canola-growing areas of the province. He says the potential impact of this pest is significant because the adult weevils can over-winter in Saskatchewan: "Although it's not known for sure how far north this insect can survive, the hardiness of the CSPW will likely enable it to survive in all canola-production areas."

Two synthetic pyrethroids for CSPW control are registered. For detailed information on these products, farmers may refer to SAFRR's 2004 Guide to Crop Protection, available at all rural service centres and on the SAFRR Web site. The "2003 Cabbage Seedpod Weevil Map," which was prepared by Agriculture and Agri-Food Canada, is available on the SAFRR Web site as well.

Crop losses from CSPW can result from the over-wintering adults feeding on flower buds in the spring, and the next generation of emerging adults feeding on pods in the fall. Between these adult stages, the larva feed on the seeds within the developing pods. Humid weather after the larvae exit from the pod can promote fungal infections within the pod and reduce seed set. Infested pods are more likely to shatter before harvest.

Native to Europe, CSPW is a serious pest of cruciferous crops such as canola and rapeseed in Europe and the northwest United States. It has established populations in the interior of British Columbia since the mid-1930s and, since its confirmed discovery in Alberta, has been steadily spreading eastward. Monitoring for CSPW in Saskatchewan has taken place annually since 1997 by AAFC, assisted by SAFRR. The survey has also resulted in the discovery of several species of parasitoids of CSPW. The potential of these natural enemies to help manage this pest is currently being investigated.

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