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2-Plants: Canadian experiences with Bt-refugia

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TITLE:  Farmers embrace refugia recommodations
(Farm and Country, Canada, by Tom Button)
DATE:   May 6, 1999 (May 3, 1999)

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Most corn growers who plant Bt hybrids are, according to this story, also planting the 20 per cent refugias that have been designed to prevent corn borers from developing quick resistance to the technology. When the 20 per cent rule was announced mid-winter, many skeptics believed growers couldn't be convinced to plant the non-Bt refugias. The thinking was, the story says, that farmers wouldn't want to add an extra complication to their already hectic planting season, and that farmers who face borer pressure wouldn't want to give in to yield losses in their refugias.

Ken Hough, research manager for the Ontario Corn Producers Association, was quoted as saying, "There's a good understanding of why we need refugias. There will be the odd individual who won't pay attention, but the large majority are supporting the concept of resistance management." Bob Jenkinson, former product manager for Novartis, has surveyed over 300 growers who have purchased Bt seed from the company for planting this spring and, says Jenkinson, all but a handful are going to plant refugia. Overall, awareness of the resistance-management strategy was very high. Jenkinson found that over 99 per cent knew that they should be planting refugias, although many others weren't certain exactly how to go about it. Like other seed companies, Novartis has been supplying refugia recommendations through its dealers and through publicity campaigns, and Jenkinson believes the message is getting through. Some growers will plant blocks of non-Bt hybrids, some will run non-Bt seed through!
 three rows of a 12-row planter, and others are planting non-Bt sections with the goal of taking them off for silage.

Scientists such as Mark Sears, University of Guelph entomologist and chair of the Ontario Corn Borer Coalition, say corn borers can mutate and produce individuals that can survive on Bt corn. In order to pass that resistance on to the next generation, however, the resistant borer must mate with another resistant borer. If the entire crop was switched to Bt hybrids, Sears adds, the only borers to mate with would be borers that were also resistant: All the others would have been killed off. The pair would mate, producing a new generation of resistant borers. Refugias work by ensuring there are non-resistant borers for any resistant borer to mate with. The progeny would then have middle-strength resistance, and still be killed by the high doses of protein in Bt hybrids. Without refugias, Sears says, resistant borers could overwhelm the Bt technology in as little as five years. With refugias, the technology should keep working at least two to three times as long.

Companies including Pioneer and Dekalb are, the story adds, requiring Bt buyers to sign a pledge that they will plant a 20 per cent refugia. Both of the companies and Ottawa say they will monitor compliance after planting. Novartis marketing manager Doug Knight was cited as predicting the industry will find a high rate of refugia compliance, adding, "The growers understand why refugias are necessary," and that with planning during the off-season, there's also no need to make planting overly complicated. "The coalition was able to make the rules quite flexible."  


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