|
Breeding mite-proof honeybees |
|
|
|
|
Saturday, 13 March 1999 |
by Cameron Smith From a cluttered laboratory desk at Guelph University overrun with bee paraphernalia -- posters, coffee mugs, clippings, oversized plastic replicas on springy coils, you name it and it’s there -- Medhat Nasr is directing a honey bee recovery program the old fashioned way.He’s fighting the mites that kill honey bees. And he’s succeeding, not with fancy, high tech bioengineering, but through the long, arduous process of selective breeding. ``They used to laugh at us because we were doing this the old fashioned way,’’ he says. ``Now, we’re at the leading edge in North America. Two kinds of mites have been killing honey bees: tracheal mites, for which Nasr and the Ontario Beekeeping Association have bred resistant bees, and verroa mites, for which they are half way to a breeding solution. So successful have they been that Ontario is now exporting queen bees. California used to be the capital of exports, but beekeepers there relied too heavily on pesticides for killing mites. And now mites have been developing resistance to the main pesticide, Apistan. Meanwhile Ontario, which, in 1990, produced 2,500 queen bees for commercial beekeepers, now produces 14,000 to 15,000. ``So,’’ says Nasr, ``we’ve moved very fast.’’ What I find exciting about their work is its impact on the wild. There probably are almost no honey bees in the wild. They will have been killed by mites. But by breeding resistant bees, Nasr and Ontario beekeepers will ensure that swarms of resistant bees will migrate from commercial operations to the wild. As far as I can find out, no one knows how important honey bees are to pollination in the wild. There are all sorts of other insects that pollinate. But honey bees are prodigious workers, so the prospect of their returning is reassuring. For farmers, the breeding of resistant bees is an immediate cause for celebration. Honey bees are essential to some crops. According to a study by Agriculture Canada, they pollinate 90 per cent of the sweet cherries, pears, blueberries, cranberries, and cucumbers grown in Canada. And 85 per cent of the apples, 80 per cent of the melons, 72 per cent of the prunes, plums, and brambleberries, 70 per cent of the clover, 64 per cent of the buckwheat, and 60 per cent of the pumpkins and squash. Other crops they pollinate to a lesser degree, but some, such as canola at 18 per cent, are grown in such vast quantities that the honey bee contribution is significant. According to Nasr, crops pollinated by honey bees are worth $600 million a year in Canada, and $93 million a year in Ontario. Tracheal mites puncture the breathing (trachea) tubes of the bees to get blood, either killing them directly or so weakening them that they die of other causes. Verroa mites attack bees in the pupal stage. Either the pupa is killed, or the bee that develops is deformed. Tracheal mites arrived in Canada in 1987, verroa mites two years later. Nasr works for the beekeepers association as a technology transfer specialist based at Guelph University. His approach is to find honey bees with desirable traits, and to strengthen those traits through controlled breeding. It has resulted in developing bees resistant to tracheal mites, and a drop in their mortality rates from a high of about 90 per cent to 10 per cent. Dealing with verroa mites is proving more difficult. Within two years, Nasr hopes to have bred what he calls a ``hygienic’’ bee that will throw out of the hive an infected pupa. That will lower the mortality rate to about 30 per cent. To get down to 10 per cent, however, he thinks it will be necessary to develop other characteristics, such as honey bees that will groom one another, cleaning themselves of mites. And pupae that mature earlier, so mite eggs will have less time to develop. I suppose it would have been possible to achieve these kinds of results with gene splicing in a laboratory. But I find this old fashioned way more respectful of life.
|
|
