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2-Plants: Canadian study shows variability of Bt corn benefits



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TITLE:  Bt corn makes a good insurance
SOURCE: Farm and Country, Canada, by Tom Button
        sent by AGNET, Canada
DATE:   June 21, 1999

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BT CORN MAKES GOOD INSURANCE

A new study on growing the borer-resistant corn hybrids in
Ontario was cited as concluding not to bet on Bt genetics for a
healthier bottom line every year. Tracy Baute, University of
Guelph researcher hired through a Novartis grant to study Bt
corn, was quoted as saying, "You have to look at Bt as an
insurance policy. You won't get a return on investment unless
there's heavy corn borer pressure." Ontario corn growers have
planted 700,000 acres of Bt hybrids this spring. OMAFRA corn
specialist Greg Stewart was cited as saying that's one-third of
the crop.

The story says that the cost is hard to pinpoint. On average,
seed premiums work out to $10 to $14 per acre, depending on
seeding rate and the deal offered by specific companies. So seed
companies are likely earning $8 to $10 million extra each year
from corn sales. Since Bt is new - and most Bt seed is only
available in higher-priced elite and introductory hybrids -
growers buying Bt can pay an additional $5 to $15 or more per
acre. Baute studied Bt hybrids versus their non-Bt twins in 40
plots across Ontario in 1996 and 1997. For comparison, the
research team also planted popular conventional hybrids adapted
to each area. Now, Baute has put all the results together in a
report she used to earn her M.Sc. Her strongest conclusion is
that Bt works. She rates its effectiveness for preventing boring
damage by European corn borers at 96 per cent - "at least."
Hybrids protected with Bt had fewer broken stalks and damaged
ears. Baute was cited as saying they also had less ear rot and
fewer mouldy kernels, adding, "The difference was great enough
that it can make sense for a swine producer to go for Bt, whether
there's a yield advantage or not."

Over the two years, Baute found the Bt hybrids outyielded their
non-Bt twins by four per cent. But the yield responses were
sporadic. In 1996, borer pressures in the extreme southwest were
intense, and some Bt-protected hybrids gave yield hikes of 10 per
cent. In central and eastern Ontario, there were few if any extra
bushels. In 1997, tables turned, with little response in the
southwest and big gains in the east. Baute plugged her results
into a computer, together with seed premiums ranging from $10 to
$14 per acre, and corn prices of $2.25 to $3.70 per bushel, and
found that growers can expect Bt to pay for itself one year in
three. Her studies suggest a field needs an average 16
centimetres of tunneling per plant in order to pay the premium
cost. Baute's conclusions aren't out of line with tests by the
seed companies. Pioneer Hi-Bred agronomist Tim Welbanks was cited
as pointing out that an intensive two-year research project
through the northeastern corn belt has found an average 8.8
bushel per acre yield benefit with Bt hybrids. Most of the gains
came in 1997, however, with little response in '98 because of low
borer numbers.

Welbanks was quoted as saying that, "The Guelph study is probably
pretty realistic. As long as borer pressures are so hard to
predict, you do have to look at Bt as insurance....It isn't going
to pay every year." Baute adds a warning for growers to keep an
eye on the yield potential of non-Bt hybrids. While in her trials
the Bt hybrids outyielded their non-Bt twins, they rarely
outyielded good conventional hybrids for the area.





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