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GMO
seeds benefit environment
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[July 30, 2007]
URBANA -- Genetically modified seeds that are
resistant to a low-toxicity herbicide, glyphosate, have a positive
environmental impact compared with other technologies to combat
weeds, according to a recent University of Illinois study.
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"With the emergence of glyphosate-resistant weeds, the
environmental consequences of alternatives to the use of
genetically modified seed are of increasing importance,"
explained Gerald Nelson, a professor in the U of I Department of
Agricultural and Consumer Sciences. Nelson and his doctoral
student Justin G. Gardner conducted a study that simulated the
environmental effect of abandoning the glyphosate-resistant, or
GR, seed if weeds develop immunity to it. They used a well-known
mammalian toxicity measure, the LD 50 dose for rats (the volume
of pesticide needed to kill 50 percent of a test population of
rats), to assess one potential environmental impact. They
simulated the consequences for corn, soybeans and cotton.
"With conventional tillage, we found that the use of GR seeds
reduces the number of LD 50 doses applied per hectare by 17
percent to 98 percent, depending on the crop," said Nelson.
"With no-till, the use of GR seeds reduces LD 50 doses only in
corn.
"If farmers switch to conventional seeds
because of GR-resistant weeds but maintain the same tillage
practices, our simulation suggests that LD 50 doses could
increase by as much as 100 LD 50 doses per hectare in soybeans
and 500 LD 50 doses per hectare in cotton, or 11.4 and 19.8
percent, respectively."
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 Reducing LD 50 doses per hectare generally depends on the crop
and whether the tillage system changes.
"Because no-till replaces mechanical weed control with chemical
weed control, we expect it to increase the LD 50 doses, as in fact
it does for all three crops, even with the use of GR seeds," Nelson
noted.
The simulation assumed the extreme case of all farmers switching
to non-GR seed technology. Nelson added that due to the small number
of farms that use GR seed in the sample, the corn results are
suspect.
Recently summarized in Science magazine, available online at
http://www.sciencemag.org/
cgi/content/full/316/5828/1116, the detailed results are
available in a paper forthcoming in the Journal of Pest Management
Science.
[Text from file received from
the University of
Illinois Extension]
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