Transgenic Revolution
Potential For Resistance Spurs Utilization Of 20 Percent Refuge
DIXON SPRINGS, ILL.
A transgenic revolution has occurred in agriculture,
dating back to 1996 when the first
Bt hybrids came to the marketplace. Dr.
Mike Gray, professor of entomology with the Department
of Crop Sciences University of Illinois,
detailed the revolution at the recent Dixon
Springs Field Day.
Those early Bt hybrids were bred to control
European corn borer. There was a very rapid increase
in the use of that technology from 1996
to today.
“If you look, for instance, in
Illinois in 2006, about 19
percent of the corn that was
planted was a stacked hybrid
containing maybe a herbicide
tolerant trait as well as a Bt
event,” he pointed out. “Then
just one year later, in 2007,
the use of stacked hybrids in
Illinois went up to 40 percent,
so we saw doubling in
the use of that technology.
We’ve all seen again a
tremendous adoption of the
herbicide tolerant soybeans
that are dominant now
throughout the Midwest.
Gray continued to compare
this revolution, in terms of
how pests, insects and weeds
are managed with what happened
following World War II
when there was a very successful
use of the corn aided
hydrocarbon insecticides
that were used against a
number of insect pests.
“We saw the use of the herbicides
really being highly effective
as well against a
number of important weeds,
especially with the movement
away from cultivation,” he
said. “I compare the two revolutions
and point out that
despite some very spectacular
successes early on with
DDT and some of the other
corn aided hydrocarbons,
that eventually some problems began to surface
– unwanted residues on fruits and vegetables,
bio magnification of some of the corn aided hydrocarbons
in the food chain and, ultimately because
of overuse, resistance.”
One thing Gray discussed was his concern of
the potential for development of resistance.
“Obviously there have been a lot of benefits
with the use of transgenic plants where we’re
not seeing the unwanted residues on food and
that’s a real plus, or we’re seeing certainly in
corn reductions in insecticide use and I think
that’s a plus from an environmental, human
health and safety vantage point,” he said. “So
the primary concern with transgenic crops is an
overuse of a technology in some cases and that
increases selection pressure and potential for
resistance development.”
He reminded the audience of the importance
of the 20 percent refuge to make sure there are
survivors which can mate with any rare individual
that does survive in a Bt field. He made
a point of reinforcing those points.
Gray ran through a checklist of the different
products that are in the marketplace to control
resistance, such as the Herculex hybrids, the
Yield Bred hybrids, and the AgriSure hybrids.
“I wanted to make sure farmers knew what
proteins were being expressed in those hybrids
and what insects those proteins would target,”
he said. “I reminded them the western corn
rootworm evolved in a way to circumvent the
benefits of crop rotation and this was an insect
we used to control just by rotating corn and soybeans.
As we now know, back in the mid 1990s
a variant of the corn rootworm took advantage
of the regular rotation of corn and soybeans and
instead of laying their eggs exclusively in
corn began to lay their eggs in the soil of soybean
fields. The eggs overwintered and the following
year in that first year corn field farmers
began to see some very significant root damage.
“So if this is an insect that can adapt to a control
like crop rotation I think we need to be at
least leery and respectful that similarly the
prospect is out there for resistance at some
point if we don’t utilize refuges like the EPA
mandates,” Gray concluded. Δ
Dr. Mike Gray, Professor of Entomology with the Department of
Crop Sciences, University of Illinois, holds a root wad that has
been damaged by corn rootworm. Gray proposes that refuges
be utilized to minimize the chances corn rootworm will devastate
a crop.
Photo by John LaRose, Jr.