The main Bt corn includes borer and root worm protection
(yielgard plus) while earlier yieldgard was borer
or root worm specific.
Today, if one buys "ordinary Bt corn" based either on Mon 11 or
Herculex trait, one does not get the rootworm trait thrown in as a
bonus. Oh no, they want more money for that. My impression is that
"ordinary" Bt corn is still a more important, higher volume product
than the various "stacked" products (that is, more than one transgenic
trait in the same variety). Part of the problem being sorted out in
the market is that when you start adding up the price they want for
multiple transgenic traits, the cost of a bag of seed gets too high.
No one is going to pay $150 for a bag of corn seed, I don't care what
My understanding is that root worm protection
generally involves both Bt and soil insecticide treatment.
That is true in a sense, but not for control of rootworm. When farmers
use high rates of soil-applied insecticide to control rootworm, the
secondary pests (wireworm, white grub etc.) are controlled too. But
when the corn is resistant to rootworm, and the farmer doesn't apply
soil insecticide, suddenly these "secondary" pests become more
important. Virtually all the rootworm-resistant corn seed sold is
treated with a low rate of one of the neonicotinoid insecticides
(Gaucho, Poncho, Cruiser) to control things like white grubs. These
insecticides are applied at such a low rate that they contribute
nothing to rootworm control. Rootworm is difficult to control with
"The grower may apply insecticide treatments for control of corn root
worm larvae with the refuge corn"
Yeah, in the rootworm refuge corn, many growers are using seed treated
with a *high rate* of one of the neonicotinoids. There are plenty of
beetles produced by the crop in this case. Escapes are guaranteed due
to the narrow placement of the insecticide.
My understanding is that chemical insecticide use is costly but used
a great deal to market corn from the refuge.
Much corn has been produced for many years with no insecticide at all.
The pests we are talking about generally do not destroy the crop. They
lower yield, make harvest difficult and often necessitate the use of
artificial drying. I guess if I were a farmer, I would not worry too
much about insect control in the refuge. I would make sure I didn't
plant corn after corn in the refuge, and I would harvest that field
Corn resistance to Bt has been described as recessive
while cotton resistance was observed to be recessive at high toxin
levels but to be partially dominant in strains expressing low toxin
I don't understand what you are getting at here.
I disagree with your view that the study I mentioned could not detect
resistance in a short time span.
You misunderstood me. I agree that the study was *capable* of
detecting resistance of the pest to Bt corn. My point was that 8 years
is not a very long time, that resistance would be expected to take
longer than this to evolve even if nothing were done to prevent it. For
that reason it would be erroneous to claim that resistance management
is a success. I would like to see this kind of study done after 20
The study was capable of detecting resistance but failed to mention
that refuges were sprayed with chemicals that likely killed the
But using insecticidal controls in the refuge of non-Bt corn would be
more likely to kill insects *susceptible* to Bt corn, right? The
resistant ones (if any are present) are in the Bt corn! This is a
numbers game. As long as there are way more non-resistant individuals
flying around than heterozygotes (that is heterozygous for the
resistance gene), the chances of heterozygotes mating is very small.
Finally, both borer and root worm corn have used chemical
insecticides that certainly render the "refuge" more public
relations than resistance control.
That would be true, except the chemical controls...well, they kind
of... suck. They just don't work very well with these insects. That
is why so much effort was put into developing varieties resistant to
ECB and rootworm.
The promoters of gm corn for used in developing countries
seem to ignore the need for chemical insecticides and costly
licenses for using gm corn.
You are creating a straw-man argument IMO. Farmers don't really need
to apply insecticides to the refugia in most cases. In the fields
planted with resistant varieties, the need for insecticide is reduced,
and sometimes eliminated. Regarding licenses, well, it will be amusing
to see what happens when small farmers in developing countries start
trading this stuff around among themselves. And remember, the patents
will begin to expire in, what, 10-11 years? These traits will enter
the public domain. Let us hope they are still efficacious.
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