Bt and Thee
by Steve Gilman
Something was wrong when I went to pick up my seed potato order
this Spring. When Jeff pulled the bill he said he was unable to get my
usual russets and his supplier had substituted a variety called "New
Leaf" instead. What's more, the price was 30% higher. Out back in the
warehouse I could see why. The"New Leaf" potato is one of the recently
available commercial transgenic varieties genetically engineered by
Monsanto. It contains a Bt bioinsecticide gene implanted right in the
potato along with other genes designed to switch on the active pesticide
proteins in the plant as well as a marker gene to verify that the total
genetic package is functional. Jeff had some nice looking regular
Kennebecs stacked nearby that I gladly took in substitution -- GMO's
(genetically modified organisms) are prohibited under Organic
Certification standards.
Bacillus thuringiensus (Bt) is a naturally occurring bacterium able to
manufacture certain proteins that are toxic to some insect pests. It has
been in widespread agricultural use by organic and conventional growers
alike for almost 40 years now. Depending on the strain, Bt formulations
target everything from cabbage worm, European corn borer (ECB) and boll
weevil to Colorado potato beetle (CPB) and mosquito larvae. Generally it
works by paralyzing the gut of the pest(after they eat a little),
whereupon they starve to death.
Jeff wasn't too worried about being able to sell off the "New Leaf"
spuds. The transgenic Bt crops have a technological seductiveness to
farmers and gardeners alike. After all, you don't have to spray anything
or try to get the timing right -- it1s sometimes tricky hitting the
first instar of the newly emerging CPB larvae. The insect toxin gene in
the seed potato becomes part of the growing plant and then part of the
genetics of the new potatoes. Often, the pest only has to take a few
small bites of a leaf before succumbing to the Bt protein. Also, growers
don't have to re-spray each time after a heavy rain, worry about
incomplete spray coverage or have to reapply product after a relatively
rapid environmental degradation in the field due to heat, UV radiation
and desiccation.
The beauties of Bt
From the organic perspective, however, that's one of the beauties of
Bt. The foliar spray applications DO break down fairly rapidly in the
field -- after delivering a knock-out dose. This is one of the major
factors that has helped to preclude pest resistance, thus insuring its
effectiveness over time. Indeed, sales of Bt foliar formulations have
steadily grown into a $60 million/year industry in the U.S. with very
little evidence of developed resistance despite its long term,
widespread use.
Another major beauty of Bt biopesticides for both growers and eaters is
their safety. Each strain is extremely specific to its particular
targeted pest, as opposed to the actions of many chemical pesticides
which are highly toxic to a large number of other "non-targeted species"
including beneficial insects and soil microorganisms -- as well as
humans, pets, wildlife, fish, birds, frogs and a host of other life
forms. The loss of Bt (due to resistance, for example) as an effective
biopesticide would be an immediate and immense blow to organic growers
who have no other alternatives. For conventional growers its loss would
require the substitution of many more, highly toxic chemical pesticides
using more frequent applications to control the same dominant pests
which then would have 'side-effects' of their own.
The real problem with transgenic Bt is that its inherently ephemeral
nature has been transformed into a constant presence in the environment
-- a recipe ripe for breeding resistance. This isn't rocket science:
resistance particularly occurs when high concentrations of insecticides
are used repeatedly. Using specific pesticides on large scale
monocropped acreage may kill off fully 99% of the pest species (as well
as decimating many beneficial species that may be holding other
potential "secondary pests' in check) but the remaining 1% of the
(resistant) pests are left free to breed unencumbered, along with some
new outbreaks of secondary pests that themselves will now have to be
controlled by yet another pesticide. In this modern new world of
chemical agriculture, over 500 pest species have developed resistance to
insecticides and miticides alone.
The pesticide business is built on such planned obsolescence. As
insects become resistant to insecticides, weeds to herbicides and fungi
to fungicides the industry comes out with a new model whose new
formulations are generally proved to be as short lived. Bt is quite
different than a chemical formulation however. It is a naturally
occurring bacterium and as such has been classified as a 'public good'.
Once Bt is gone there are no equivalent biopesticide replacements
waiting in the wings and an incredibly valuable agricultural tool will
be lost forever.
High dose plus refugia
As yet, the Environmental Protection Agency (EPA) doesn't even have
full regulatory authority over plants genetically engineered to produce
pesticides. The "Plant Pesticide Rule", proposed back in 1994, is
meeting new opposition from industry groups long after the comment
period has closed. EPA does license the current commercial releases of
transgenic Bt in potatoes, corn and cotton with other crops including
cranberries soon to follow but must rely on the resistance management
plans submitted by Monsanto, Novartis and the other giant genetic
engineering agribusinesses in the industry.
The problem with the industry plans is that they are based on highly
theoretical laboratory based models along with experiments using captive
pest populations. Coupled with secretive provisions that precludes
extensive peer review scientific monitoring, most of the field data
available to independent scientists comes from transgenic Bt cotton
crops grown in Australia as the industry has refused to divulge the
identities and locations of its U.S. growers.
The core of the industry's resistance management plan is based on a
"high dosage plus refugia" strategy. While doses of over twice the
amounts needed to kill targeted pests are genetically inserted into the
crop strain, actual field conditions create regular anomalies. In
transgenic cotton, for instance, Bt dosage was found to be considerably
diminished in the lower leaves and bolls of the plant, thus failing to
deliver a knockout kill. In transgenic corn, it was found that the Bt
vigor lessened over the course of the season in the plants, again
producing less than a full kill for European corn borer, setting the
stage for the creation of resistance in both crops.
The highly experimental "refugia" theory is designed as a complimentary
practice. Its purpose is to set aside acreage next to the transgenic Bt
crop land that is planted to the same crop but without the Bt, providing
food and habitat for the target pests. These refuges would become a
source of pests purposely non-exposed to the Bt toxin. Consequently,
there would be no pressure for them to select for resistance. They would
then mingle and breed with any resistant pests surviving from the nearby
high dose transgenic Bt acreage, constantly providing a high population
of susceptible biotypes to the overall pest populations. (Presumably
organic farms and gardens, hitherto useless to the agrichemical
industry, now are valuable as the ultimate refugia...)
The major question for the efficacy of such a practice is determining
the relative size of the refuge. The industry seems to have settled on a
standard of 4% to 5% -- any more than that severely impacts the overall
cost of the program and the transgenic Bt seed stock is already
considerably more expensive. Outside experts estimate, however, that for
refugia to work at all it should be a minimum of 40%-50% of the
transgenetic Bt acreage. Now that transgenic Bt is hitting full
commercial release, actual refugia size, if any, is being left pretty
much up to the growers. The industry even claims that for the moment the
widespread cropping of conventional cultivars is refugia enough without
having to create more. At this point EPA has no regulatory power to set
or enforce refugia compliance and the usage standards the industry has
suggested for their farmer/customers are entirely voluntary.
Curiously, not even advocates of the refugia theory claim that it will
prevent resistance -- but only delay it. Rosy industry scenarios put
this at over 150 generations (30 years) while actual field conditions
indicate that full resistance will occur in 12 generations or less -- a
time frame of 3 to 4 years!
Cross resistance and cross contamination
Under conventional resistance management theory, one of the ways out of
creating a widespread problem would be for the industry to proactively
identify and monitor outbreaks of resistance wherever they occur by
users around the world and then suspend the use of all forms of Bt in
those areas -- with a "sorry" to the organic growers there who have no
substitutes. This the industry clearly has no intentions of doing and it
would also be an admission to the flaws in its system. Another way would
be to substitute other genetically engineered hybrid Bt protein strains
that could both kill the pests and provide an end run around their
resistance. Unfortunately, long term experiments with diamond backed
moths that have built up resistance to one strain of Bt are also now
showing multiple resistance to other strains. In an important new study
for the National Academy of Sciences, researchers found (contrary to
industry research) a single recessive gene that confers extremely high
resistance to four other major use Bt endotoxins. This resistance was
found to Bt foliar sprays as well.
The pronounced differences between the "pure" Bt used these many years
in foliar spray applications and the new mutant transgenic Bt holds
further implications for the ruin of Bt as a biopesticide -- and for the
disastrous contamination and "genetic pollution" of the environment.
While the spray Bt protein is large and only becomes activated in the
pest's gut, the bioengineered protein is artificially truncated and
doesn't need the presence of the pest to become activated. It also has
the ability to maintain its toxic effects for long periods. In fact,
researchers have discovered its ability to persist in the soil, even
nine months after the crops were harvested, boding ill for its
progressive accumulation thru conventional continuous cropping systems.
What this will do to wipe out soil organisms, insects and their complex
biological networks is incalculable at this stage and holds grave
consequences.
Because of its persistence, transgenic Bt is also feared to have a
severe impact on other non-targeted species and beneficial organisms. In
a recent experiment, corn borers that died after being fed transgenic Bt
corn were then fed to their natural enemies, lacewing larvae. From this
contaminated food the larvae also received a lethal dose of transgenic
Bt, suffering twice the normal mortality rate. The non-transgenic
(spray) Bt formulation showed no such effects.
There is also serious concern that transgenic Bt crops could produce a
"gene flow" of the mutant Bt into wild related species and weeds through
simple cross pollination. This would dramatically increase the amount of
persistent mutant Bt throughout the world, becoming a widespread
permanent selection pressure for resistance development. A study in
Denmark showed such a cross contamination flow into a nearby weed
species occurring in just one generation. Astoundingly, in another study
using potatoes, 35% to 72% of nearby normal potatoes (some growing over
a kilometer away) were cross contaminated by the transgene.
This genetic pollution has further long term ramifications, however.
Wild, progenitor species of many of our most important crops still
thrive in the wild in their lands of origin. These primitive cultivars
are the ultimate source of invaluable genetic traits necessary for
dealing with present and future disease and pest outbreaks as well as
for providing increased nutritional and healing qualities for our food.
Wild corn varieties in Mexico and indigenous potatoes in Central and
South America, for instance, have already contributed major resources to
our modern day crops and the current preservation efforts around the
world to preserve such seminal species are greatly endangered by a
potentially uncontrolled transgenic gene flow able to pollute our
precious wild gene reservoirs.
Now that transgenic Bt is let loose in the marketplace to the tune of
three million acres in the U.S. alone in 1997 -- of "Bollgard" cotton,
"New Leaf" potatoes and "YieldGard" and "KnockOut" field corn -- with
no public scientific monitoring and no mandatory compliance requirements
for growers, it is evident there is NO valid resistance management plan
and it's just a matter of a very short time until all forms of Bt are
entirely worthless. Most articles in the press, while constantly
enthralled with the wonders of genetic engineering, at least acknowledge
the possibility and a few even cite the negative ramifications of that
loss for organic farmers. Meanwhile, the industry is hard at work
developing still more transgenic Bt crops for commercial release --
cranberry, sweet corn, rice, rapeseed, eggplant, grape, tomato, apple,
poplar, walnut and tobacco, so far.
Getting away with biocide
Upon this slender thread lies the fate of Bt. That the problem is
barely being publicly addressed is due more to the power and hegemony
of the multinational agribusiness corporations than to any true science
conducted in the public interest. There is also substantial ongoing
investment of public funds in genetic engineering through USDA and Land
Grant college research and development programs, which is routinely
leveraged by agribusiness for their own purposes.
Here, might makes right and what's right is the corporate bottom line.