AgBioView - http://www.agbioworld.org, http://agbioview.listbot.com
Angela Ryan has recontacted me again and has sent me two
articles she is circulating on her network and would like these
circulated on yours if you are agreeable.
Can I suggest that comments be sent directly to her at
PS at some stage scientists from both sides are going to have to
sit down and straighten things out if possible. i don't know how or
when. Sorry to overload people again particularly Bob Goldberg. I
am not getting over consumed Bob it is just busy at present. I wish it
wasn't but I aim to get back to research in about one hour from now.
Here are two articles in upcoming ISIS News #5
Swallowing the Tale of the Swallowtails
No "Absence of toxicity" of Bt Pollen
The paper which claims "absence of toxicity" of Bt-pollen under field
conditions is faulty in experimental design and actually demonstrates
toxicity of Bt-pollen in the laboratory.
A study in Cornell University last year (1) prompted widespread concern
pollen from Bt-corn may be harmful to the Monarch butterfly. Researchers
from the University of Illinois now claims that a field study on the
swallowtail, Papilio polyxenes, shows that Bt-pollen is not toxic to
The black swallowtail feeds on host plants found in narrow strips
roads and crop fields in midwestern USA. A day after the start of
release, researchers set up five rows of five potted host-plant beside a
field of Bt-corn (Pioneer variety 34R07 expressing the CrylAB gene in
pollen), at various distances from the edge of the field. Pollen traps
consisting of a microscope slide coated with vaseline was placed with
plant to measure total pollen deposited. A second set of potted plants
placed behind the first set three days later. Ten first instar larvae
put on each plant, and the number of live larvae on each plant recorded
daily for 7 days.
However, no control experiments were set up. A proper control experiment
would have consisted of a replicate set of potted host plants and larvae
placed next to a non-GM corn field.
It rained during the 5th and 7th day of the first experiment, and during
2nd, 4th and 5th day of the second experiment. Would that not have
away the pollen from the surface of the leaves. If so, what relevance
the pollen counts - on greasy pollen traps - have on actual pollen
by the larvae?
Pollen counts decreased sharply with distance from the field as
but there was no correlation between pollen counts and mortality. Even
though the larvae were counted everyday for seven days, the detailed
were not given. Instead, the aggregate percentage mortality was
Not only were the mortalities high, they were also highly variable. The
means ranged from 45 to 82%, and in many cases, the standard deviation
each direction was almost as large as the mean. It was obviously
to draw any conclusion from such an experiment. But they stated, "No
significant relationships between larval survivorship or mass were
either as a function of distance from the edge of the field or as a
of pollen deposition." That was true, but the main reason may be that it
a bad experiment. They suggested that the high mortalities might be due
predation. If so, would mortality not be correlated with "larval mass"?
no such correlation was reported.
Back in the laboratory, they deposited different amounts of Bt and non
pollen on leaf-discs and fed each in a single dose to a first instar
which was observed over the next three days. They found no effect with
Bt-pollen collected from the field, even at the highest dosage. But
how much Bt toxin did each larva consume? From the figures presented, it
be calculated that at the highest dose used - 10 000 pollen grains - the
larva would have consumed only 1 picogram of Bt protein, ie, 1/1 000
000 000 or one trillionth of a gram, over the three days.
With another Bt-corn pollen - Novartis Max 454 - which expresses 40 times
much Bt protein, ie, 40 picograms, a highly significant increase in
mortality was found on the third day: 80% compared with about 10% for
As the laboratory experiments involved feeding a single dose over three
days, it gave no information as to the effects on mortality of
doses over the entire life-cycle of the butterfly, such as it may
in the field.
The claim of "absence of toxicity" in the title of this paper is thus
misleading to say the
least. It will be an abuse of science if this report were to be accepted
evidence that Bt-pollen is safe for black swallowtails.
References and Notes
1. Losey, J.E., Rayor, L.S. and Carter, M.E. (1999). Transgenic pollen
harms monarch larvae. Nature 399, 214.
2. Wraight, C.L., Zangeri, A.R., Carroll, M.H. and Berenbaum, M.R.
(2000). Absence of toxicity of Bacillus thuringiensis pollen to black
swallowtails under field conditions. PNAS early Ed.
To Bt or Not to Bt
The Sound Science that brought down Bt Crops
Since the publication of Losey's study in the journal Nature showing
Bt-corn pollen harms monarch butterflies, things have gone into a
spiral for Bt-crops. Bt-corn is now banned in Austria, France and
and Monsanto's Bt-potato division has been closed down by its new parent
'Bt' is short for Bacillus thuringiensis, the soil bacterium providing
genes for making toxins that kill insects; different forms of which are
incorporated into GM crops. The adverse environmental impacts of Bt
are now well documented in the scientific literature, ranging from harm
non target organisms to the evolution of resistance in insect pests,
it necessary to plant a high proportion of non-Bt crop for 'resistance
management'. Aberrant gene expression in the field results in low-dose
varieties which are ineffective
in pest control and foster resistance. Cross pollination with non GM
varieties creates Bt-weeds, and the Bt-plants themselves cause major
problems as volunteers. Active Bt toxin leaks from plant roots into
soil where it is not biodegradable and accumulates over time. This
have major impacts on soil health, with knock-on effects on all other
trophic levels of the ecosystem. The recent report that a GM gene has
transferred from GM pollen to microbes in the gut of bee larvae
the fact that Bt toxin genes, like all other GM genes, will spread out
control. The case for withdrawing all Bt-crops is now compelling.
The way the case has been built is exemplary of the power of good
independent science, which is indispensable for sound policy decisions.
No less than eighteen Bt crops were approved for field testing by the US
Dept. of Agriculture between 1987 and 1997 (1). Bt cotton was the first
be approved for commercial use (USA 1995), followed by corn, potato and
The first specific concerns on the safety of Bt crops were raised from
within the scientific community in 1997 when Angelicka Hilbeck and
colleagues (2) showed that lacewings fed on pests that have eaten
took longer to develop and were two to three times more likely to die.
Organic farmers also started to voice their fears - they have been using
spores of Bacillus thuringiensis as an occasional insecticide spray.
fear was founded in the rapid development of resistance to Bt toxin in
populations continuously exposed throughout the GM plant's growing
with the potential loss of their only organic insecticide. They were
worried about GM contamination via cross-pollination - now admitted as
unavoidable by our regulators.
Then came Losey's famous Monarch butterfly study (3), which was
another from the University of Iowa (4), showing that milkweed in and
varying distances from Bt crops in the field does cause an increase in
mortality to Monarch butterflies. Milkweed samples were taken from
and at the edge of the Bt corn field and were used to assess mortality
first instar monarch, D. plexippus exposed to Bt and non-Bt corn pollen.
Within 48 hours, there was 19% mortality in the Bt corn pollen
compared to 0% on non Bt-corn pollen exposed plants and 3% in the no
controls. This second study counters all the spurious arguments that
Losey's study was a 'worse case scenario' that bears no relevance to
conditions. Besides which, when Losey conducted his experiments he did
spatula Bt pollen on to the leaves of milkweed, as was reported by
he dusted the leaves in accordance with levels observed in the field.
In a desperate recent attempt to counter this evidence, the pro-biotech
lobby has just released a story claiming that pollen from Bt corn does
harm the black swallowtail. This story has been thoroughly deconstructed
(see "Tale of the Swallowtail", this issue).
The biotech industry is fully prepared to misreport research results in
order to confuse and mislead the public. On Nov 2nd 1999, a scientific
meeting took place in Rosemount, Illinois, to discuss Bt corn and
That same morning, all the major news desks round the US received a fax
carrying a News article about the meeting - which had only just begun at
that point - headlining 'Researchers conclude Bt corn poses little risk
Luckily, Carol Yoon of the NY Times was at the meeting and received word
from her editor in New York. She asked the participants if they agreed
what was obviously a press release from industry. The answer from the
was a resounding "No" - her report was the only accurate account of the
meeting, but unfortunately, the majority of US citizens got the
take on it (5).
After months of heated debate on the effects of Bt on non-target
the US Environmental Protection Agency (EPA) convened a Scientific
Panel (SAP) meeting in Dec 1999 and asked the panel to review EPA's
non-target organism testing requirement, applicable to Bt crops. The
found EPA requirements inadequate and urged the agency to substantially
expand the scope and quality of the studies that it relies upon (6).
Plans for managing the development of Bt-resistance in insect pests have
been actively debated in the scientific literature, and earlier this
the EPA revised their original mandate and ruled for larger refuges of
GM crop planted with the GM crop. This was hailed as a step in the right
direction and now refuges have to be at least 20%. But major
remain as to whether or not the refuges should be sprayed by
insecticides (7). A study in the University of Arizona (8) showed that
boll worm larva fed on GM and non GM develop at different rates and it
highly unlikely that they will interbreed, dashing any hopes of diluting
or slowing down the evolution of resistance. These moths mate within
days of hatching and the males only live for a week. Also, dilution only
works if the Bt-resistance is recessive, ie, requiring two copies of the
resistance gene to be expressed, and the EPA's resistance management
relies on the trait being recessive. Unfortunately, studies on the
inheritance of Bt resistance showed that it is a dominant trait (9) as
insects with only one copy of the resistance gene survive
exposure to Bt. Low levels of Bt expression in Bt crops has also been
documented and also serves to foster resistance.
Other scientists (10) have designed elaborate choice experiments that
to understand insect behavior in terms of 'pollen avoidance', which will
affect the evolution of Bt-resistance. However, by their own admission,
these data can not be used to arrive at any conclusions about the effects
Bt toxin-containing pollen. This work does however highlight the need to
consider complex behavioural as well as toxicological aspects.
In June1999, Monsanto applied for the first Experimental Use Permit on
CRY3Bb transgenic corn, another Bt corn line aimed at corn rootworm.
application has been thoroughly assessed by an alliance of four
non profit organizations (11), who report the most astonishing findings.
technical study submitted by Monsanto in July 1999 contained no
data, nor data on the breeding regime, for three different Bt lines.
on the levels of protein expression in different tissues was included.
300 corn plants were produced for only two of the transformation
experiments, and some of the critical measurements of expression levels
done on only two plants. Despite this, the data clearly indicate that
different transformations led to significantly different levels and
of protein expression. Such differences are of crucial important in
assessing efficacy, resistance management and non-target impacts, as well
changes in the microflora of the digestive systems of livestock and
using the crop for food.
Monsanto then submitted its application in full in August 1999, moving
greenhouse-scale research to unrestricted field use in one year. In the
covering letter they wrote; "Please note that approval of this
by May 2000 would reduce the need for additional submissions and reviews
year 2000 field trials". This statement makes it blatantly obvious
Monsanto has no intention of investigating their findings any further
respect to health and environmental impacts. To date their application
full is still pending in the US but has been granted commercial
in Puerto Rico and Hawaii for this growing season.
In Dec 1999, Gunther Stotsky and colleagues (12) reported that Bt toxin
released into the rhizosphere - around the plant roots in the soil - in
exudates from the roots of Bt corn, where the toxin is protected from
biodegradation and accumulates. This raised, for the first time, the
question of what is happening underground? A total of 15 million acres
Bt corn were planted in the US in 1998, 20% of the total acreage. The
toxin enters the soil in an activated form - Bt transgenes are truncated
produce active toxin, unlike the precursor-form produced in the
which has to be cleaved in the gut of susceptible insect pests.
the toxin is expressed continuously, and hence exuded for extended
In organic farming the toxin is sprayed sporadically in an inactive
precursor form, only becoming active in the gut of the target insects
ingested. Furthermore, it is sprayed onto the surface of plants where it
readily biodegraded. Stotsky suggests that the widespread planting of
crops is equivalent to added large doses of active toxin to the soil,
only from the plant root but also from the plant residues after
in, as well as from pollen. There is at present no clear indication as
how soil communities might be affected by Bt toxin from root exudates.
may promote selection of toxin resistant target insects. But receptors
Bt toxins are present in both target and non-target insects, therefore
will be affected. Bt toxins are active against insects in the Order of
Coleoptera (bettles, weevils and styloplids) which contains some 28,600
species, far more than any other Order (13). The widespread use of Bt
genes in crops and the build up of active toxin in the soil will have
term ecologically risks to non-target species and organisms in higher
trophic levels, such as birds.
Simultaneously, it was reported that Novartis had filed a patent for
insecticide to be used in conjunction with Bt crops (14). It turns out
the pest-control spectrum of Bt toxins is limited, and other pesticides
to be used, that have been shown to be very damaging to health. This
completely discredits the industry's claim that Bt is essential for
harmful pesticide use.
This April brought further reports on pockets of Bt-resistance among
in GM fields, and of GM cotton plants turning up as weeds in other crops
(15). The cotton boll weevil may make a come back if such volunteers
ignored. An entomologist at Clemson Univ. said, "I could look across
fields and see hundreds of these Bt cotton plants". A return of this
to parts of the American Cotton Belt would be a disaster, considering it
cost $1.3 million to eradicate them by 1995.
The ecological interaction between organisms is complex and
challenging. The behaviour of insects with regard to choice' of food can
have important impacts. This aspect has been overlooked completely in
environmental risk assessments of GM crops. Researchers at Rothamstead
the UK (16) have pointed out that killing non-target species is a risk
unique to GM technology, as conventional regimes actually kill insects in
indiscriminate manner that is equally unsustainable. They highlight the
need to find alternatives to conventional practices and suggest that
management and good husbandry of bio-control agents should act in an
integrated manner to eliminate caterpillars.
The health assessment of Bt crops relies totally on past experiences with
sprays in organic farming. It is wrong to assume that Bt toxin in GM
is the equivalent to what has been used for over thirty years on organic
produce with no effects. As with all GM crops, comprehensive feeding
have yet to be conducted and therefore there is no data supporting the
safety of eating Bt crops. Furthermore, there is a general lack of
scientific transparency with all GMOs and Bt-crops are no exception.
data are withheld from the public domain under various confidentiality
statements made by the biotech companies in their applications for
Leading US Agronomist, Charles Benbrook has just completed a
review on EPA's management of Bt-corn (17). It provides important
into the structural and legal shortcomings in the approval process, the
major among which was the failure to adhere to the precautionary
The summary of findings reported by independent scientists investigating
evaluating environmental risks are sufficiently compelling to warrant
immediate withdrawal of all Bt crops from use.
Notes and references
1. ISB Environmental Releases Database for USDA APHIS website :
2. Hilbeck, A., Baumgartner, M., Fried, P.M. abd Bigler, F. (1997).
of transgenic Bacillus thuringiensis-corn-fed prey on mortality and
development time of immature Chrysoperla carnew (Neuroptera:
Enivronmental Entomology 27, 480-487
3. Losey. J., Raynor. L., & Carter. M. E., (1999) Nature 399,214
4. See: http://www.ent.iastate.edu/entsoc/ncb99/prog/abs/D81.html
[Non-target effects of Bt corn pollen on the Monarch butterfly
(Lepidoptera:Danaidae) *L. Hansen, Iowa State University, Ames , IA
and J. Obrycki, Iowa State University, Ames, IA 50011. Contact e-mail:
5. First Hand Account ^ Industry manipulation of Bt research, by Beck
Goldburg, Environmental Defense Fund. Forwarded to Biotech Activists
6. The final report of the SAP panel is accessible at
7. Shelton, A.M., Tang, J., Roush, R.T., and E. Earle. (2000) "Field
tests on managing resistance to Bt- engineered plants, Nature
8. Liu, Y-B., Tabashnik, B.E., Dennehy, T.J.,Patin, A.J., & Bartlett,
(1999) Nature 400:519
9. Huang, F., et al. (1999) Science 284, 965-967
10. Tanja H. Schuler, Roel P.J. Potting, Ian Denholm, Guy M. Poppy
Parasitoid behaviour and Bt plants. Nature Vol 400 pp 825
11. Comments Submitted to Docket No OPP-30487a: Registration
CRY3BB transgenic corn modified to control the corn rootworm March 20
On behalf of Environmental Defense, the Institute of Agriculture and
Policy, the Science and Environmental Health Network, the Center for
Safety, and the Consumer Policy Institute/Consumer Union.
12. Deepak Saxena, Saul Flores, G. Stotzky (1999) Insecticidal toxin
root exudates from Bt corn. Nature Vol 402 pp 480
13. Arnett, R.H., and R.L. Jacques. Guide to Insects, Simon and
14. Genetically modified plants may still need pesticides, By Andy
and Barry Fox, New Scientist, 18.12.99
15. Pockets of resistance : A pest might make a comeback thanks to
engineered weeds. New Scientist, By Andy Coghlan April 15 2000.
16. Poppy, G. (2000) GM crops:environmental risks and non-target
Trends in Plant
Scienc 5 , 4-6.
17.Charles Benbrook and Steve Suppan June 2000. Applying the
Principle in Assessing Transgenic Corn Technologies in the US. See
>From: "Tony Trewavas"
>To: "Angela Ryan"
>Date: Fri, Jun 23, 2000, 9:43 am
Anthony Trewavas FRS
Institute of Cell and Molecular Biology
University of Edinburgh
Edinburgh EH9 3JH
Phone 44 (0)1316505328
Fax 44 (0)1316505392
web site http://www.ed.ac.uk/~gidi/main.html
To view the web site simply click on the address