The claim that genetically modified organisms are the most
promising way of increasing crop yields is falsified by many independent
scientific studies, as well as direct experience with GM crops in India, China, Argentina and the United States. Dr. Eva
Sirinathsinghjireviews evidence on Bt crops
This report has been submitted to the EPA on behalf of the
Institute of Science in Society. Please circulate widely and forward to your
insect resistance to genetically modified (GM) crops including Monsanto’s
biggest selling crop, Bt corn, is threatening their utility and profitability.
Insect resistance has prompted a new investigation by the Environmental
Protection Agency (EPA). According to documents in the newly opened docket
(Docket No: EPA-HQ-OPP-2011-0922) , “severe” damage to corn by rootworm has
occurred in four states in the US. Further, the EPA describe Monsanto’s insect
resistance monitoring program as “inadequate”. The EPA will collect public
information to tackle the damage that could cause serious crop and economic
damage. Amidst this investigation, Monsanto are seeing significant falls in
their share prices . Comments
and information regarding insect resistance can be submitted to the EPA on their
2010, GM crops engineered to produce insecticidal toxins from the Bacillus
thuringiensis (Bt) bacterium, were grown on more than 58 million hectares
of land globally . First commercialised in the US in 1996, it is also the
only commercialised GM crop grown in the EU, with Spain being the largest
producer. Despite their widespread commercialisation, the evidence for their
functionality is still elusive, while evidence of their harm to the
environment, people’s health, economic security and self-determination is
GM proponents have repeatedly claimed that Bt crops can help
combat world hunger by increasing crop yields while reducing pesticide use, thereby
providing a more productive and environmentally safe option over traditional
varieties. However, as highlighted by a recent report conducted by 20 Indian, Southeast
Asian, African and Latin American food and conservation groups representing
millions of people, these claims are false. Pesticide use has increased, while GM
crop yields are lower than conventional varieties (see  Transgenic
Cotton Offers No Advantage, SiS 38) and world hunger is at epic
Risk assessments of Bt toxins to date have been
inadequate, not least due to inexplicable lack of reliable data on the
concentrations of Bt toxin produced in plants, including
the roots and pollen. The purported efficacy and safety of these
products cannot be established when exposure levels have not be reliably
determined. A new study reported a standardised method to test Bt toxin levels
and still found significant variation in results, highlighting the variability
in previous studies . In particular, reports of declining concentrations in
the food chain and soils are unreliable and need to be re-evaluated and
repeated. Despite these inadequacies in risk assessments so far, evidence of
the Bt toxicity to environment and health is steadily accumulating.
The present review summarises all the evidence surrounding
the efficacy and safety of Bt crops with regards to pest control, human health
and environmental impact.
of pest control
hypothesis that Bt crops can boost yields by reducing pest numbers can be
questioned on three levels. First, the expression of the toxin is not reliably
sufficient to kill all target pests. Second, secondary pests that are not
susceptible to the Bt toxins can emerge as a result of reduced pesticide use,
bad agricultural practices e.g. monoculture farming, and the reduction of food
or niche competitors (target pests). Third, pests can develop resistance to Bt
toxins, rendering them completely ineffective.
toxin levels are not sufficient to kill pests
modification of plants is unpredictable by nature. Bt toxins were inserted in
plants so that they can be expressed consistently, across the whole plant. However, studies have found that expression of the
Bt toxin is not even across the whole plant or its life-span, resulting in parts
of the plant not containing enough toxin to kill pests [7,8]. Low levels of
toxin can also exacerbate pesticide resistance. Indeed, farmers have reported
crop failures as a result of target pests. In the US, 25 farmers filed a law
suit against Monsanto for the failure of their Bt cotton to protect from
bollworm infestation . A 2005 survey of over 100 Indian farmers in Andhra
Pradesh found that 32.5 percent of farms had infestations of American bollworm
(see  Organic Cotton
Beats Bt Cotton in India, SiS 27). Interestingly, organic farmers
reported a 4.1 percent incidence of infestation, suggesting that the Bt cotton
approach may not be the best for pest control, at least in this region.
Secondary pest and disease infestations
rationale that Bt crops reduces pesticide use is also challenged by the
emergence of secondary pests. A study published in Science last year
found that over a period of 10 years, the mirid bug, previously considered an
occasional or minor pest, acquired pest status, with increasing population
sizes that corresponded with decreased pesticide use on Bt cotton fields in Northern China. Not only is this a problem for Bt crops, but many others as well. The emergence of secondary pests that are not
susceptible to Bt toxin now means that alternative pesticides are necessary 
(see  GM-spin
Meltdown in China, SiS 47). With expensive GM seeds and additional
pesticide costs, farmers are left worse off than before. Bt cotton fields in India are also
showing infestations of new pests such as the mealy bug, gall midges, mosquitos
and safflower caterpillars that were not previously a problem (see  Mealy Bug Plagues Bt
Cotton in India and Pakistan, SiS 45). Although initially, Bt cotton
had partial success in reducing bollworm infestations, cotton can be targeted
by 165 different species of pests that are not all susceptible to the Bt toxin,
and secondary pest infestations as well as new illnesses such as leaf ‘streak’
virus and lalya are on the rise (see  Farmer
Suicides and Bt Cotton Nightmare Unfolding in India, SiS 45). The
new mealy bug infestations seen across India and Pakistan are causing
considerable reductions in crops yields (45-50 percent in 2007-2008); the two
predominant species originate from the U.S and have arrived since the
introduction of Bt cotton. They have also now been found on other crops
including brinjal, okra, tomato, chilli, potato, cluster bean, green gram,
papaya and sunflower . Independent studies in India show significant
reductions in crop yields that correlate with reduced profits as well as
devastating numbers of farmer suicides due to indebtedness from expensive Bt
seed varieties, combined with the low yielding crops . A study comparing
organically grown cotton and Bt cotton on over 200 farms in Andhra Pradesh in India have highlighted the propensity of Bt cotton to accumulate diseases and pests, along
with reduced yields .
resistance in target pests
predicted by many scientists as the cultivation of Bt crops expanded, Bt
resistance has now emerged and is spreading. So far, 8 populations of Bt
resistant pests have been documented, 2 of those resistant to Bt sprays, with
the rest resistant to Bt crops (see  Bt Resistant Rootworm
Spreads, SiS 52). This is not a surprising consequence of Bt
crop cultivation, and even Monsanto admit it to be a natural and expected
biological process. It now appears that the resistance, at least in the Western
rootworm in Iowa fields, is not a recessive trait, meaning that only one copy
of a resistant gene is necessary to survive, as opposed to two copies. This has
major consequences for the speed at which resistance can spread through pest
As a consequence of Bt resistant pests, Agrotech businesses
are busy making next generation crops that carry more and more Bt toxins. For example, the original
Bolgard Cotton contained one Bt toxin Cry1Ac, Bollgard II cotton contains 2
toxins, while Bollgard III contains 3 toxins. The latest Smartstax has 8 genes,
6 for insecticide resistance and two for herbicide resistance.
Although on the surface it may appear that failures of GM
crops may prove bad business for agrotech companies, the failure of first
generation transgenic crops can actually prove profitable business for
Industry. Farmers become locked into a cycle of dependency, having to return to
buy stronger or more expensive products. The business term to describe the
design for a limited useful life-span of a product is ‘planned obsolescence’
regards to human health
Bt toxin has been shown to cause damage to multiple organs including the heart,
kidney and liver in lab animals . Furthermore, adverse immune responses
have been observed in lab animals as well as humans. One study has found immune
responses from the Bt toxin to be similar to that seen with the Cholera toxin .
Allergenicity has also been observed in farmers and factory workers handling Bt
crops, with effects in eyes, skin and the respiratory tract (see  (More illnesses linked to Bt crops,
SiS 30). Contrary to industry’s claims, the Bt gene as well as the
toxin, remain in the body; it is not degraded in the gut as has been claimed. A
recent study in Canada found that over 90 percent of women and their unborn
babies had the toxin in their blood streams, just from eating a typical
Canadian diet . Crossing the placental barrier is of obvious concern.
Reduced fertility in mice fed Bt maize has been documented in a lab study (see
 GM Maize
Reduces Fertility & Deregulates Genes in Mice, SiS 41).
concerns of environmental and ecological damage
addition to human health, the Bt toxin has consequences on the planets
ecosystems, spreading to aquatic and soil organisms. A common model organism of
ecotoxicological studies is the water flea Daphnia magna. One study has
shown that when fed a diet of 100 percent Bt maize, these organisms showed
increased mortality, reduced numbers of females reaching sexual maturity, and
overall egg production was reduced . Overall mortality was also higher. The
authors concluded that the effects caused by Bt maize
were a result of toxic effects and not decreased nutritional content of thee Bt
maize. Pollen from Bt maize has also been shown to increase mortality of
monarch butterfly larvae. This along with glyphosate destruction of their
habitats, may be at least partially responsible for declines in Monarch
butterfly numbers migrating from the US to Mexico for winters [23,24] (see  Glyphosate
and Monarch Butterfly Decline, SiS 52).
Because the toxin is also expressed in the roots of the
plants, it also seeps into the soil where it has shown to persist for 180 days.
This affects the soil fertility by harming soil organisms, thereby depleting
the land and reducing crop yields. A study conducted in India found that soil
bacteria in Bt cotton fields were reduced by 14 percent, while total microbial
biomass was reduced by 8.9 percent (see  Monsanto's Bt
Cotton Kills the Soil as Well as Farmers, ISIS Report 23/02/09). This has
implications for yields of crops as well as illnesses, with a new disease
termed lalya emerging as a result of nutrient deficiencies in the soil. This
causes the plants to redden and wilt. Cross contamination of GM varieties with
non-GM varieties also poses big risks for biodiversity, as has been documented
with GM corn in Mexico .
By-products of Bt crops have been shown in field studies to
reduce the growth rate of aquatic insects (caddisflies) by 50 percent and
increase mortality rates  (see  Bt Crops
Threaten Aquatic Ecosystems, SiS 36). Half the caddisflies
living near Bt maize fields were shown to have Bt maize pollen in their guts. Potential
off-target effects are possible in soil as well as streams and rivers.
crops are at best useless in pest control, and at worst, an exacerbating factor
for pest infestation and reducing crop yields. They are also proving hazardous
to non-target species in the ecosystem and to human health. All the evidence
favours non-GM integrated pest control as a far superior strategy.
6. Székács A,
Weiss G, Quist D, Takács E, Darvas B, Meier M, Swain T, Hilbeck A.
Inter-laboratory comparison of Cry1Ab toxin quantification in MON 810 maize by
enzyme-immunoassay. Food and Agricultural Immunity 2011, DOI:10.1080/09540105.2011.604773,
7. Kranthi KR,
Naidu S, Dhawad CS, Tatwawadi A, Mate K, Patil E, Bharose AA,. Behere GT,
Wadaskar RM and Kranthi S. Temporal and intra-plant variability of Cry1Ac
expression in Bt-cotton and its influence on the survival of the cotton
bollworm, Helicoverpa armigera (Hübner) (Noctuidae: Lepidoptera). Current
Science 2005, 89, 291-7.
8. Wan P, Zhang
Y, Wu K, Huang M. Seasonal expression
profiles of insecticidal protein and control efficacy against Helicoverpa
armigera for Bt cotton in the Yangtze River valley of China. Journal of Economic Entomology 2005, 98, 195-201.
17. SéraliniG-E,Mesnage R, ClairE,GressS,VendômoisJ,CellierD.Genetically
modified crops safety assessments: present limits and possible improvements. Environmental
Sciences Europe 2011, 23,
18. Vázquez-Padrón RI,
Gonzáles-Cabrera J, García-Tovar C, Neri-Bazan L, Lopéz-Revilla R, Hernández M,
Moreno-Fierro L, de la Riva GA. Cry1Ac protoxin from Bacillus thuringiensis sp.
kurstaki HD73 binds to surface proteins in the mouse small intestine. Biochemical
Biophysical Research Communications 2010, 271, 54-8.
22. Bøhn T, Primicerio R,
Hessen DO, Traavik T. Reduced fitness of Daphnia magna fed a Bt-transgenic
maize variety. Archives of Environmental Contamination and Toxicology
2008, 55, 584-92
23. Losey JE, Rayor LS,
Carter ME. Transgenic pollen harms monarch larvae. Nature 1999, 399,
24. Brower LP, TaylorOR,
Williams EH, Slayback DA, Zubieta RR, Ramírez MI. Decline of monarch
butterﬂies overwintering in Mexico: is the migratory phenomenon at risk?
Insect Conservation and Diversity 2011, doi:
25. Sirinathsinghji E.
Glyphosate and Monarch Butterfly Decline. Science in Society 52, (to appear)
26. Navdanya. Monstanto’s Bt
Cotton Kills the Soil as Well as Farmers. ISIS report 23/02/09. http://www.i-sis.org.uk/BtCottonKillsSoilandFarmers.php
27. Quist D, Chapela IH.2001.
Transgenic DNA introgressed into traditional maize landraces in Oaxaca, Mexico. Nature 2001, 414, 541-3.
28. Rosi-Marxhall EJ, Tank
JL, Royer TV, Whiles MR, Evans-White M, Chamgers C, Griffiths NA, Pokelsek J
and Stephen ML.Toxins in transgenic crop byproducts may affect headwater stream
ecosystems. Proceedings of the National Academy of Sciences 2007, 104,
Prof Amyan Macfadyen Comment left 14th December 2011 16:04:28 this really ought to put the final nail in the coffin of Bt but of course it won't. What is to be done to bring to heal both Monsanto and its friends and also the Canadian and U.S. government agencies which are in hock to the cemical maunfacturers?
James Cooley Comment left 14th December 2011 20:08:43 One promising strategy to eliminate GM crops is the California citizens initiative to require labeling of all GM foods. If this initiative passes, food manufacturers will either have to label their foods or(more likely)abandon GM ingredients. Congress seems willing to eat any GM crap Monsanto puts before it, but consumers don't have the same economic incentives.
ajhelms Comment left 16th March 2012 08:08:57 this looks like the end of mansanto corp watch the ceo dump there stock and run, the world is fixing to sue the hell out of mansanto for shipping bad seed filled with insect eggs they have infected the world with insect that never should have left the usa by seed sack,stock dump I not buyin any not after reading this sue happy farmer statement.
aj Comment left 16th March 2012 08:08:42 I am not going to buy any stock not with all this sue happy farmer world wide, and the thought of mansanto distribution of insects world wide with the seed in sack program is not going to go over good either might as well flush mansanto stock down the toilet for what it worth it all ready sliding down and the ceo with start to dump next the law suet will mount up in the 100's billions before it over and if the us farmer grap a wind of this it over no body will buy corn chips any more, what a dummer deal for me, first bernake rapes us of our money now this crap! way to go mansanto you lyin piece of crap company!I like to kick them scientist ass.
Eva Sirinathsinghji Comment left 20th March 2012 17:05:51 Hi Eric, from what I can gather Bt toxins, whether natural or expressed in GM crops, are toxic to many insects, so inevitably will have effects on off-target insects. However, the natural sprays allow topical application whenever necessary, and in addition, it can be washed off. Bt toxins in GM crops on the other hand, are expressed throughout the life-time of the plant and in all the cells including roots, therefore giving more potential to damage biodiversity. I would expect that minimal applications of pesticides only when strictly necessary would be best.Bt toxins are potential allergens so this is something else to consider.
eric Comment left 20th March 2012 17:05:37 so, im confused if the same harm can be caused by spraying bt on crops, or is the harm coming from the genetic modification of the plant?
i am a small scale organic farmer who debated using bt for quite a while because of the harm to benficial insects. I finally broke down this winter and sprayed my brassicas. any thoughts?