AGNET AUGUST 8, 2000 -- III
Monsanto biotech seeds blocked by Brazil court
Seven questioned over GM crops attack
Franceıs Glavany wants EU limit on GMO seed content
MSU police strike back at eco-terrorists
Meanwhile, a battle rages to stop our fields turning into `green concreteı
Backgrounder: genetically-engineered Bt-containing field corn
Agnet is produced by the Centre for Safe Food at the University of Guelph
and is sponsored by the Ontario Ministry of Agriculture, Food and Rural
Affairs Plants Program at the University of Guelph, with additional support
provided by the U.S. National Pork Producers Council, the U.S. National Food
Processors Association, Ag-West Biotech, Novartis Seeds, AGCare
(Agricultural Groups Concerned About Resources and the Environment),
Monsanto Canada, Pioneer Hi-Bred Limited (Canada), Ontario Egg Producers,
U.S. National Cattlemen's Beef Association, Ontario Agri-Food Technologies,
Novartis Crop Protection Canada, Halton Regional Health Department, the
Rutgers Food Risk Analysis Initiative, the Crop Protection Institute,
Agriculture and Agri-Food Canada, Ontario Corn Producers Association,
Capital Health, Plant Protection Branch Dept of Agriculture Fisheries
Forestry Australia, Performance Plants, Cargill AgHorizons, the Ontario
Soybean Growers Marketing Board, the Canadian Cattlemen's Association,
AdCulture, Food Industry Environmental Network, Dow AgroSciences, W.G.
Thompson & Sons, Crop and Food Research New Zealand, and the Agricultural
Adaptation Council (CanAdapt Program).
MONSANTO BIOTECH SEEDS BLOCKED BY BRAZIL COURT
By Scott Kilman and Matt Moffett
Staff Reporters of The Wall Street Journal
A Brazilian appeals court was cited as blocking Monsanto Co. from selling
genetically modified seed to that nation's soybean farmers, closing for
another year what is potentially a huge market for crop biotechnology.
The story says that a three-judge appeals panel in the Brazilian capital of
Brasilia yesterday upheld a lower court's order blocking the
commercialization of Monsanto's seed.
The story adds that the judges still have to rule on the merits of the case,
in which a consumer group is trying to force the government to do more
testing on genetically modified seeds before approving their use. But the
judges' decision signals that they think the government's approval process
is probably unconstitutional.
Monsanto, the agricultural unit of drug maker Pharmacia Corp., Peapack,
N.J., was cited as saying it is considering just how to appeal the decision.
The problem for Monsanto is that the legal fight is now between the courts
and the executive branch. Monsanto spokesman Gary Barton was quoted as
saying, "We've done everything to comply with the laws and regulations of
the Brazilian authorities." The ruling effectively eliminates any chance
that Monsanto can get its seeds into the hands of Brazilian farmers in time
for the planting season.
SEVEN QUESTIONED OVER GM CROPS ATTACK
August 8, 2000
Seven people were, according to this story, arrested after genetically
modified crops were trampled and pulled up in a field in Essex, police said.
A police spokeswoman was cited as saying the group of five women and two
men, from London, Oxford and Cambridge, were arrested last night for
criminal damage after 300-worth of GM maize was destroyed.
The story also cited Essex police as confirming that the area, on the edge
of Wivenhoe, had been attacked "several times" in the past.
The seven, who have not been named, were arrested and taken to Clacton
police station, where they remain in custody and were being questioned.
FRANCEıS GLAVANY WANTS EU LIMIT ON GMO SEED CONTENT
August 8, 2000
PARIS -- French Farm Minister Jean Glavany, whose country currently holds
the presidency of the European Union, was cited as saying on Tuesday he
would push member states to agree a maximum threshhold for GMO content in
The story says that in an editorial published in daily Le Monde, Glavany
said the law was necessary in light of the recent discovery that rapeseed,
soybean and maize seeds planted in Europe had accidentally included
genetically modified organisms (GMOs).
EU rules currently oblige food producers to label their products as
containing GMOs if they cannot guarantee each of the ingredients contains
less than one percent of GM material.
MSU POLICE STRIKE BACK AT ECO-TERRORISTS
August 6, 2000
The Associated Press
Michigan State University police are, according to this story, taking the
battle to eco-terrorists, assigning a detective to prevent attacks like the
New Yearıs Eve arson which caused $900,000 damage.
The story says that Kristine Kirby will assess the security of Michigan
State biotechnology research labs, ascertain where eco-terrorists might
strike and help scientists work more safely.
Capt. Dave Trexler was quoted as saying, "Thereıs going to be an increase in
the next several years of research in the biotech area. We need to stay
ahead of the game. We need to ... beef up security where the research is
Michigan State researchers have done work in the field of genetic
engineering, trying to make plants more nutritious and resistant to pests,
disease and weather.
But some - including a group called the Earth Liberation Front, which claims
it set the December fire - believe genetically modified crops could be
unsafe to eat or harm the environment.
The ELF and its ally, the Animal Liberation Front, are believed to have
committed a string of violent acts against universities, fur farmers,
loggers and others nationwide.
Since 1997, theyıve claimed responsibility for 11 criminal acts in nine
states, causing at least $16 million in damage.
Kirby will spend 50 to 75 percent of her time on eco-terrorism and the rest
on computer crimes.
MEANWHILE, A BATTLE RAGES TO STOP OUR FIELDS TURNING INTO `GREEN CONCRETEı
August 4, 2000
Michael McCarthy Environment Correspondent
THERE HAS been a chorus of criticism throughout the spring and summer, there
have been meetings of anxious locals in parish halls, there have been
farmers who have changed their minds, sometimes under pressure, and there
have been attacks on fields across the country, yet the Government announced
yesterday it was pressing on with its controversial programme of farm-scale
trials of GM crops.
But the hostility of the green activists, and the Governmentıs unwavering
decision to press on, mark a genuine, profound and honestly held
disagreement about the trialsı value.
The four-year test programme has nothing to do with food safety: it is
designed to test the effects on wildlife of the weedkillers the GM crops
have been bred to tolerate, which are "broad spectrum" herbicides: they kill
virtually everything they come into contact with.
The idea of the agrochemical companies, such as the German firm Aventis, is
simple: farmers get rid of all their weeds and get a much higher crop yield.
But this may well mean getting rid of everything else in the field apart
from the crop, and turning the countryside into "green concrete".
It was the Governmentıs wildlife advisers, English Nature, who first wanted
the trials and called loudly for a four-year moratorium on the commercial
growing of GM crops. Tony Blair, a GM enthusiast, publicly ruled out any
official ban, but in one of the deftest political moves of the current
administration, the Environment minister Michael Meacher persuaded the GM
companies to bring in a moratorium voluntarily.
The point of the trials, as Mr Meacher never tires of pointing out, is to
gather solid scientific information that may well prevent GM crops being
grown commercially in the United Kingdom, ever. People who disrupt them, he
says, are shooting themselves in the foot.
Yet for the more radical pressure groups, such as Greenpeace and Friends of
the Earth (FoE), any value the trials might eventually have is outweighed by
the immediate threat of releasing GM genes into the countryside.
Their opposition is colored by their hostility to the big companies which,
often ruthlessly, have promoted GM technology - Monsanto above all - but
they also have science on their side.
While separation distances have been set for the trials, a report
commissioned last year by the Government itself from the John Innes Centre
in Norwich, Europeıs leading GM research institute, found that contamination
of other plants by either pollen or seed cannot be "entirely eliminated",
whatever the distance between crops.
Both bees and the wind can carry pollen several miles, while seeds from
oilseed rape could be accidentally dispersed during harvesting or
transferred to fields from machinery, the report found. Crucially, it also
found that the buffer zones, set at 200 metres for oilseed rape, would have
to be increased, especially if the organic farming industry is to maintain
its "GM-free" certification.
The radical pressure groups have won some notable victories. Of the 66
farmers who agreed to host trial sites this spring, 18 dropped out, usually
after loud local opposition. In West Portholland, Cornwall, the farmerıs
milk buyer was not happy to take milk if the farm was growing GM crops.
In Ainderby Steeple, North Yorkshire, beekeepers feared honey might be
contaminated. In Tittleshall, Norfolk, a parish meeting voted 94-4 against
the trial continuing, while in St. Osyth, Essex, a parish referendum went
against the farmer. There have been 10 attacks on sites this year, mostly by
So the trials go on, but the problem of separation distances remains. If the
Government does find that the Advanta seeds were contaminated over a
distance of four kilometres, how can it then set its separation distances at
any less? But with those intervals, officials admitted yesterday, it would
be virtually impossible to find trial sites, and the programme would
Tough one, eh, Michael? Wrestle with it on holiday. Thatıs what we pay our
BACKGROUNDER: GENETICALLY-ENGINEERED BT-CONTAINING FIELD CORN
Updated Aug. 2000
Technical Report No. 11, July 21, 1999
Juhie Bhatia, Sarah E. Grant, and Douglas A. Powell
Dr. Douglas Powell
dept. of plant agriculture University of Guelph
Guelph, Ont. N1G 2W1
tel: 519-824-4120 x2506 fax: 519-763-8933
Corn is one of the worldıs most important cereals with an annual global
harvest approaching 560 million tons with main producers in the USA, China
and Brazil (Novartis, 1998). However, 40 million tons of corn (or 7%) never
reach the market because of damage by European corn borer (ECB). European
corn borer, Ostrinia nubilalis, is the most damaging insect pest of corn
throughout the United States and Canada. Entomologists estimate that losses
resulting from ECB damage and control costs exceed $1 billion each year
(Alstad, 1997; Dekalb, 1998; Andow and Hutchison, 1998; Haag, 1999). ECB
typically go through two life cycles during the corn growing season, the 2nd
generation usually causing the most damage. In 18 tests over the last six
years, Iowa State University researchers saw losses of 4 bu/acre or more
from 94 percent of the fields they examined due to ECB (Dekalb, 1998) ECB
damage also causes human health concerns. Maize kernel feeding by ECB often
leads to infection by fungi in the genus Fusarium, including the
fumonisin-producing species (Munkvold et al., 1999). Fumonisins are a class
of mycotoxins. Esophageal cancer in humans has been associated with
consumption of maize with high concentrations of the fumonisins (Munkvold et
Bacillus thuringiensis (Bt) is a gram positive soil bacterium that produces
an insecticidal protein in the form of a crystal. The insecticidal proteins
are commonly designated as cry proteins and the genes encoding the proteins
are known as cry genes (Lambert and Peferoen, 1992). The Bt-toxin is
regarded as an environmentally friendly insecticide because of its target
specificity and its decomposition to non-toxic compounds when exposed to
environmental factors (Gould, 1995). Bacillus thuringiensis Berlinerı is
the most commonly used biopesticide (Wearing and Hokkanen, 1995). Bt has
been widely used in both conventional and organic farming operations as an
insecticidal spray with some drawbacks. In order for the Bt endotoxin to be
effective, the insect must ingest it (Webber, 1995), before it is broken
down by environmental factors such as ultraviolet light. One advantage of
genetically-engineered Bt-corn is that the insecticidal protein has been
incorporated into the plant, limiting environmental exposure. Insecticidal
properties of Bt can vary in activity against insects within a single insect
Order. The toxins encoded by the cryI genes are toxic to Lepidopterans such
as the European corn borer.
Bt-corn hybrids have been genetically engineered to contain the cry genes
which subsequently produce cry proteins in the plantıs leaves, stalk and
pollen (Lambert and Peferoen, 1992; Novartis, 1998). The cry proteins must
be ingested to be fatal for the insects. Once eaten, the crystal breaks down
and releases a toxin that attacks and destroys the insectıs gut lining
(Anon, 1998; Novartis, 1998). Insects stop feeding within two hours of a
first bite and, if enough toxin is eaten, die within two or three days
(Anon, 1998; Alstad et al., 1997).
The Bt toxin provides protection by selectively killing specific groups of
insect larvae. The Bt subspecies kurstaki is toxic to certain caterpillars,
including ECB (Anon, 1998). For all Bt-corn varieties developed thus far,
the primary pest target is ECB (Andow and Hutchison, 1998). Several Bt
varieties, however, also provide reasonably high levels of control of
southwestern corn borer (Diatrea grandiosella) and lesser cornstalk borer
(Elasmopalpus lignosellus) and, for Bt sweet corn, corn earworm (Helicoverpa
zea Boddie) and fall armyworm (Spodoptera frugiperda). There are several
strains of Bt, each with differing cry proteins. There are over 100 patented
Bt cry toxin genes, but only those toxins encoded by the cryI genes are
functionally active against ECB (Alstad, 1997; Andow and Hutchison, 1998).
Specifically, these include cry1Ab, cry1Ac, and cry9C (Alstad, 1997; Andow
and Hutchison, 1998). Most of the Bt-corn hybrids produce only the cry1Ab
protein; a few produce the cry1Ac protein or the cry9c protein (Alstad,
1997). Several seed companies have incorporated this technology. Dekalb
Genetics uses the cry1Aİ gene and trademarks its event as "Bt-Xtra" (DBt
418)(Andow and Hutchison, 1998). The other groups are based on the cry1A(b)
gene. These are trademarked as: "KnockOut" (176) by Novartis, "NatureGard"
(176) by Mycogen, "YieldGard" (MON810) by Monsanto and "Bitegard" (BT11) by
Northrup King (now Novartis Seeds)(Alstad, 1997;
Andow and Hutchison, 1998).
Bt-corn was approved by Canadian regulators and the U.S. Environmental
Protection Agency (EPA) in 1995 (USDA, 1999). The total number of acres
planted with Bt-corn in the U.S. has risen from 5.5 million in 1997 to 16
million acres in 1998. In 1999, approximately 30 per cent of all corn
planted in the U.S. will be Bt hybrids (Haag, 1999). In Ontario in 1998,
approximately 15 per cent of the corn crop was planted was to Bt varieties.
One-third of the field corn in Ontario in 1999 will be Bt-corn (Anon,
Yield and Economic Impacts
ECBs cause significant yield loss. One corn borer per plant typically causes
a 3 to 5 per cent yield loss, two borers a 6 to 10 per cent yield loss, and
three borers, a 15 per cent yield loss. This can cost $27/acre or more
(Dekalb, 1998). According to Sears and Schaafsma (1998), yield losses in
Ontario averaged 11 bushels per acre for the 1998 growing season. Bt-corn
should prevent these yield losses, but yield results will depend on
Bt-events, specific hybrids and ECB infestation levels (Alstad, 1997). ECB
levels are inconsistent from year to year, and therefore, an investment in
Bt-corn is an economic risk. The premium paid for Bt-corn seed will likely
only be returned in years when corn borer infestations are moderate to heavy
(Alstad, 1997; Anon, 1998; Haag, 1999). European corn borer populations
typically go through a boom and bust cycle over about a 7-year period. Some
years there is little corn borer pressure, while other years show losses as
high as 20 percent (Dekalb, 1998).
Munkvold et al. (1999) conducted field experiments in 1995, 1996, and 1997
where transgenic maize hybrids and non-transgenic hybrids were manually
infested with ECB larvae. ECB infestation increased Fusarium ear rot
severity and fumonisin concentrations in kernels of non-transgenic hybrids.
Transgenic hybrids consistently experienced less insect feeding on kernels,
less Fusarium ear rot, and lower concentrations of fumonisins than their
Further support of Bt-cornıs efficacy has been shown in field tests against
natural and supplemented ECB infestations. Bt-corn hybrids (regardless of
event) provided more than 99 per cent control of first generation ECB larvae
in whorl-stage corn (Alstad et al, 1997; Anon, 1998). However, the level of
control against late-season European corn borer infestations varied between
Bt events, since each produces the Bt protein in different parts of the
plant (Alstad, 1997). For example, because the level of expression of the Bt
protein declines in Mycogenıs hybrids after pollination, some
second-generation borers may survive. The YieldGard Bt gene protects the
plant from corn borers for a longer period of time (Anon, 1998). Novartis
conducted Ontarioıs largest ever scouting program in the summer of 1998,
walking 248 fields and following 89 through to harvest (Button, 1998). It
compared yields between Bt and isoline (non-Bt) corn. The results showed
that in plots with low borer damage, Bt hybrids produced 6.6 extra bushels
in 1998, compared to 3.0 extra bushels in 1996 and 1997. In moderate borer
plots, yield gains were 10.1 bushels, compared to 4.3 (Button, 1998).
Finally, in plots with severe damage, gains reached 16.7 bushels, up from
10.1. Overall, Novartis agronomist Cathy Soanes (1998) reported, Bt hybrids
notched 11.1 extra bushels per acre compared to their non-Bt isolines. In a
dozen of the sample fields, the yield gains topped 20 bushels (Soanes, 1998;
Increased yield should translate into increased profit. However, the
variability in ECB infestation, corn yields and market prices raises
concerns about fluctuations in yearly economic benefits of Bt-corn. For
example, the risk of investing in Bt-corn was scrutinized for southern
Minnesota over an eight-year period 1988-1995 (Alstad et al., 1997). This
period included three outbreak (high) years for ECB and five endemic (low)
years. The average benefit for this period was $17.24 per acre, but returns
varied considerably between endemic and outbreak years. During the endemic
years, the yield protection offered by Bt-corn barely covered the price
premium for seed, currently $7 to $10 per acre. During outbreak years, yield
savings were four to five times the added seed cost ($28 to $50 per acre).
Therefore, as with any type of natural resistance, Bt-corn only delivers an
economic benefit when European corn borer outbreaks occur. The availability
of Bt-corn hybrids was the first opportunity to experimentally determine the
impact of ECB on field corn by comparison of performance with the isolines
of each Bt event (Sears and Schaafsma, 1999). In this study over the past
two years, yield protection provided by the Bt hybrids was generally 3 to 5
bushels per acre in areas of low infestation (0-2 cm tunneling damage), 5 to
8 bushels in areas of moderate infestation (2-6 cm tunneling) and 10 to 15
bushels in areas of high infestation (6-12 cm). Sears and Schaafsma (1999)
found that for every centimeter of stalk tunneling per plant by corn borer,
yield was reduced by 0.007 to 0.01 bu/A, or 0.7 per cent to 1 per cent
reduction. At high levels of infestation (10-15 cm tunnels/plant) this
equaled 8 to 15 bu/A loss in a typical field that averaged 120-140 bu/A. At
an average price of $2.50/bu this was equivalent to $20-$37.50 potential
loss/A, which was greater than the premium of $9-14/A. Low infestations
resulting in 5 cm or less of damage would reduce yield by 5 to 6 bu/A or
$12.50-15.00/A. This value was at, or just above, the break-even point for
seed premium costs. The USDA Economic Research Service (ERS) released a
report on June 25th 1999 regarding the benefits of genetically-engineered Bt
and herbicide-tolerant crops. The report, Genetically Engineered Crops for
Pest Management, presented data on the yield of GE crops in 1996, 1997 and
1998 in various regions of the U.S. It stated that the "use of Bt-corn is
associated with significantly higher yields in most years for some regions"
(USDA, 1999). In a comparison of mean yields of Bt-corn, it was found that
in 2 of 5 regions over the three years, adopters of Bt-corn obtained
statistically higher yields than non-adopters. It was also noted that crop
yield differences between adopters and non-adopters could also be due to
other factors not controlled for in the analyses. The report is available
at: http://www.econ.ag.gov/whatsnew/issues/biotech/ In July 1999 the
National Center for Food and Agricultural Policy in Washington, D.C. (BIO,
1999) released the first-ever study aimed at assessing whether crops
genetically modified to resist pests, like Bt-corn, actually yield benefits.
It found that in 1997 when ECB infestation was high, Bt-corn increased total
yields in the U.S. by 47 million bushels, boosting profits by $72 million.
That year, however, only 4 million acres of Bt-corn were planted among the
80 million acres nationwide. In 1998, when 14 million acres of Bt-corn were
planted, corn borer infestation was extremely light, but farmers still saw
an increase of 60 million bushels. However, this did not translate into
higher profits. Despite the fact that in 1998 three times more acreage was
planted to Bt-corn, growers lost $26 million because pest infestation levels
and the price of corn dropped well below average. An analysis of the
historical pest infestation data suggests that three non-paying years for
Bt-corn can be expected every decade (BIO, 1999).
A full copy of this 98-page study can be found at:
It has been suggested that Bt-corn represents environmental progress,
because it does not require the abundant spraying of less-effective
agricultural chemicals to control insects (Hovey, 1999). The Bt toxin is
also regarded as an environmentally friendly insecticide because of its
target specificity and its decomposition to non-toxic compounds when exposed
to environmental factors (Gould, 1995).
When evaluating environmental concerns about the use of Bt corn, it is
important to take into account the public health and environmental damage
caused by the use of pesticides in agriculture.
Human pesticide poisonings are a major health concern, with a reported
110,000 nonfatal pesticide poisonings reported each year (Benbrook, 1996),
in addition to an estimated 10,000 cases of pesticide-related cancer and
numerous other public health problems (Pimentel, 1993a). Although 97-99% of
the foods sampled in supermarkets in the U.S. have acceptable pesticide
residue levels that for the most part do not constitute health hazards,
approximately 35% of such foods do have detectable pesticide residues
(Pimentel, 1993a). In addition to the demonstrated and potential health
problems associated with their use, pesticides cause widespread and serious
environmental effects. An estimated 70 million birds are killed each year in
the U.S. as a result of pesticide use (Pimentel, 1993a), and billions of
insects, both beneficial and harmful, are also killed.
Researchers Pimentel and Raven (2000) argue that crops like Bt-corn can help
reduce the use of agricultural chemicals when used as part of an overall IPM
Bt-corn reduces the ECB population in a field and, depending on prevalence
of Bt-corn in the area, influences the local ECB population. Conceptually,
this population suppression should be greatest closer to Bt-corn than
farther away, but neighboring cornfields could experience reduced ECB
attack. It is possible that planting non-Bt-corn near Bt-corn could be
beneficial because ECB populations near Bt-corn fields should be suppressed
and most insects are likely to move shorter distances (Alstad, 1997; Andow
and Hutchison, 1998). Andow and Hutchison (1998) refer to this short-term,
localized benefit as the halo effect.
Indirect benefits may also occur through decreased incidence of corn
disease. Bt-corn reduces ECB tunnels that provide entryways for plant
pathogens. Thus, stem rots and ear rots could be reduced along with
mycotoxin production (Alstad, 1997). Fewer dropped ears with Bt-corn will
mean less volunteer corn in the following yearıs crop (Alstad, 1997).
Concerns - Resistance Management
European corn borer tend to be resilient and may have the potential to
develop resistance to Bt cry proteins (Dekalb, 1998). Insects are known for
their ability to rapidly develop resistance to certain insecticides. There
is a similar concern for Bt-corn (Hovey, 1999).
Many factors contribute to the potential for the development of resistance
in ECB, including: predictions for widespread repetitive use of Bt-corn;
high season-long mortality; two or more generations per year; the genetic
composition of the pest population; and, toxin expression in the crop plant
(Andow and Hutchison, 1998; Alstad, 1997; Anon, 1998). Recent laboratory
studies in Minnesota, Kansas and Delaware confirm that ECBs can develop
moderate levels of resistance to Bt insecticides or Bt cry proteins (Alstad,
1997; Anon, 1998). Resistant ECB strains in these studies required 30-60
times more toxin (resistance ratio) to kill 50 per cent of a test population
of young borers compared with non-resistant ECB strains. This modest level
of Bt resistance developed in relatively small lab populations after seven
to nine generations of exposure. Although these results confirm the genetic
potential of ECB to develop resistance, further study is reqired to assess
the potential of ECB to develop resistance under field conditions.
The genetics involved in development of resistance is still unclear. In any
population of ECBs, a few of the borers will have two copies of genes for
resistance, some will have one copy of the gene and most will have none. As
the Bt-corn acreage increases, more larvae carrying resistance genes could
survive to adulthood. Survival or reproductive success results in a
"selective advantage," thus, increasing the overall population of
Bt-resistant individuals with each generation (Alstad et al., 1997). Control
failure could eventually occur with resistant larvae reaching infestation
levels in Bt-cornfields similar to levels found in non-Bt-cornfields (Alstad
et al., 1997).
Resistance genes have been characterized as recessive or partially recessive
(Alstad, 1997; Huang et al., 1999). However, Huang et al. (1999) reported
that resistance in the ECB to a commercial formulation of Bacillus
thuringiensis (Bt) Berliner toxin, Dipel ES, appears to be inherited as an
incompletely dominant autosomal gene. These results have not yet been
replicated in the field or elsewhere.
The effects of ECB resistance to Bt-corn could be minor if hybrids that
express alternative cry proteins are effective and if they are introduced
rapidly into problem areas. It may however be possible for ECBs to develop
cross-resistance to two or more of the cry proteins (Alstad, 1997). This
would result in the loss of Bt-corn and Bt insecticides as management tools.
A key element of preserving the long-term effectiveness of the Bt technology
rests on delaying the development of ECB resistance through the use of
resistance management plans. This is a voluntary, long-term, proactive
approach by growers. Successful management maintains resistance alleles at
low frequencies, so resistant pests stay below economic injury levels and
product utility is maintained (Andow and Hutchison, 1998). Resistance
management in Bt-corn is currently based on two complementary principles:
high dose and refugia, though the efficacy of the strategy has not been
verified for Bt-corn in the field (Andow and Hutchison, 1998). High dose
refers to the fact that Bt-corn is created to produce levels of Bt toxin in
the crop that is 25 times the toxic concentration needed to kill susceptible
larvae. The intent is to kill all ECB larvae with no genes for resistance,
plus those with one copy of a resistance gene (Alstad, 1997). The
assumption inherent in this resistance management approach is that Bt
hybrids have achieved this high-dose objective. If a lower dose is provided,
then corn borer larvae with one copy of a resistance gene may survive to
adulthood and mate with other resistant moths, resulting in resistant
Not all Bt events are the same in satisfying this high dose recommendation.
When hybrids of the major Bt events were exposed to resistant borers by
Stewart et al. (1999), the damage to corn plants in events 176 and DBt 418
was significantly greater than in the other events. These borers were from a
population that became 70 times more resistant than wild borers after being
exposed to Dipel, a Bt spray, for 18 generations. The conclusions reached
were: the risk of developing resistance to Bt is high; and a high dose is
clearly necessary to avoid survival of partially resistant borers. The
second principle of the resistance management plan is the use of refuges.
Refugia refers to planting a portion of each field with non-Bt hybrids to
allow for interbreeding between corn borers which may have developed
resistance (from Bt-corn) and insects that are still susceptible to Bt
(Alstad, 1997; Lastovic, 1999). A refuge is any non-Bt host of ECB,
including non-Bt-corn, potatoes, sorghum or cotton that occur near Bt-corn
(Alstad et al., 1997; Andow and Hutchison, 1998). However, recent studies by
Stewart, Sears and Schaafsma (1999) have shown that non-Bt-corn is the only
crop plant that provides sufficient Bt refuge. This includes entire fields
of non-Bt-corn planted adjacent to Bt-corn, a block of non-Bt-corn planted
within a field of Bt-corn, or a designated percentage of rows of non-Bt-corn
throughout the field (Anon, 1998; Stewart et al., 1999). The goal is to
produce an overwhelming number of susceptible moths to every resistant moth,
thereby diluting the number of resistant individuals in the population. Two
questions of significance regarding refuges are: How large a refuge is
needed to provide enough susceptible moths and how close should it be to the
To be effective, ECB moths must emerge from the refuge at the same time as
resistant moths and be close enough to mate with resistant moths. Although
some ECB moths can fly substantial distances, many moths fly less than a
mile from their emergence site (Alstad, 1997). Stewart et al. (1999) found
that in the case of 2nd generation corn borer, the adult females stay within
1,500 feet from where they emerged. This implies that all Bt-corn needs be
within one quarter-mile of a non-Bt refuge for the refuge to be effective.
The actual amount of refuge required is unknown, but will vary among
regions, farms, and corn production systems. A managed refuge of 5 to 40 per
cent may be necessary, depending upon geographical location and the presence
or absence of other refuges (Anon, 1998). In continuous corn areas, the
primary available refuge is non-Bt-corn, so 20-30 per cent of the corn
acreage should be non-Bt-corn (Alstad et al., 1997). In continuous corn
areas where ECBs are typically sprayed with insecticides, the refuge should
be increased to 40 per cent to compensate for larval mortality (Alstad,
1997; Andow and Hutchison, 1998).
The challenge is to combine the properly sized refuge with the proper dose
of Bt because in theory, high doses of the Bt toxin in Bt-corn kill
virtually 100 per cent of the corn borers. However, if any borers survive,
it is highly desirable to increase the odds that surviving moths (possibly
resistant individuals) mate with moths emerging from refuges (susceptible
moths) (Anon, 1998).
The University of Minnesota (Alstad et al, 1997) recommended the following
key steps to implementing a resistance management plan for ECBs:
1. Producers should consider using Bt-corn hybrids only in fields where the
economic risk from ECB justifies the price premium for Bt-corn. High risk
factors for ECB include: early planted fields; significantly delayed
planting; late-pollinating, full-season hybrids; light, sandy soils;
irrigated fields; weedy fields and grassy borders; hybrids with low native
resistance to corn borer and high-yield environments (Dekalb, 1998). 2.
Carefully record and mark where Bt and non-Bt-corn hybrids are planted, so
Bt-corn performance can be monitored and non-Bt-corn can be scouted, and if
needed, treated with a non-Bt insecticide.
3. Plant non-Bt-corn refuge(s) to protect 20-30 per cent of the ECB larval
populations from exposure to Bt cry proteins.
4. Continue to use an IPM approach for all pests, as Bt-corn is just one
tool for ECB management.
5. Monitor Bt-corn to verify ECB control for both first and second
generations. Do not wait until harvest. Monitoring offers a means of
tracking resistance evolution so that local resistance management can be
adapted to prevent, delay or detect resistance as it arises (Andow and
Hutchison, 1998). If corn borer resistance to Bt occurs, alternate
management tactics will be suggested and all growers in the area surrounding
the initial detection will be notified (Anon, 1998). A concern is that,
irrespective of the management strategy, will such recommendations be
adopted and followed by growers and seed dealers? Lastovic (1999) found
that only 40 per cent of producers think that it is somewhat possible for
ECB to develop resistance to the Bt toxin. Since a large proportion of
producers are not fully convinced the ECB will develop resistance,
persuading Bt-corn growers in Ontario to implement management strategies may
be difficult. Also, growers are primarily economically motivated, and there
is little immediate economic benefit to implementing these strategies. In
some cases, growers may feel that by planting a refuge they are limiting the
profitability of using the technology (Lastovic, 1999). Nevertheless,
surveys to assess producer adoption of Bt-refugia guidelines were conducted
in Ontario in April 1998, with a follow-up survey in June 1999 (Lastovic and
Powell, 1998; Powell, et al., 1999). Both showed extremely high levels of
grower adoption of refugia planting strategies. In Ontario two scientists
at the University of Guelph, Ontario initiated the Bt-corn Coalition with a
mandate to foster the responsible deployment of the Bt technology in
Ontario. The Coalition is a group that represents the private and public
sector and consists of growers, provincial extension personnel and publicly
funded researchers from the Canadian Food Inspection Agency and the
University of Guelph, and seed industry representatives. In November 1998
the Coalition adopted recommendations made by the NC-205 Committee. NC-205
is a United States Department of Agriculture (USDA) North Central Regional
Research Committee that has conducted research on stalk-boring pests of corn
continuously since 1954. The initial recommendations of NC-205 regarding the
management of resistance were published in North Central Regional
Publication 602 during 1997. An electronic version is located at:
recommendations made by this group pertaining to resistance management can
be found at: http://ent.agri.umn.edu/ecb/nc205doc.htm. The Bt-corn
Coalition also unanimously agreed that a single, clear and concise message
concerning stewardship of Bt technology was essential for all groups and
individuals concerned and for public awareness and acceptance (Sears and
The following recommendations were adopted by the Bt-corn Coalition:
All growers should plant a minimum of 20per cent non-Bt-corn not sprayed
with insecticides on their planted acreage each year;
Non-Bt-corn should be planted within 1/4 mile of the farthest Bt-corn in a
field to provide a refuge where Bt-susceptible moths may exist;
Non-Bt-corn hybrids for use as refuges in a field should be selected for
growth, maturity and yield traits similar to the Bt hybrid used in the
remainder of the field;
Refuge areas may be planted in blocks on the edges or headlands of fields
or in strips across the entire field with a minimum of 6 rows should be
planted with non-Bt-corn alternating with Bt hybrid across the entire field;
The Bt-corn Coalition recommends that individual corn producers using Bt
technology be responsible to ensure that the minimum 20 per cent refuge
occurs on their farm.
In the U.S. in April 1999, the industry insect resistance management (IRM)
plan for Bt-corn was submitted to the U.S. Environmental Protection Agency
for regulatory approval by Monsanto Company, Mycogen Seeds/Dow AgroSciences,
Novartis Seeds, Inc., and Pioneer Hi-Bred International, Inc. in conjunction
with the National Corn Growers Association. If approved, registrants said it
could be implemented in the U.S. for the 2000-growing season. The plan is
based on an approach recommended by an EPA scientific advisory panel last
year (NCGA, 1999a).
The plan stated, "Critical to the success of this IRM plan is grower
acceptance and implementation of key crop production and pest management
practices designed to preserve pest susceptibility to Bt proteins. The
Bt-corn Industry IRM Plan therefore seeks to balance the need to protect Bt
technology with the need to establish a practical approach that growers will
implement. To promote grower acceptance, the IRM plan should be
cost-effective, flexible, easily adopted, and compatible with common
production practices" (NCGA, 1999b).
Under the plan, refuge requirements will be imposed for all corn growing
regions of the United States. Growers will have to plant a minimum of 20 per
cent non-Bt-corn in the corn belt states and the northern portion of the
corn/cotton region. A minimum 50 per cent refuge of non-Bt-corn will be
required in the southern portion of the corn/cotton-growing region (NCGA,
1999a, NCGA, 1999b). In primary corn country, the 20 per cent refuge
requirement increases to 40 per cent (60 per cent Bt hybrids) if growers
plan to spray insecticides to control corn borers in the refuge area
(Horstmeier, 1999). In addition, the plan encourages growers to plant
non-Bt-corn within one-quarter mile of Bt-corn, where feasible, but requires
refuges within one-half mile (NCGA, 1999a, NCGA, 1999b). Previously, the
amount of refuge varied according to the brand of seed and where corn was
planted (Horstmeier, 1999).
Growers will also receive a comprehensive guide to IRM measures with the
purchase of Bt hybrids and must sign a stewardship agreement stipulating
they will follow IRM requirements. Annual surveys will be conducted to
determine grower adoption and grower education will be targeted (NCGA,
1999a, NCGA, 1999b).
A complete copy of the Industry Insect Resistance Management Plan for Bt
Field Corn can be obtained by linking to
http://www.ncga.com/02profits/insectMgmtPlan/toc.htm Other management
strategies have also been proposed. Among these schemes are: rotation of
plantings between transgenic and non-transgenic crops (in the years when
non-transgenic crops are planted, use of other insecticides would be
required); mixing seeds so that each field contains a variety of crops, each
carrying different toxin genes; engineering two or more toxin genes into a
single plant (the latter two assume other toxin genes have been identified
and are effective); modifying the transgene such that the toxin is only
produced in certain plant parts, or at certain times during plant
development; using low-dose toxins, similar to the classical approaches in
plant breeding using partial resistance in crops (Control of the pest is
achieved usually imposed by other control agents)(Andow and Hutchison,
Research related to the underpinnings of the Bt-refugia strategy appeared in
the spring of 1999. Losey et al. (1999), reported in Nature that Bt-corn
could have a damaging effect on the Monarch butterfly population through the
drift of Bt-containing pollen. However, both the author of the study and
farmers agreed the genetically-modified corn was effective in controlling
damage from the ECB and reducing pesticide spraying. The study concluded
that up to 44 per cent of young larvae died in laboratory tests with
milkweed leaves covered with the pollen from Bt-corn. The results of Losey
et al. were discussed at a June 7, 1999 meeting of the Ontario Bt corn borer
coalition, which agreed that the results, while only a simulation, need to
be replicated under field conditions. In July 1999, the Canadian Food
Inspection Agency (CFIA) and Environment Canada awarded $60,000 in funding
over two years to help determine the ecological impact of Bt-corn pollen on
populations of selected non-target butterfly species, including the Monarch
butterfly, in Ontario and Quebec (Anon, 1999b). This research will be led by
Dr. Mark Sears of the University of Guelph, and chair of the Ontario Bt-Corn
Coalition. It will also assess whether differences exist among different
sources of Bt-corn, and recommend strategies for reducing any potential
risks to butterfly populations while retaining benefits to farmers and
consumers (Anon, 1999b).
Impact on Non-target organisms such as the Monarch Butterfly Laboratory
studies done in 1999 by Losey et al. showed that milkweed leaves dusted with
heavy concentrations of Bt corn pollen are toxic to Monarch butterfly larvae
(Danaus plexippus) feeding on them. Much speculation followed the initial
report, despite the warning offered by Losey et al. that "it would be
inappropriate to draw any conclusions about the risk to Monarch populations
in the field based solely on these initial results". In the laboratory,
Monarch larvae were given no feeding choice other than milkweed leaves
coated with Bt pollen. Additionally, leaves in the field are exposed to
wind and rain may have a lower concentration of corn pollen than those
provided in the lab.
In a recent issue of PNAS, Wraight et al. reported their experiments with
populations of a butterfly related to Monarchs, the black swallowtail
(Papilio polyxenes). These tests were performed in the field. The authors
found no effects of Bt corn pollen on the mortality of black swallowtail
larvae. It has not been demonstrated, however, that Monarch butterflies and
black swallowtails are equally susceptible to Bt endotoxins.
Field studies of the effects of Bt corn pollen on both black swallowtails
and Monarch butterflies are underway in the summer of 2000. Looking at the
overall picture, survival of butterfly populations is likely to be strongly
influenced by factors other than Bt, such as loss of habitat in Mexico and
the US, as well as traditional pesticide applications.
Extensive safety trials as of 1998 in the laboratory, greenhouse, and field,
found that Bt-corn has had no direct effects on lady beetles, green lacewing
larvae, spiders, minute pirate bugs, and parasitic wasps (Alstad, 1997;
Anon, 1998; Novartis, 1998). The same conclusion was reached by the
American, Canadian, European and Japanese authorities (Novartis, 1998). Any
indirect effects on populations of beneficial insects caused by the removal
of corn borers as a food source for predators and parasitoids remain unknown
Indirect impacts of Bt-corn on natural enemies of ECB may occur. Predators,
parasites and pathogens of the corn borer might decline as corn borer
populations decline (Alstad, 1997). Unfortunately, little data on the
subject exists. In contrast, minor pests may become more predominant, such
as the western bean cutworm (Alstad, 1997). Pest status of this insect could
change, though, when foliar insecticides are reduced and if this insect is
not controlled by current Bt events or natural enemies.
The EPA considered 20 years of human and animal safety data before
registering Bt-corn (Alstad, 1997). Various sources state that Bacillus
thuringiensis is highly selective against certain moth larvae, attacking
only the stomach lining of insects with a specific pH (Haag, 1999).
Therefore, it is safe to the environment and non-target insects and animals,
including other predators found in cornfields, humans, birds, fish, or bees
(Alstad, 1997; Anon, 1998; Dekalb, 1998; Novartis, 1998). It is safe for
consumption because the toxin is digested like any other food protein
Recent studies by Berstein (1999) however have reported that crops treated
with Bt spores may cause increased allergenicity. Testing 48 farm workers
before and after Bt was sprayed on crops (with allergic reaction skin
tests), 8 per cent showed sensitivity before, 50 per cent showed positive
reactions one month after exposure, 70 per cent tested positive after 3
months. The conclusion of the research was that Bt "has the potential to
elicit allergic responses."
Another indication that the primary risk to human health from Bt is from the
application of whole spores as a pesticide spray - the method practised by
organic growers - was published in Nature Biotechnology in August 2000
(Bouchie, 2000). Researchers at the Biotechnology centre in Oslo found
that the bacteria Bacillus thuringiensis, B. cereus, a common cause of food
poisoning and B. anthracis, the cause of anthrax, all belong to the same
species. Researchers warn that use of the whole Bt bacterium as a pesticide
spray may be dangerous due to possible genetic transfer between the related
species. B. anthracis owes its pathogenicity to its ability to collect and
harbour virulent plasmids; it is not yet known if they can be transferred to
Some dairy producers have had additional concerns over farmers producing
grain corn. Don Aanonson, Pioneerıs corn product line manager for crop
protection traits, says that the widespread acceptance of Bt corn by grain
corn growers isnıt shared by their silage-producing counterparts.
"Significantly less than 10 per cent of the 6 to 7 million acres of corn
chopped for silage is Bt-corn." (Haag, 1999). One of their concerns is,
"What are the nutritional implications of growing Bt silage?" (Haag, 1999).
A 1998 Iowa State University study conducted by Marjorie Faust compared the
feeding characteristics of Bt-corn with similar non-Bt varieties (Haag,
1999). Results showed that dry matter, protein solubility, non-fiber
carbohydrates and ash levels were higher and crude protein, lignin and net
energy levels lower for Bt hybrids. However, Faust believes the differences
were not significant enough to impact milk production. She conducted a
feeding trial using 12 Holstein dairy cows. The animals were divided into
three diet groups and fed for 14 days. The control group was given a
non-transgenic hybrid corn, while each of the other two groups were given Bt
hybrids. No difference in quantity or quality was detected in the milk from
any of the three groups. Faust concluded that in spite of slightly lower
nutritional scores for Bt-corn, its feeding performance levels were equal to
Brake and Vlachos (1998) conducted a feeding study evaluating whether the
addition of Bt-corn (Event 176) to broiler chickenıs diets had any adverse
effects on them compared to diets prepared with non-transgenic (isogenic)
control corn grain. No statistically significant differences in survival or
body weight were observed between birds reared on transgenic corn and
similar diets prepared using control corn. Broilers raised on diets prepared
from the transgenic corn actually exhibited significantly better feed
conversion ratios and improved yield of the Pectoralis minor breast muscle.
Based on studies in Canada and the U.S., genetically-engineered Bt-corn has
the potential to significantly increase field corn yield, as well as reduce
the environmental impacts of corn production. Continual management and
vigilance on the part of producers, regulators, scientists and industry
should ensure the future viability of this production management tool.
Alstad, D.N., J.F. Witkowski, J.L. Wedberg, K.L. Steffey, P.E. Sloderbeck,
B.D. Siegfried, M.E.
Rice, C.D. Pilcher, D.W. Onstad, C.E. Mason, L.C. Lewis, D.A. Landis, A.J.
Keaster, F. Huang, R.A. Higgins, M.J. Haas, M.E. Gray, K.L. Giles, J.E.
Foster, P.M. Davis, D.D. Calvin, L.L. Buschman, P.C. Bolin, B.D. Barry,and
D.A. Andow & D.N. Alstad. [Editors: K.R.
Ostlie, W.D. Hutchison, & R. L. Hellmich]. 1997. Bt-corn & European Corn
Borer- Long-Term Success Through Resistance Management. University of
Andow, D.A. and W.D. Hutchison. 1998. Now Or Never: Serious New Plans to
Save a Natural Pest Control: Chapter 3-Bt-Corn Resistance Management.Union
of Concerned Scientists.
Anonymous. December 15, 1998. Bt-Corn for Control of European Corn Borer.
Insect Pest Management for Field and Forage Crops.
Anonymous. July 1999a. Butterfly Brouhaha. ISB News Report.
Anonymous. July 13 1999b. Farmers Applaud New Research On Butterflies And
Biotech Corn. AgCare press release
Benbrook, C. M., Groth, E., Hoaaloran, J. M., Hansen, M. K. & Marquardt, S.
(1996) Pest Management at the Crossroads (Consumers Union, Yonkers, NY).
**Berstein, Leonard I. July 1999. Environmental Health Perspectives. Need
rest of ref.
Biotechnology Industry Organization (BIO). July, 1999b. Agricultural
Biotechnology: Insect Control Benefits.
Bouchie, A. August 2000. Bacillus Identity Crisis. Nature Biotechnology.
Brake, J. and D. Vlachos. May 1998. Evaluation of transgenic event 176 "Bt"
corn in broiler chickens. Poultry science. 77 (5): 648-653.
Button, Tom. December 7, 1998. The Bt difference. Farm and Country
Dekalb. December 15, 1998. Corn Borers and Bt-corn.
Greg D. Horstmeier, Greg D. March 1999. Restricted Zone -New Rules May Let
Southern Farmers Shift To More Bt-corn. Farm Journal.
Haag, Ed. March 1999. Is Bt-corn right for silage? Farm Journal - Dairy
Hovey, Art. April 22, 1999. Corn borers, beware. Lincoln Journal Star
Huang, F., Buschman, L.L., Higgins, R.A., and W.H McGaughey. May 7, 1999.
Inheritance of Resistance to Bacillus thuringiensis Toxin (Dipel ES) in the
European Corn Borer. The American Association for the Advancement of
Science. 284 (5416): 965 - 967.
Lastovic, S. 1999. Bt-corn And Resistance Management. Ontario Corn Producers
Association (OCPA) Magazine. March.
Lastovic, S. and Powell, D.A. 1998. Producer perceptions of, and barriers
to, implementation of resistance management strategies for
genetically-engineered Bt-containing corn in ntario.
Losey, J. E., Rayor, L. S. & Carter, M. E. 1999 Nature 399, 214[Medline].
Munkvold, G.P., Hellmich, R.L., and Rice, L.G. 1999. Comparison of fumonisin
concentrations in kernels of transgenic Bt maize hybrids and nontransgenic
hybrids. Plant Disease. 83:130-138.
National Corn Growers Association. April 19, 1999a. Companies, Corn Growers
Finalize IRM Measures For Bt-corn. (Press Release).
National Corn Growers Association. April 21, 1999b. Industry Insect
Management Program. http://www.Ncga.Com/02profits/Insectmgmtplan/Toc.Htm
Novartis. December 7, 1998. Bt-corn- About the benefits of Bt-corn.
Pimentel, D., Acquay, H., Biltonen, M., Rice, P., Silva, M., Nelson, J.,
Lipner, V., Giordano, S., Horowitz, A. & D1Amore, M. 1993. in The Pesticide
Question: Environment, Economics and Ethics, eds. Pimentel, D. & Lehman, H.
(Chapman & Hall, New York), pp. 47-84.
Pimentel, D., and Raven, P., 2000. BT Corn Pollen Impacts on Nontarget
Lepdidoptera: Assessment of Effects in Nature. Proc. Natl. Acad. Sci. USA,
Vol. 97, Issue 15, 8198-8199.
Soanes, Cathy. 1998. Ontario and Quebec Combined Summary (Novartis Seeds).
Borer News: Issue 4
Stewart, G., Schaafsma, A. and Sears, M. 1999. Practical considerations for
Bt refuge management. Ontario Corn Producers Association (OCPA) Magazine.
U.S. Department of Agriculture (Economic Research Service). June 25, 1999.
Genetically Engineered Crops for Pest Management.
Wraight, C. L., Zangerl, A. R., Carroll, M. J. & Berenbaum, M. R.
2000.Proc. Natl. Acad. Sci. USA 97, 7700-7703.
For more information about the Agnet research program, please contact:
Dr. Douglas Powell
dept. of plant agriculture
University of Guelph
tel: 519-824-4120 x2506