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Bt cottonCotton and other monocultured crops require an intensive use of pesticides

as various types of pests attack these crops causing extensive damage. Overthe past 40 years, many pests have developed resistance to pesticides.

So far, the only successful approach to engineering crops for insecttolerance has been the addition of Bt toxin, a family of toxins originallyderived from soil bacteria. The Bt toxin contained by the Bt crops is nodifferent from other chemical pesticides, but causes much less damage tothe environment. These toxins are effective against a variety ofeconomically important crop pests but pose no hazard to non-targetorganisms like mammals and fish. Three Bt crops are now commerciallyavailable: corn, cotton, and potato.

As of now, cotton is the most popular of the Btcrops: it was planted on about 1.8 million acres(728437 ha) in 1996 and 1997. The Bt gene wasisolated and transferred from a bacterium bacillusthurigiensis to American cotton. The Americancotton was subsequently crossed with Indian cottonto introduce the gene into native varieties.

The Bt cotton variety contains a foreign gene obtained from bacillusthuringiensis. This bacterial gene, introduced genetically into the cottonseeds, protects the plants from bollworm (A. lepidoptora), a major pest ofcotton. The worm feeding on the leaves of a BT cotton plant becomeslethargic and sleepy, thereby causing less damage to the plant.

Field trials have shown that farmers who grew the Bt variety obtained 25%–75% more cotton than those who grew the normal variety. Also, Bt cotton

requires only two sprays of chemical pesticide against eight sprays fornormal variety. According to the director general of the Indian Council ofAgricultural Research, India uses about half of its pesticides on cotton tofight the bollworm menace.

Use of Bt cotton has led to a 3%–27 increase in cotton yield in countrieswhere it is grown.

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Bacillus thuringiensis

Bacillus thuringiensis isa Gram-positive, soil-

dwelling bacterium ofthe genus Bacillus .Additionally, B.

thuringiensis also occursnaturally in the gut ofcaterpillars of varioustypes of moths andbutterflies, as well as onthe dark surface ofplants.[1]

B. thuringiensis was discovered 1901 in Japan by Ishiwata and 1911 inGermany by Ernst Berliner, who discovered a disease called Schlaffsucht inflour moth caterpillars. B. thuringiensis is closely related to B. cereus , a soilbacterium, and B. anthracis , the cause of anthrax: the three organismsdiffer mainly in their plasmids. Like other members of the genus, all threeare aerobes capable of producing endospores.

Upon sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal δ-endotoxins (Cry toxins) which are encoded by cry genes. Crytoxins have specific activities against species of the orders Lepidoptera (Moths and Butterflies), Diptera (Flies and Mosquitoes) and Coleoptera (Beetles). Thus, B. thuringiensis serves as an important reservoir of Crytoxins and cry genes for production of biological insecticides and insect-resistant genetically modified crops. When insects ingest toxin crystals thealkaline pH of their digestive tract causes the toxin to become activated. It

becomes inserted into the insect's gut cell membranes forming a poreresulting in swelling, cell lysis and eventually killing the insect.

Use in pest control

Bacillus thuringiensis 

Spores and bipyramidal crystals of Bacillus thuringiensis morrisoni strain T08025

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Spores and crystalline insecticidal proteins produced by B. thuringiensis areused as specific insecticides under trade names such as Dipel and Thuricide.Because of their specificity, these pesticides are regarded asenvironmentally friendly, with little or no effect on humans, wildlife,

pollinators, and most other beneficial insects. The Belgian company PlantGenetic Systems was the first company (in 1985) to develop geneticallyengineered (tobacco) plants with insect tolerance by expressing cry genesfrom B. thuringiensis .

B. thurigiensis -based insecticides are often applied as liquid sprays on cropplants, where the insecticide must be ingested to be effective. It is thoughtthat the solubilized toxins form pores in the midgut epithelium ofsusceptible larvae. Recent research has suggested that the midgut bacteriaof susceptible larvae are required for B. thuringiensis insecticidal activity.

Bacillus thuringiensis serovar israelensis , a strain of B. thuringiensis iswidely used as a larvicide against mosquito larvae, where it is also consideredan environmentally friendly method of mosquito control. Genetic engineeringfor pest control

Bt-toxins present in peanut leaves (bottom image) protect it from extensivedamage caused by European corn borer larvae (top image).

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Usage

Bt crops (in corn and cotton) were planted on 281,500 km² in 2006 (165,600

km² of Bt corn and 115900 km² of Bt cotton). This was equivalent to 11.1%and 33.6% respectively of global plantings of corn and cotton in 2006.Claimsof major benefits to farmers, including poor farmers in developing countries,have been made by advocates of the technology, and have been challenged byopponents. The task of isolating impacts of the technology is complicated bythe prevalence of biased observers, and by the rarity of controlledcomparisons (such as identical seeds, differing only in the presence orabsence of the Bt trait, being grown in identical situations). The main Btcrop being grown by small farmers in developing countries is cotton, and arecent exhaustive review of findings on Bt cotton by respected and unbiasedagricultural economists concluded that "the overall balance sheet, thoughpromising, is mixed. Economic returns are highly variable over years, farmtype, and geographical location"

Environmental impacts appear to be positive during the first ten years of Btcrop use (1996-2005). One study concluded that insecticide use on cottonand corn during this period fell by 35.6 million kg of insecticide activeingredient which is roughly equal to the amount of pesticide applied to arablecrops in the EU in one year. Using the Environmental Impact Quotient (EIQ)

measure of the impact of pesticide use on the environment,the adoption ofBt technology over this ten year period resulted in 24.3% and 4.6%reduction respectively in the environmental impact associated withinsecticide use on the cotton and corn area using the technology.

Advantages

There are several advantages in expressing Bt toxins in transgenic Bt crops:

• The level of toxin expression can be very high thus deliveringsufficient dosage to the pest.

• The toxin expression is contained within the plant system and henceonly those insects that feed on the crop perish.

• The toxin expression can be modulated by using tissue-specificpromoters, and replaces the use of synthetic pesticides in the

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environment. The latter observation has been well documented world-wide.

SafetyOverall, Bt-modified crops appear to be safe for farmers and consumers.Additionally, the proteins produced by Bt have also been used in sprays infarming techniques for many years with seemingly no ill effects onenvironment or human health. Thus, Bt toxins are considered environmentallyfriendly by many farmers and may be a potential alternative to broadspectrum insecticides. The toxicity of each Bt type is limited to one or twoinsect orders, and is nontoxic to vertebrates and many beneficialarthropods. The reason is that Bt works by binding to the appropriate

receptor on the surface of midgut epithelial cells. Any organism that lacksthe appropriate receptors in its gut cannot be affected by Bt.

Not all scientific reports on Bt safety have been positive. A 2007 studyfunded by the European arm of Greenpeace, suggested the possibility of aslight but statistically meaningful risk of liver damage in rats. While smallstatistically significant changes may have been observed, statisticaldifferences are both probable and predictable in animal studies of this kind,and are known as Type I errors- that is, the probability of finding a false-

positive due to chance alone. In this case, the number of positive results waswithin the statistically predicted range for Type I errors. The observedchanges have been found to be of no biological significance by the EuropeanFood Safety Authority. A 2008 Austrian study investigating the usefulnessof a long-term reproduction mouse model for GM crop safety reported thatBt-treated corn consumption in mice appeared to be correlated with reducedfertility via an unknown biochemical mechanism.

Limitations to Bt crops

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Kenyans examining insect-resistant transgenic Bt corn.

Constant exposure to a toxin creates evolutionary pressure for pestsresistant to that toxin. Already, a Diamondback moth population is known tohave acquired resistance to Bt in spray form (i.e., not engineered) when used

in organic agriculture. The same researcher has now reported the firstdocumented case of pest resistance to biotech cotton.

One method of reducing resistance is the creation of non-Bt crop refuges toallow some non-resistant insects to survive and maintain a susceptiblepopulation. To reduce the chance that an insect would become resistant to aBt crop, the commercialization of transgenic cotton and maize in 1996 wasaccompanied with a management strategy to prevent insects from becomingresistant to Bt crops, and insect resistance management plans are mandatoryfor Bt crops planted in the USA and other countries. The aim is toencourage a large population of pests so that any genes for resistance aregreatly diluted. This technique is based on the assumption that resistancegenes will be recessive. This means that with sufficiently high levels oftransgene expression, nearly all of the heterozygotes (S/s), the largestsegment of the pest population carrying a resistance allele, will be killedbefore they reach maturity, thus preventing transmission of the resistancegene to their progenies. The planting of refuges (i. e., fields of non-transgenic plants) adjacent to fields of transgenic plants increases thelikelihood that homozygous resistant (s/s) individuals and any survivingheterozygotes will mate with susceptible (S/S) individuals from the refuge,instead of with other individuals carrying the resistance allele. As a result,the resistance gene frequency in the population would remain low.

Nevertheless, there are limitations that can affect the success of the high-dose/refuge strategy. For example, expression of the Bt gene can vary. For

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instance, if the temperature is not ideal this stress can lower the toxinproduction and make the plant more susceptible. More importantly, reducedlate-season expression of toxin has been documented, possibly resultingfrom DNA methylation of the promoter. So, while the high-dose/refuge

strategy has been successful at prolonging the durability of Bt crops, thissuccess has also had much to do with key factors independent ofmanagement strategy, including low initial resistance allele frequencies,fitness costs associated with resistance, and the abundance of non-Bt hostplants that have supplemented the refuges planted as part of the resistancemanagement strategy.

 Possible problems

The most celebrated problem ever associated with Bt crops was the claimthat pollen from Bt maize could kill the monarch butterfly. This report waspuzzling because the pollen from most maize hybrids contains much lowerlevels of Bt than the rest of the plant and led to multiple follow-up studies.In the end, it appears that the initial study was flawed; based on the waythe pollen was collected, they collected and fed non-toxic pollen that wasmixed with anther walls that did contain Bt toxin. The weight of theevidence is that Bt crops do not pose a risk to the monarch butterfly.

There was also a report in Nature , that Bt maize was contaminating maize inits center of origin. Nature later "concluded that the evidence available isnot sufficient to justify the publication of the original ." A subsequent large-scale study failed to find any evidence of contamination in Oaxaca.

There is also a hypothetical risk that for example, transgenic maize willcrossbreed with wild grass variants, and that the Bt-gene will end up in anatural environment, retaining its toxicity. An event like this would haveecological implications, as well as increasing the risk of Bt resistance arising

in the general herbivore population. However, there is no evidence ofcrossbreeding between maize and wild grasses.

As of 2007, a new phenomenon called Colony Collapse Disorder (CCD) isaffecting bee hives all over North America. Initial speculation causes rangedfrom cell phone and pesticide use to the use of Bt resistant transgeniccrops. The Mid-Atlantic Apiculture Research and Extension Consortium 

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published a report on 2007-03-27 that found no evidence that pollen fromBt crops is adversely affecting bees. CCD has since been attributed to a newvirus, unrelated to Bt crops.on possible

Bt cotton acreage rises 20%Bollgard Bt cotton is India’s first biotech crop technology approved forcommercialisation in India in 2002.

Indian farmers seem to have taken to Bacillus thurengiensis (Bt) cottonseeds in a big way. According to technology supplier Mahyco MonsantoBiotech (MMB), India, the farmers have brought 20 per cent more areaunder cotton cultivation in 2008. This is likely to shoot up cotton production

in the country, which is already the second largest producer of cotton in theworld.

As per an estimate by the MMB, India, approximately 4 million farmerscultivated Bollgard II and Bollgard Bt cotton on 172 lakh acres equivalent to76 per cent of India’s total 225 lakh cotton acres in Kharif 2008.

The acreage has steadily increased from 87 lakh acres in 2006 to 144 lakhacres in 2007. The farmers have a choice from over 150 Bollgard II and

Bollgard Bt cotton hybrid seeds.

Bollgard II acreage area increased to 45 lakh acres during the ongoing cropseason as compared to 12.2 lakh acres during the last season. Similarly,Bollgard continued to be widely adopted on 127 lakh acres.

Bollgard II has a superior double-gene technology that offers farmersbetter Insect Resistance Management (IRM), along with higher yield, morepesticide savings, and thereby higher income.“Within six years of the launchof Bollgard Bt Cotton in 2002, India’s cotton production has doubled, making

it the second largest producer, and second largest exporter of cotton in theworld,” said Raj Ketkar, Deputy Managing Director, MMB.

  B(L)OOMING

States Total Total Bt cotton areas

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areasBollgard -

IIBollgard

Maharashtra 75.1 21.6 50.5

Andhra Pradesh 37.2 8.4 25.5

Gujarat 56.9 5.3 20.6

MadhyaPradesh

16.9 3.4 11.6

Punjab 10.6 1.9 7.3

Haryana 10.3 1.5 6.4

Karnataka 9.0 1.4 3.4

Tamil Nadu 2.0 1.2 0.8

Rajasthan 7.7 0.4 1.1

Total 225.7 45.1 127.2Figures in lakh acres 

The highest growth for Bollgard II was witnessed in Maharashtra with 21.6lakh acres (up 70 per cent as against 6.3 lakh acres in 2007), AndhraPradesh with 8.4 lakh acres (up 88 per cent as compared to 1.01 lakh acres in2007), and Gujarat with 5.3 lakh acres (up 42 per cent versus 3.1 lakh acresin 2007).

Dr B B Bhosle, professor and head, Department of Entomology, MaharashtraAgriculture University, Parbhani, Maharashtra said, “Bollgard II - double

gene cotton technology has two Bt proteins, Cry1Ac and Cry2Ab2 which arebetter for insect resistance management (IRM). With both the Bt proteinshaving different modes of action, the chance of resistance to both proteinsin Bollgard II is highly unlikely, and this makes Bollgard II an effective toolin insect resistance management. The US EPA has removed the need for 20per cent refuge for Bollgard II and if we do in India, we can increase ourcotton productivity even more.”

Bollgard Bt cotton (single-gene technology) is India’s first biotech croptechnology approved for commercialisation in India in 2002, followed byBollgard II - double gene technology in mid-2006, by the GeneticEngineering Approval Committee (GEAC) - the regulatory body for biotechcrops.These technologies were launched in India by MMB, a 50:50 jointventure between Mahyco and Monsanto Company, USA. MMB has sub-licensed the Bollgard and Bollgard II technologies to 23 Indian seed

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companies, all of which have introduced the Bollgard technology into theirown germplasm.

Indian Bt cotton to help boost

productionNovember 26, 2008 (Philippines)

In order to upgrade the domestic cotton production, the Government ofPhilippines plans to import and test hybrid cotton from India in January2009.

While talking to reporters at the 4th National Biotechnology Week inDiliman, Quezon City, Ms Alicia G Ilaga, Director of the AgricultureDepartment’s Biotechnology Program Office said, “The Bureau of PlantIndustry has already issued a permit to allow the entry of the Bt cottonseeds within a month or two, the materials will start coming in”.

Further she said, "We will test the Indian Bt cotton, licensed by China, forthe efficacy, and if it matches with the climate for six months to one year.If the tests prove successful, the Government will encourage local companiesto commercialize the variety by forming a joint venture with the stateChinese Academy of Sciences.”

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"It would be a good strategy if we buy existing technology instead of takingtoo much time developing our own. The Government paid Peso1.5 million forinitial access to the hybrid cotton technology," stated Ms Ilaga.

Presently, Bt cotton seeds will be planted in Luzon and Mindanao, two biggestislands in Phillipines.

The available data from USDA shows that Philippines imports near about 89percent of its total consumption. In 2007, the country imported around18,506.568 metric tons of cotton lint worth Peso2.4 million.

Studies show that the Bt cotton can produce 20 percent more than normalcotton, and is pest-resistant. Boll warm, pest can destroy 25 to 90 percent

 yield. Thus experts are of the opinion, once this experimentation with BtCotton is proved to be successful, the commercial propagation of the cropcould be undertaken by 2010.

A brief statement on the studies of

the ecological impact of Bt cotton

conducted by Dr. Kongming Wu's lab,

Institute of Plant Protection,CAAS

Dr. Kongming Wu is an entomologist who has been engaged in the study ofcotton insect pests since 1985 and the ecological impact of Bt cotton since1996. He is a professor and director of the Department of AgriculturalEntomology, Institute of Plant Protection, Chinese Academy of AgriculturalSciences (CAAS), Beijing, China; a member of the National GMO BiosafetyCommittee; and Chief Scientist of the National High-Tech Program on theecological safety of Bt cotton in China. His laboratory is one of fourmentioned by the Greenpeace-published Report on the environmental impact

of Bt cotton in China.

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Global Impact of Insect-Resistant

(Bt) Cotton

Insect-resistant (Bt) cotton has been rapidly adopted since its introductionin 1996. Farmers around the world.both large and smallholders.benefit fromthis technology through increased productivity, convenience, and timesavings. The vast majority of farmers using Bt cotton globally aresmallholder farmers. Theeconomic, environmental, and social benefits derived from adoption of thisimportant tool have very positive implications for the farmers, theirsurrounding communities, and the future of agriculture.

IntroductionInsect-resistant cotton was first introduced commercially in 1996. It iscommonly referred to as Bt cotton,because it produces an insecticidalprotein from the naturally occurring soil bacterium Bacillus 

thuringiensis (Bt). Global adoption of Bt cotton has risen dramatically from800,000 hectares in its year of introduction in 1996 to 5.7 million hectares(alone and stacked with herbicide-tolerant cotton) in 2003. Significanteconomic and production advantages have resulted from growing Bt cotton

globally. Bt cotton can substantially reduce the number of pesticidesprayings, which reduces worker and environmental exposure to chemicalinsecticides and reduces energy use. The quality of life for farmers andtheir families can be improved by the increased income and time savingsoffered by Bt cotton. These economic, environmental, and social benefits arebeingrealized by large and smallholder farmers alike in eight countries around theworld.

Development of Bt CottonBt cotton produces an insecticidal protein (Cry1Ac ) from the naturallyoccurring soil bacterium Bacillus thuringiensis (Bt) that protects the cottonplant from certain lepidopteran (caterpillar) insect pests (Perlak et al.,2001).Coker 312 cotton was transformed to express the Cry1Ac gene from Bt,resulting in cotton plants that were resistant to attack from major

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lepidopteran pests(Perlak et al., 1990). Many years of development followedto deliver the trait in germplasm varieties that meet the strict agronomicrequirements of growers worldwide (Perlak et al., 2001). In the UnitedStates, Monsanto.s Bt cotton is known as Bollgard® cotton. Extensive

testing of Bt plants has demonstrated theirsafety and advantages (Betz, Hammond, & Fuchs,2000). The food, feed, andenvironmental safety of Bollgard® cotton was evaluated by regulatoryagencies prior to commercialization. Regulatory approval has been granted incountries where Bt cotton is grown as well as in countries that import Btcottonseed products. Studies were conducted on the safety of the producedproteins,food/feed composition, and environmental safety. On the basis of thisevaluation, Bollgard® cotton and its processed fractions were found to be

substantially equivalent to conventionally bred cotton, and the Bt protein wasshown to be safe for human and animal consumption.Bt cotton was found topose comparable orfewer risks to the environment than traditional cotton treated withcommercially approved insecticides. Safety data on Bollgard® has beenprovided to additionalregulatory authorities globally, and regulatory review continues in thesecountries.

Economic and Production BenefitsSignificant economic advantages have resulted from growing Bt cottonaround the world (Figure 1). Bt cotton provided US farmers with an averagenet incomeincrease of $20/acre and increased the total net value of US cottonproduction by $103 million in 2001 (Gianessi,Silvers, Sankula, & Carpenter,2002). In China, net revenue increases have ranged from $357/hectare to$549/hectare in the three years studied when one compares Bt cotton withnon-Bt cotton (Pray et al., 2002). In South Africa, smallholder farmers in

the Makhathini region raised their yields and reduced their applicationcosts, netting an economic advantage for Bt cotton growers of about$25.51/hectare (Ismael et al., 2002a, 2002b). Yield advantages have beennoted in a number of studies, ranging from 5.10% in China, more than 10% inthe United States, and more than 20% in four other countries (James,2002).

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Figure 1. Potential economic and production benefits of Bt cotton. Adapted from

Purcell et al. (2004).

Environmental BenefitsBt cotton can substantially reduce the number of pesticide sprayings, whichcan provide significant environmental benefits (Figure 2). A number ofstudies havedemonstrated that insecticide sprays are reduced by using Bt cotton

(Carpenter et al., 2002; Edge et al., 2001; James, 2002). Growers in theUnited Statesreduced insecticide use by 1,870,000 pounds of active ingredient (AI) per

 year in 2001 (Gianessi et al., 2002).In China, insecticide applications werereduced by an average of 67% and the kilograms of active ingredient by 80%(Huang, Rozelle, Pray, & Wang, 2002), while South African growers reducedsprays by 66% (Ismael et al., 2002a). The use of Bt cotton in place ofconventional systems can positively impact nontarget organisms(NTOs) andbeneficial organisms by preserving populations (Head et al., 2001; Smith,

1997; Xia, Cui,Ma, Dong, & Cui, 1999) and is compatible with integrated pestmanagement initiatives (Benedict & Altman,2001). In addition, Bt cottonadoption can provide secondarypositive environmental impacts such as (a) saving on raw materials needed tomanufacture chemical insecticides; (b) conserving fuel oil required tomanufacture, distribute, and apply such insecticides; and (c)eliminating theneed to use and dispose of insecticide containers (Leonard & Smith, 2001).

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Figure 2. Potential environmental benefits of Bt cotton. Adapted from Purcell et al.

(2004).

Benefits for Smallholder FarmersBt cotton and other tools which lead to more productive agricultural systems

can benefit smallholder farmers and their broader agricultural communities(Figure 3). At the macroeconomic level, the increased productivity canstabilize production and reduce risks for lenders. At the farm level,improvements in the insect control system being used can positively impactthe quality of life for farmers and their families by increasing incomes,reducing insecticide sprayings, and offering savings in time(Ismael et al.,2002a; Pray et al., 2002). The nutritional demands of families may also bebetter met, as these families now have increased income that couldpotentially be used for more food purchases and food consumption

(James, 2002; Pray, Ma, Huang, & Qiao,2001). Time savings may beparticularly important for women in South Africa, where women serve asheads of many of the households. The time saved by using Bt cotton mayallow these women to care for children, elderly,or the sick or to engage inincome-generating activities(Ismael et al., 2002a). Children were also a beneficiary of this technology, asthose children in South Africa who no longer have to spray insecticides

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could now potentially devote more time to educational or other worthwhilepursuits (Ismael, 2002a). Water savings from using Bt cotton by reducinginsecticide sprays are another source of significant benefits for smallholderfarmers. The use of Bt cotton on a typical 1.7 hectare farm in the

Makhathini Flats region of South Africa would result in a labor reduction of12 days ofspraying, eliminate 100 km of walking, and save 1,000 liters of water whileincreasing income by $85 (James,These cumulative benefits have dramaticsocial relevance for a segment of society that can benefit most.

Figure 3. Potential smallholder farmer benefits of Bt cotton. Adapted from Purcell et

al. (2004).

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Contents

•

1 Introduction• 2 Bt cotton• 3 Use in pest control• 4 Genetic engineering for pest control 

o 4 .1 Usageo 4 .2 Advantageso 4 .3 Safetyo 4 .4 Limitations to Bt crops

o 4 .5 Possible problems• 3 Bt cooton acreage rises20%• impact of Bt cotton