Has the Bt gene reduced pest infestation
and decreased expenditure on pesticides? - The Theory
Resistance is a decrease in pest susceptibility that can be
measured over human experience. When you use an insecticide to control a pest,
some populations eventually evolves resistance." (Tabashnik).
Under the stress of intensive chemical
spraying the weaker members of the insect populations get weeded out.”
(Carson). Evolution of insecticide resistance in >400 species of insects not
only confirmed Darwin's survival of the fittest theory besides threatening
agriculture and human health worldwide. This was the global experience of using
hybrid seeds. Bt Cotton is just an accentuation of this trend as the only
change now was usage of the same hybrids with a Bt gene inserted into their
germplasm.
Although scientists are trying to directly increase yield of some agronomically
important crops using transgenic technology, success are so far eluding them
(Jenner 2003). So any direct contribution to yield increase has to be accounted
by the (hybrid cotton) germplasm in which the Bt gene is inserted. Accordingly,
the Bt gene does not directly increase yields but only does so indirectly by
reducing yield loss due to pests. But the Bt gene is not designed to
protect against all pests but only against the Lepidopteran insects that
account for 50% of yield reduction attributed to pests in the country.
So theoretically the Bt gene’s contribution
to increased yield is limited to the degree it offers crop resistance to
Lepidopteran insects and thereby preventing loss in yields. Actual increase or
decrease in Bt yield has to be in relation to the yield loss of the
non-transgenic counterparts under the same cropping practice. But in
India presently there are an estimated 680 brands of BT cotton seeds whose
vulnerability to different kinds of pests vary greatly, that includes the
degree of their vulnerability to Lepidopteran insect pests.
But because it confers cotton plant
resistance to Lepidopteran insects, the Bt lobby further claims that farmers
are able to reduce their input costs enabled by a decrease in the volume of
insecticides sprayed (and associated costs) which in turn boosts income margins
as spraying less insecticide also means lower application costs. For
small-scale farmers who do most farming activities by hand, this means less
time for weeding and other management practices.
The history of insecticide resistance however
informs us that adaptation by insects could diminish the long-term efficacy of
Bt crops. Meihls et al report that resistance evolved quickly without refuges
and slower or not at all with refuges. So as a technological fix, a refuge
management strategy was mandated in many countries including India, to delay
insect resistance, which requires refuges of host plants without Bt toxins near
Bt crops to promote survival of susceptible pests.
The concept was based on the assumption that
most of the rare resistant pests surviving on Bt crops will mate with abundant
susceptible pests from nearby refuges of host plants without Bt toxins. If
inheritance of resistance is recessive, the hybrid progeny from such mating
will die on Bt crops, substantially slowing the evolution of resistance.
This approach is sometimes also called the
“high-dose refuge strategy” because it works best if the dose of toxin ingested
by insects on Bt plants is high enough to kill all or nearly all of the
aforementioned hybrid progeny. In principle, if a high dose is not achieved,
resistance can be delayed by increasing refuge abundance, which lowers the
proportion of the population selected for resistance to compensate for survival
of hybrid progeny on Bt plants.
NGOs and environmentalists on the other hand
ridiculed this theory. They highlighted there is ample evidence that suggests
that pests develop resistance to just about any pesticide thrown at them. Bt
toxin secreted by the Bt crops is no different from other chemical pesticides.
Early on it will cause a temporary reduction of pesticide use (and associated
costs), but resistance will eventually develop. They predicted that pest
resistance to Bt could appear in the field within three to five years.
Evidence vs Theory
Dr. Kehsav Kranthi, the Director of India’s
Central Institute for Cotton Research in a 3 part paper entitled 10 Years of Bt
in India provides a review of the Bt gene’s actual performance in the field.
This is really a Government of India (GoI) review. Here's some extracts:
"The
leaf curl virus started to resurface as a major problem in north India,
primarily due to the introduction of more than 270 Bt hybrids in north India,
most of which were susceptible to the leaf curl virus. Until 2005, 100% of
cotton area in the north was under varieties. Now 95% of the area is under
hybrids in Punjab and Haryana, while 40% of the area is under hybrids in
Rajasthan.
Productivity
in north India is likely to decline because of the declining potential of
hybrids; the emerging problem of leaf curl virus on the new susceptible
Bt-hybrids; a high level of susceptibility to sucking pests (straight varieties
were resistant); problems with nutrient deficiencies and physiological
disorders; and mealybugs, whiteflies and miscellaneous insect problems that are
likely to increase.
The tobacco
caterpillar, Spodoptera litura, resurfaced as a problem again as predicted,
because of the low toxicity of the Cry1Ac toxin on the species. Bollworms started
reappearing on Bt cotton.
In February
2010, Monsanto, India declared that pink bollworm had developed resistance to
Cry1Ac and that only Bollgard-II would be effective thereafter. Resistance
monitoring studies at CICR showed that the American bollworm Helicoverpa
armigera was also showing incipient tolerance in some parts of India.
The leaf
hoppers showed very high levels of resistance of up to 5,000-fold to
imidacloprid and other neonicotinoid insecticides in central India. The
neonicotinoids were introduced barely a decade ago.
Progressive
nutrient (macro and micro) depletion due to the source sink relationship
because of Bt-cotton after Bt-cotton hybrid cultivation. Bt-cotton hybrids
utilize more nutrients and water for higher yields and profits, therefore the
soils are getting progressively depleted and need more nutrient recharging.
The cotton crop is showing nutrient deficiency symptoms in many regions,
especially in rainfed zones where wilt and leaf-reddening problems are getting
more severe over the years. The productivity is maximum in good soils."
The
salient points of the GoI’s evaluation of Bt Cotton’s performance during the
last decade accordingly are as follows:
1. Imidacloprid ( used as seed
treatment in cotton) that gave a 20-30% yield gain was succumbing to
resistance, significantly, coinciding with the observed yield decline of cotton
seen during the last 3 years.
2. The Bt gene was touted basically a protection against the bollworm complex,
particularly effective against the American bollworm. A review of
literature suggests the single-protein Cry1Ac products continue to more or less
control the bollworm complex other than pink bollworm (Pectinophora gossypiella).
Two possible reasons are attributed to its
ineffectiveness against the latter - either the period of expression of the Bt
endotoxin does not coincide with the time of the bollworm attack or it's
populations harbour three genetic mutations that confer resistance to Bt toxin
(Morin et al, 2003), the latter being a more popularly accepted explanation.
The real setback for Bt is that after proving
that it could reduce the incidence of American Bollworm for some years, there
is growing evidence of incipient resistance in the Central region accounting
for nearly 60% of all cotton cultivation in the country. Some of the
reasons for that are as follows:
- The
toxic expression depending on the parental background of the hybrid varies
widely due to the proliferation of brands.
- In some
plants, toxin expressions decreases 110 days after sowing to levels that are
inadequate to protect the plants from bollworm attacks. (Doyle et al) However
maximum and extensive damage potential from bollworms is in their early stages.
- In India,
cotton bollworm is more serious than in USA or in China; this means that Indian
farmers needed to spray more pesticides against bollworm as resistance built
up.
The second-generation Bt cotton technology,
Bollgard II containing two proteins, Cry1Ac and Cry2Ab introduced in 2006 was
supposed to check both these limitations on the assumption that the combination
overcomes pests that are resistant to just one toxin. But this too has not
fully succeeded. The assumption that the hybrid offspring produced by
mating between susceptible and resistant moths are resistant had been falsified
with the appearance of incipient resistance, indicating the opposite happening
- the inheritance tends to be dominant.
3. Bt cotton by inserting a gene into hybrid
cotton was intended to make manual spraying obsolete. In fact, that was the
claim of their hardsell when it was first introduced in this country. The
object was to make the entire plant toxic so that the insects feeding on it are
killed by increasing toxicity to 1,000 times to prevent resistance build up.
But in reality, Bt toxins Cry34Ab and Cry35Ab often does not meet this
high-dose standard (Meihls et al) so it does not kill all insects feeding on
the Bt crop but permits support to a significant population of resistant
insects.
Further since Bt’s endotoxins do not confer
protection in the entire life cycle of the Bt plant, manual sprays though
reduced cannot be eliminated pointed out Suman Sahai of Ngo, Gene Campaign.
She explains:
“The expression of the Bt cotton gene worked for
only 90 days while Indian cotton took 160 days to mature. In other words,
during the crucial period when the crop needed protection from pests, it
remained unprotected”
Besides, since the Bt gene confers protection
against only Lepidopteran insects and not others like sucking insects, farmers
continued spraying broad spectrum pesticides. This realization made Bt
advocates such as Keshav Kranti to clarify that Bt is just one element in the
total package of pest management, which is a big come down by Bt lobbyists who
had claimed at entry that Bt will make manual spraying obsolete.
4. The impact of (2 and 3) was two-fold. On
one hand it catalyzed the rise of hitherto unknown insect pests like mealybugs
and on the other hand it also catalysed the resurgence of major pests that
previously was brought under control. Besides it elevated other minor pests to
major pests. If all these are an India specific development, Bt as a technology
could be given a benefit of doubt. But it ties very well with similar
happenings in other Bt growing countries, whether the US, China or Pakistan.
Thus the rise of predation by non-target
crops completely neutralized the gains of the Bt gene reflected on productivity
rates which began to decline after peaking in 2006-07. Keshva Kranti observed:
A mealybug named Phenacoccus solenopsis, not
observed earlier in India, has spread across northern, central and western
states after it was first recognised as a cotton pest about five years ago. In
desperation, farmers have begun to spray "extremely hazardous"
pesticides on the cotton to fight the insect, which has a waxy coating over its
surface that makes it hard to kill with less toxic pesticides”.
We neither have a transgenic gene nor a
variety, whether hybrid or desi, that is resistant to this mealybug. As a
result, farmers need to spray at least 6 times, just to contain its damages, at
the cost of Rs 3,000-4,000 per hectare.
5. The combined unintended side effect was
these limitations of transgenic technology reinforced each other, spiking
pesticide consumption and usage that resulted in indiscriminate killing of both
pest and beneficial insects or bacteria including predators of till then minor
pests of cotton. It was also found to having adverse effects on natural
predators or parasites of bollworms themselves.
Pesticide consumption after moderately declining till 2006-07 started rising
again and accordingly input expenditure of farmers for pesticides which after
declining till 2006-07 doubled by 20010-11. A new study by a Washington
University in St. Louis anthropologist by Dr Glen Stone (2011) used
triangulation methods to confirm this trend. Stone observed that the prices of
Lepidopteran insect’s pesticides remaining more or else constant at 2003 prices
while those of sucking insecticides commanding a premium.
So while Bt moderately succeeded in keeping
in check one set of pest (Lepidopteran insects) damages, it created several
sets of new pest damages (e.g. sucking insects) that completely negates its
gains. The result had a telling reflection on productivity that peaked in
2006-07 at 554 kgs/link per hectare and then declined for three consequent
years to 474 kgs/link per hectare.
6. Perhaps the most loaded statement in
Keshva Kranti’s paper is when he notably observed:
“The area under Bt cotton has reached above 90% in
many parts of the country but farmers are not following the recommended refugia
practices. The intensive Bt cultivation and the noncompliance of refugia is
likely to hasten resistance development.”
The concept of a refuge on one hand reflects
the inefficiency and on the other hand, the inappropriateness of Bt technology:
a. Inappropriateness: In countries like the
US or China, land is less of a constraint than it is India, and so they can
more afford to set aside 20% of the cultivation area for refuge as their
average land holding sizes are much larger. In India, this is viewed as waste
to put arable land for non-productive purpose.
b. Inefficiency: Bt was touted to have been
designed to kill pests by increasing toxicity levels to 1,000 times. But this
did not happen at all or at all the times as Bt endotoxins lacked consistency
and timing of production of high dosage toxins. At other times, despite the
high dosages, pests survived by mutation to acquire toxin resistance all the
same.
According to regulatory conditions, the size
of the refuge belt should be either 5 rows of non-Bt cotton or 20% of total
sown area, whichever is more. Due to small and marginal land holdings In the
country, these norms are not followed. If in the US the default rate is 20%,
whereas in India the compliance rate is less than 10%.
For quicker adoption of Bt seeds, sections of
the Bt industry even argued there was in fact no need for a refuge. Manjunath
(2004 & 2005) a former director of Monsanto India argued instead that
there existed a large number of alternative hosts like chickpea; pigeon pea;
sorghum and tomato which could serve as natural refuge. Bt had then a share in
overall cultivation less than 15%. So non-compliance of refuge requirements
cannot per se explain the hastening of resistance build up. What can more
probably completely explain it is that as Bt reached a share of 90% of area
cultivation, it did so at the cost of cannibalizing this ‘natural’ refuge.
There are several implications arising from this:
a. The effectiveness of Bt’s endotoxins reduces as the
technology expands its share in area of cultivation. The more it expands
its share in area of cultivation, greater the prospects of pests acquiring
resistance to its endotoxins. Now that Bt commands nearly 90% of area of
cultivation, it signed its own death warrant. The question of ‘mass’ resistance
is not of if but when it explodes. This is the real import of Dr Keshav Kranti
comment: “Reduction in area of
intercrops can hasten the development of bollworm resistance to Bt-cotton” .
b. The concept of refuge was for its touted utility to
slow down the onset of resistance. The assumption is that pests surviving on Bt
crops will mate with abundant susceptible pests from nearby refuges of host
plants without Bt toxins and the inherited resistant gene will be recessive so
that pests will be killed by endotoxins of the Bt crop.
Now recent studies show these series of
assumptions as not completely correct. One bunch of studies point that the
inherited resistant gene instead can be dominant too, particularly if the
resistant insects mate among themselves! (Meihls et al & Ranjith et al).
Further a study (Anilkumar et al) published
in the Applied and Environmental Microbiology concluded that in the case of
Helicoverpa zea,, thought to have evolved from the American bollworm), the
inheritance trait appears to be statistically more dominant than in other cotton
pests. Accordingly, this might explain why Helicoverpa zea developed resistance
to Bt.
All these simply mean even if there is full
compliance of the refuge system, its efficiency is highly questionable. The
refuge is just a red herring explanation why Bt as a technology failed.
c. Further, if resistant insects visit a
refuge, then it is not only for mating, it is also for food. Now here lies the
danger of treating alternative hosts like chickpea; pigeon pea; sorghum and
tomato serving as “natural” refuge. Damage from infestation to these crops
increases, causing significant yield drops for them. Consequently, any
benefit-cost analysis on Bt cotton should encompass its impact on “natural”
refuge. A review of literature suggests that this is never done.
Despite the refuge system being integral in
the Bt package, the irony is that cost implications whether land set aside,
seeds and other inputs are not considered in the benefit-cost analysis of the
Bt crop. Once factored in, it would look less rosy even if economical
otherwise.
So back to the question: Has the Bt gene reduced pest infestation and
decreased expenditure on pesticides?
Bt’s weakness as a technology stems from not
incorporating the lessons of our hybrid experience. To prevent resistance build
up in insects, pesticide management should reflect its judicious use - finding
the right toxin-pest fit; right dosage-degree of infestation fit combined with
timely and required frequency of applications. This principle was observed to
be violated in common practices of hybrid cultivation resulting in contributing
to resistant build up in insects, necessitating application of new toxins and/or
higher dosages to control the same degree of pest infestation.
The endotoxins secreted from Bt besides does
not permit effective control over of either their timing or dosage. The very
fact that it targets only one set of insects, necessitates manual spraying of
other categories of broad spectrum acting pesticides, including ‘cocktails’
that violates judicious norms of sustainable pest management principles. Since
Bt does not offer protection for bollworms during the entire life cycle of the
plant, it also entails limited manual spraying to complement its endotoxins.
Multiple stacking of genes, the new generation of Bt’s are in fact no different
from a ‘cocktail’ in effect except that it is much worse in impact.
The refuge system was neither complied with
by farmers or if complied with, was ineffective to prevent the build up
resistance. In fact, the goal of refuge was defensive to begin with.
Prevention was never its aim but only to delay resistance from developing long
enough so that it becomes manageable, so that, perhaps, by the time
super-bollworms evolve, there are new versions of super-Bollgard available to
farmers to contain the threat so that the cycle begins again, escalating seed
costs for farmers and boosting revenue earnings for seed companies.
The refuge system was a poor alternate to the
system of crop rotation, one of the oldest and most effective cultural control
strategies. It meant that the succeeding crop must be a different family than
the previous one, based on the appreciation that most significant pests are
crop specific and their populations can naturally decline if deprived of food
by rotating crops, dying due to absence of food. Bt however created the
illusion that it was a superior alternative by offering the refuge system.
It is no surprise that the attempt to stall the evolution of insect resistance
through transgenic crops producing Bacillus Thuringiensis (Bt) toxins ended up
a failure as instead of pests getting killed, they instead began thriving on
it. (MT Ranjith et al). But Glenn Gladstone of Washington University in
St. Louis in his study warns the failure goes much beyond this level:
"Looking beyond the field level to the farm
level you see the real problem was a set of factors that eroded the normal
process of farmer evaluation of technologies — there were too many rapid,
undecipherable changes.
Each new technology — hybrids, then pesticide after
pesticide — brought short-term gains but further eroded farm management. Bt
cotton has raised yields on average, but already we are seeing erosion of
benefits as non-target pest populations are booming. It has also brought a
quickening of technological change and undecipherability, which is the real
underlying problem."
Here ends Part III
Click here for Part I and Part II. This paper is
written by Rajan Alexander, Development Consultancy Group, Bangalore. Rajan is
a livelihood consultant and had been in the NGO sector for more than 31
years. He can be contacted at rajan.alexander@yahoo.co.in
I am a college educated multi-disciplined major from california USA and I find that everything that was stated in this paper makes total logical sense and that the "arrogance of USA corporation companies" have lost "logical sense" when trying to solve problems and only look at one issue and do not look at all other factors that go into "mother nature and how animal and plant species have evolved" over centuries. To engineer a plant with gene manipulation to combat one particular pest completely fails to look at the "entire environment" that the plant or animal exists in and this arrogance needs to stop until "ALL" ramifications of changing something mother nature evolved has got to stop now because we are "inventing" technologies that do not take the time to ask the question, "how is this going to play out with other factors in "mother nature". All our plants and animals and insects and germs have evolved over thousands of years for a reason and if you mess with this very complicated inter-dependence you are going to mess things up worse than what you were trying to solve one problem.
ReplyDeleteWe had a mass media commercial advertisement in the late 60's to market a margarine for a substitute for butter and it said "It is not nice to fool mother nature"..
I do not have a college degree in agriculture but I did have the basic education in plant and animal science and the ramifications regarding introducing a plant seed with a gene added to stop just one variety of pest I even knew from just logical common sense what this would do in the future to the environment around the plant and also that there is a huge difference between dry land and irrigated crops and how they perform. I have found that Americans tend to specialize too much in scientific areas and this makes them neglect how all things in life are interconnected and this is how life has evolved on this planet. I have studied the long civilization and culture of India and how Indian culture has evolved as the oldest in the world is actually the most correct when it comes to the interdependence of all things. Americans have been indoctrinated from the time they are babies to believe in the "exceptionalism" of American ideas above everyone else as not as good as Americans. I find this idea so repugnant and can totally understand why the rest of the world has grown to "hate Americans" because we have not been taught the greatness of other cultures or religions around the world that are far older than our country and that they should be respected and honored and taught because whenever we try to go anywhere in the world and say our ideas and values are better than other peoples and that we know what is best this is what has caused all our failures since the end of WWII and we should stop meddling in other countries affairs.
My name is Kerry Pay Mann and you can reach write to me at 1155-C Arnold Dr. #453, Martinez, California .
I would be honored to belong to the great Indian country and culture that should be an example to the rest of the world as to the inter-connectiveness of all things in this world.