GENET archive


2-Plants: Are GM crops compatible with sustainable agriculture?

                                 PART I
------------------------------- GENET-news -------------------------------

TITLE:  GM crops are compatible with sustainable agriculture
SOURCE: SciDev.Net, UK, by Christine Gould
DATE:   08 Feb 2006

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GM crops are compatible with sustainable agriculture
Christine Gould argues that transgenic crops have much to offer farmers
who use integrated past management techniques

Do crops that have been genetically modified -- for example to increase
their resistance to insects and other threats -- have a place in
integrated pest management (IPM)?

We at CropLife International, the global federation that represents the
plant science industry, feel strongly that they do, and that genetic
modification is a useful and beneficial technology that can make a
significant contribution to sustainable agriculture.

IPM is a system of protecting crops that meets the requirements of
sustainable development by allowing farmers to manage diseases, insects,
weeds and other pests in a way that is cost-effective, environmentally
sound and socially acceptable, as well as appropriate to local conditions.

To achieve this, farmers need to take into account all relevant and
locally available pest control tactics. They will adopt and exploit
techniques they see as practical and can add value to their activities.

Genetic modification can make a substantial contribution to the options
that farmers have available. It can be combined with other practical
strategies to optimise IPM programmes, thus preventing pest populations
from reaching economically damaging levels.

Indeed, like all technologies that help make crop protection and
production more efficient, genetically modified crops are most effective
when they are used as part of an IPM system.

Handled with care

The UN Food and Agricultural Organization (FAO) defines integrated pest
management as "the careful consideration of all appropriate measures that
discourage the development of pest populations and keep pesticides and
other interventions to levels that are economically justified and reduce
or minimise risks to human health and the environment."

The plant science industry supports this characterisation of IPM -- taken
from the FAO's Code of Conduct on the Distribution and Use of Pesticides
-- and in particular the concept that IPM "emphasizes the growth of a
healthy crop with the least possible disruption to agro-ecosystems, and
encourages natural pest control mechanisms".

A farmer's choice of which crops to plant -- and thus the ability to
select disease- and pest-resistant ones -- has always been a cornerstone
of IPM. Crop varieties with disease and pest resistant characteristics --
including those produced using precise and targeted transgenic methods --
can reduce the need for other protection measures, thus providing greater
choice in other areas.

So called Bt crops are a case in point. Gene technology has contributed
to the development of plants that express insecticidal toxins using genes
from the naturally occurring soil bacterium Bacillus thuringiensis.

Bt toxins have been used as an alternative to chemical insecticides for
almost 60 years. They control several important pests, and are regarded
as highly selective and environmentally friendly, with decreased impact
to other, potentially beneficial, insects. Indeed many farmers, including
organic farmers, already use spray formulations containing Bt.

Bt toxins, even when introduced into crops using genetic techniques, are
very useful in IPM strategies, which build on natural mechanisms for
controlling pest populations. In practice, whether farmers use Bt sprays
or plant Bt crops, the issues concerning environmental impact are
essentially the same. The main difference, in our opinion, is that Bt
crops can help deliver the toxin more effectively, and can reduce the
need for conventional insecticides.

A range of options

When assessing any action to combat pests, it is naturally important to
distinguish between harmful and beneficial insects. If and when a pest
outbreak occurs, a variety of control strategies should be considered,
which can be physical, biological or chemical.

At present, farmers in developing countries follow a number of strategies
to control pests. These include:
- Growing crops that are appropriate to local climate, soil and topography;
- Rotating crops to limit the build-up of pests and reduce weed problems;
- Not planting crops that can host similar pests next to each other;
- Using efficient irrigation methods;
- Reducing pest pressures in individual crops by inter-cropping;
- Adding soil nutrients to maintain soil fertility and plant health.

In each instance, a variety of factors must be taken into account when
deciding which method or combination of methods should be used. These
include costs, benefits, timing, available labour force, machines/tools
and control agents, as well as economical, environmental and social factors.

With Bt crops, for example, a key element of resistance management is
creating a 'refuge' -- an area or strip of land planted with non-Bt crop
varieties that reduces the environmental pressures encouraging insects to
develop resistance to Bt.

As far as other risks are concerned, transgenic crops -- like all crops --
require routine inspections and observation. This is required to assess
how well plants are growing, and what actions need to be taken on
cultivation, fertiliser use, and the control of weeds, insects, other
pests and disease -- as well as when to harvest.

Farmers in control

Other biotech crops also have much to contribute to IPM strategies.
Herbicide-tolerant crops, for example, can be useful for farmers pursuing
minimum tillage systems, in which fields are left unploughed before
sowing, and any weeds present are sprayed with herbicide.

The method can help to reduce labour inputs, enhance soil biodiversity,
and lead to more efficient use of water, as well as preserve organic
matter and decrease soil erosion. In addition to these benefits, using
herbicide-tolerant crops in such contexts can reduce the amount of
herbicide used, as well as the risks associated with chemical run-off,
and contribute to weed management strategies.

Furthermore, the development of transgenic crops has enabled minimum
tillage systems to be expanded into areas where they have been difficult
to implement in the past. These farming practices have become popular
with farmers worldwide, especially in North and South America, and in China.

Farmers remain the primary decision-makers in IPM programmes. The role of
the plant science industry is to provide access to the widest possible
range of appropriate technologies, services and products, and as much
information as possible on their characteristics, costs and optimal use
within IPM strategies.

Transgenic crops are just one such product, and have already a proven a
boon to millions of farmers. The evidence endorses our conviction that
they have a vital role to play in integrated pest management, indeed in
sustainable agriculture more generally.

Christine Gould is communications manager for CropLife International.
This article was written with the collaboration of other CropLife staff.

                                 PART II
------------------------------- GENET-news -------------------------------

TITLE:  GM crops are not the answer to pest control
SOURCE: SciDev.Net, UK, by G. V. Ramanjaneyulu
DATE:   08 Feb 2006

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GM crops are not the answer to pest control
G. V. Ramanjaneyulu argues that insect-resistant crops will eventually
require an increased use of pesticides, and that farmers around the
developing world will suffer as a result.

Thousands of farmers in the Indian state of Andhra Pradesh have committed
suicide since the 1990s, and many of these deaths have been blamed on so-
called pest disasters. This refers to the way farmers' heavy use of
pesticides has led to increased resistance in pests, which in turn has
caused substantial crop losses and a slide into crushing debt.

Given this situation, what should be the response to those suggesting
that we apply high doses of toxins over extended periods, irrespective of
whether the pests are present? After all, this is what supporters of
genetically modified (GM) insect-resistant crops are encouraging farmers
to do.

We do not have to look far to find well-established and credible
alternatives, namely the use of integrated pest management (IPM), or even
non-pesticidal management and organic farming.

These strategies are based on the farmers' own knowledge, management
skills and labour, rather than external farm inputs. Their demonstrated
effectiveness shows that farmers can manage insect pests successfully and
affordably without resorting to chemical pesticides -- or to insect-
resistant GM crops. [1]

The experience of these farmers suggests that widespread use of such GM
crops violates the principles of sound pest management.

Weighing the costs

It is generally accepted that under IPM, insecticides should be applied
only when the projected cost of damage from pests is greater than the
estimated cost of control measures, and only after all other effective
insect-control techniques have been considered.

Furthermore IPM practitioners look at the entire range of pests
associated with a crop, rather than individual insect species. They seek
to understand all the factors regulating pest populations within a
particular context. Finally, they devise and implement strategies to keep
the pest population below level at which growing the crops becomes
uneconomic -- known as the 'economic threshold level' (ETL).

Among the many positive aspects of this combination of strategies is that
it effectively prolongs the useful life of a pesticide by ensuring that
insects do not rapidly develop resistance to it. Such resistance can
develop in two ways.

The first is via 'selection for resistance'. In any natural population of
pests there is normal genetic variation, which includes variation in the
genes that deal with pesticide resistance. Pesticide use inevitably
favours the survival and reproduction of individual pests bearing the
genes that confer increased resistance.

The second mechanism is 'induced selection'. Even if the insect
population has no naturally resistant insects, high doses of a pesticide
causing mutations could increase the probability of resistance emerging.

Both of these are known to occur with chemical pesticides, and it is
likely that insect-resistant transgenic plants -- such as those producing
the Bacillus thuringiensis (Bt) toxin -- will have the same effect.

Unlike sprays, however, insect-resistant GM plants maintain constant
levels of the Bt toxin over an extended period, regardless of whether the
pest population is at economically damaging levels. The selection
pressure with insect-resistant GM crops is therefore likely to be much
more intense than with pesticide sprays.

Toxin consumption

In order to slow the emergence of insecticide resistance, IPM strategies
seek to avoid the use of pesticides altogether, unless the pest
population reaches the economic threshold level. If this happens, farmers
using IPM try to ensure that pesticides are only applied in doses that
are appropriate for the severity of pest problem.

By contrast, insect-resistant GM crops aim to eliminate pests by
encouraging them to eat high doses of toxins. Researchers, for example,
are now reported to be trying to amplify the expression production of the
Bt toxins to 25 times more than is needed to kill the relevant pest. [2]

In practice, the number of pests killed depends on the amount of toxin
they consume when feeding on the plant tissue. So producing the toxin in
the right dose, at the right time, and in the plant tissues where the
pest feeds, becomes crucial.

Unfortunately, reports indicate that levels of the Bt toxin can vary
between different Bt varieties, between different parts of individual
plants, and over time.

In particular, key parts of the plants' flowers, such as the pollen,
anthers, pistils and ageing flower petals, tend to have lower
concentrations of the toxin than other parts of the plant. [3]

Admittedly these studies have only looked at the variability of Bt
production under controlled conditions, rather than in farmers' fields.
But the experience of Indian farmers shows that, in practice, the extent
to which Bt cotton resists pests is extremely uneven within a season, as
well as across years, hybrids and locations.

Refuges are no solution

Another factor that increases the likelihood that pesticide resistance
will develop is that a single gene -- the Bt cry1ac gene -- has been
introduced into all the most widely-used cotton hybrids in India, while
the same gene is also being introduced into other crops.

In contrast, rather than relying on one technology or method of pest
control, IPM encourages farmers to alternate between chemicals that work
in different ways. This so-called 'mortality-source diversification'
helps prevent pests from developing resistance as quickly as they would
if faced with a single toxin.

Advocates of Bt cotton -- and government officials responsible for
regulating its use -- argue that resistance can be slowed by planting
'refuges' of non-Bt cotton, on the basis that this will encourage the
survival of insects that are susceptible to the Bt toxin.

In India, however, it is difficult to impose this requirement, given the
small size of many farmers' plots. Furthermore such 'biosafety' measures
are also very difficult to monitor and enforce -- indeed, there is
evidence in India that refuges are not in fact being implemented. [4]

The danger is that the widespread use of Bt varieties and other insect-
resistant crops will lead to a rise in the number of resistant pests,
which will in turn mean that the environment is subject to an ever-higher
volume of spraying, and more poor farmers are driven to despair.

The cost is too high. Insect-resistant GM crops have no place in a
rational pest management strategy

G. V. Ramanjaneyulu is executive director of the Centre for Sustainable
Agriculture, Hyderabad, India.


[1]	Ramanjaneyulu G.V. et al. (2004) No Pesticides...No Pests.... Centre for
Sustainable Agriculture, Secunderabad, India (2004)
[2]	Benedict J.H., Ring D.R. Transgenic crops expressing Bt proteins:
Current status, challenges and outlook. In: Koul O., Dhaliwal G.S., eds.
Transgenic Crop Protection: Concepts and strategies.Oxford University
Press and IBH Publishing Co, New Delhi (2004)
[3]	Kranthi K.R. et al. Temporal and intra-plant variability of Cry1Ac
expression in Bt-cotton and its influence on the survival of the cotton
bollworm, Helicoverpa armigera (Hübner) (Noctuidae: Lepidoptera). Current
Science 89, 2 291-299 (2005)
[4]	Central Institute for Cotton Research (CICR). Report on Bt Cotton in
India. (2004)


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