Fwd: FW: [Food-news] The Role of Transgenic Crops in Pest Control

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>

> www.foodnews.ca

>

> Editor's Note: The articles below represent

> divergent views on the role of

> GM crops in pest control. Those who support the use

> of GM crops to control

> pests posit that Bt crops reduce the need for

> conventional insecticides,

> herbicide tolerant crops assist low till approaches

> to agriculture. These

> and other benefits can apparently play an important

> role is sustainable

> agriculture. Opponents hold that the complexity of

> agricultural systems

> requires contingent responses to problems of pest

> management. Transgeneic

> crops contain high and constant amounts of toxins,

> not responding to

> contingent factors and therefore encouraging the

> very rapid development of

> resistance. We invite readers to weigh in with

> their thoughts and

> experiences. Please visit www.fodnews.ca.

>

>

http://www.scidev.net/content/opinions/eng/gm-crops-iarei-compatible-with-sustai\

nable-agriculture.cfm

>

> GM crops are not the answer to pest control

>

> G. V. Ramanjaneyulu

> 8 February 2006

> Source: SciDev.Net

>

> 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.

>

> SciDev.Net:

>

http://www.scidev.net/content/opinions/eng/gm-crops-are-inoti-the-answer-to-pest\

-control.cfm

>

>

> GM crops are compatible with sustainable agriculture

>

> Christine Gould

> 8 February 2006

> Source: SciDev.Net

>

>

> 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.

> Click here to read an opposing view from G. V.

> Ramanjaneyulu, executive

> director of the Centre for Sustainable Agriculture

> in Secunderabad, India.

>

>

>

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