7/28/2019 Use of Bt Cotton linked to rise in aphid numbers

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09/04/2013 Use of GM cotton linked to rise in aphid numbers - SciDev.Net

www.scidev.net/en/ag riculture-and-environment/gm-crops/news/use-of-gm-cotton-linked-to-rise-in-aphid-numbers.html

Bt cotton is genetically

engineered to produce an

insecticide against a

caterpillar pest

Flickr/abhisheksrivastavaSPEED READ

Previous research linked the surge in aphids on Btcotton to reduced insecticide use

The new study ties it to a fall in plant defencechemicals as caterpillars no longer eat the plant

Bt cotton should be part of a wider pest-management system, the study recommends

NEWS

Use of GM cotton linked to rise in aphid numbersRicha Malhotra

8 April 2013 | EN

In an unexpected trade-off, the cultivation of cotton that has been genetically

engineered to reduce caterpillar damage by producing its own insecticide has been

linked to higher numbers of another pest aphids.

Previous studies had linked the increase in aphids to reduced insecticide use by

farmers cultivating Bt (Bacillus thuringiensis) cotton.

Now researchers have for the first time tied the suppressed production of natural

defence compounds in Bt cotton caused by the lack of caterpillar attacks to a

surge in non-target pests such as the cotton aphid.

Non-Bt plants respond to

caterpillar infestation byproducing defence compounds, which also protect

the plant against other pests.

The researchers studied the correlation between Bt

and non-Bt cotton plants, defence compound levels

and aphid populations in both glasshouse and field

conditions.

In the glasshouse, they artificially infested Bt and non-Bt cotton plants with caterpillars and monitored the

levels of various defence compounds known as terpenoids that are released in response to caterpillardamage. The plants were then artificially infested with aphids.

In the field, one set of Bt and non-Bt cotton plants were artificially infested with caterpillars and another was

left to natural infestation by caterpillars. Terpenoid levels were measured and both sets were then exposed to

natural aphid infestations.

In the glasshouse, caterpillars on the Bt cotton plants died. As a result, the plants were less damaged and

therefore contained less defence compounds than their non-Bt counterparts.

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7/28/2019 Use of Bt Cotton linked to rise in aphid numbers

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09/04/2013 Use of GM cotton linked to rise in aphid numbers - SciDev.Net

www.scidev.net/en/ag riculture-and-environment/gm-crops/news/use-of-gm-cotton-linked-to-rise-in-aphid-numbers.html

The researchers thus attribute the resulting increase in aphid populations on these plants, compared with

non-Bt plants, to lowered terpenoid production.

Although a relative r ise in aphid numbers was noted on a few occasions on Bt cotton plants in the field, the

scientists found no correlation between aphid populations and terpenoid levels in this part of the experiment

Jrg Romeis, one of the paper's authors and head of the biosafety research group at the Agroscope

Reckenholz-Tnikon Research Station ART, Switzerland, tells SciDev.Net, "Our study shows that a technolog

like Bt cotton should not be used in isolation".

"To control other herbivores we have to use the technology as part of integrated pest management

approach."

T. M. Manjunath, a consultant in agrobiotechnology and integrated pest management from India, where Bt

cotton is cultivated, says: "What this study shows with Bt cotton can happen with any other insect-control

measure. Infestation by aphids and other non-target pests has been seen before the introduction of Bt

cotton".

The study was published in the Proceedings of the Royal Society B last month (13 March).

Link to the study abstract

REFERENCES

Proceedings of the Royal Society B doi: 10.1098/rspb.2013.0042 (2013)

http://www.scidev.net/en/agriculture-and-environment/gm-crops/news/use-of-gm-cotton-linked-to-rise-in-aphidnumbers.htmlPrinted on: Tuesday, April 9, 2013 08:18 2013 SciDev.Net

http://rspb.royalsocietypublishing.org/content/280/1758/20130042.abstract