Insects Developing Resistance to GM Bt Crops
GM Freeze, 10 Nov 2011
http://www.gmfreeze.org/news-releases/171/
GM Freeze today published a review of insect resistance to Bt toxins in GM maize
and Bt cotton crops around the world. It shows how, contrary to promises from GM
companies, pesticide use is increasing to keep up with insects in GM crops. [1]
Scientists have confirmed five incidents of insects evolving resistance to Bt
toxins in the field to date: Bt cotton in India (2010) and US (2008), moth pests
in maize in Puerto Rico (2007) and South Africa (2007) and a beetle pest in
maize in the US (2011).
Reasons for resistance developing are:
*Failure to provide adequate non-GM refuges in GM crops to ensure non-resistant
adult insects can survive to breed with resistant ones so that the resistance
gene does not become dominant. Refuges are required by US laws that are widely
flouted.
*Levels of Bt toxin in the crops too low to deliver lethal doses to pests.
Sub-lethal doses mean resistance can develop as pests survive, mate and pass on
the resistance gene. If the number of resistant individuals is high they can
multiply quite rapidly and become dominant.
Monsanto has admitted the failure of their Bt cotton to control the pink
bollworm has caused widespread damage in crops in Gujarat, but has tried to
shift the blame onto farmers. [2] Pesticide costs on infested crops are reported
to have risen by a nearly a third.
In Iowa in 2011 the first beetle pest resistance to a Bt toxin was confirmed, in
western corn rootworm, which has caused "severe rootworm feeding injury to Bt
maize". [3] The problem appears to be emerging in other key maize producing
states.
Commenting Pete Riley of GM Freeze said:
"There are two confirmed cases where GM resistance to major crop insect pests
has broken down and widespread damage to crops has occurred. Biotech companies
are not liable, so farmers have no recall when infestations are economically
damaging.
"Strategies to prevent pests becoming resistant are either not being correctly
implemented, are failing, or are suffering from a combination of both. The
result is more pesticide use rather than less. Throwing more GM at the problem
may work in the short term, but the history of artificial pest control in
agriculture has repeatedly shown the pests will win over the longer term.
"The sooner we switch to agroecological farming techniques, such as avoidance of
monocultures, long rotations and the use of natural predators to control pests,
the better."
ENDs
Calls to: Pete Riley 07903 341065
Notes
[1] See GM Freeze briefing Insect Resistance to Bt Toxins in GM Insect Resistant
Crops
http://www.gmfreeze.org/publications/briefings/123/
[2] See Sharma, Dinesh, 6 March 2010. Bt Cotton Has Failed Admits Monsanto.
India Today.
http://indiatoday.intoday.in/site/Story/86939/India/Bt+cotton+has+failed+admits+
Monsanto.html
and
Monsanto, 5 May 2010. Cotton in India.
http://www.monsanto.com/newsviews/Pages/india-pink-bollworm.aspx
[3] Gassmann AJ, Petzold-Maxwell JL, Keweshan RS, Dunbar MW, 2011.
"Field-Evolved Resistance to Bt Maize by Western Corn Rootworm". PLoS ONE 6(7):
e22629. doi:10.1371/journal.pone.0022629
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