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2-Plants: Do GM crops mean less pesticide use?

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TITLE:  Viewpoint: Do GM crops mean less pesticide use?
SOURCE: Pesticide Outlook, October 2001, pp 204 - 207, by Charles Benbrook
DATE:   November 2001

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Charles Benbrook of the Northwest Science and Environmental Policy Center 
at Sandpoint (Idaho, USA) gives his views on the contention than GM crops 
have led to a reduction in pesticide use in the USA


Spirited debate in the USA continues over the impact of genetically 
modified (GM) crop varieties on pesticide use. Biotechnology proponents 
have claimed since the mid-1990s that both herbicide-tolerant and Bt-
transgenic varieties significantly reduce pesticide use, despite much 
empirical evidence to the contrary. This contention lies at the heart of 
industry efforts in the U.S. and Europe to build public support for 
contemporary GM crop technologies.

Four years of official U.S. Department of Agriculture data are now 
available to test the claim that GM crops grown in the U.S. have 
significantly reduced pesticide use. Most independent analysts working with 
the USDA data have reached similar conclusions; with the possible exception 
of Bt-cotton, they have not.

Herbicide-tolerant varieties have modestly reduced the average number of 
active ingredients applied per acre but have modestly increased the average 
pounds applied per acre. So, those who choose to measure herbicide use 
based on the former metric conclude that herbicide-tolerant varieties 
reduce herbicide use; those who favor the latter metric reach the opposite 
conclusion. Both are reasonable but incomplete ways to assess the overall 
impact of herbicide-tolerant varieties on herbicide use and the performance 
and sustainability of weed management systems.

Bt corn and cotton account for most acres planted to Bt-transgenic 
varieties. Again, the insecticide use data are pretty clear. Bt cotton has 
reduced insecticide use in several states, whereas Bt corn has had little 
if any impacts on corn insecticide use.

These findings come as no surprise to astute farmers or pest management 
experts. Herbicide tolerant varieties are designed to make it possible for 
farmers to rely on post-emergence herbicides as the backbone of weed 
management programs. Any grower spending the extra money on such a variety 
is obviously going to rely more prominently on herbicides as the principle 
method for controlling weeds, in contrast to other farmers using 
multitactic integrated weed management systems that both spread out the 
burden in managing weeds and strive to reduce weed pressure in the first 

[download whole article at]


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