As a former Executive Director of the Board on Agriculture of the U.S. National Academy of Science for seven-years, Dr Charles Benbrook represents an authoritative voice on agricultural science.

His latest technical report, drawing on 9 years of US Dept of Agriculture data, confirms that the claim of GM proponents that the use of GM crops in the US has led to a major reduction in pesticide use is quite simply a lie. The data shows that overall GM crops have led to an increase in pesticide use involving millions of pounds.
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Benbrook report on pesticide use on GM crops in the first nine years
Genetically Engineered Crops and Pesticide Use in the United States: The First Nine Years
Dr. Charles M. Benbrook
Northwest Science and Environmental Policy Center
Sandpoint Idaho
October 25, 2004

The HTML link takes you to the Abstract
http://www.biotech-info.net/technicalpaper7.html

The PDF Link takes you to the 53-page report.
http://www.biotech-info.net/Full_version_first_nine.pdf

EXCERPT:

Pesticide Reduction Claims are Unfounded

The debate over the costs, risks, and benefits of agricultural biotechnology has been underway for about a decade, with no end in sight. Throughout this period, biotech proponents have claimed repeatedly that today's GE crop technologies are reducing pesticide use. A comprehensive accounting of the impacts of HT and Bt transgenic varieties on total pesticide use demonstrates unequivocally that in the first three years of
commercial use, this claim was justified. But since 1999 it has not been.

GE corn, soybeans and cotton have led to a 122 million pound increase in pesticide use since 1996. While Bt crops have reduced insecticide use by about 15.6 million pounds over this period, HT crops have increased herbicide use 138 million pounds.

Bt crops have reduced insecticide use on corn and cotton about 5 percent, while HT technology has increased herbicide use about 5 percent across the three major crops. But since so much more herbicide is used on corn, soybeans, and cotton, compared to the volume of insecticide applied to corn and cotton, overall pesticide use has risen about 4.1 percent on acres planted to GE varieties.

The increase in herbicide use on HT crop acres should come as no surprise. Weed scientists have warned for about a decade that heavy reliance on HT crops would trigger changes in weed communities and resistance, in turn forcing farmers to apply additional herbicides and/or increase herbicide rates of application. The ecological adaptations predicated by scientists have been occurring in the case of Roundup Ready crops for three or four years and appear to be accelerating... Reliance on a single herbicide, glyphosate, as the primary method for managing weeds on millions of acres planted to HT varieties remains the primary factor that has led to the need to apply more herbicides per acre to achieve the same level of weed control.