ngin - Norfolk Genetic Information Network

5 December 2001


(Dec. 5, 2001 - CropChoice opinion) -- James Dargie, a director of the FAO's agriculture department, told a recent seminar in Stockholm that use of transgenic crops in the United States had helped farmers reduce their use of herbicides and thus saved them $15 per acre on weed control.

"One estimate puts the overall reduction in pesticide use within the United States at 1.2 million kg (2.646 million lbs) per year, suggesting significant environmental benefits,"  Dargie said.

Mr. Dargie is wrong.

The work of Dr. Charles Benbrook of the Northwest Science and Environmental Policy Center helps to debunk the myth that herbicide-resistant and Bt-laden transgenic crops  have spurred a reduction in pesticide applications.

Farmers spending extra money to grow Roundup (glyphosate)-resistant soybeans and corn do so largely so that they can simplify their weed management program by relying on post-emergence herbicides, mainly glyphosate.

Growers producing Bt crops, transgenically engineered to express the natural insecticidal bacterium bacillus thuringiensis (Bt), have devoted most of that acreage to Bt corn and cotton.  While Bt cotton has reduced insecticide use in several states, Bt corn has not, Benbrook wrote in the October 2001 edition of Pesticide Outlook.

"Corn herbicides account for about 40% of the total pounds of herbicides, insecticides, and fungicides that are applied annually by U.S. farmers (Table 3.2, Economic Research Service [ERS], 1997). Soybean weed management is the second biggest market, accounting for about 68 million pounds of applied annually.  For this reason, attainment of national pesticide use reduction goals and minimizing environmental damage and public health risks in corn-soybean production areas depends in large measure on innovation in weed management systems in these two major crops. Four years of USDA soybean use data (1997-2000) are available and support four conclusions (ERS, 1999; Duffy, 1999; Benbrook, 2001a): Slightly more pounds of herbicides are applied on the average acre of Roundup-Ready (RR) soybeans compared to the average acre planted to conventional soybean varieties.

Fewer herbicide active ingredients are applied on the average acre of RR soybeans relative to the average conventional acre.

Average per acre pounds of herbicide applied on RR soybeans exceeds by 2-to 10-fold herbicide use on the approximate 30% of soybean acres where farmers depend largely on low-dose imidazolinone and sulfonylurea herbicides.

Herbicide use on RR soybean acres is gradually rising as a result of weed shifts, late-season weed escapes leading to a buildup in weed seedbanks, and the loss of susceptibility to glyphosate in some weed species (Hartzlet, 1999; HRAC, 2001)."

Benbrook also touched on Roundup Ready corn, which appeared on the market in 1997:

"Total corn herbicide use under the "Residual Herbicide Applied" program averages about 2.75 pounds per acre, with Roundup accounting for 0.75 pounds of this total.  USDA data suggest that average per acre use on RR corn acres has risen from about 2.5 pounds in 1999 to 2.75 pounds in 2000 (Benbrook, 2001b).  On conventional acres, about 2.25 pounds were applied in 1999 and 2.08 pounds in 2000.  Accordingly, in 2000 the average RR corn acre was treated with about 30% more herbicide than the average non-GM corn acre."

He summed up his discussion of Roundup-resistant corn and soybeans by writing that farmers are applying more, not less, Roundup because weeds have grown resistant to the chemical and the appearance of other weeds on which Roundup has little or reduced effect.

Insecticide use on Bt corn acreage has slightly increased, while it has fallen in several states for Bt cotton, though credit for some of this decline goes to the boll weevil eradication program.

"Cotton insecticide use trends must be studied carefully to accurately identify cause-effect relationships.  The biggest reductions in bollworm-budworm complex insecticide use have occurred in the use of methyl parathion, profenofos, and thiodicarb.  The former two are highly toxic OPs [organophosphates] that have triggered resistance problems and regulatory restrictions.  As a result, most of the reduction in their use had occurred by the end of the 1996 season, prior to widespread use of Bt-cotton," Benbrook wrote.

"In some high adoption states, especially Arizona, BBW applications have fallen dramatically from over 3 acre-treatments per acre in 1994 to just 0.1 in 2000ÖRemarkably, only 2000 pounds of BBW complex insecticides were applied in 2000 in Arizona, down from 397,000 in 1995.  Much of this decline is likely attributable to Bt cotton, which was planted on over 75 percent of acres planted (revised EPA benefits assessment, Table E.8).

But in Alabama, another high Bt-cotton adoption state (62% acres planted), BBW insecticide applications almost doubled from 1997 to 2000.  Moreover, there was a clear shift in Alabama toward very toxic, broad-spectrum materials."

To see more on this subject, visit  To view this article, click on
scroll down to "General Discussion and Opinions" and then click on the headline "Do GM Crops Mean Less Pesticide Use?"

E. Ann Clark, a professor of plant agriculture at the University of Guelph, has also touched on the problems with genetically engineered crops -- Ten reasons why farmers should think twice before growing GE crops;

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