In the following letter Dr Bert Christie, a Canadian agrologist, not only draws attention to how the recent Benbrook study demolishes the constantly repeated claim that GM crops reduce pesticide use, showing the opposite is the case in the longer term, but he also notes:

"Dr. Benbrook's study also points out the often ignored fact that growers of conventional (non-GM) crops are reducing the use of chemicals substantially, without turning to GM technology."

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GM crop technology needs more study to settle the controversies
The Guardian (Charlottetown, Canada), January 22, 2004 [via Agnet]

Bert Christie, Ph.D., of Stratford, a professional agrologist, writes that any discussion of genetically modified (GM) crops or of the foods derived from such crops generates a lot of discussion.

In a recent commentary 'Banning genetically modified crops would be a backward step' (The Guardian, Jan. 14, 2004), Jay M. Holmes makes the claim that GM crops reduce pesticide use, and suggests that the Island should not turn its back on a technology which has the potential to reduce pesticide use, and thus, reduce pesticide runoff. As always, no data are presented to support that claim.

Fortunately, Dr. Charles Benbrook, a researcher from Idaho, has recently published a report entitled: 'Impacts of Genetically Engineered Crops on Pesticide Use in the United States: the First Eight Years'. Dr. Benbrook is a private consultant and undertook this study at the request of a number of organizations, including Iowa State University and the Consumers Union. He studied the use of pesticides on GM and non-GM varieties of corn, cotton and soybeans, during the crops years of 1996 though to 2003. (The full report can be found on the internet at http://www.biotech-info.net/Technical_Paper_6.pdf)

Dr. Benbrook found that farmers who grew genetically altered herbicide-tolerant varieties did indeed reduce the amount of chemicals for the first two or three years, but then, herbicide use increased. For GM corn, by 2003, the amount of chemical herbicide applied per acre was greater than that applied to non-GM corn. Dr. Benbrook suggested that the use of one chemical as the sole source of weed control led to resistance to the herbicide in weed populations "triggering the need for additional herbicides and/or increased rates of application." During the same time that herbicide use was increasing on GM corn it was declining for non-GM corn. This has been a trend since the early 1980s. By 2003, the average rate of herbicides applied to GM corn was 2.40 pounds per acre. As a result, the use of GM corn hybrids increased pesticide use by an estimated 70 million pounds. On the other hand, the average rate for non-GM corn was 1.81 pounds per acre. The decline in the use of chemicals on non-GM corn was attributed to the desire of farmers to reduce chemical dependency coupled with the use of other practices to control weeds; chemical and non-chemical.

Similar results were reported for the GM herbicide tolerant cotton and soybeans.

In the case of corn and cotton, genetically engineered to have the Bt gene for insect control, insecticide use has indeed declined. Dr. Benbrook estimates that the introduction of Bt corn and cotton has lead to a seven per cent reduction in insecticide use on those two crops; or about 2.3 million pounds.

These results show that it is not possible to substantiate blanket statements that the use of GM crops will reduce the use of chemical pesticides. Each case needs to be considered on its own merits.

Dr. Benbrook's study also points out the often ignored fact that growers of conventional (non-GM) crops are reducing the use of chemicals substantially, without turning to GM technology.  

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