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Pastimes : Let's Talk About Our Feelings!!! -- Ignore unavailable to you. Want to Upgrade?

To: Ish who wrote (107073)	8/2/2005 12:44:58 AM
From: Grainne	Respond to of 108807

No, that is not what we were talking about, Ish. That study I posted about the increase in pesticide/herbicide use in GM crops was an argument against your statement that GM technology would eliminate pesticides/herbicides. Clearly, the exact opposite is happening as they become pesticide/herbicide resistant. So when you say "He misses what the increase would be on non-GMO crops. If it would be higher, there would be a net decrease," that is a logical statement, but has nothing to to with the broad argument we are having. Here is the most relevant piece of the article again, where it discusses the increasing need for pesticides/herbicides on GM crops: i-sis.org.uk The report acknowledges that the other major category of GM crops – Bt corn and cotton – continues to reduce insecticide use by 2 million to 2.5 million pounds annually. The reduction in insecticide pounds applied per acre planted to Bt corn and cotton ranges from 0.33 pounds in 1996 to 0.06 pounds in 2003, and from 0.38 pounds in 1996 to 0.2 pounds in 2001-2003, respectively. However, the increase in herbicide use on HT crops far exceeds the modest reductions in insecticide use on Bt crops, especially since 2001. The calculations also don’t take into account the volume of Bt toxin that is continuously expressed in the Bt crops’ plant cells. This amount is significant compared to the rates of application in today’s low-dose pesticides. In short, over the last eight years, HT crops have increased pesticide use an estimated 70.2 million pounds, while Bt transgenic varieties have reduced pesticide use an estimated 19.6 million pounds. Thus, total pesticide use has risen some 50.6 million pounds over the eight-year period. The increase in pesticide use, largely due to increased use in HT crops, especially HT soybean, is of no surprise, given that scientists had warned that heavy reliance on HT crops and a single herbicide (in this case, glyphosate) for weed management might lead to changes in weed communities and resistance. This triggers the need to apply additional herbicides and/or increase application rates to achieve the same level of weed control. Many farmers have had to spray more herbicides on GM acres in order to keep up with shifts in weeds toward tougher-to-control species, coupled with the emergence of genetic resistance in certain weed populations. "For years weed scientists have warned that heavy reliance on herbicide tolerant crops would trigger ecological changes in farm fields that would incrementally erode the technology’s effectiveness. It now appears that this process began in 2001 in the United States in the case of herbicide tolerant crops," said Benbrook. According to Prof. Bob Hartzler, an extension weed management specialist from Iowa State University, glyphosate-resistant marestail in Roundup Ready soybeans first appeared in Delaware in 2000, spreading since as far west as Indiana, and identified in the Southeastern US where Roundup Ready cotton is grown. Other records of glyphosate- resistant weeds (not necessarily linked to HT crops) are rigid ryegrass in an orchard in Australia and in wheat production systems in Australia and California, Italian ryegrass in Chile and goosegrass in Malaysia. Furthermore, waterhemp populations with individuals capable of surviving ‘normal’ user rates were identified in Iowa and Missouri the first year Roundup Ready soybeans were marketed. While Hartzler doesn’t think that waterhemp can as yet be considered glyphosate resistant, the potential exists and should be closely monitored. Since the first report of glyphosate resistant rigid ryegrass in 1996, four additional resistant species with this trait have been identified. According to Harztler, this rate of development suggests that new resistant biotypes will continue to arise. Prospects for GM crops leading to reduced pesticide use in the long-term don’t bode well either. The pounds of herbicides required to achieve acceptable weed control is rising on most farms planting HT varieties, compared to the rates of application common between 1996-1998. In contrast, the amount of herbicides and insecticides applied per acre on conventional farms continue to trend downward as a result of incremental shifts toward newer low-dose pesticides and regulatory restrictions phasing out high-dose herbicides. As a result, the difference in total pounds of herbicides applied on HT versus conventional acres has increased steadily since 2000. Given the emergence and spread of weeds resistant or less sensitive to glyphosate, this difference is likely to widen further if HT technology continues to be relied on as heavily as in recent years. Sources: Benbrook CM (2003) Impacts of Genetically Engineered Crops on Pesticide Use in the United States: The First Eight Years, BioTech InfoNet, Technical Paper No 6, Nov 2003, wwww.biotech-info.net Hartzler B ‘Are Roundup Ready weeds in your future II’, Submission to UK GM Science Review, 28 February 2003, gmsciencedebate.org.uk