Herbicides, glyphosate resistance and acute mammalian toxicity: simulating an environmental effect of glyphosate-resistant weeds in the USA
2008
Gardner, Justin G. | Nelson, Gerald C.
BACKGROUND: With the emergence of glyphosate-resistant (GR) weeds, the environmental consequences of alternatives to GR technology are of increasing importance. A well-known acute mammalian toxicity measure, the LD₅₀ dose for rats, is used to assess one potential environmental impact of the loss of GR technology. A new dataset with this index is used to estimate and simulate the effects for corn, soybeans and cotton.RESULTS: With conventional tillage it is found that the use of GR seeds reduces the number of LD₅₀ doses applied per hectare by 17-98% depending on crop. With no-till, the use of GR seeds reduces LD₅₀ doses only in corn. If farmers switch to conventional seeds because of GR weeds but maintain the same tillage practice, the present simulations suggest that LD₅₀ doses could increase by as much as 100 LD₅₀ doses per hectare in soybeans, and 500 LD₅₀ doses per hectare in cotton, or 11.4 and 19.8% respectively.CONCLUSIONS: This is the first study to use field-level data to assess GR technology with a mammalian toxicity environmental indicator. It has been found that GR crops have a positive environmental effect, and that alternatives to GR technology increase toxicity.
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