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Shawn Askew

Extension Specialist and Associate Professor, Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University

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Q: Does GMO corn reduce the amount of herbicides used by farmers?

Answered By Shawn Askew - Sep 23, 2014

A: This question is too general for a simple answer, so a brief discussion is in order. Before the advent of GM corn, farmers were reliant on a host of different herbicide-active ingredients to manage various weed populations in corn. Base programs would have typically included triazine and chloroacetamide herbicides, each applied at one or more pounds active ingredient per acre (lb ai/A), followed by an early postemergence treatment for grasses, broadleaf weeds or sedges, as appropriate.   Based on this scenario, use of glyphosate in GM corn would have resulted in half as much herbici [...]


Q: Do herbicide resistant GMOs lead to higher herbicide usage?

Answered By Shawn Askew - Sep 24, 2014

A: Generally speaking, probably not. Glyphosate, the active ingredient in most herbicides used on GM crops, is used at a rate of 0.9 to 1.9 pounds per acre. By comparison, standard preemergence herbicide mixtures are typically used at two to more than three pounds active ingredient per acre. Comparisons, however, can also be made to the contrary. If you were using glyphosate for Johnsongrass control, for example, and compared that with nicosulfuron, the glyphosate would equate to 40 times more active-ingredient weight than the nicosulfuron. The relationship of herbicide usage all depends on the h [...]

GMO Basics Health & Safety