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Answers

Question

Do Roundup Ready crops reduce chemical use?

Submitted by: Bryce


Answer

Expert response from Michael Horak

Former Weed Resistance Platform Lead, Monsanto Company

Friday, 05/02/2016 12:27

Thank you for the question. Roundup Ready® crops (a brand name for some glyphosate-tolerant crops) have been enhanced through biotechnology to no longer be susceptible to glyphosate. Corn, soybean, cotton, canola, sugar beet and alfalfa are all examples of crops that have some glyphosate-tolerant varieties. Farmers use herbicides as one method to control weeds on their farms. 

 

Methods that farmers use to control weeds include cultural control methods (e.g., growing a healthy crop to compete with weeds; cover crops that suppress weed growth), physical methods (e.g., hand weeding or tillage that relies on tools, machinery or other means to physically disrupt the weed’s growth), biological methods (e.g., using other organisms such as insects to kill weeds – although there are limitations to this type of weed control that do not allow it to work well in annual crops) and chemical control (e.g., using herbicides to control weeds). Glyphosate is an herbicide that is very effective against weeds, and when sprayed over the top of Roundup Ready crops will not kill the crop plant that would otherwise be damaged. There are many herbicides on the market that farmers can use to control weeds. In many cases, to get good weed control and protect the crop from weed competition, farmers use one or more herbicides to control their weeds. When Roundup Ready crops were first introduced many farmers used glyphosate alone to get their desired level of weed control. However, due to changes in weed communities, better understanding about best management practices to control weeds, and the occurrence of some weeds that have resistance to glyphosate, many farmers are now using practices that combine glyphosate and other herbicides and other methods (like cover crops and cultural methods) to control their weeds.

 

Thus, in some cases where Roundup Ready crops are used, herbicide use may be reduced compared to other weed control systems, in other circumstances herbicide use has roughly remained the same, and in certain cases to adopt best management practices or where there are new and emerging weed problems, additional herbicides are used to control the weed community. Shawn Askew, Extension Specialist and Associate Professor in the Dept. for Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University offers his perspective in this response to a similar question: Does GMO corn reduce the amount of herbicides used by farmers?

 

Additionally, Graham Brookes discusses this topic in the published journal article Weed control changes and genetically modified herbicide tolerant crops in the USA 1996-2012. He states, “The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods.”  

 

The observation of changes in herbicide use rates are true of many other herbicides that have been introduced into agricultural use over the last 50 years. Andrew Kniss used free and accessible data from USDA-NASS to depict the trends of total herbicide use in corn from 1990-2014. He notes that, “total herbicide use in corn (in weight of herbicide applied) has remained relatively constant at about 2 to 2.5 lbs./acre since around 2000 (Top panel A). There have certainly been changes in which herbicides contributed to that total, though.”

Answer

Expert response from Michael Horak

Former Weed Resistance Platform Lead, Monsanto Company

Friday, 05/02/2016 12:27

Thank you for the question. Roundup Ready® crops (a brand name for some glyphosate-tolerant crops) have been enhanced through biotechnology to no longer be susceptible to glyphosate. Corn, soybean, cotton, canola, sugar beet and alfalfa are all examples of crops that have some glyphosate-tolerant varieties. Farmers use herbicides as one method to control weeds on their farms. 

 

Methods that farmers use to control weeds include cultural control methods (e.g., growing a healthy crop to compete with weeds; cover crops that suppress weed growth), physical methods (e.g., hand weeding or tillage that relies on tools, machinery or other means to physically disrupt the weed’s growth), biological methods (e.g., using other organisms such as insects to kill weeds – although there are limitations to this type of weed control that do not allow it to work well in annual crops) and chemical control (e.g., using herbicides to control weeds). Glyphosate is an herbicide that is very effective against weeds, and when sprayed over the top of Roundup Ready crops will not kill the crop plant that would otherwise be damaged. There are many herbicides on the market that farmers can use to control weeds. In many cases, to get good weed control and protect the crop from weed competition, farmers use one or more herbicides to control their weeds. When Roundup Ready crops were first introduced many farmers used glyphosate alone to get their desired level of weed control. However, due to changes in weed communities, better understanding about best management practices to control weeds, and the occurrence of some weeds that have resistance to glyphosate, many farmers are now using practices that combine glyphosate and other herbicides and other methods (like cover crops and cultural methods) to control their weeds.

 

Thus, in some cases where Roundup Ready crops are used, herbicide use may be reduced compared to other weed control systems, in other circumstances herbicide use has roughly remained the same, and in certain cases to adopt best management practices or where there are new and emerging weed problems, additional herbicides are used to control the weed community. Shawn Askew, Extension Specialist and Associate Professor in the Dept. for Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University offers his perspective in this response to a similar question: Does GMO corn reduce the amount of herbicides used by farmers?

 

Additionally, Graham Brookes discusses this topic in the published journal article Weed control changes and genetically modified herbicide tolerant crops in the USA 1996-2012. He states, “The evidence shows that use of the technology has resulted in a net reduction in both the amount of herbicide used and the associated environmental impact, as measured by the EIQ indicator when compared to what can reasonably be expected if the area planted to GM HT crops reverted to conventional production methods.”  

 

The observation of changes in herbicide use rates are true of many other herbicides that have been introduced into agricultural use over the last 50 years. Andrew Kniss used free and accessible data from USDA-NASS to depict the trends of total herbicide use in corn from 1990-2014. He notes that, “total herbicide use in corn (in weight of herbicide applied) has remained relatively constant at about 2 to 2.5 lbs./acre since around 2000 (Top panel A). There have certainly been changes in which herbicides contributed to that total, though.”