Photo: Crops in Eastern Washington. © 2007 Delena Norris-Tull
Herbicide Resistant Crops
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Biological discoveries regarding the genetic traits that enable noxious weeds to become herbicide resistant led to the development of herbicide resistant crops.
According to Hellerstein, et al., 2019, “Corn, cotton, and soybean growers have widely adopted genetically engineered…herbicide-tolerant… and insect-resistant… seeds since 1996. By 2018, 90 percent of corn, cotton, and soybean acres planted in the United States used [herbicide-tolerant] seeds, and 80 percent of corn and cotton acres used seeds also containing [insect-resistant] traits.”
Green, 2007, provides some history of this technological development, along with explanations of the genetic mutations that make it possible to develop herbicide-resistant crop seeds. Green stated that, “The increasing use of HRCs [herbicide-resistant crops] reduced the opportunity for new herbicide active ingredients and made the industry reluctant to invest capital because of shrinking market opportunities… As the use of glyphosate increased, the use of other herbicides decreased and pressured industry to reduce support of product registrations. Additionally, as herbicide markets declined, the number of chemicals that must be screened to discover a new herbicide increased from less than 1,000 in 1950 to more than 500,000 today… The first HRCs used traditional breeding methods and were modestly successful… The revolution with HRCs really began in 1996, when transgenic glyphosate-resistant soybeans were first sold … In 2004, herbicide-resistant corn, canola…, cotton…and soybeans accounted for 72% of the transgenic crop hectares… Despite concern about an overreliance on glyphosate for weed management, the use of glyphosate and glyphosate-resistant crops is still rapidly growing and expanding into other crops and turfgrass.”
Green, 2007, points out that, “Since the discovery of 2,4-D, no innovation has had as much impact on weed management as glyphosate-resistant crops. Glyphosate-resistant crops provide growers with a highly effective weed control program that has less risk of crop injury. Glyphosate has been so effective that some growers have abandoned other weed control technologies. Today, glyphosate resistance is the most widely planted transgenic trait, and use is still increasing. Unfortunately, the risk of glyphosate-resistant weeds evolving increases with the increased use of glyphosate.”
Green, 2007, found that, “Glyphosate-resistant technologies are generally perceived as safe to crops; however, there are concerns about unwanted effects for residual glyphosate in sensitive tissues, increased sensitivity to diseases, increased fruit abortion, reduced pollination efficiency, increased sensitivity to environmental conditions, difference in agronomic characteristics…, and soybean yield reduction.”
Green, 2007, stated that an analysis of “potential risk factors in herbicide-resistant canola… identified the following risk factors: reduced biodiversity, limited herbicide options, outcrossing with closely related weed species, and resistant weeds,” with the emergence of additional herbicide-resistant weeds being the greatest risk.
Green, 2007, found that, while in some cases, farmers that use herbicide-resistant crops used more herbicide, in most cases, the use of herbicide decreased, thus lowering expenses. Because of the increase in herbicide-resistant weeds, an economic analysis done in 2005 indicated that, in the long-term, the use of multiple herbicides is economically justified. However, Hellerstein, et al., 2019, reported that, “Herbicide application rates per planted acre in 2014 compared to 2010 were up 21 percent for corn, 25 percent for cotton, 26 percent for wheat, and 24 percent for soybeans.”
Blatt, 2020, reported that the benefits of the widespread use of glyphosate-resistant crops worldwide has included much-needed increased crop yields, increased use of no-till farming, and reduced fuel consumption in agriculture. But the cross-pollination of herbicide-resistant crops with nearby weeds has resulted in the rapid expansion of herbicide-resistant weeds, sometimes called superweeds. This has resulted in farmers using more herbicides rather than less.
References:
Links to additional information on Herbicide Resistance:
Next Sections on Herbicides and other Pesticides:
Herbicide Resistant Crops
Summaries of the research and commentary by Dr. Delena Norris-Tull, Professor Emerita of Science Education, University of Montana Western, October 2020.
Biological discoveries regarding the genetic traits that enable noxious weeds to become herbicide resistant led to the development of herbicide resistant crops.
According to Hellerstein, et al., 2019, “Corn, cotton, and soybean growers have widely adopted genetically engineered…herbicide-tolerant… and insect-resistant… seeds since 1996. By 2018, 90 percent of corn, cotton, and soybean acres planted in the United States used [herbicide-tolerant] seeds, and 80 percent of corn and cotton acres used seeds also containing [insect-resistant] traits.”
Green, 2007, provides some history of this technological development, along with explanations of the genetic mutations that make it possible to develop herbicide-resistant crop seeds. Green stated that, “The increasing use of HRCs [herbicide-resistant crops] reduced the opportunity for new herbicide active ingredients and made the industry reluctant to invest capital because of shrinking market opportunities… As the use of glyphosate increased, the use of other herbicides decreased and pressured industry to reduce support of product registrations. Additionally, as herbicide markets declined, the number of chemicals that must be screened to discover a new herbicide increased from less than 1,000 in 1950 to more than 500,000 today… The first HRCs used traditional breeding methods and were modestly successful… The revolution with HRCs really began in 1996, when transgenic glyphosate-resistant soybeans were first sold … In 2004, herbicide-resistant corn, canola…, cotton…and soybeans accounted for 72% of the transgenic crop hectares… Despite concern about an overreliance on glyphosate for weed management, the use of glyphosate and glyphosate-resistant crops is still rapidly growing and expanding into other crops and turfgrass.”
Green, 2007, points out that, “Since the discovery of 2,4-D, no innovation has had as much impact on weed management as glyphosate-resistant crops. Glyphosate-resistant crops provide growers with a highly effective weed control program that has less risk of crop injury. Glyphosate has been so effective that some growers have abandoned other weed control technologies. Today, glyphosate resistance is the most widely planted transgenic trait, and use is still increasing. Unfortunately, the risk of glyphosate-resistant weeds evolving increases with the increased use of glyphosate.”
Green, 2007, found that, “Glyphosate-resistant technologies are generally perceived as safe to crops; however, there are concerns about unwanted effects for residual glyphosate in sensitive tissues, increased sensitivity to diseases, increased fruit abortion, reduced pollination efficiency, increased sensitivity to environmental conditions, difference in agronomic characteristics…, and soybean yield reduction.”
Green, 2007, stated that an analysis of “potential risk factors in herbicide-resistant canola… identified the following risk factors: reduced biodiversity, limited herbicide options, outcrossing with closely related weed species, and resistant weeds,” with the emergence of additional herbicide-resistant weeds being the greatest risk.
Green, 2007, found that, while in some cases, farmers that use herbicide-resistant crops used more herbicide, in most cases, the use of herbicide decreased, thus lowering expenses. Because of the increase in herbicide-resistant weeds, an economic analysis done in 2005 indicated that, in the long-term, the use of multiple herbicides is economically justified. However, Hellerstein, et al., 2019, reported that, “Herbicide application rates per planted acre in 2014 compared to 2010 were up 21 percent for corn, 25 percent for cotton, 26 percent for wheat, and 24 percent for soybeans.”
Blatt, 2020, reported that the benefits of the widespread use of glyphosate-resistant crops worldwide has included much-needed increased crop yields, increased use of no-till farming, and reduced fuel consumption in agriculture. But the cross-pollination of herbicide-resistant crops with nearby weeds has resulted in the rapid expansion of herbicide-resistant weeds, sometimes called superweeds. This has resulted in farmers using more herbicides rather than less.
References:
- Blatt, T. (Winter, 2020). Superweed saga: Australia’s creative tools to fight herbicide-resistant weeds. In Harvard International Review, vol. 41, A quiet desperation: Modern agriculture and rural life, pp. 48-50.
- Green, J.M. (Apr-June, 2007). Review of glyphosate and ALS-inhibiting herbicide crop resistance and resistant weed management. Weed Technology, 21(2): 547-558.
- Hellerstein, D., Vilorio, D., & Ribaudo, M. Eds. (May, 2019). Agricultural resources and environmental indicators, 2019. USDA, Economic Research Service.
Links to additional information on Herbicide Resistance:
- Herbicide Resistance in Invasive Plants
- Controlling herbicide-resistant weeds in herbicide-resistant crops
- Best Management Practices
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