- Impacts on Herbicide Use
- Impacts on Use
- Net Impacts of Crop Technology
- 2012 Environmental Sciences Europe Paper
- Glyphosate Use
- 2,4-D and Dicamba
Pesticide use encompasses the applications of herbicides, on pesticide use is the crop technologynet change , fungicides, soil fumigants, and several other types of pesticides targeting other organisms. Accordingly, the impact of in total pesticide use brought about by the planting of crops, compared to what pesticide use would likely be on cropland planted to non- seeds.
Impacts on Herbicide Use
Genetically engineered (herbicide-tolerant (HT) cotton and soybeans were commercialized in 1996 and quickly transformed weed management systems. HT corn followed a few years later. Prior to 1996, there had been very little meaningful independent research on the costs, benefits, and risks of -HT technology.
The vast majority of HT crops have been modified to tolerate post-emergent applications of the broad-spectrum herbicide glyphosate (Monsanto’s Roundup, and many other brands). So-called “Roundup Ready” (RR) crops account for around two-thirds of all acres planted globally to crops since 1996. As glyphosate use rose sharply, the use of other herbicides declined, at least for the first five to 10 years of steady use.
Over time, excessive reliance on one weed management tactic (herbicides), and one herbicide (glyphosate), triggered shifts in weed communities to species less sensitive to glyphosate. It also led to the emergence of weed that were first partially tolerant of glyphosate, and eventually resistant to it. Both shifts forced conventional farmers to spray additional herbicides, apply some herbicides more than once, and often at higher rates per acre.
Independent weed scientists had warned since the early 1990s that excessive reliance on glyphosate and RR technology would trigger the emergence and spread of resistant weeds, warnings that were dismissed by Monsanto and other industry leaders. Instead, the pesticide-seed industry promised that crops would reduce pesticide use, a claim that soon became part of the often-repeated PR advanced by proponents of crop technology.
Yet glyphosate is a relatively high-dose herbicide, typically applied at a one-time rate of between 0.66 and 0.75 pounds per acre. As farmers adopted RR crops and came to rely largely on glyphosate, over a dozen low dose (~ 0.1 pound/acre) and another near-dozen very low dose (~ 0.01 pound/acre) herbicides were displaced.
This dramatic shift in herbicide choices led to an obvious question — how could replacing herbicides applied mostly at 0.01 to 0.1 pound/acre with a herbicide (glyphosate) applied at 0.66-0.75 pounds/acre reduce overall herbicide use?
To address this question, Chuck Benbrook began a series of analyses quantifying the impact of crops on pesticide use. The resulting reports are listed from most recent to oldest below. The last item below — a 1986 paper in Technology Review paper — is one of the first published discussions of the likely impact of -HT technology on herbicide use.
About one-third of all acres planted to crops since 1996 have been engineered to express Bacillus thuringiensis () throughout the tissues and roots of corn and cotton plants. So-called corn and cotton manufacture their own, natural bioinsecticide targeting certain Lepidopteran insects like the European corn borer, corn rootworm, and the cotton budworm. See the Ag Biotech section on for much more on this technology. Transgenic Crops
By reducing the need for targeting insects susceptible insects to the expressed , crops reduce the use of conventional net impact . But they also add insecticidal toxins to the environment and food supply, and hence, the of crops on use must take both the reduction and expression of toxins into account.
crop technology modestly reduced use in the first decade of use, but recently has actually increased net use because of the trend toward varieties of corn and cotton that express two to six different . For example, Monsanto-Dow’s SmartStax corn expresses over 3.5 pounds of toxins per acre, while displacing perhaps 0.2-0.5 pounds of use.
crop technology has reduced conventional use modestly for another reason — the pesticide industry has made steady progress since 1996 in discovering and commercializing that are applied at much lower rates than products typically used before the introduction of corn and cotton. Over the last decade or so, most corn and cotton displaced by crop technology have been applied at rates at or below 0.2 pound per acre.
Moreover, over the last decade, resistance has spread in many insects targeted by corn and cotton, despite the planting varieties expressing multiple and coating seeds with one to three insecticidal seed treatment. The declining efficacy of most common has forced many farmers to once again spray conventional , essentially eliminating the once-modest reduction in use.
Net Impact ofCrop Technology
Nearly all acres planted to corn and cotton are also Roundup Ready. Accordingly, the net impact of crop technology on pesticide use must take into account the reduction in conventional use, the volume of expressed, and the net change in herbicide use.
For the first few years of crop use, the technology brought about a modest, overall reduction in pesticide use. By the early 2000s, however, increases in herbicide use dwarfed modest reductions in net use. In each year over the last decade across the three major crops (corn, cotton, soybeans), total herbicide use has risen, the volume of expressed has gone up, and about one-half the early reduction in use has fallen by the wayside as more and more farmers spray corn and cotton in the hope of slowing the spread of insects resistant to the expressed in - crops.
Further details on trends in pesticide use on crops are provided in the following sections.
Benbrook Papers and Reports on the Impact ofCrops on Pesticide Use:
Benbrook, C. 2016. Trends in the use of glyphosate herbicide in the U.S. and globally. Environ. Sci. Europe 28:3 doi 10.1186/s12302-016-0070-0
Benbrook, C. 2012. “Impacts of Genetically Engineered Crops on Pesticide Use in the U.S. – the First Sixteen Years,” Environmental Sciences-Europe, 24:24.
Benbrook, C. 2009. “Impacts of Genetically Engineered Crops on Pesticide Use in the United States: The First Thirteen Years,” Critical Issue Report, The Organic Center.
Benbrook, C. 2004. “Impacts of Genetically Engineered Crops on Pesticide Use in the United States: The First Eight Years” Ag BioTech InfoNet Technical Paper #6.
Benbrook, C. 2001. “Do GM Crops Mean Less Pesticide Use?”, Pesticide Outlook, Royal Society of Chemistry, October.
Benbrook, C., and Moses, P. 1986. “Engineering Crops to Resist Herbicides,” Technology Review, MIT Press, 89 (8): 55‑61, 79.
The 2012 Environmental Sciences Europe Paper
- The Paper
- WSU Press Release
- “Hard lessons emerge from new study on the impacts of crops on pesticide use,” October 2, 2012 WSU Blog Post by Charles Benbrook
Use of the glyphosate herbicide has increased dramatically in the years since the introduction of glyphosate-tolerant crops. Data from the shows that over three quarters of corn acres and nearly all of soybean and cotton crops in the US are now treated with glyphosate.
Glyphosate is now, by far, the most heavily applied pesticide in the U.S., and globally, in history. Enough glyphosate was applied on U.S. cropland in 2014 to spray about 0.8 pounds of on every cropland acre in the country.
Worldwide, enough glyphosate is now applied each year to spray about 0.5 pound of this one herbicide on every cultivated cropland acre on the planet.
The unprecedented volume of glyphosate now applied annually is why concern has grown so acute over the spread of resistant weeds, the collapse of glyphosate-dependent weed management systems, this herbicide’s environmental effects, and human exposures and risk. See the items below for more details.
- “Trends in glyphosate herbicide use in the United States and globally,” Dr. Charles Benbrook (2016). Environmental Sciences Europe 28:3. DOI 10.1186/s12302-016-0070-0
- February 2, 2016 EWG Press Release “Study: Monsanto’s Glyphosate Now Most Heavily Used Weed-Killer in History; Nearly 75 Percent of All Glyphosate Sprayed on Crops in the Last 10 Years”.
- Detailed FAQs on Findings, Health Implications, and Funding
Other Glyphosate Resources:
- “Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement”, Myers et al., 2016. Environmental Health, 15:19. DOI 10.1186/s12940-016-0117-0).
2,4-D and Dicamba
Problems triggered by the spread of glyphosate-resistant weeds in corn, soybean, and cotton crops continue to worsen. Industry sources project that over 100 million acres in the U.S. are now infested with one or more glyphosate-resistant weed, and over 30 million are infested with two or more. The presence of glyphosate-resistant weeds forces farmers to add additional herbicides to their control programs, and apply herbicides more often and/or at higher rates. Weed control costs have gone up by $25 per acre, to well over $75 per acre (two or more resistant weeds).
The primary response by the biotechnology-seed industry has been to develop a second-generation 2,4-D or dicamba have been approved, or are coming on the market soon. Many of these -HT crops are also tolerant of glufosinate (Liberty herbicide), as well as the “fop” family of ~ six grass herbicides. -HT crops that can tolerate direct applications of multiple herbicides. New varieties of cotton, soybeans, and corn engineered to tolerate the phenoxy herbicides
The basic hope is that glyphosate-resistant weeds can be controlled, and new ones avoided, by hitting weeds with three or four different chemical modes of action. But more intensified spraying will also increase selection pressure, thereby hastening the emergence of weeds resistant to multiple herbicides. This harsh reality is likely to push the herbicide treadmill into an even high gear, unless the industry and/or government takes decisive steps to assure that farmers adopt essential herbicide resistance management plans.
Many weed scientists and farm leaders have expressed concerns over the pending approval of 2,4-D and dicamba-tolerant crops.
Dr. Benbrook’s concerns were communicated to the via June 30, 2014 comments submitted to the agency’s public docket on the choline salt formulation of 2,4-D. Excerpts from these comments follow:
“The pending decisions by and over whether to allow unlimited planting of 2,4-D and dicamba herbicide-tolerant crops will, in all likelihood, be the most consequential to occur over my 30+ year career working on the evaluation of agricultural pest management systems and technology.”
“If the technologies are approved, and should take several actions to:
- Reduce the risk of collateral damage,
- Rapidly detect it, if and as it occurs, and
- Quickly take actions to prevent the damage from spreading, as it surely would if 2,4-D and dicamba-resistant crops come to dominate corn, soybean, and cotton production to the degree Roundup Ready technology has been embraced by farmers.”
Further Information on 2,4-D and Dicamba Tolerant-Crops
- Projections of 2,4-D Use on Three Major Crops if Next Generation 2,4-D Crops are Approved Without Restrictions
- Historical Use of 2,4-D on Major Crops
- Historical Use of Dicamba on Major Crops
- Comments to on 2,4-D Health Risks from 70 Health Care Professionals
- Reproductive Impacts and Birth Defects Associated with 2,4-D Exposures: Bibliography with Abstracts
- Cancer Risks Associated with 2,4-D Exposures: Bibliography with Abstracts
- Human Health Risks Associated with Dicamba Exposures: Bibliography with Abstracts