Weed Study Outlines Challenges Of Glyphosate Resistance

Dow AgroSciences study outlines importance of different modes of action, systems in fight against glyphosate resistance.

Published on: Aug 19, 2011

Since the introduction of the glyphosate-tolerant cropping system in 1996, growers have benefitted from the system's agronomic, economic and environmental advantages. These benefits are being challenged by a growing weed problem: glyphosate resistance. A recently released study1 quantifies the impacts of glyphosate resistance, and the potential implications of reverting to more costly weed control options.

The study, commissioned by Dow AgroSciences and conducted by the IHS Global Insight's Agriculture Group from information and analysis provider IHS, and James E. Nelson Consulting, concluded that glyphosate-resistant weeds now impact up to 20 million acres. Further, those weeds will reduce farm income by $1.9 billion this year, and up to $2.5 billion by 2017. Losses could total $22 billion over 10 years without the introduction of complementary herbicide-tolerant trait technology. Registration of Dow AgroSciences Enlist Weed Control System is pending.

Benefits at risk

According to figures from the U.S. Department of Agriculture, growers in 2009 planted 91% of soybean acres and 68% of corn acres with glyphosate-tolerant seed. The glyphosate system provides growers with benefits such as lower production costs, increased yields through reduced weed pressure, convenience and the ability to practice conservation tillage or no-till. Increased no-till helps reduce fuel consumption, reduces soil and nutrient loss from runoff, and increases carbon sequestration in the soil.

The study concluded that without complementary herbicide-tolerant trait technology such as the Enlist system, more farmers would have to revert to tillage to get adequate weed control. The authors predict the switch to tillage would occur on an estimated 1.2 million acres, resulting in 25 million tons of soil loss in addition to carbon emissions, and could affect water quality over the decade. Additionally, increased fuel usage from tillage would be equivalent to adding almost 180,000 cars on the road by 2020.

"No-till has helped growers decrease production costs and field time," says James Nelson, Ph.D., a technical agronomy consultant who worked on the study. "The economics of soybean production for many growers will be turned upside down if they have to use tillage to manage resistant weeds, and some growers will have to buy additional equipment."

Need for new technology
The study demonstrates that growers need new technologies to manage hard-to-control and resistant weeds to sustain the long-term viability of the glyphosate-tolerant system and preserve its multiple benefits. According to study results, the Enlist system has the potential to cut farm losses from resistant and hard-to-control weeds by 18 percent over a decade, translating into $4 billion in reduced costs for U.S. growers, and $563 million in consumer welfare.

"This research underscores the importance of preserving glyphosate-tolerant technology to help growers sustain the benefits from current herbicide-tolerant systems," says Damon Palmer, Dow AgroSciences U.S. commercial leader, Enlist Weed Control System. "The Enlist system will partner with and improve on the current glyphosate-tolerant system, allowing growers to continue to farm in an economically and environmentally sustainable way."

Pending regulatory approvals, the Enlist system will provide tolerance to a new 2,4-D product and will be stacked with the glyphosate-tolerant trait. The Enlist system - which is expected to be available in corn in 2013, followed by soybeans in 2015 and cotton in 2016 pending regulatory approvals - will help prevent and manage resistance to glyphosate by adding another mode of action to sustain the long-term viability of the glyphosate-tolerant system.

About the study

The impact study was conducted by the IHS Global Insight's Agriculture Group in partnership with James E. Nelson Consulting, which helped develop the economic benefits assessment for the study's report. The research was conducted through an in-depth evaluation of current grower weed control practices, interviews with university Extension weed scientists and case study scenarios on nine corn and soybean farms in Arkansas, Georgia, Illinois, Iowa, Minnesota and Ohio.

"We were able to: study, and take apart in detail, the weed control practices that growers are using today in corn and soybeans; and show the impact of practices that growers will be forced to implement as they adapt to glyphosate resistance without access to new technology," Nelson says. "By studying what growers are doing today, it's clear that they are going to have to make significant changes to manage resistant weeds, particularly in soybeans."

Researchers used agronomic and economic data to quantify estimated impacts at both the individual farm and national levels. A combination of farm case studies and interviews with Extension weed scientists was used to characterize specific geographic-based data and to identify current challenges and available options.

Scenarios compared alternative weed management options such as the use of conventional herbicides and tillage, to incorporation of new technology such as the Enlist Weed Control System. All scenarios were compared to a baseline that assumed no resistance problems. National-level benefits of the Enlist system were estimated by using the case study farm data in combination with a national average that examined factors driving economic impacts such as types of glyphosate-resistant weeds, methods of control, impact of tillage and input costs.