4A: Weed Management System Change

The phrase “Many Little Hammers” is widely used to describe a diverse approach to weed management, as in this American Society of Agronomy report.

As herbicide use rose and resistant weeds began to spread, weed scientists began to raise concerns about the reliance on herbicide use for weed control. Around the same time period, organic agriculture was being standardized and regulated; USDA’s National Organic Program was founded in 2000.

These circumstances led the formalization of an ecological approach to weed management that became known as “integrated weed management (IWM).”  IWM is “characterized by the use of sets of farming practices that as a group suppress weed emergence, survival, growth, resource use, and competition against crops” (Liebman, 2017).  The two key elements of IWM are using several different weed control methods, possibly including some herbicide use, and varying crop densities and rotation to, in a sense, keep the weeds guessing.

There is near-universal agreement on the recommended alternative to weed management systems that rely too heavily on herbicides. Instead, academic weed scientists and professional societies urge farmers to use “many little hammers” in controlling weeds (Davis et al., 2012; Evans et al., 2015Fisher, 2012; Harker et al., 2012; Mortensen et al., 2012, Zimdahl, 2011).

Through the integration of a set of mechanical (e.g., tillage), chemical (herbicides), and cultural (cover crops, crop rotation) practices, farmers can successfully manage weeds in the long-run, while minimizing costs and collateral damage.

Most conventional corn and soybean producers do not deploy such systems, however, because of their near-universal embrace of genetically engineered-herbicide resistant (GE-HR) technology and the well-financed and effective public relations and marketing efforts promoting the technology.

Individual producers and farm management companies can implement a variety of proven changes in weed management systems that will help reduce reliance on herbicides and prevent the further spread of resistant weeds. On many farms, this process began a few years ago, and will likely spread to others as the cost of dealing with resistant weeds rises further.

There are several non-herbicide weed control options available including  (from left to right): tillage (Photo: KBS LTER), corn and soybean rotation (Photo: OSU), mechanical control, and the use of cover crops such as this rye grass in a winter corn field.

One of the most important tactical decisions will be whether to plant newly approved, multiple herbicide GE-HR seeds. Hopefully, these new varieties will be planted sparingly on fields with the worst infestations of glyphosate-resistant weeds, or not at all.

This outcome is unlikely, however, given that the pesticide-seed-biotech industry has plans to move the new, multiple HR traits into most of the corn and soybean seed supply within the next three years.

Farm industry groups such as the American Soybean Association and the National Corn Growers Association have an important role to play in efforts to minimize herbicide use and exposure.

Some farm organizations are already working to address worrisome trends in the cost and intensity of herbicide use. But the organizations that represent farmers will have to do more if they hope to bring about meaningful change.

A clear and consistent message must be sent to the pesticide-seed-biotech industry, and the EPA, that farmers not only will accept, but support science-based, mandatory resistance management requirements as part of the mandatory directions for use on herbicide labels, and/or in the technology use agreements farmers must sign when purchasing GE-HR seeds.

Attitudes among farmers are shifting, because GE-HR technology is clearly not working as well as it once did, and a growing portion of farmers worry that the technology may be rendered obsolete within just a few years.

Plus, costs are escalating at a time when crop prices are dropping. Farmers alone pay the price for dealing with resistant weeds on their farm, a problem they were told would not arise back in the late 1990s when GE-HR technology was introduced with great fanfare.  Farmers, their families and neighbors must also contend with the adverse impacts of herbicide drift on both plant life and human health.

“Farmers alone pay the price for dealing with resistant weeds on their farm. Plus, farmers, their families and neighbors must contend with the adverse impacts of herbicide drift on both plant life and human health.”

Many farm organizations manage check-off programs that generate research funding. Nearly all farm groups also work the political process to increase state and federal funding for agricultural research, and provide guidance when a change is needed in research priorities.

An incrementally rising portion of both check-off financed and government research on weed management systems should be dedicated to three key needs:

  • Better, real-time data on the spread, number, and severity of resistant weeds;
  • New, non-chemical methods and multi-tactic systems to prevent the emergence of resistant weed phenotypes, and slow their spread once created; and
  • Monitoring of exposure levels and health-status on selected farms using a diversity of weed management systems, to amass more precise, real-world data on practical interventions to reduce human exposures and risk.

 The most viable way to reverse the trend toward more intensive herbicide use would be for farmers, farm organizations, and the pesticide-seed-biotech industry to develop a multi-faceted plan to aggressively mitigate resistance.

Given the economic and political climate, the spark for change in weed management needs to come from farmers and farm industry groups, not from the government or the pesticide industry.

The need to do so is compelling, and how to accomplish this goal is clear, but there is no precedent, nor model or path to achieve such a monumental change in farming systems and technology.

Plus, and regrettably, opinions differ on whether there is even any need for change.

The current, GE-based business model adopted by the pesticide-seed-biotech industry is producing healthy profits and returns to investors, especially for the major companies developing and holding patents on GE-HR technology. For these reasons, it is unlikely that the science acumen and political clout of the industry will be brought to bear in promoting adoption of multi-tactic, prevention-based weed management systems.

This is why the spark for change, and the energy needed to drive it, will have to come from farmers and farm organizations, with support from government science and regulatory agencies.

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