New herbicide technology needed

Introduction of new technology can change the world of agricultural production. The biggest example is how Roundup Ready crops, which allowed Roundup herbicide to be applied postemergence over emerged crops changed crop production in the U.S. beginning in 1996.

In a Rabobank report in 2012, a “Rabo AgFocus” noted how agricultural production practices were altered substantially with the introduction of soybeans which were resistant to the active herbicide ingredient glyphosate, sold by Monsanto under the trade name Roundup. Farmers jumped into using the herbicide and traited seed fast.

Every company introducing a new weed-control technology for the future is trying to steward their herbicide programs/platforms much more different than the Roundup Ready era. Farmers are thought to have learned some important lessons, too.

The history of Roundup Ready technology introduction and why weed resistance has occurred was outlined by the bank as follows.

This (Roundup Ready) allowed farmers to plant soybeans and spray Roundup for complete weed control, even on a post-emergence basis. Rapid adoption of the new technology was driven by cost savings from the reduced total herbicide applications and the significant convenience gained from a one-size-fits-all weed management program.

As a result of the unprecedented effectiveness of the new technology, soybean production became more profitable and expanded from 25 percent to 32 percent of the total major crop plantings in the United States within five years. Although over time profitability decreased as the cost of the seed specifically engineered to resist glyphosate rose, farmers have been able to better control a wide spectrum of weeds for no more cost than previous methods. Consequently, the value of soybean production as a rotation crop and, depending on the region, as a replacement crop for wheat and cotton increased.

By the mid-2000s, over 90 percent of soybeans planted in the US were glyphosate resistant. Due in part to the new ease of weed control, production practices that minimized tillage became increasingly prevalent.

As a result, many producers moved to two post-emergence applications of the herbicide each season. In cases where pre-emergence application was used, glyphosate was frequently the herbicide of choice. In many cases, glyphosate was even effective enough to allow farmers to apply lower rates than the label recommendations.

Within five years of the introduction of widespread annual application of glyphosate, a weed population with resistance to the herbicide began to be identified. Introduction of glyphosate-resistant corn and cotton in the early 2000s exacerbated the problem by expanding resistance selection from continuous soybean fields to fields where rotation was occurring. The geographically wide area of glyphosate utilization across different crops saw an increase in weeds resistant to glyphosate. Some of these weeds had already developed resistance to one or more other herbicides or modes of action. By 2011, 13 weed species with resistance to glyphosate had been identified in the US, with over 85 confirmed biotype observations in 28 states. Of the confirmed biotype observations, 15 percent were resistant to more than one mode of action (MOA).

The increasing prevalence of weeds with resistance to one or more herbicides, including glyphosate, is increasing the cost of row crop production in the US. Soybeans and cotton are the most susceptible of these crops as they have fewer chemical options for controlling key weeds which are developing resistance to multiple herbicides.

While chemical herbicides will remain the primary control mechanism of choice, tillage is likely to increase. Glyphosate will continue to be an important platform for weed control; however, a variety of modes of action will need to be made available in order to supply much more robust soybean weed management programs.

Concurrently, new seed products will be required to increase chemical diversity while allowing farmers to continue low tillage practices. In addition, a widespread return to older chemistries to add diversity to herbicide rotations is likely. Corn planting is likely to increase in the Midwest and eastern Corn Belt in the near-to-medium term as soybean production margins decline relative to soybeans.