Herbicides Making A Comeback
2 September 2011 US farmers are increasing their usage of older herbicides on a massive scale. The trend could provide opportunities for manufacturers and distributors poised to capitalize on the trend.
According to a Farm Chemicals International exclusive source who follows the global importation of active pesticide products, older active substances have been resurfacing to help manage glyphosate resistance in weeds.
There are several notable examples of higher adaptation of older chemistries. First, fomesafen, a postemergence used over the top of soybeans developed by Syngenta, has made a gigantic leap in recent years. Between the 2006/07 cropping season and 2010/11, consumption by US farmers has risen 16 times, or a 1,600% increase. Today, more than 20 companies originate fomesafen.
Second, acifluorfen, a postemergence control of annual broadleaf weeds, has risen rapidly, particularly under the United Phosphorus trade name Blazer. Between the 2008/09 cropping season and 2010/11, consumption by US farmers has risen six-fold. Acifluorfen was originally commercialized by Bayer AG, and today there are close to 10 companies that make a post-patent version.
A third chemistry on the upswing is lactofen, a herbicide that controls a wide variety of broadleaf weeds. In the 2010/11 cropping season, the US has imported more than 100 tons, most notably under Bayer’s Cobra label. Originally commercialized by PPG Industries, there are more than 10 companies that make a version of the chemistry.
Metolachlor, a preemergence and preplant incorporated weed control for corn, cotton, grain sorghum (seed treated with safener), peanuts, pod crops, potatoes, safflower, soybeans, and woody ornamentals, has been on the rise as well. Between the 2006/07 cropping season and 2010/11, consumption by US farmers has risen 300%. The active was originally commercialized by Syngenta and is sold by the company under the Dual label. There are more than 20 companies that make granule and emulsified concentrate formulations.
Also, the use of fluometuron, a herbicide formulated as a liquid, dry flowable or wettable powder, has doubled recently in the US, primarily because of weed resistance in Roundup Ready cotton varieties. The active was originally commercialized by Syngenta, and its recent uptick in sales has largely been attributed to Makhteshim Agan North America’s Cotoran label. There are close to 10 companies that originate the molecule today.
Although this data primarily outlines trends in the US, the resurgence of older chemistries could provide ample opportunities in other key markets as well, notably in South America where there is a high adoption of Roundup Ready technology. Most notably, Brazil and Argentina grow a significant amount of Roundup Ready soybeans and cotton. Additionally, with cotton’s high prices, markets like China and India could be a potential boon for crop protection product makers and distributors.
Don’t Forget Glufosinate
These legacy chemistries aren’t the only opportunity. Glufosinate makers could be poised to profit from glyphosate resistance as farmers increasingly opt for LibertyLink to help with their glyphosate resistance management. In some cases, crop advisors in the US are advocating for the complete rotation away from glyphosate-tolerant GMOs, specifically to Bayer’s Liberty Link, which relies on glufosinate for weed control. Again, this could provide notable opportunities in key cotton-producing markets. LibertyLink seeds for traditional row crops are beginning to gain favor with farmers as well.
• Glyphosate Continues To Take a Beating
Bill Johnson, professor of weed science at Purdue University, says that if LibertyLink technology is used more often there, it would help to slow the pace of resistance.
“We basically need to find new herbicides and try to diversify as much as possible with the herbicides that we have available so we can slow the development of resistance,” Johnson says.
If farmers do not rotate their chemicals, selection pressure could occur and weeds could become immune to the chemical. For the weeds, it is survival of the fittest and that isn’t what any farmer would want.
Natural Selection
Changes in weed populations begin when a small number of plants within a species, called a “biotype,” have a distinct genetic makeup that allows them to tolerate a particular herbicide application.
As a grower continues to use a particular herbicide without any other modes of action, or doesn’t use other cultural practices, resistant biotype continues to survive and produce seed.
Aaron Hager, associate professor of Weed Science from the University of Illinois, surveyed 122 waterhemp samples from 24 different fields in Illinois to see what percentages of plants were herbicide resistant in 2010. He found 28% were glyphosate resistant, and 13% were sensitive to ALS inhibitors, PPO inhibitors and glyphosate.
Furthering Education
Monsanto works to educate farmers on its products so they can get the full advantage. The company’s website is a centralized resource for getting useful facts about weed management, including how to reduce risk, how to manage it and how to receive rebates to offset some costs. Monsanto recommends farmers rotate their chemicals and often offers to subsidize chemical protocols.
“Weed resistance is an issue that farmers have confronted for decades and which has grown in complexity. We have a cost-effective system, under the Roundup Ready PLUS umbrella, which will work across farms as well as various crops, geographies and technologies,” says John Combest, media communications manager at Monsanto.
Multiple modes of action could result in weeds being resistant to 2,4-D. Dow AgroSciences will be coming out with a new form of 2,4-D choline product, Colex-D, which contains quaternary ammonium salt. It will provide the same weed control as previous products and provide growers new advantages for managing hard-to-control weeds. Various components of the system are currently pending US regulatory approvals.
Recommended Protocols
Almost all of the corn, soybeans and cotton grown in the US are Roundup Ready, says Dr. Mark Peterson, global biology team leader for Enlist herbicide traits of herbicide solutions for corn and soybeans from South Dakota State. By using Roundup Ready weed resistance practices, the system became easier for farmers. When farmers begin to notice that the weeds they are trying to manage could not be controlled, their first response is to add more glyphosate.
“It is better to utilize tools with old products,” says Dr. Peterson.
Dr. Peterson also suggests managing weeds can become simpler by using multiple modes of action. One way of management is use of a soil-applied herbicide and 2,4-D with glyphosate.
An example of this is using Sonic Combo then, as a top layer, use glyphosate and 2,4-D. This will give four different combinations.
David Wright, director of contact research of the Iowa Soybean Association, recommends farmers attend meetings to further education. In the summer and winter, meetings are held at either university extensions or chemical companies.
“For states that have the challenge of feeding the world, we cannot afford to make a mistake and make decisions that will reduce yields not increase yields,” Wright says.
If farmers notice a patch of weeds that have not been controlled even with the application of glyphosate, then the first step is diagnosis, which involves understanding if there are herbicide-resistant weeds in their field.
The second step is to stop using only glyphosate. Farmers need to diversify their weed control program. Soil-applied herbicides should be used on uncontrollable weeds which not only slows development of resistance, but it also offers maximum crop yields.
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