A panel discussion1 representing farmers, crop consultants, lenders, and scientists with different perspectives who identified common impediments to shifting to a new weed-management mindset
Ben Barstow, Past-President, Washington Association of Wheat Growers
Herbicide resistance is nothing new. The Pacific Northwest wheat industry experienced the equivalent of glyphosate-resistant Palmer amaranth in the early 1980s in the form of sulfonylurea (SU)-resistant prickly lettuce. In that case, the major registrant of SU herbicides voluntarily changed its labels to require tank mixes with alternate mechanisms of action. That voluntary strategy was able to preserve the effectiveness of SUs for another 20-30 years. Today, however, species that were hardest to control with those tank-mix products 30 years ago are now widely tolerant, if not resistant, to the combinations. I can remember 40 years ago, when my grandfather's primary weed control relied on mechanical cultivation. His worst weed problems were deep-rooted perennials, species most adapted to repeated tillage in our climate of dry summers. My point is strict reliance on any single control method, be it a class of chemistry or even mechanical tillage, eventually will select for a population that overcomes that control method. Further, this process happens just as readily in the absence of herbicide-resistant, genetically engineered crops as it does when their use is widespread.
One key to combating resistance is to keep as many strategies available as possible and to change strategies frequently. We have not done a very good job of that. Our toolbox for managing resistance has fewer tools than it once did, and new tools have become rare. Registrations of older chemistries are difficult to profitably maintain, and the flow of new chemistry has almost stopped. Regulators have targeted whole classes of chemistry for cancelation. Farm bill conservation strategies have encouraged farmers to eliminate tillage as an option to the point that many farmers no longer have the equipment to consider that option. Market forces sometimes discourage crop rotation, and farmers, after all, are human; if a control strategy is available, cheap, and effective, we will use it until it doesn't work anymore.
1Ken Root ably moderated this panel.
Chuck Farr, Crop Consultant, Mid-South Ag Consultants, Inc.
Q: Why do growers resist using best management practices for herbicide-resistant weeds?
A: I think this has many answers, but one of the major concerns is from the crop insurance industry. Growers who insure their crops or some who are just “insurance farmers” will plant a crop and put the least amount of inputs into a crop whether they have resistant weeds or not. They know that they are getting paid on yields or income and not on how well they manage resistant weeds. Therefore, they have no concerns for resistance. Also, there are still a small group of growers who think resistance is not on their farms. This is a small number, but there are still a few around.
Q: Do consultants make recommendations on best management practices or the one that has the easiest convenience?
A: I really think that all consultants make recommendations based on best management practices. Now there may be many choices in the best management practices, and we all tend to make the most logical recommendations based on mixing ability of herbicides or the pounds of material that may be used or ones that have rotation restrictions, but best management practices are a large part of our business.
Q: Are there recommendations you make that growers are particularly resistant to?
A: We do make recommendations that growers are resistant to. Generally these recommendations require more money than they budgeted for, an extra trip across the field, a product that requires a large amount of water during application, or an application that requires water or rainfall for activation. Growers do want to resist some recommendations, but they always make the recommended applications because they know the consequences if they do not.
Q: Where do you get your information about best management practices? Where do crop consultants get their information in general?
A: We get most of our information from other consultants in the business, from all university programs, from basic manufacturers’ development trials, and from our on-farm trials. We look for trends in what works and what does not. We feel very comfortable with the science that we have to make recommendations. The major problem that we have is the lack of currently available products and the lack of products in development that we have to choose from. We are very limited in our product selection with weed resistance.
David Miller, Director of Research and Commodity Services, Iowa Farm Bureau Federation
I farm approximately 550 acres (corn-soybean rotation) in the central part of southern Iowa. As far as I know, I do not have a problem with herbicide-resistant weeds on my farm. Some of the management practices that I use to minimize the risk of weeds developing herbicide resistance on my farm include regular crop rotation, use of multiple herbicide technologies, and avoidance of “half-rate” applications.2
But the question to be addressed is, “What are the impediments to using best management practices?” I believe the primary impediment is the near-term costs associated with implementation of best management practices to forestall a problem that may or may not develop at some unspecified time in the future. The corn seed I buy often has multiple stacked traits. Imbedded in the cost of that seed are technology fees for these traits. I pay those fees even if I choose to use a different herbicide and not use the herbicide-resistant trait incorporated into the seed. I do this because I want (or need) the other traits contained in the stack, but the choice to not use the herbicide-resistant trait can result in a $15 to $20 per acre increase in my herbicide costs in those years when I use alternative herbicide technologies.
The second most important deterrent to implementing best management practices with respect to minimizing herbicide resistance in weeds is strict adherence to no-till production practices. Eliminating tillage from the production protocol increases reliance on post-emergence herbicides and, realistically, on glyphosate-based formulations.
There are other impediments to using best management practices for managing herbicide resistance in weeds. They include weather-induced delays that can result in untimely herbicide applications, monoculture crop rotations due to dominant economics for that particular crop, and the “ease” of using a single herbicide technology across multiple crops, rotations, and geographies.
Steve Reeves, Vice President, Bank of Fayette County
Lending institutions have to be careful as to how they guide producers because of lender liability laws. I encourage best farm practices such as rotation, mowing end rows before weed seeds mature, and applying recommended herbicide application rates. As I perform preseason cash flows, all formulas are based on the recommendations. Any variance could result in changes in the net income to the producer. I do see the possibility of herbicide-resistant weeds adding to the variable cost (e.g., labor, fuel, and herbicide) in the future as farm margins are narrowing.
Dale Shaner, U.S. Department of Agriculture, Agricultural Research Service
The major impediment to using best management practices from an industry point of view is the difficulty in coordinating recommendations except in general terms. The
2Half-rate application refers to using less than the amount of herbicide recommended on the label instructions.
Herbicide Resistance Action Committee, which is a committee of technical representatives from the major agrichemical companies, was created in the 1980s to deal with the rising problems of resistance to ALS and ACCase inhibitors as well as the more established triazine resistance. This committee, of which I was the chair for four years, was and still is very active in developing and publishing guidelines on managing herbicide resistance and in creating and supporting a web-based database on the instances of herbicide-resistant weeds. However, this committee is confined to technical issues and for legal reasons does not get involved in marketing issues. Industry has been criticized for acting too slowly when resistance is selected for new mechanisms of action, such as the HPPD or PPO inhibitors, but it takes time to really understand the extent of the problem and to determine how to best deal with it. Industry has been very active in urging the maintenance of registration of older herbicides that are vital tools for resistance management. With the advent of widespread glyphosate-resistant weeds, industry also is re-emphasizing the discovery of herbicides with new mechanisms of action. Industry has been supportive of regulations that actually deal with herbicide resistance, such as the addition of mechanism of action group identification to the label, but each company is reluctant to implement new strategies without the participation of all of the companies. Unilateral action can be nonproductive if it is not supported by other companies. This will continue to be an impediment for implementing best management practices and can undermine university and governmental recommendations unless industry is an active participant in developing these practices.
Prickly lettuce (Lactuca serriola), courtesy of Stan Shebs (http://commons.wikimedia.org/wiki/File:Lactuca_serriola_3.jpg).