- Author: Daniel H Putnam
“A stitch in time saves nine” – (e.g. one little repair saves a big one...but of course, who stitches anymore?)
For the majority of you out there who don't sew, here’s the point: Maybe, just maybe, it is a good idea to prevent something bad from happening rather than waiting for it to happen!
Such is the case for the prevention of weed resistance in Roundup-Ready (glyphosate-tolerant) alfalfa. In a recent posting on the UC Weed Science Blog, Dr. Brad Hanson (Weed Science Specialist, UC Davis) points out the need for prevention of weed resistance in several crops, using alfalfa as a case in point.
“Just like other RR cropping systems, alfalfa growers have a new opportunity to selectively control weeds using a simple, reliable, and effective strategy,” Hanson says. “The biggest risk for weed shifts and resistance will be if alfalfa growers use ONLY glyphosate herbicides in these crops.”
Hanson, along with other weed scientists from UC, Fresno State and private industry have prepared a series of articles and presentations for an upcoming volume of the California Weed Science Society Research Update and News http://www.cwss.org/CWSSJournal/2013_01_CWSSResearch.pdf). The Weed Science Conference will be held January 23-25, 2013 in Sacramento (see www.cwss.org).
Weed resistance to glyphosate (Roundup) has been a major and increasing problem for cotton, corn, canola and soybean farmers, and it is not a stretch to see that it could be a major issue for alfalfa growers as well.
There are a range of common-sense techniques available to growers to prevent weed shifts and weed resistance in alfalfa, including crop rotation and diversification of herbicides. The 2009 publication "Avoiding Weed Shifts and Weed Resistance in Roundup Ready Alfalfa Systems" by S. Orloff, D. Putnam, M. Canevari, and T. Lanini details widely-recognized techniques to prevent unwanted weed resistance and weed shifts to glyphosate-tolerant weeds. You can download this free UC publication (#8362) as well as hundreds of others at http://anrcatalog.ucdavis.edu/.
Roundup Ready alfalfa was introduced in 2005 but new plantings were stopped by a lawsuit in early 2007. After an extensive 4-year review by USDA-APHIS, RR alfalfa was found to be no different than conventional alfalfa in plant pest risk or impacts on threatened or endangered species. It was re-released in January 2011. US growers have been planting RR alfalfa since that time. Steve Orloff wrote a nice summary of grower experiences here. The many issues surrounding Roundup-Ready alfalfa systems (efficacy, coexistence) were reviewed extensively at the 2011 Western Alfalfa and Forage Symposium in Las Vegas (see: Biotechnology and Roundup Ready Alfalfa at the Alfalfa Workgroup Website).
Hanson finds it imperative that alfalfa growers pay attention to what has happened in other crops. “It is clear that if alfalfa growers make the same mistake that soybean, cotton, and corn producers made and only use glyphosate, there will undoubtedly eventually be problems with resistance or shifts to tolerant species.” In the Orloff et al. publication, weed shifts away from annual bluegrass and shepherd's purse to burning nettle and sowthistle were documented within a very short time.
The authors recommended using other conventional herbicides and crop rotation as part of an integrated weed management program in RR alfalfa.
Hanson reminds folks that RR technology should be used to EXPAND selective weed control choices NOT REPLACE all others; otherwise, a very useful weed management tool could have a very short useful lifespan.
Several publications that would be useful on this issue of weed resistance in alfalfa are:
- Avoiding Weed Shifts and Weed Resistance in Roundup Ready Alfalfa Systems
- Roundup Ready Alfalfa - What Have We Learned to Date?
- Roundup Ready Alfalfa - An Emerging Technology
- UC Weed Science blog alfalfa posts
- Roundup Ready alfalfa info at Biotechnology and Roundup Ready Alfalfa
Ben Franklin Quote for the Day: “An ounce of prevention is worth a pound of cure.”