A quick post today on a recent report of resistance to glufosinate, the active ingredient in Rely herbicide (also sold as Liberty, Ignite, Basta, etc in other markets).
Researchers in Malaysia reported a few years ago on a population of goosegrass resistant to glufosinate in vegetable and orchard systems (Lee L J & Ngim J (2000). A first report of glyphosate-resistant goosegrass (Eleusine indica (L) Gaertn) in Malaysia. Pest Management Science, 56, 336-339). For a number of years this was the only reported case of resistance to this herbicide.
At a meeting last month, I saw a presentation by Wilson Avila and Carol Mallory-Smith from Oregon State University documenting the first case of glufosinate resistance in North America. Wilson's presentation at the Weed Science Society of America meeting was entitled "INVESTIGATING CROSS-RESISTANCE TO GLUFOSINATE IN GLYPHOSATE-RESISTANT ITALIAN RYEGRASS POPULATIONS. W. V. Avila*, C. Mallory-Smith; Oregon State University, Corvallis, OR (abstract #292)" showed that three previously characterized glyphosate-resistant ryegrass populations also were somewhat resistant (about 2-fold) to glufosinate. They are still trying to figure out the mechanism(s) of resistance; however, it does not appear to be a site-of-action mutation according to Wilson.
To my knowledge, this is the first case of cross-resistance to both glyphosate and glufosinate. Given the increasing importance of Rely in California orchard and vineyard systems, it is more important than ever to use good practices to minimize the dependence on one herbicide for weed control. No weed control system is immune to resistance or weed shifts - if you depend entirely on one control tactic, you eventually run into trouble with it.
I'll probably post on this again as new information on glufosinate-resistant ryegrass becomes available.
Brad
Mar 6, 2011