A real mare's tale: glyphosate-resistant horseweed has been confirmed in Tennessee and suspected in Kentucky. What can you do about it?

摘要

What some Tennessee farmers have been suspecting for the past two years has been confirmed. Horseweed, also called marestail, has developed some resistance to glyphosate herbicides in their fields. Bob Hayes, University of Tennessee weed scientist,started checking out reports of horseweed control failures with Roundup in 2000, but was leery of using the term "resistant" until proper research was completed. The control failures we've seen in recent years in West Tennessee inade a strong case that resistance did exist, Hayes says. We would see instances where the rates of glyphosate we normally applied to get complete control were not providing control -- only stunting in some cases. Now, lab and greenhouse studies have confirmed the problem does exist in Tennessee. The problem was first reported in 2000 by a Lauderdale County farmer who used glyphosate and did not get, good horseweed control. Many horseweed plants were not killed after the field was retreated with double the normal rate of Roundup Ultra. A field trial the following year confirmed the observation. Other growers in Haywood, Crockett and Gibson counties started seeing the same problem. Most of these fields had been no-filled and had a history of glyphosate use. In some cases, glyphosate had been used exclusively for a number of years.