TURF TIPS
By Jeffrey Derr, Ph.D., Weed Scientist and Professor of Weed Science, Virginia Tech
Goosegrass
Herbicide Resistance in Turfgrass W e are probably all familiar with turfgrass diseases developing resistance to fungicides, as well as insects developing resistance to insecticides. The issue of weeds developing resistance to herbicides, however, is a relatively recent development, especially in turfgrass situations, although herbicide-resistant weeds have been a problem in agronomic crop production for a number of years. I have been involved in investigating two situations of herbicide resistance in turfgrass: Acclaim-resistant smooth crabgrass and simazine-resistant annual bluegrass. Both of these instances occurred in golf course locations, but the situations could occur in other areas where turf is maintained. I am not trying to single out these two herbicides. Resistance could develop to any herbicide on the market.
Crabgrass
Although we all tend to stick with something that has worked well for us in the past, consider doing some rotations every few years. [Editor’s Note: This article originally ran in the July/August 2004 issue of the Virginia Turfgrass Journal. The study’s results may be equally helpful, however, to turfgrass managers in Tennessee.]
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TENNESSEE TURFGRASS
AUGUST/SEPTEMBER 2004
Acclaim-Resistant Crabgrass
A golf course used Acclaim for crabgrass control in their tees, making multiple applications per year. This was highly effective until about eight years later when control decreased on certain tees. I evaluated the resistance in this biotype of smooth crabgrass, and I found that the resistant type was still not controlled when eight times the maximum use rate of Acclaim Extra was applied. An important point at that course was that the crabgrass growing in places other than the tees was still susceptible to Acclaim Extra. Other grasses, like goosegrass, were not resistant, so the golf course could still use Acclaim Extra in their program. That course switched to Drive for control of smooth crabgrass on their tees. A concern here is that crabgrass resistance to Drive has been reported in California.
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