By Pam Sherratt
Creeping bentgrass is considered a weed on athletic fields and lawns. It produces a superb playing surface for golf and it has great recuperative potential, but it’s shallow roots and lack of wear tolerance make it unsuitable for most athletic sports.
Tenacity (mesotrione) is the first herbicide that results in rapid, easy to visualize reductions in weedy perennial grasses, including creeping bentgrass. Best control, according to most research of creeping bentgrass, is achieved if three applications are made on 14-21 day intervals.
Mesotrione has excellent safety on Kentucky bluegrass and good safety on perennial ryegrass and tall fescue. Some phytotoxicity has been reported when repeat applications are made to perennial ryegrass. However, this problem can be minimized by applying in cooler weather and also by avoiding making sequential applications too close together (make applications 21 days apart on ryegrass and 14 days apart on bluegrass).
At OSU, we were able to achieve 98% control of creeping bentgrass. Fall is the best time to begin a bentgrass removal program. Since mesotrione is safe to turfgrass seedlings, you should time the three applications so that you can seed your desired turfgrass when the third application is made.
For example, in a mixed sward of ryegrass and bluegrass, applications could be made August 1st, August 21st, and September 15th. Turf seed would be applied on the September 15th date. Mesotrione rate on each date would be 5 oz per acre.
Authors: Dr. Dave Gardner & Pam Sherratt