Annual bluegrass (Poa annua L.) can be a troublesome weed to control in established turfgrass stands; it has developed herbicide resistance after repeated use of products with similar modes of action, and several new herbicides have been registered for use on turfgrasses. Four field studies were conducted near Clemson, S.C., from 2003 through 2005 to evaluate postemergence annual bluegrass control in dormant, nonoverseeded bermudagrass [Cynodon dactylon (L.) Pers.] turf using various herbicides applied in either December or February of each year and rated in the spring. Annual bluegrass control can be accomplished in dormant, nonoverseeded bermudagrass turf using a wide range of products applied in either December or February. Flazasulfuron, foramsulfuron, glufosinate, glufosinate + clethodim, glufosinate + glyphosate, glyphosate + clethodim, glyphosate + diquat, pronamide, rimsulfuron, and trifloxysulfuron provided 87% or greater annual bluegrass control regardless of application timing. Imazaquin and simazine controlled annual bluegrass greater than 85% when applied in December but less than 80% when applied in February. Glyphosate provided 93% annual bluegrass control when applied in February but only 72% control with December applications. No detrimental effects on bermudagrass spring greenup were observed for any herbicide treatment or application time. The availability of several effective herbicide options with differing modes of action provides turfgrass managers with the opportunity to use herbicide rotations that may prevent, or at least delay, the development of resistant annual bluegrass populations to these chemical products.

Ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] cultivars require considerable field research to determine best management practices for successful long‐term culture. A field study was conducted in 2004 and 2005 on an experimental ‘TifEagle’ bermudagrass putting green in Clemson, SC, to examine effects of plant growth regulators (PGRs) applied bimonthly and three mowing heights on turf performance. The PGRs included ethephon [(2‐chloroethyl)phosphonic acid] at 1.91 kg a.i. ha−1, flurprimidol [α‐(1‐methylethyl)‐α‐[4‐(trifluoro‐methoxy)phenyl]‐5‐pyrimidine‐methonol] at 0.07 kg a.i. ha−1, trinexapac‐ethyl [4‐(cyclopropyl‐α‐hydroxymethylene)‐3,5‐dioxo‐cyclohexane carboxylic acid ethyl ester] at 0.0175 kg a.i. ha−1, all pairwise PGR combinations at half the individual rates, and a nontreated control. Turf was mowed five times weekly at 2.50, 3.25, or 4.00 mm. Lateral regrowth with ethephon and trinexapac‐ethyl was comparable to nontreated turf, while flurprimidol impeded lateral regrowth ∼25%. All three PGRs reduced dry clipping weights, with flurprimidol most effective (>50% each harvest) and ethephon least effective (maximum 17%). Turf quality for trinexapac‐ethyl, ethephon, and flurprimidol was excellent (8.0–8.4), acceptable (6.8–7.1) and unacceptable (3.6–5.2), respectively. Compared to the control, root length density increased 33% with trinexapac‐ethyl, unaffected by ethephon, and reduced 25% with flurprimidol. Flurprimidol increased ball roll distances in morning (AM) and (PM) by 21 and 26 cm, respectively, trinexapac‐ethyl provided increases of 5 and 10 cm, respectively, while ethephon had no effect, compared to the control. No evidence of synergistic effects was observed for PGR combinations. Raising mowing heights increased lateral regrowth, turf quality, and root length density but decreased ball roll distances. Best overall performance of TifEagle bermudagrass was achieved with trinexapac‐ethyl, as it increased root length density, provided excellent turf quality, reduced vertical growth, did not impede lateral regrowth, and increased ball roll distances, compared to the control.

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