Bermudagrass is a major forage species throughout Georgia and the Southeast. An essential part of achieving high-yielding, top-quality forages is proper weed control. Indaziflam is a residual herbicide that controls many broadleaf and grass species by inhibiting cellulose biosynthesis. Research conducted in Tift and Colquitt counties in Georgia determined optimal PRE rates for indaziflam for bermudagrass forage production. Treatments applied at spring greenup of established ‘Alicia’ bermudagrass included indaziflam at 47, 77, 155, or 234 g ai ha−1 PRE, pendimethalin at 4,480 g ha−1 PRE, a split application of indaziflam at 47 g ha−1 PRE followed by the same rate applied POST after the first cutting, and a nontreated control (seven treatments in all). Forages were machine harvested three times each year for each location beginning at least 47 d after treatment (DAT), with final cuttings up to 168 DAT. For all treatments, fresh- and dry-weight yields at each harvest and totals for the season did not differ from the nontreated control. Indaziflam at 155 and 234 g ha−1 did cause minor stunting at 44 DAT, but this was transient and not observed at the second harvest. Indaziflam applied PRE has the potential to provide residual control of troublesome weeds in bermudagrass forage and hay production, with ephemeral stunting at the recommended application rates.

Experiments were conducted to evaluate the impact of spray volume, nozzle type, adjuvants, the presence of dew, and their interactions on foliar retention of creeping bentgrass. Tartrazine, a common food dye, was used as a tracer in this study. Increasing spray volume from 95 L ha−1 to 1,500 L ha−1 decreased foliar retention efficiency from 98% to approximately 85%. Compared with flat-fan nozzles, air-induction nozzles delivered similar retention efficiency at all spray volumes evaluated. However, flat-fan nozzles provided higher uniformity and more thorough coverage. Adding nonionic surfactants, organosilicone adjuvants, or methylated seed oils at typical concentrations yielded retention efficiency of approximately 90% to 93% regardless of spray volumes. In contrast, with water alone, increasing spray volume reduced retention efficiency from 95.9% to 87.3%. Simulated dew applied at 1,950 L ha−1 increased retention efficiency by approximately 3% when spray application volume was 190 L ha−1, while no difference was observed at 750 L ha−1. The presence of dew reduced the impact of adjuvants on retention efficiency. Large quantities of dew, 3,800 L ha−1, did reduce retention efficiency.

We conducted research to evaluate various herbicides for POST false-green kyllinga control in cool-season turfgrass (primarily creeping bentgrass). In a preliminary evaluation, single and sequential applications of halosulfuron-methyl (70 g ai ha−1), mesotrione (175 g ai ha−1), and sulfentrazone (140 g ai ha−1), as well as a single application of imazosulfuron (740 g ai ha−1), were evaluated in New Jersey. Imazosulfuron and sequential applications of halosulfuron-methyl controlled false-green kyllinga >93% at 9 and 18 wk after initial treatment (WAIT). Sulfentrazone and mesotrione controlled false-green kyllinga <50%. Additional experiments were conducted to evaluate single and sequential applications of halosulfuron-methyl (70 g ha−1), imazosulfuron (420 and 740 g ha−1), and sulfentrazone (140 g ha−1) in New Jersey and Indiana at two locations in each state. At 12 WAIT, imazosulfuron generally controlled false-green kyllinga more effectively than other treatments at all locations. Sequential applications of imazosulfuron controlled false-green kyllinga 100% at 12 WAIT. Halosulfuron-methyl was less effective in Indiana than in New Jersey. Sulfentrazone controlled false-green kyllinga <40% at 12 WAIT. This research demonstrates that imazosulfuron is more effective than halosulfuron-methyl and sulfentrazone for POST false-green kyllinga control in cool-season turf.

Some fineleaf fescues have demonstrated tolerance to glyphosate, and this broad-spectrum, nonselective herbicide would be a valuable tool for controlling various weeds in low-input turf areas. A study was conducted to evaluate tolerance of 56 fineleaf fescue varieties to glyphosate applied at 0.0, 0.4, 0.6, and 1.0 kg ae ha−1. The defunct 2003 National Turfgrass Evaluation Program fineleaf fescue variety trial at the Turfgrass Research Center in Blacksburg, VA, provided main plots on which glyphosate treatments were randomized independently on May 16, 2011, and June 26, 2013. Hard (HF) and sheep fescues (SF) were the most tolerant to glyphosate, followed by strong creeping red fescues (STC) and slender creeping red fescues (SLC). The most sensitive species was Chewings fescue (CH), most varieties of which were injured 50% to 65% per kilogram of glyphosate at 2 wk after treatment (WAT). At 8 WAT, 12 of 14 CH varieties were injured over 30% per kilogram of glyphosate, but predicted injury and normalized difference vegetation index (NDVI) of all varieties were acceptable at a more typical 0.5 to 0.7 kg ha−1 glyphosate rate. Nontreated seed head density of CH varieties ranged from 87 and 126 seed heads m−2 at 8 WAT compared with 2.8 to 42 seed heads m−2 from HF varieties. Glyphosate at 0.15 to 0.5 kg ha−1 eliminated 90% of seed heads regardless of fineleaf fescue variety. These data suggest that all fineleaf fescue varieties are inherently tolerant of glyphosate at rates at or below approximately 0.7 kg ha−1, but can be generally separated from most to least tolerant in the following order: HF, SF, STC, SLC, and CH.

Cogongrass is commonly found in disturbed areas in Florida, where it is increasingly becoming a problem in bahiagrass pastures. Soil pH has been suggested as a possible mechanism for this invasion; to evaluate this, replacement series competition studies were conducted under greenhouse conditions at two soil pH levels: pH 4.5, or pH 6.8. Cogongrass ramets and bahiagrass seedlings were planted at proportions of 0:40, 1:20, 2:10, 4:1, and 8:0, respectively. Aboveground biomass was measured after 8 weeks and used to calculate relative yield, relative crowding coefficients, and aggressivity values. At soil pH 4.5, the relative competitiveness of cogongrass and bahiagrass was similar, with both species contributing equally to relative yield. At soil pH 6.8, bahiagrass seedlings showed greater competitive ability than cogongrass ramets. Relative crowding coefficient and aggressivity values supported this, with bahiagrass showing increased competitiveness under higher soil pH. This indicates that decreases in soil pH, often associated with poor soil fertility, is likely a contributing factor for cogongrass invasion into bahiagrass pastures. Soil amendments to raise pH may provide a cultural management tool for cogongrass infestations in pastures.

Palmer amaranth resistance to protoporphyrinogen oxidase (PPO)-inhibiting herbicides has become an increasing problem to producers throughout the southeast region of the United States. Traditionally, these herbicides can be used as foliar-applied and soil-applied in glyphosate resistant (GR) cropping systems to control GR Palmer amaranth. Heavy reliance on PPO herbicides has contributed to the increased selection for PPO inhibitor-resistant (PPO-R) Palmer amaranth biotypes. Dose response greenhouse research was conducted to evaluate the efficacy of soil-applied flumioxazin, fomesafen, saflufenacil and sulfentrazone on a known susceptible (S) and resistant (R) Palmer amaranth biotype. Both R and S populations reached maximum germination at 14 d after treatment (DAT). The data from this study suggests complete control (100%) was achieved for the S biotype at 35 d after treatment (DAT) with all herbicides. The R biotype showed difference among herbicide treatments with flumioxazin and saflufenacil having similar responses in control and fomesafen and sulfentrazone resulting in less control of the R Palmer amaranth biotypes. The calculated relative resistance factor ranged from 3.5 to 6.0, and averaged 5X for the four herbicides. This research indicated that the PPO-R population was still responsive to all tested herbicides, but a low level of resistance was present.