Purple nutsedge response to various rates and timings of imazosulfuron was evaluated in 2007 and 2008 in Abilene, TX. Bermudagrass phytotoxicity never exceeded 4% throughout the duration of the trial and all bermudagrass recovered within 7 d of herbicide application. Imazosulfuron (0.56 kg ai ha−1) followed by (fb) imazosulfuron 1 wk after initial treatment (WAIT), imazosulfuron at 1.12 kg ai ha−1, and trifloxysulfuron at 0.03 kg ai ha−1exhibited 94 to 96% control 4 WAIT. Imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 2, 3, and 4 WAIT exhibited 99% control 4 WAIT. Eight weeks later (12 WAIT), imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 3 WAIT controlled purple nutsedge 91%, whereas similar control (82 to 84%) was observed with a single application of trifloxysulfuron and imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 2 and 4 WAIT. A single application of imazosulfuron at 1.12 kg ai ha−1and sequential treatment with imazosulfuron (0.56 kg ai ha−1) on a 1-wk interval only controlled purple nutsedge 51 to 69% 12 WAIT. Timing of sequential imazosulfuron application was identified as an important component of the purple nutsedge control program. Waiting 2, 3, or 4 WAIT for sequential imazosulfuron applications, rather than 1 WAIT, increased purple nutsedge control 31 to 40% 12 WAIT. The highest level of purple nutsedge control (91%) was observed with applications of imazosulfuron (0.56 kg ai ha−1) fb imazosulfuron 3 WAIT applied during midsummer. However, control with this treatment was statistically similar to control with a single application of trifloxysulfuron (82%).

The effect of mowing regimens on lateral spread of khakiweed (Alternanthera pungens Kunth) was determined through field studies conducted over a 3-month period in Texas during 2009 and 2010. Treatments were selected to simulate mowing regimens common to intensively managed common bermudagrass [Cynodon dactylon (L.) Pers.] turf and included heights of 1.3 cm (three times/wk), 2.5 cm (two times/week), and 5.1 cm (two times/week). A non-mowed control was included for comparison. Differences in lateral spread of khakiweed among mowing regimens were apparent 4 weeks after initial treatment (WAIT). However, plant diameter increased for all mowing regimens over the course of the trial. Khakiweed plants subjected to the 1.3-cm mowing regimen did not increase in diameter from Week 2 through Week 12, whereas the other two mowing regimens exhibited steady increases in plant diameter over the same time period. By 12 WAIT, non-mowed control plots measured 80.8 cm in diameter, whereas those maintained at 1.3 cm measured 55.3 cm. Comparatively, plants subjected to the 2.5- and 5.1-cm mowing regimens measured 64.7 and 68.8 cm, respectively. Therefore, khakiweed infestations may be more prevalent in bermudagrass mowing heights commonly used for golf course roughs, athletic fields, and home lawns (2.5 cm or greater). However, the production of a thick taproot high in carbohydrate content may enable khakiweed to regenerate from frequent defoliation common to fairway mowing regimes (2.5 cm or less). Adjustments in mowing height may not be enough to effectively reduce khakiweed populations in bermudagrass turf.

Field experiments were conducted in Texas to examine the recovery of a bermudagrass [Cynodon dactylon × C. transvaalensis (L.) Pers.] fairway from spring dead spot (SDS) disease following preemergence (PRE) herbicide applications. In 2011 and 2012 bermudagrass recovery from SDS in the non‐treated check plots (46 and 59%, respectively) was similar to bermudagrass recovery in response to oxadiazon at 3.4 kg/ha (55 and 57%, respectively) 14 weeks after treatment (WAT). Pendimethalin at 2.5 kg/ha resulted in 33 to 38% bermudagrass recovery from SDS 14 WAT. In 2011, oryzalin (1.68 kg/ha), dithiopyr (0.56 kg/ha), prodiamine (0.73 kg/ha), and dimethenamid (1.68 kg/ha) applications resulted in 21 to 25% bermudagrass recovery from SDS 14 WAT. In 2012, bermudagrass exhibited similar recovery in response to prodiamine and oryzalin (24 and 26%, respectively), while response to dithiopyr and dimethenamid was 33 and 34%, respectively, 14 WAT. Bermudagrass exhibited the least amount of recovery (13 to 14%) in response to indaziflam at 0.035 kg/ha, regardless of year. Oxadiazon can be safely used as a PRE option when bermudagrass is recovering from SDS, while the use of oryzalin, prodiamine, dithiopyr, dimethenamid, pendimethalin, and indaziflam may limit recovery and further contribute to a weakened turfgrass system.

Khakiweed (Alternanthera pungens Kunth) response to single and sequential herbicide applications was evaluated during the summer of 2009 and 2010 in Texas. No bermudagrass phytotoxicity was observed throughout the length of each trial regardless of herbicide treatment. Carfentrazone at 0.034 kg a.i./ha, metsulfuron + carfentrazone at 0.021 + 0.034 kg a.i./ha, and trifloxysulfuron + carfentrazone at 0.018 + 0.034 kg a.i./ha exhibited 74% to 85% khakiweed control 2 weeks after initial treatment (WAIT) regardless of application regime. Control with carfentrazone (0.017 kg a.i./ha) was only 63% to 65% 2 WAIT regardless of application regime. Metsulfuron and trifloxysulfuron treatments exhibited 54% or less khakiweed control 2 WAIT regardless of rate. Six weeks later (8 WAIT), sequential applications of metsulfuron exhibited 98% control regardless of rate, whereas control with single applications was 79% to 87%. Sequential applications of trifloxysulfuron exhibited 86% to 88% khakiweed control 8 WAIT regardless of rate, whereas single applications exhibited 47% or less control. Carfentrazone treatments exhibited 5% or less control regardless of rate or sequential application 8 WAIT. Tank-mixing metsulfuron or trifloxysulfuron with carfentrazone did not improve control 8 WAIT compared with either sulfonylurea herbicide applied alone. Although initial khakiweed injury was observed in all treatments, effective long-term control was difficult to achieve. Excellent control (95% to 97%) was exhibited by sequential metsulfuron applications 12 WAIT regardless of rate. Sequential applications of trifloxysulfuron (0.018 or 0.028 kg a.i./ha) and single applications of metsulfuron at 0.042 kg a.i./ha exhibited moderate khakiweed control (75% to 80%) 12 WAIT. All other treatments exhibited 57% or less khakiweed control 12 WAIT. Efficacy of sequential metsulfuron applications is a strong incentive for its adoption over trifloxysulfuron applications for the control of khakiweed in bermudagrass turf.

Growing concern over the sufficiency and variability of present water supplies in the arid Southwest has led to the examination of buffalograss [Buchloe dactyloides (Nutt.) Engelm.] for water conservation. Increasing acceptance of buffalograss will require investigation into conversion techniques for its establishment. The objectives of this study were to evaluate the effects of seedbed preparation and seeding rate on the establishment of buffalograss after bermudagrass desiccation with glyphosate. Research was conducted at the Texas Tech Quaker Research farm in 2009 and 2010 on a mature ‘Riviera’ common bermudagrass [Cynodon dactylon (L.) Pers.] rough. Bermudagrass was sprayed with glyphosate at 1.1 kg acid equivalent (ae)/ha 5 and 1 weeks before seedbed preparation. Plots were scalped after desiccation. Treatments were arranged in a two × four factorial, randomized complete block design with four replications. two buffalograss seeding rates and four seedbed preparation treatments. Seedbed preparation treatments consisted of no seedbed preparation, topdressing alone (0.6-cm layer), hollow-tine aerification + topdressing, or verticutting + topdressing. ‘TopGun’ buffalograss was planted on 1 June 2009 and 4 June 2010 at 146 or 195 kg·ha−1. Grid counts were conducted to determine buffalograss cover one, two, and three months after planting (MAP). Counts were then converted to percent cover (0% to 100%). Greater buffalograss cover was observed when seed was applied at the higher rate (196 kg·ha−1) except within treatments that did not receive seedbed preparation treatment. No seedbed preparation resulted in unacceptable buffalograss cover. Percent buffalograss cover three MAP was 75%, 83%, and 86% for topdressing alone, aerification + topdressing, and verticutting + topdressing treatments seeded at 195 kg·ha−1, respectively.

The dark green color and abundant seed production of khakiweed (Alternanthera pungens Kunth) interfere with playability and aesthetic quality of home lawns, golf courses, and athletic fields. In 2009 and 2010, the effect of rolling on lateral spread of khakiweed was investigated in Lubbock, TX. Rolling treatments were conducted using a ride‐on roller that applied a static pressure of 58 kPa at a speed of 1.55 m s−1. Weekly rolling treatments were: nonrolled, low (4 passes × 3 events), moderate (8 passes × 3 events), and high (12 passes × 3 events). Khakiweed lateral plant diameters were recorded at trial initiation and every 2 wk over 12 wk. Statistical differences in khakiweed diameters were not observed until 10 wk after initial treatment (WAIT). Nonrolled plots exhibited 30.1 cm plant diameter, similar to low rolling (24.4 cm) but greater than moderate (23.3 cm) and high (20.4 cm) rolling 10 WAIT. A decrease in plant diameter was observed in response to high rolling (19.9 cm) 12 WAIT compared with nonrolled plots (28.8 cm). Although numerically less than the nonrolled check (28.8 cm), khakiweed plant diameters in response to low (23.5 cm) and moderate (23.1 cm) rolling were statistically similar. Although rolling treatments reduced khakiweed diameter compared with the nonrolled check, plants increased in size from initial trial diameters while hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] cover decreased over time in response to high rolling. Therefore, practices that reduce soil compaction may be important to increase bermudagrass competition with khakiweed.

No abstract