Imazapic is an acetolactate synthase-inhibiting herbicide labeled for weed control in pastures, rangeland, and noncrop areas. Field research was conducted in Knoxville, TN, USA, during 2020 and 2021 to evaluate the tolerance of four hybrid bermudagrass ( Cynodon dactylon × Cynodon transvaalensis Burtt Davy) cultivars to applications of imazapic for growth suppression. Separate experiments were conducted on ‘TifTuf’, ‘Tifway’, ‘Tahoma 31’, and ‘Latitude 36’ hybrid bermudagrass. Experiments included plots (1.5 m 2 ) arranged in a randomized complete block design with four replications and were repeated. Treatments were applied 14 Aug 2020 and 6 Aug 2021, and were mixed with methylated seed oil. Imazapic rates were 0, 35, 52.5, 70, or 105 g⋅ha –1 . Cultivar tolerance was assessed via visual ratings of turfgrass injury relative to untreated check plots. Normalized differential vegetation index data were collected on each date turfgrass injury was evaluated. Growth suppression was quantified via reductions in dry clipping weight after mowing. Hybrid bermudagrass injury increased with imazapic rate for all cultivars, and peak injury (> 30%) following all imazapic treatments occurred within 14 days. At the lowest imazapic rate (35 g⋅ha –1 ), injury was transient, with all hybrid bermudagrass cultivars fully recovered by 28 days. All rates of imazapic reduced hybrid bermudagrass dry clipping weight for 21 days for all cultivars. Further research is warranted to explore lower application rates than those tested in our study, in addition to determining tolerance and growth suppression of other turfgrass species commonly managed on golf courses.

Controlling unwanted annual bluegrass ( Poa annua L.) in desirable turfgrass species often relies heavily on herbicide use. As a result, increasing populations of herbicide-resistant annual bluegrass have become a concern. In 2018, a university research and extension initiative began addressing the increasing herbicide-resistant annual bluegrass epidemic. Preliminary findings produced by this research initiative were presented to golf course employees at the 2022 Golf Course Superintendents Association of American Educational Conference in San Diego, California. Findings were presented by a panel of scientists working on various annual bluegrass research sub-objectives. A survey was designed to match the sub-objectives within this panel presentation and determine what recommendations the attendees were most likely to use. The survey also identified environmental zones where participants originated and what turfgrass species they are managing in various areas of the golf course. The goal of sharing these survey findings is to assist turfgrass extension specialists and managers interested in designing annual bluegrass management programs that match stakeholder needs. Survey results determined that extension material pertaining to controlling annual bluegrass with cultural practices would interest the largest stakeholder cross section regardless of environmental turfgrass zone. Another major topic was annual bluegrass emergence patterns for herbicide timing, which was the most important or interesting topic for golf course employees in the warm-season turfgrass environmental zone.

Perennial broadleaves such as dandelion ( Taraxacum officinale G.H. Weber ex Wig-gers) and white clover ( Trifolium repens L.) are known to be pervasive weeds in stands of maintained turfgrasses. The use of synthetic herbicides is the most common and effective method of control for these weeds. As pesticide use in European countries, Canada, and the United States is becoming more scrutinized, identifica-tion of alternative weed control options may be necessary. However, few organic or natural weed control products exist. A field study was conducted to evaluate the efficacy of various fertilizers and organic and bio-herbicides including chelated iron, ammonium nanonate, citrus oil, acetic acid, and sodium chloride on dandelion and white clover control as compared to that of two synthetic herbicides containing 2,4-dichlorophenoxy-acetic acid (2,4-D), mecoprop-p (MCPP), and dicamba. Injury to perennial ryegrass ( Lolium perenne L.) was also evaluated with the objective of deter-mining which products effectively suppressed weed populations while imposing minimal injury to desirable turfgrasses. Chelated iron was effective in controlling dandelion and white clover populations equal to that of both synthetic herbicides with minimal injury to turfgrass. Other organic and bio-herbicide treatments provided some control of both weed populations but generally were too injurious the turfgrass. Fertility treatments and citrus oil did not reduce populations of either weed. This research indicates that some natural products currently on the market may serve as effective alternatives to synthetic herbicides. This information will be beneficial to homeowners and turfgrass managers controlling weed populations in geographic areas with restricted pesticide use or where control with organic products is desired.

Fraise mowing is a maintenance practice that may serve as a non-chemical means of controlling the problematic weed annual bluegrass (Poa annua L.) in bermudagrass (Cynodon spp.) given reports of efficacy on other turfgrass species. However, an understanding of practitioner decision-making in implementing fraise mowing as a weed-control measure remains unknown. A field study was conducted in Knoxville, TN and repeated in space in Jay, FL during summer 2019 to assess bermudagrass regrowth and subsequent annual bluegrass control, following fraise mowing at depths of 1.5 and 3.0 cm compared to a non-treated check (0 cm). Bermudagrass recovered more quickly at the 1.5 cm depth than the 3.0 cm depth and was the swiftest in Florida. Fraise mowing at either depth resulted in a 41–97% reduction in annual bluegrass populations. A qualitative study was conducted in spring 2021, which engaged eight turfgrass managers from Tennessee and Florida via individual interviews in order to understand barriers and challenges to fraise mowing application. Turfgrass managers had positive views of fraise mowing but described challenges in implementation for weed control including cost, labor, area closure, and debris removal.

Poa annua L. is a common component of turfgrass systems both as a weed and a desirable species. Since first classified by Carl von Linne in 1753, nearly 50 taxa of P. annua have been described, with delineations made on the basis of plant morphology and not life cycle. Yet, peer-reviewed turfgrass literature has recognized only two of these taxa over the past 50 yr, P. annua L. var. annua and P. annua var. reptans, categorizing var. annua ecotypes as upright growing annuals and var. reptans ecotypes as laterally growing perennials. Herein we provide a comprehensive review of peer-reviewed literature to highlight that these associations between life cycle and plant morphology are flawed given that morphology is plastic and strongly influenced by environment. We conclude by exploring knowledge gaps regarding P. annua perennation that, if addressed through research, would help turfgrass managers better understand the biology of the ecotypes they aim to eradicate or maintain.

Soil seedbank management via collecting clippings may be a means of combatting herbicide resistance in annual bluegrass (Poa annua L.) by minimizing recruitment from the deposition of viable seed into the soil. Our objective was to assess the germinability of annual bluegrass seed in spring to determine when collecting clippings would be most impactful. Research was conducted across 2019 and 2020 in five locations: Knoxville, TN; Starkville, MS; Griffin, GA; West Lafayette, IN; and University Park, PA. Annual bluegrass seed was harvested every 100 growing degree-days (GDD(0C); base 0 degrees C with accumulation beginning on 1 January each year from 400 to 1,100 GDD(0C). Seeds from each harvest timing were placed on moistened blotter paper in petri dishes and randomized in a growth chamber set to a 77:68 degrees F and 8:16 h light-dark cycle. Germination was assessed every 3 d until 21 d of incubation. Cumulative germination percentage after 21 d of incubation increased at research locations in northern latitudes. In Tennessee, germination was greatest from 600 to 900 GDD(0C). In Indiana, germination did not exceed 50% until 600 GDD(0C) and increased with GDD(0C) accumulation. Clippings should not be collected until at least 600 GDD(0C) in these locations. In Pennsylvania, little variation existed among GDD(0C) harvest times, indicating that clipping collection may be a valuable practice any time mature seedheads are present. Turfgrass managers should consider geographic location when selecting a time to implement clipping collections and will probably need to conduct multiple clipping collection events.

During putting green renovation in northern regions of the United States, golf course superintendents must select a method to quickly establish creeping bentgrass (Agrostis stolonifera L.)(CBG). This study aimed to assess the impact of cultivation method, seeding rate, and cumulative starter fertilizer rate on CBG establishment during putting green renovation. A field study on putting greens at the Joseph Valentine Turfgrass Research Center (University Park, PA) was initiated in late summer-autumn of 2017 and 2018. Cultivation treatments included slicing + 0.5-inch hollow tines, slicing + 0.25-inch hollow tines, slicing only, surface dimpling with the Job-saver attachment, and no cultivation. Seeding rates included 0.75 and 1.5 lb seed 1,000 ft(-2) with a 50-50 blend of 'Penn A-1' and 'Penn A-4' CBG. Cumulative starter fertilizer treatments were 0.5-0.4-0.3, 1.0-0.9-0.6, or 1.5-1.3-0.8 lb N-P-K 1,000 ft(-2). Seedling vigor and turfgrass cover were visually assessed at 1 wk and 6, 10, and 36 wk after seeding, respectively. Slicing alone produced turfgrass cover equal to or greater than slicing + hollow-tine cultivation. At the high seeding rate, surface dimpling produced similar turfgrass cover to treatments involving slicing. The 1.5 lb 1,000 ft(-2) seeding rate increased the turfgrass cover of CBG compared with 0.75 lb 1,000 ft(-2). Establishment rate improved as cumulative fertilizer rates increased. The results indicate that slicing alone is effective for establishing CBG during late summer and autumn in sand rootzone putting green renovation programs and may be more cost-effective than core cultivation.

Abstract Topramezone and carfentrazone + 2,4-D + mecoprop-p + dicamba (SpeedZone®) are herbicides labeled for POST goosegrass (Eleusine indica L. Gaertn.) control in hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt Davy). Field research was conducted in Knoxville, TN, during 2019 and 2020 to evaluate goosegrass control and hybrid bermudagrass tolerance to these herbicides applied alone and in mixture. Treatments included topramezone (12.2 g ha–1), SpeedZone® [carfentrazone (33.6 g ha–1) + 2,4-D (1,029 g ha–1) + mecoprop-p (322 g ha–1) + dicamba (91 g ha–1)] and SpeedZone® + topramezone at 12.2, 6.1, 3.6, or 2.4 g ha–1. A nontreated control was included for comparison. Hybrid bermudagrass tolerance was assessed on four cultivars (‘Northbridge’, ‘Tifway’, ‘Tahoma 31’, and ‘TifTuf’) via visual ratings of turfgrass injury and assessments of normalized difference vegetation index (NDVI). At the termination of the experiment, SpeedZone® alone and in mixture with topramezone controlled goosegrass better than or equal to topramezone alone. Mixtures of SpeedZone® + topramezone reduced injury on all cultivars compared to topramezone alone, particularly when mixtures delivered ≤6.1 g ha–1 topramezone. Injury subsided on all cultivars by 28 d after treatment regardless of herbicide. Findings suggest that SpeedZone® can be mixed with topramezone at the rates tested herein to minimize hybrid bermudagrass injury from topramezone applications for goosegrass control. Nomenclature: 2; 4-D; carfentrazone; dicamba; mecoprop-p; topramezone; bermudagrass; Cynodon spp.; goosegrass; Eleusine indica L. Gaertn; hybrid bermudagrass; C. dactylon × C. transvaalensis Burtt Davy

A 2-yr field experiment was conducted at three locations across Tennessee during 2017-2018 to determine if early-postemergence (EPOST) applications of FreeHand [pendimethalin (3,4-dimethyl-2,6-dinitro-N-pentan-3-ylaniline) + dimethenamid (2-chloro-N-[2,4-dimethylthiophen-3-yl]-N-[1-methoxypropan-2-yl]acetamide)] could control annual bluegrass (Poa annua L.)(ABG) similar to Kerb SC [pronamide (3,5-dichloro-N-[2-methylbut-3-yn-2-yl]benzamide)] and Princep [simazine (6-chloro-2-N,4-N-diethyl-1,3,5-triazine-2,4-diamine)]. Across all locations and years, EPOST applications of FreeHand at 200 lb acre(-1) controlled ABG by 88 to 100% 23 wk after the initial treatment, more than or equal to Kerb SC and Princep. Follow-up research was conducted in Knoxville, TN, during 2018-2019 to compare the efficacy of FreeHand applied EPOST with Pendulum AquaCap (pendimethalin) and Tower (dimethenamid) applied individually. Sequential EPOST applications of Tower controlled ABG similar to FreeHand on all ratings dates, whereas single applications of Tower resulted in less control. Annual bluegrass control efficacy with EPOST applications of Pendulum AquaCap varied over years. Over the course of eight trials, EPOST applications of FreeHand at 200 lb acre(-1) controlled ABG by 88 to 100%, suggesting that it is a new option turfgrass managers can use to control ABG in bermudagrass (Cynodon spp.).

Results of the Iowa Corn Yield Test are published to aid Iowa farmers in selecting corn hybrids. This is the seventy-sixth consecutive year for the test. These data are first released on Iowa State University Extension's electronic information delivery system (EXNET), usually around the end of November. Anyone can access the information on EXNET and receive the data as soon as they are released. Information provided on EXNET can be accessed in three ways: by modem at (515) 294-8354 and logging in as "guest," through Internet using World Wide Web (WWW) at URL:http://www.exnet.iastate.edu, or through Internet using telnet to exnet.iastate.edu and logging in as "guest." For additional information about EXNET. contact EXNET, 110 EES Bldg., Haber Rd., Iowa State University, Ames. Iowa 50011-3070, telephone number (515) 294-8658.

Turfgrass managers attempting to establish creeping bentgrass (Agrostis stolonifera L.) from seed following winterkill episodes may benefit from cultivars that germinate and establish quickly during cold temperature periods. The purpose of this study was to identify the percentage and time until germination of different cultivars of creeping bentgrass under a suboptimal temperature regime. Twenty-seven seed samples showing >= 90% germination under the optimal temperature regime of 77:59 degrees F on an 8:16-hour light-dark cycle were selected for germination tests at the suboptimal temperature of 50 degrees F on an 8:16-hour light-dark cycle. The results show differences among creeping bentgrass samples with respect to cumulative germination percentages (CGP) and days to germination when incubated at 50 degrees F. Seed samples of 'Pure Select', 'Penn A'-4, 'Crystal BlueLinks', and '007' were most consistent with respect to high germination percentages and days to germination at 50 degrees F. However, where multiple seed samples of the same cultivar were examined, variation in CUP and days to germination were detected among samples. Cultivars with superior germination characteristics at low temperatures may improve creeping bentgrass establishment from seed following winterkill episodes. However, practitioners should be aware that germination at low temperatures may vary among seed samples or seed lots of individual cultivars because of factors associated with seed vigor, such as seed age, preharvest environmental conditions, seed storage methods, and other factors, which could result in variable rates of establishment in early spring.