Annual bluegrass weevil (Listronotus maculicollis) and paclobutrazol control annual bluegrass (Poa annua) in creeping bentgrass fairways

The annual bluegrass weevil (ABW; Listronotus maculicollis Kirby) host preference for annual bluegrass (Poa annua L.) is well documented, but ABW efficacy for annual bluegrass control in mixed turfgrass stands has not been researched. This study evaluated threshold‐based insecticide ABW control for annual bluegrass control in mixed‐species golf course fairway turfgrass. To investigate integrated pest management programs for annual bluegrass control in fairways, the effects of creeping bentgrass (Agrostis stolonifera L.) overseeding, three insecticide programs (preventative, threshold‐based, and no insecticide), and the plant growth regulator paclobutrazol (280 g ha–1, applied monthly) were evaluated for annual bluegrass control in field experiments conducted over 2 yr on golf fairways in North Brunswick and Bloomfield, NJ. Treatments were replicated four times and arranged in a split‐split‐plot randomized block design. Overseeding (whole‐plot factor) did not affect annual bluegrass cover at either location. Paclobutrazol (split‐plot factor) reduced annual bluegrass cover each year at both locations. At the North Brunswick site, paclobutrazol resulted in 0% annual bluegrass cover, compared with 37% in the nontreated control at the conclusion of the 2‐yr experiment. Insecticide program (split‐split‐plot factor) only affected annual bluegrass cover at the North Brunswick site. In the absence of paclobutrazol, the no insecticide program had lower annual bluegrass cover (23%) than the threshold (37%) and preventative (44%) programs at the conclusion of the experiment. These findings show that monthly paclobutrazol applications during the growing season can reduce or eliminate annual bluegrass after 2 yr. This is the first study to show that omitting ABW insecticidal control can also reduce annual bluegrass, although efficacy was site specific.

Annual bluegrass ( Poa annua L.) control with postemergence herbicides in cool-season turfgrass is often inconsistent. Amicarbazone and mesotrione have complementary modes of action but have not been evaluated in tank-mixtures for control of mature annual bluegrass in cool-season turfgrass. Field experiments were conducted during 2018 in New Jersey, and in Indiana, Iowa, and New Jersey during 2019 to evaluate springtime applications of amicarbazone and mesotrione for POST annual bluegrass control in cool-season turfgrass. On separate tall fescue ( Festuca arundinacea Schreb.) and kentucky bluegrass ( Poa pratensis L.) sites in 2018, three sequential applications of amicarbazone (53 g⋅ha −1 ) + mesotrione at 110 to 175 g⋅ha −1 provided >70% annual bluegrass control, whereas three sequential applications of amicarbazone alone at 53 and 70 as well as two sequential applications at 110 g⋅ha −1 provided <15% control at 14 weeks after initial treatment (WAIT). In 2019, results in New Jersey were similar to 2018 where amicarbazone alone provided less control than mesotrione + amicarbazone tank-mixtures. In Indiana, where the annual bluegrass infestation was severe and most mature, tank-mixtures were more effective than amicarbazone alone at 6 WAIT, but at 12 WAIT all treatments provided poor control. In Iowa, where the annual bluegrass infestation was <1 year old, all treatments provided similar control throughout the experiment and by >80% at the conclusion of the experiment. This research demonstrates that sequential applications of mesotrione + amicarbazone can provide more annual bluegrass control than either herbicide alone, but efficacy is inconsistent across locations, possibly due to annual bluegrass maturity and infestation severity.

Methiozolin is a new isoxazoline herbicide being investigated for selective POST annual bluegrass control in creeping bentgrass putting greens. Glasshouse and field research was conducted from 2010 to 2012 in Tennessee and Texas to evaluate annual bluegrass control efficacy with methiozolin. Application placement experiments in the glasshouse illustrated that root absorption was required for POST annual bluegrass control with methiozolin at 1,000 g ai ha−1. Soil-plus-foliar and soil-only applications of methiozolin reduced annual bluegrass biomass greater than treatments applied foliar-only. Field experiments evaluated annual bluegrass control efficacy with two application rates (500 and 1,000 g ha−1) and six application regimes (October, November, December, October followed by [fb] November, November fb December, and October fb November fb December) on sand- and soil-based putting greens. Annual bluegrass control with methiozolin at 1,000 g ha−1on sand-based greens ranged from 70 to 72% compared to 87 to 89% on soil-based greens. Treatment at 500 g ha−1controlled annual bluegrass 57 to 64% on sand-based greens compared to 72 to 80% on soil-based greens. Most sequential methiozolin application regimes controlled annual bluegrass more than single applications. On sand-based greens, sequential application programs controlled annual bluegrass 70 to 79% compared to 85 to 92% on soil-based greens. Responses indicate that methiozolin is a root-absorbed herbicide with efficacy for selective control of annual bluegrass in both sand- and soil-based creeping bentgrass putting greens.

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short-cut turfgrass in Eastern North America. Wide spread insecticide resistance warrants the development of alternative management strategies for this pest. ABW damage typically occurs in areas with a high percentage of annual bluegrass, Poa annua L., the preferred ABW host. Damage to bentgrasses, Agrostis spp., is much rarer and usually less severe. To aid the implementation of host plant resistance as an alternative ABW management strategy we investigated the tolerance of three bentgrass species to ABW feeding. Responses of P. annua, creeping bentgrass, Agrostis stolonifera L., colonial bentgrass, Agrostis capillaris L., and velvet bentgrass, Agrostis canina L., to adult and larval feeding were compared in greenhouse experiments. Grass responses were measured as visual damage, dry weight of the grass stems and leaves, color, density and overall grass quality. To determine possible mechanisms of grass tolerance constitutive fiber and silicon content were also determined. The three bentgrass species tolerated 2-3 times higher numbers of ABW adults and larvae than P. annua before displaying any significant quality decrease. Creeping bentgrass had the lowest damage ratings. ABW infestation caused higher plant yield reduction in P. annua (up to 42%) than in bentgrasses. Observed differences among the grass species in fiber and silicon content in the plant tissue are unlikely to play a role in the resistance of bentgrasses to ABW. Our findings clearly show that A. stolonifera is the best grass species for the implementation of host plant resistance in ABW management.

The postemergence herbicide ethofumesate and the plant growth regulator paclobutrazol were evaluated for annual bluegrass control in creeping bentgrass turf managed as golf fairways. Both products were applied under several different timing regimes relative to the time of the year. Paclobutrazol treatments provided significantly greater annual bluegrass control than ethofumesate. There were no differences between rates of paclobutrazol (0.28 and 0.14 kg ai/ha) when applied from spring through summer. Annual bluegrass control after spring and summer applications of paclobutrazol was 85% or more. Clipping weight data indicated that paclobutrazol suppressed growth in annual bluegrass longer than in creeping bentgrass. It was concluded that prolonged suppression of annual bluegrass by paclobutrazol resulted in creeping bentgrass dominance and subsequent annual bluegrass control. Additionally, applications of ethofumesate in autumn–winter, followed by paclobutrazol applied in spring–summer, provided significan...

Selective annual bluegrass (ABG) control with mesotrione is often inconsistent, and sequential applications might be required for complete control. The complementary nature ofp-hydroxyphenylpyruvate dioxygenase (HPPD)- and photosystem II (PSII)-inhibiting herbicides is well documented. The HPPD-inhibiting herbicide mesotrione and the PSII-inhibiting herbicide amicarbazone both have efficacy against annual bluegrass and safety on certain cool-season turfgrasses. Topramezone is a HPPD-inhibiting herbicide being investigated for use in turfgrass. Field and greenhouse experiments were conducted to examine single applications of topramezone and mesotrione alone or in combination with amicarbazone for POST ABG control in spring. In greenhouse experiments, the combination of mesotrione (280 g ai ha−1) and amicarbazone (75 g ai ha−1) controlled ABG 70% by 21 d after treatment, > 29% more than either herbicide applied alone; these combinations were determined to be synergistic. Amicarbazone combined with topramezone (14.5 g ai ha−1) provided < 10% ABG control and was not synergistic. When combined with mesotrione, increasing amicarbazone rate to 150 or 255 g ha−1did not increase ABG control compared to 75 g ha−1in field experiments. Combining mesotrione with amicarbazone resulted in a synergistic increase in POST ABG control at 1 and 2 wk after treatment (WAT). When applied alone or in combination with amicarbazone, increasing the mesotrione rate from 90 to 280 g ha−1increased efficacy on ABG in field experiments. The combination of mesotrione at 280 g ha−1and amicarbazone at 75 g ha−1provided > 90% ABG control in field experiments. Future research should focus on sequential applications of mesotrione–amicarbazone combinations for ABG control in locations where ABG is historically more difficult to control.

Core Ideas Research done on annual bluegrass (ABG) control in other areas of the US are likely applicable to Nebraska. However, extreme weather can dramatically affect short‐term annual bluegrass cover and emphasize the need for long‐term control studies. Three fall POST applications of mesotrione plus prodiamine applied preemergence in August and/or November were effective for ABG control in Kentucky bluegrass fairways. Replacing mesotrione with ethofumesate was also effective when combined with prodiamine in August and November. June applications of bispyribac‐sodium at 4 oz/ac was highly effective for controlling ABG in creeping bentgrass fairways, and adding two more fall applications at the same rate improved control slightly, but there was no benefit to raising the rate to 6 oz/ac. Annual bluegrass (Poa annua L.) (ABG) is common in golf courses, and its control has been thoroughly researched in cool‐season turf east of the Mississippi River in the United States. However, ABG response to herbicides varies widely among environments and/or biotypes, and little ABG control research has been done in the northern Great Plains. Therefore, our objective was to validate ABG herbicide control systems in golf course fairways of Kentucky bluegrass (Poa pratensis L.) (KBG) or creeping bentgrass (Agrostis stolonifera L.) (CBG) in Nebraska. Preemergence (PRE) treatments of prodiamine or mesotrione were applied in late summer over 3 yr with or without fall postemergence (POST) treatments of mesotrione or ethofumesate for ABG control in a low‐mow KBG fairway. We also evaluated rate and frequency of bispyribac‐sodium applications with or without a late summer–applied PRE (dithiopyr) in early September for ABG control over 3 yr in a CBG fairway. Our research indicates that ABG control work done in other areas are likely applicable to Nebraska. Three fall POST applications of mesotrione plus prodiamine applied as a PRE in August and/or November was effective for ABG control in KBG fairways. Replacing mesotrione with ethofumesate was also effective when combined with prodiamine in August and November. June applications of bispyribac‐sodium at 4 oz/ac were highly effective for controlling ABG in CBG fairways, and adding two more fall applications at the same rate improved control slightly, but there was no benefit to raising the rate to 6 oz/ac. Lastly, extreme weather in one summer and one winter dramatically affected short‐term ABG cover and emphasized the need for long‐term control studies in areas with dramatic weather cycles.

The annual bluegrass weevil (ABW), Listronotus maculicollis Kirby, is an economically important pest of short cut turfgrass. Annual bluegrass, Poa annua L., is the most preferred and suitable host for ABW oviposition, larval survival and development. We investigated the involvement of grass volatiles in ABW host plant preference under laboratory and field conditions. First, ovipositional and feeding preferences of ABW adults were studied in a sensory deprivation experiment. Clear evidence of involvement of olfaction in host recognition by ABW was demonstrated. Poa annua was preferred for oviposition over three bentgrasses, Agrostis spp., but weevils with blocked antennae did not exhibit significant preferences. ABW behavioral responses to volatiles emitted by Agrostis spp. and P. annua were examined in Y-tube olfactometer assays. Poa annua was attractive to ABW females and preferred to Agrostis spp. cultivars in Y-tube assays. Headspace volatiles emitted by P. annua and four cultivars of Agrostis stolonifera L. and two each of A. capillaris L. and A. canina L. were extracted, identified and compared. No P. annua specific volatiles were found, but Agrostis spp. tended to have larger quantities of terpenoids than P. annua. (Z)-3-hexenyl acetate, phenyl ethyl alcohol and their combination were the most attractive compounds to ABW females in laboratory Y-tube assays. The combination of these compounds as a trap bait in field experiments attracted adults during the spring migration, but was ineffective once the adults were on the short-mown turfgrass. Hence, their usefulness for monitoring weevil populations needs further investigation.

Methiozolin is a selective herbicide that has been reported to control annual bluegrass in creeping bentgrass putting greens. Golf course managers frequently tank-mix fertilizers with herbicides to reduce time and labor, but no information is available regarding such mixtures with methiozolin. Research was conducted to evaluate methiozolin for annual bluegrass control and creeping bentgrass safety when tank-mixed with ammonium sulfate or iron sulfate. Mixtures with ammonium sulfate did not influence annual bluegrass control while they did reduce creeping bentgrass injury in some instances. Mixtures with iron sulfate varied by experimental run but annual bluegrass control was either similar or increased while creeping bentgrass injury did not vary. Paclobutrazol was included as an alternative agrochemical comparison for annual bluegrass management; its application resulted in similar control and injury with and without iron sulfate addition, and injury and control were similar to methiozolin at appropriate rates. While some differences were observed, overall annual bluegrass and creeping bentgrass response to methiozolin was not affected by tank-mix nutrient partner relative to methiozolin applied alone.

Selectivity of Methiozolin for Annual Bluegrass (<i>Poa annua</i>) Control in Creeping Bentgrass as Influenced by Temperature and Application Timing

Xanthomonas campestris pv. poannua has potential as a biological control agent for perennial ryegrass (Lolium perenne L.), and it is being evaluated as a commercial bioherbicide. Field experiments were conducted on dormant `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy × C. dactylon (L.) Pers.] and `Tifway' bermudagrass overseeded with perennial ryegrass to determine the effects of two isolates of X. campestris pv. poannua on annual bluegrass (Poa annua L.) control. Annual bluegrass control was 82% on 27 Apr. 1992 after isolate MB 218 was applied to dormant bermudagrass at 109 cfu/ml in three applications on 11 and 28 Feb. and 12 Mar. When isolate MB 245 was applied at the same rate and dates, it controlled only 60% of the annual bluegrass. The response from isolate MB 245 at the same rate and number of applications on 28 Apr. 1993 was similar to that in Apr. 1992, with 64% control on dormant turf and 52% control on overseeded turf. There was no significant advantage in annual bluegrass control when isolate MB 245 was applied at 109 cfu/ml in more than three applications during the fall and winter, compared to three applications on 15 Feb. and 1 and 11 Mar. when ratings were made on 28 Apr. 1993. The control of annual bluegrass in late Apr. 1992 and 1993 from X. campestris applied in three applications (11 and 28 Feb. and 12 Mar. 1992 and 15 Feb. and 1 and 11 Mar. 1993) at 109 cfu/ml was greater than when l08 cfu/ml was applied on the same dates.

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.

Effectiveness of Herbicide Programs for Annual Bluegrass (<i>Poa annua</i>) Control in Bermudagrass (<i>Cynodon dactylon</i>)

Methiozolin and cumyluron are experimental herbicides that are reported to control annual bluegrass PRE or POST; however, no studies have compared these new herbicides to currently-registered herbicides for annual bluegrass control on putting greens over multiple years. Studies were conducted on three Virginia putting greens for 2 yr to compare methiozolin and cumyluron each at two rates to bensulide and bensulide plus oxadiazon at labeled rates for effects on annual bluegrass and creeping bentgrass cover, turf injury, normalized difference vegetative index (NDVI), turf quality, and annual bluegrass seedhead suppression. Methiozolin, cumyluron, bensulide, and bensulide plus oxadiazon did not significantly injure creeping bentgrass putting green turf, reduce quality, or reduce NDVI. Only methiozolin at 500 or 750 g ai ha−1 and cumyluron at 8,600 g ai ha−1 reduced area under the progress curve (AUPC) for annual bluegrass cover following four treatments over 2 yr applied in spring and fall each year. A concomitant increase in creeping bentgrass cover AUPC was also observed from the three treatments that reduced annual bluegrass cover. Methiozolin also reduced annual bluegrass seedhead cover at least 85% 1 mo after spring treatments and more than all other treatments except cumyluron at 8,600 g ha−1 (66%). These studies suggest that single treatments of methiozolin in spring and fall will not rapidly control existing annual bluegrass but can slowly reduce populations over time, presumably by preventing new seedling emergence. Methiozolin and cumyluron appear to be more effective than currently available herbicides bensulide and bensulide plus oxadiazon for PRE annual bluegrass control and seedhead suppression on golf putting greens.

Amicarbazone is a photosystem II–inhibiting herbicide recently registered for annual bluegrass control in established turf systems that include creeping bentgrass. However, research to date reveals potential issues with creeping bentgrass tolerance to amicarbazone. Currently, the plant-growth regulator paclobutrazol is widely adopted by turf managers for chemical annual bluegrass suppression in creeping bentgrass putting greens. Field experiments were conducted throughout North Carolina in the spring of 2010 and 2011 to assess treatment regimens that included amicarbazone (49, 65, or 92 g ai ha−1) and paclobutrazol (70, 140, or 280 g ai ha−1) applied alone, as tank-mixtures, or used in tandem, at varying rates and sequential timings for annual bluegrass control in creeping bentgrass putting greens. In general, regimens including both compounds provided greater annual bluegrass control and acceptable turfgrass tolerance compared with stand-alone applications of amicarbazone at 8 and 12 wk after initial treatment (WAIT). When comparing regimens that included amicarbazone at 49 or 65 g ha−1, creeping bentgrass tolerance was greater for the higher application rate applied less frequently. These results indicate amicarbazone usage on creeping bentgrass greens may be beneficially affected with the incorporation of paclobutrazol to treatment regimens because annual bluegrass control with the combination was equal to or greater than stand-alone amicarbazone applications, and creeping bentgrass tolerance was superior 8 and 12 WAIT.