Patrick E. McCullough

Temperature Influences Creeping Bentgrass (Agrostis stolonifera) and Annual Bluegrass (Poa annua) Response to Bispyribac-Sodium'

Bispyribac-sodium is a POST herbicide that selectively controls annual bluegrass in creeping bentgrass, but inconsistent results with seasonal applications are believed to occur from temperature influences on bispyribac-sodium efficacy. Growth chamber experiments at the New Jersey Experimental Greenhouse Research Complex, New Brunswick, NJ, investigated three temperature regimes on ‘L-93’ creeping bentgrass and annual bluegrass responses to bispyribac-sodium. Annual bluegrass and creeping bentgrass exhibited contrasting responses to bispyribac-sodium as temperature increased from 10 to 30 C. Regressions of 4 week after treatment (WAT) data revealed as temperature increased from 10 to 30 C, required bispyribac-sodium rates for 50% clipping reduction (CR50) of annual bluegrass decreased from 85 to 31 g ai/ha and required rates for 50% leaf chlorosis decreased from greater than 296 to 98, indicating increased herbicidal efficacy at higher temperatures. In contrast, required bispyribac-sodium rates for creeping bentgrass CR50 increased from 200 to greater than 296 as temperature increased from 10 to 30 C. Bispyribac-sodium discolored creeping bentgrass 0 to 20% at 20 and 30 C and discoloration increased 10 to 50% at 10 C. Thus, warmer temperatures (20 and 30 C) increase bispyribac-sodium efficacy for annual bluegrass control with minimal bentgrass discoloration; however, cooler temperatures (10 C) have minimal efficacy on annual bluegrass and increase bentgrass chlorosis. Nomenclature: Bispyribac-sodium; annual bluegrass Poa annua L. #3 POANN; creeping bentgrass, Agrostis stolonifera L. # AGSST, ‘L-93’. Additional index words: Chlorosis, efficacy, turfgrass.

PRE and POST Control of Annual Bluegrass (Poa annua) with Indaziflam

Abstract Indaziflam controls annual grassy weeds by inhibiting cellulose biosynthesis. Research was conducted from 2008 to 2011 in Tennessee, Texas, and Georgia evaluating the efficacy of indaziflam for PRE and POST control of annual bluegrass in bermudagrass turf. In Texas, indaziflam at 30, 40, 50, and 60 g ai ha−1 applied PRE provided 93 to 100% annual bluegrass control through 28 wk after treatment. When applied PRE at 80 g ai ha−1 and at 4, 8, and 12 wk after PRE (WAP), indaziflam controlled annual bluegrass 67 to 100% 32 wk after initial treatment (WAIT) in Tennessee; however, reduced efficacy was observed with 12 WAP treatments in a single year of a 2-yr study. Similarly, annual bluegrass control with PRE applications or with 4 and 8 WAP applications of indaziflam at 35 and 52.5 g ai ha−1 ranged from 88 to 100% at 30 WAIT in Tennessee. In Georgia, these rates of indaziflam applied PRE and 4 WAP controlled annual bluegrass 96 to 100% on all evaluation dates and resulted in 97 to 100% reduction in plant counts relative to the untreated control at 30 WAIT. When applied 8 WAP, the 35 and 52.5 g ai ha−1 rates of indaziflam controlled annual bluegrass only 51 to 71% at 30 WAIT in Georgia. Although increasing the application rate of indaziflam treatments 8 WAP provided greater annual bluegrass control, each rate provided significantly lower control when applied 8 WAP compared with PRE or at 4 WAP. No bermudagrass injury was observed in this research. Results suggest indaziflam provides effective PRE and early POST control of annual bluegrass in bermudagrass turf. However, additional research is needed to determine the effects of plant size and maturity on indaziflam efficacy for POST annual bluegrass control. Nomenclature: Annual bluegrass, Poa annua L.; bermudagrass, Cynodon dactylon (L.) Pers.

Smooth Crabgrass Control with Indaziflam at Various Spring Timings

Abstract Indaziflam is an alkylazine herbicide that controls annual grasses by inhibiting cellulose biosynthesis. Compared with other PRE herbicides like prodiamine, indaziflam has a longer half-life in soil (> 150 d), which may allow for greater flexibility with application timing. Research was conducted in 2010 in Tennessee and Georgia evaluating smooth crabgrass control efficacy with indaziflam applied at early PRE, PRE, and early POST timings on the basis of soil temperature. Regardless of application timing, all rates of indaziflam (35, 52.5, and 70 g ai ha−1) controlled smooth crabgrass 89 to 100%. Prodiamine at 840 g ai ha−1 applied PRE provided ≥ 99% smooth crabgrass control on all rating dates. Smooth crabgrass plant counts were significantly correlated (r  =  −0.961; p < 0.0001) with visual ratings of smooth crabgrass control at the end of the study. Application flexibility with indaziflam may benefit turf managers in scheduling herbicide applications for smooth crabgrass control in Tennessee and Georgia. Nomenclature: Indaziflam; prodiamine; smooth crabgrass [Digitaria ischaemum (Schreb.) Schreb. ex Muhl.].

Amicarbazone Efficacy on Annual Bluegrass and Safety on Cool-Season Turfgrasses

Abstract Amicarbazone has potential for selective annual bluegrass control in cool-season turfgrasses, but seasonal application timings may influence efficacy. To test this hypothesis, field experiments in New Jersey and Indiana investigated amicarbazone efficacy from fall or spring applications and growth chamber experiments investigated the influence of temperature on efficacy. Fall treatments were more injurious to creeping bentgrass and Kentucky bluegrass than spring applications, but fall applications were also more efficacious for annual bluegrass control. In growth chamber experiments, injury and clipping weight reductions were exacerbated by increased temperatures from 10 to 30 C on annual bluegrass, creeping bentgrass, Kentucky bluegrass, and perennial ryegrass. Results suggest that amicarbazone use for annual bluegrass control in cool-season turf may be limited to spring applications, but increased temperature enhances activity on all grasses. Nomenclature: Amicarbazone; annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L. ‘L-93’; Kentucky bluegrass, Poa pratensis L. ‘Baron’, ‘Fairfax’, ‘Freedom’, ‘Merit’, ‘Midnight’, ‘SR2100’; perennial ryegrass, Lolium perenne L. ‘Manhattan IV’.

Absorption, Translocation, and Metabolism of Amicarbazone in Annual Bluegrass (Poa annua), Creeping Bentgrass (Agrostis stolonifera), and Tall Fescue (Festuca arundinacea)

Abstract Amicarbazone controls annual bluegrass in cool-season turfgrasses but physiological effects that influence selectivity have received limited investigation. The objective of this research was to evaluate uptake, translocation, and metabolism of amicarbazone in these species. Annual bluegrass, creeping bentgrass, and tall fescue required < 3, 56, and 35 h to reach 50% foliar absorption, respectively. At 72 h after treatment (HAT), annual bluegrass and creeping bentgrass translocated 73 and 70% of root-absorbed 14C to shoots, respectively, while tall fescue only distributed 55%. Annual bluegrass recovered ≈ 50% more root-absorbed 14C in shoots than creeping bentgrass and tall fescue. Creeping bentgrass and tall fescue metabolism of amicarbazone was ≈ 2-fold greater than annual bluegrass from 1 to 7 d after treatment (DAT). Results suggest greater absorption, more distribution, and less metabolism of amicarbazone in annual bluegrass, compared to creeping bentgrass and tall fescue, could be attributed to selectivity of POST applications. Nomenclature: Amicarbazone; annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L.; tall fescue, Festuca arundinacea Schreb.

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

Abstract Methiozolin controls annual bluegrass in creeping bentgrass but application timing and temperature could influence efficacy in turf. In field experiments, sequential methiozolin applications totaling 3.36 kg ai ha−1 provided excellent (> 90%) annual bluegrass control at 8 wk after initial treatment when treatments were initiated in February/March or May but programs totaling 0.84 and 1.68 kg ha−1 provided poor control (< 70%) at both timings. Methiozolin at all rates caused minimal turf injury (< 8%) but creeping bentgrass was only injured from February/March applications. In growth chamber experiments, creeping bentgrass injury from methiozolin at 10 C was 2 and 4 times greater than at 20 C and 30 C, respectively, while annual bluegrass injury was similar across temperatures. In laboratory experiments, annual bluegrass had more foliar absorption of 14C-methiozolin than creeping bentgrass at 30/25 C (day/night), compared to 15/10 C, but translocation was similar at both temperatures as > 90% of absorbed 14C remained in the treated leaf after 72 h. Annual bluegrass distributed and recovered more radioactivity to shoots from root-applied 14C-methiozolin than creeping bentgrass while both species had about 2 times more distribution to shoots at 30/25 C than 15/10 C. Metabolites were not detected in annual bluegrass or creeping bentgrass at 1, 3, or 7 d after treatment when grown at 15/10 C or 30/25 C suggesting uptake and translocation contributes to methiozolin selectivity in turfgrass. Nomenclature: Annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L.

Spray Adjuvants Influence Bispyribac–Sodium Efficacy for Annual Bluegrass (Poa annua) Control in Cool-Season Turf Grass

Field and laboratory experiments were conducted in New Jersey to investigate the influence of spray adjuvants on foliar absorption and efficacy of bispyribac–sodium on annual bluegrass, creeping bentgrass, and perennial ryegrass. In laboratory experiments on annual bluegrass, 14C–bispyribac–sodium without an adjuvant had 25% foliar absorption by 8 h after treatment, whereas absorption increased to 45, 46, and 75% when applied with crop oil concentrate, nonionic surfactant, and methylated seed oil, respectively. In creeping bentgrass fairways, sequential bispyribac–sodium applications at 37 g ai/ha with spray adjuvants controlled annual bluegrass similarly to 74 g ai/ha applied sequentially without adjuvants. In perennial ryegrass, treatments with methylated seed oil and nonionic surfactant required 25 and 41% lower bispyribac–sodium rates, respectively, to obtain annual bluegrass control levels comparable to bispyribac–sodium rates without adjuvants. Spray adjuvants did not exacerbate turf-grass discoloration from bispyribac–sodium. Overall, spray-adjuvant use with bispyribac–sodium may allow practitioners to reduce application rates and enhance efficacy for annual bluegrass control. Nomenclature: Bispyribac–sodium, annual bluegrass, Poa annua L., creeping bentgrass, Agrostis stolonifera L., ‘L-93’, ‘Penncross’, perennial ryegrass, Lolium perenne L., ‘Manhattan 4’

Efficacy of Preemergence Herbicides for Controlling a Dinitroaniline-Resistant Goosegrass (Eleusine indica) in Georgia

Abstract Goosegrass is a problematic weed in turfgrass, and overuse of dinitroaniline (dna) herbicides has resulted in evolution of resistant populations. The objectives of this research were to (1) evaluate responses of a susceptible (S) goosegrass compared to a suspected resistant (R) biotype from Griffin, GA to prodiamine, and (2) evaluate efficacy of various PRE herbicides for control. Prodiamine rates required for 50% control and 50% shoot reductions after 6 wk for R-goosegrass measured > 13.44 and 3.2 kg ai ha−1, respectively, whereas rates for the S-population measured 0.45 and < 0.42 kg ha−1, respectively. In field experiments, sequential applications of dithiopyr and prodiamine provided < 20% control of R-goosegrass over 2 yr. Single applications of dimethenamid-P at 1.68 kg ai ha−1 provided < 50% goosegrass control in 2011 but provided excellent control (≥ 90%) at 7 mo after initial treatments (MAIT) in 2012. Single and sequential applications of indaziflam provided excellent control of goosegrass in both years, and oxadiazon controlled goosegrass > 85% at 7 MAIT in 2011 and ≥ 90% in 2012. Single and sequential PRE sulfentrazone applications controlled goosegrass < 60% in 2011 but averaged 94% control in 2012. Overall, indaziflam and oxadiazon provided good (80 to 89%) to excellent control of dna-resistant goosegrass in both years, but dimethenamid and sulfentrazone were inconsistent. Nomenclature: Dimethenamid; dithiopyr; indaziflam; oxadiazon; prodiamine; sulfentrazone; goosegrass; Eleusine indica (L.) Gaertn. Resumen Eleusine indica es una maleza problemática en céspedes, y el sobreuso de herbicidas dinitroaniline (dna) ha resultado en la evolución de poblaciones resistentes. Los objetivos de esta investigación fueron (1) evaluar la respuesta a prodiamine de un biotipo de E. indica susceptible (S) y un biotipo supuestamente resistente (R) proveniente de Griffin, GA, y (2) evaluar la eficacia de varios herbicidas PRE para su control. Las dosis de prodiamine requeridas para alcanzar 50% de control y reducciones del 50% del tejido aéreo después de 6 semanas para E. indica-R fueron >13.44 y 3.2 kg ai ha−1, respectivamente, mientras que para E. indica-S fueron 0.45 y <0.42 kg ha−1, respectivamente. En experimentos de campo, las aplicaciones secuenciales de dithiopyr y prodiamine brindaron <20% de control de E. indica-R durante 2 años. Aplicaciones de solo dimethenamid-P a 1.68 kg ai ha−1 brindaron <50% de control de E. indica en 2011, pero en 2012, brindaron control excelente (≥90%) a 7 meses del tratamiento inicial (MAIT). Aplicaciones solas y secuenciales de indaziflam brindaron un control excelente de E. indica en ambos años, y oxadiazon controló >85% a 7 MAIT en 2011 y ≥90% en 2012. Aplicaciones PRE solas y secuenciales de sulfentrazone controlaron <60% en 2011, pero promediaron 94% de control en 2012. En general, indaziflam y oxadiazon brindaron un control de bueno (80 a 89%) a excelente de E. indica resistente a dna en ambos años, mientras el control con dimethenamid y sulfentrazone fue inconsistente.

Sulfonylurea Herbicides' Fate in Soil: Dissipation, Mobility, and Other Processes

Abstract Sulfonylurea herbicides used in turfgrass—including chlorsulfuron, flazasulfuron, foramsulfuron, halosulfuron, metsulfuron, rimsulfuron, sulfometuron, sulfosulfuron, and trifloxysulfuron—are all weak acids, with disassociation constants ranging from 3.3 to 5.2. Sulfonylureas are used at low rates ranging from 4 to 280 g ha−1. Although these use rates put their soil concentration in parts per billion, they still have residual activity with variable persistence. They have limited susceptibility to soil leaching with weak adsorption to soil clay minerals. Sulfonylurea herbicides used in turfgrass have variable soil organic matter adsorption, which is soil dependent. The persistence and activity of these sulfonylureas are affected by soil pH. At soil pH of 7.0 and greater, some of these sulfonylurea herbicides tend to persist for longer periods with half-lives extending into years rather than days. In normal use patterns with soil pH of 7.0 and less, dissipation occurs via chemical hydrolysis and microbial degradation with half-lives ranging from days to months. Overall, sulfonylurea herbicide adsorption is negatively correlated to increasing pH (increased persistence) and positively correlated to increased organic matter (decreased activity). Nomenclature: Chlorsulfuron, flazasulfuron, foramsulfuron, halosulfuron, metsulfuron, rimsulfuron, sulfometuron, sulfosulfuron, trifloxysulfuron.

Creeping Bentgrass (Agrostis stolonifera) Tolerance to Sulfosulfuron

Sulfosulfuron was recently registered for grassy weed control in creeping bentgrass, but turf sensitivity is a concern for intensively managed golf courses. Field and growth chamber experiments in New Jersey investigated creeping bentgrass growth responses and tolerance to sulfosulfuron. Creeping bentgrass chlorosis increased with sulfosulfuron rate but turf had less chlorosis from sequential sulfosulfuron applications compared to bispyribac–sodium. Herbicide-treated turf had similar root weight compared to untreated turf on six sampling dates. In growth-chamber experiments, creeping bentgrass treated with sulfosulfuron had chlorosis and clipping weight reductions exacerbated by reductions in temperature from 25 to 15 C. Overall, creeping bentgrass appears to tolerate sequential sulfosulfuron applications better than or comparable to bispyribac-sodium in early summer, whereas creeping bentgrass sensitivity to sulfosulfuron increases at cooler temperatures. Nomenclature: Bispyribac–sodium; sulfosulfuron; creeping bentgrass, Agrostis stolonifera L. AGRST