Diego Gómez de Barreda

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.

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.

Nicosulfuron Use with Foramsulfuron and Sulfentrazone for Late Summer Goosegrass (Eleusine indica) Control in Bermudagrass and Seashore Paspalum

Abstract Late summer goosegrass control is difficult in turfgrass as POST herbicide efficacy is reduced on mature plants. Field experiments were conducted to evaluate single and sequential nicosulfuron applications tank-mixed with foramsulfuron or sulfentrazone for late summer goosegrass control and safety to bermudagrass and seashore paspalum. All single-treatment applications controlled goosegrass < 62%, whereas sequential sulfentrazone, nicosulfuron, and nicosulfuron + sulfentrazone applications controlled goosegrass 52, 73, and 84%, respectively. Sequential foramsulfuron applications controlled goosegrass < 55% but nicosulfuron tank-mixtures did not improve control. Bermudagrass was injured < 20% by 1 and 3 wk after all single and sequential treatments. Sequential treatments of nicosulfuron alone or tank-mixed with sulfentrazone caused unacceptable seashore paspalum injury (> 20%) 1 and 3 wk after the second application, whereas foramsulfuron or sulfentrazone alone applied sequentially caused < 17% injury. Seashore paspalum seedhead control at 9 wk after intial treatment was poor (< 70%) from all single-application treatments and sequential sulfentrazone applications, but control was good (80 to 89%) to excellent (> 90%) from all other treatments. Overall, sequential treatments of nicosulfuron alone or tank-mixed with sulfentrazone appear to have potential for POST control of mature goosegrass in bermudagrass, but seashore paspalum injury was unacceptable. Nomenclature: Bermudagrass, Cynodon dactylon L.; goosegrass, Eleusine indica L.; seashore paspalum, Paspalum vaginatum Sw.

Seashore Paspalum (Paspalum vaginatum) Tolerance to Pronamide Applications for Annual Bluegrass Control

Abstract Annual bluegrass is a troublesome weed in turf management and there are currently limited POST herbicides labeled for use in seashore paspalum. Field and greenhouse experiments were conducted to evaluate seashore paspalum tolerance to pronamide and other herbicides for annual bluegrass control. In field experiments, turf injury never exceeded 7% from pronamide applied at dormancy, 50% green-up, or complete green-up of seashore paspalum in spring. Annual bluegrass control from pronamide was initially similar across timings and averaged 67, 90, and 98% control from 0.84, 1.68, and 3.36 kg ai ha−1, respectively, after 6 wk. In greenhouse experiments, the aforementioned pronamide rates caused less than 10% injury on seashore paspalum. Seashore paspalum injury in the greenhouse was excessive (> 20%) from atrazine, bispyribac-sodium, and trifloxysulfuron and moderate (7 to 20%) from foramsulfuron, rimsulfuron, and ethofumesate. Seashore paspalum seedhead count reductions by 4 wk after treatment (WAT) were good to excellent (87 to 98%) from atrazine, bispyribac-sodium, rimsulfuron, and trifloxysulfuron and poor (≤ 0%) from ethofumesate, foramsulfuron, and pronamide. By 4 WAT, seashore paspalum clippings were reduced 0 to 39% from pronamide, whereas atrazine, bispyribac-sodium, and trifloxysulfuron reduced clippings by 54 to 69% from the untreated and ethofumesate, foramsulfuron, and rimsulfuron reduced clippings by 27 to 39%. Nomenclature: Annual bluegrass, Poa annua L.; seashore paspalum, Paspalum vaginatum Sw.

Cool-Season Turfgrass Reseeding Intervals for Methiozolin

Abstract Methiozolin selectively controls annual bluegrass in cool-season turfgrasses, and practitioners may wish to reseed desirable species in treated areas. Field experiments were conducted to evaluate reseeding intervals for creeping bentgrass, perennial ryegrass, and tall fescue following methiozolin applications. Turfgrass establishment varied for species, application timing (0, 2, 4, or 6 wk before seeding, WBS), and rates tested (0.56, 1.12, or 2.24 kg ai ha−1). Reductions in turf cover suggest that seeding of creeping bentgrass, perennial ryegrass, and tall fescue should be delayed 2 wk after methiozolin treatments at 0.56 kg ha−1. However, reseeding should be delayed after methiozolin treatments at 1.12 kg ha−1 for approximately 4, 4, and 2 wk for creeping bentgrass, perennial ryegrass, and tall fescue, respectively. Similarly, establishment was reduced on all dates from the nontreated after 2.24 kg ha−1 was applied at 4 WBS, suggesting that reseeding should be delayed for at least 6 wk on all three species at the high rate. Nomenclature: Annual bluegrass, Poa annua L.; creeping bentgrass, Agrostis stolonifera L.; perennial ryegrass, Lolium perenne L.; tall fescue, Festuca arundinacea Schreb. Resumen Methiozolin controla selectivamente Poa annua en céspedes de clima frío, y los usuarios estarían interesados en resembrar especies deseables en las áreas tratadas. Se realizaron experimentos de campo para evaluar los intervalos de resiembra de Agrostis stolonifera, Lolium perenne y Festuca arundinacea después de aplicaciones de methiozolin. El establecimiento de los céspedes varió según la especie, el momento de aplicación (0, 2, 4 ó 6 semanas antes de la siembra, WBS), y las dosis evaluadas (0.56, 1.12 ó 2.24 kg ai ha−1). Las reducciones en la cobertura del césped sugieren que la resiembra de A. stolonifera, L. perenne y F. arundinacea debe ser retrasada 2 semanas después del tratamiento con 0.56 kg ha−1 de methiozolin. Sin embargo, después de tratamientos con methiozolin a 1.12 kg ha−1, la resiembra debe ser retrasada al menos 4, 4 y 2 semanas para A. stolonifera, L. perenne y F. arundinacea, respectivamente. Similarmente en comparación con el testigo no tratado, en todas las fechas de aplicación se redujo el establecimiento después de que se aplicó 2.24 kg ha−1 a 4 WBS, lo que sugiere que la resiembra debe ser retrasada al menos 6 semanas en las tres especies cuando se use esta dosis alta.

Dithiopyr Behavior in Smooth Crabgrass (Digitaria ischaemum) as Influenced by Growth Stage and Temperature

Abstract Dithiopyr provides PRE and early POST control of smooth crabgrass, but POST efficacy is often inconsistent on tillered plants. Experiments were conducted to evaluate the interaction of temperature and growth stage on dithiopyr efficacy, absorption, translocation, and metabolism in smooth crabgrass. In greenhouse experiments, I50 (predicted rate to induce 50% injury) measured < 0.14, 0.14, and 0.15 kg ha−1 at low temperatures (average 23 C) for multi-leaf, one-tiller, and multi-tiller smooth crabgrass, respectively, while I50 measured < 0.14, 0.88, and > 2.24 kg ha−1 at high temperatures (average 32 C), respectively. Multi-tiller (three to five tillers) smooth crabgrass absorbed more root applied 14C-dithiopyr than multi-leaf (three to four leaves) and one-tiller plants, but specific radioactivity (Bq mg−1) was two to three times greater in multi-leaf plants compared to tillered plants. Smooth crabgrass treated at 15/10 C (day/night) had ≈ two times greater specific radioactivity following root applied 14C-dithiopyr than at 30/25 C. Radioactivity distribution to shoots from root applications measured 43, 30, and 20% of the total absorbed for multi-leaf, one-tiller, and multi-tiller plants, respectively. Smooth crabgrass had two times more foliar absorption of 14C-dithiopyr at 15/10 than 30/25 C while 14C losses were greater at 30/25 than 15/10 C. Smooth crabgrass metabolism of 14C-dithiopyr was ≈ two times greater at 30/25 than 15/10 C, and multi-leaf plants averaged 10 to 20% more metabolism than tillered plants at 7 d after treatment. Results suggest differential absorption, translocation, and metabolism may contribute to dithiopyr efficacy on smooth crabgrass at various growth stages, but use under high temperatures (30/25 C) could increase losses from volatilization, reduce foliar absorption, and increase metabolism compared to cooler temperatures (15/10 C). Nomenclature: Dithiopyr; smooth crabgrass, Digitaria ischaemum (Schreb.) Schreb. ex Muhl.

Dithiopyr Controls Common Lespedeza (Kummerowia striata) in Bermudagrass

Abstract Common lespedeza is a problematic summer annual weed in bermudagrass lawns, with limited PRE herbicides available for control. Dithiopyr is a pyridine herbicide primarily used for PRE grassy weed control but has shown potential efficacy for controlling annual legumes. The objectives of this research were to evaluate efficacy and behavior of dithiopyr in common lespedeza. In a 3-yr field experiment, sequential dithiopyr applications at 0.42 or 0.56 kg ai ha−1 beginning in late winter and single applications of dithiopyr at 0.56 kg ai ha−1 in spring controlled common lespedeza ≥ 88%. Single and sequential applications of indaziflam at 0.035 and 0.053 kg ai ha−1 provided poor control (< 70%) of common lespedeza by late summer. In laboratory experiments, bermudagrass and common lespedeza had similar foliar absorption of 14C-dithiopyr, averaging 10% of the 14C applied, and both species retained > 80% of 14C in the treated leaf at 72 h after treatment (HAT). Common lespedeza translocated 6 times more root-absorbed 14C to shoots than bermudagrass and had 2.8 times greater absorption (Bq mg−1) at 72 HAT. In metabolism experiments, parent herbicide levels measured ≥ 84% of extracted 14C in both species at 1, 3, and 7 d after treatment. Overall, dithiopyr effectively controls common lespedeza in bermudagrass as a PRE treatment in spring. Susceptibility of common lespedeza to dithiopyr is associated with acropetal translocation and greater herbicide concentrations compared with a tolerant species, bermudagrass. Nomenclature: Common lespedeza (Kummerowia striata (Thunb.) Schindl.) ‘Kobe’; bermudagrass (Cynodon dactylon × C. transvaalensis Burtt-Davy) ‘Princess 77’.