Trinexapac-ethyl Application Research Articles

Cold hardiness in bermudagrass cultivars as affected by the sequential trinexapac-ethyl application during growing season

Bermudagrass turfs are widely used in subtropical to tropical regions and in transition zones for golf courses, landscape areas, and athletic fields. Lack of adequate cold tolerance in these grasses causes early winter dormancy and an aesthetically unpleasing surface. This study investigated the effect of sequential Trinexapac-ethyl (TE) applications during the growing season on fall color retention, spring green-up, and physiological responses related to cold hardiness in bermudagrass cultivars. Trinexapac-ethyl (untreated, 6.0, 12.0, and 18.0 mg a.i. m^-2) was applied monthly throughout the bermudagrass growing season. According to the results, TE applications enhanced spring green-up and possessed color retention for 20 and 12 days longer in the first and second years of the study, respectively. Higher proline and total carbohydrate contents were observed in the crown of TE-treated as compared to untreated turfs. Hybrid cultivars exhibited higher spring green-up, rhizome survival, proline content, total carbohydrates, and longer color retention than seeded cultivars. The higher proline content of the crown was positively associated with enhanced color retention, rhizome survival, and spring green-up. Finally, these results confirmed that accumulated osmolytes in the crown (resulting from growing-season TE application) minimized the dormancy period in winter via improvement of fall color retention and spring green-up.

Management practices for optimal kikuyugrass quality and playing conditions

AbstractKikuyugrass [Cenchrus clandestinus (Hochst. ex Chiov.) Morrone] is considered either an invasive weed or the desired species on many golf courses, athletic fields, and other turf areas along coastal and inland California. A field study was conducted at the University of California, Riverside in 2012 and 2013 on ‘Whittet’ kikuyugrass mowed at 11 mm to identify management practices for producing sufficient turf quality and optimal playing conditions for golf course fairways and athletic fields. The study evaluated the effect of mowing frequency (three vs. six times per week), cultivation practice (verticutting vs. grooming), applications of trinexapac‐ethyl (TE), and nitrogen fertilization rates (96 vs. 240 kg N ha−1 yr−1) on turf quality, Normalized Difference Vegetation Index (NDVI), turf firmness, ball roll distance (BRD), and tensile strength. Mowing six times per week produced the highest turf quality turf during summer when kikuyugrass grows most vigorously, while trends were not clear for cultivation practice effects on turf visual quality. However, verticutting twice per year produced the least scalped and firmest turf, while decreasing BRD. Application of TE increased turf quality, NDVI, and BRD, but decreased tensile strength of the sward. Slightly higher turf quality was detected in plots fertilized at 240 kg N ha−1 yr−1 compared to those fertilized with the low N rate (6.0 vs. 5.8), but results do not seem to justify higher N fertility. Overall, results demonstrated that kikuyugrass available in California could benefit from high input management practices such as TE applications, high mowing frequency, and verticutting.

Trinexapac‐ethyl applications and lightweight rolling on ultradwarf bermudagrass putting greens

AbstractPlant growth regulator (PGR) applications are a common practice in managing ultradwarf bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] putting greens. Trinexapac‐ethyl (TE) is a frequently used PGR to reduce the rapid shoot growth that could reduce ball roll distance (BRD) and increase turfgrass quality. Lightweight rolling (LWR) of putting greens is a practice implemented to sustain or increase BRD. The objective of this research was to determine effects of weekly TE applications and LWR on the BRD and turfgrass quality of an ultradwarf bermudagrass putting green. Experiments were conducted in Knoxville, TN, and Starkville, MS, on a ‘MiniVerde’ ultradwarf bermudagrass putting green. Trinexapac‐ethyl treatments included 0, 0.008, 0.024, or 0.072 lb a.i. acre−1 wk−1 and LWR five times per week. Ball roll distance was measured with a Pelzmeter in 2016 and a Stimpmeter in 2017. Turfgrass quality was visually assessed at both locations on a 1 to 9 scale, with ratings of ≥ 6 being acceptable. At both locations, the BRDs of plots treated with 0.024 lb TE acre−1 wk−1 with LWR were only 5 inch less than 0.072 lb TE acre−1 wk−1 without LWR, a difference that is likely to be imperceptible to golfers. In addition, TE applied at 0.024 lb a.i. acre−1 wk−1 consistently yielded greater turfgrass quality than 0.072 lb TE acre−1 wk−1. Implementing LWR practices with TE application rates at 0.024 lb acre−1 wk−1 can provide similar BRD and increased turfgrass quality as TE applied at 0.072 lb acre−1 wk−1 without LWR.

Maize Response to Trinexapac-Ethyl and Nitrogen Fertilization

ABSTRACT: High nitrogen rates favor maize vegetative growth and grain yield losses due to stem lodging. The use of growth regulators can mitigate such effect. This work was carried out aiming to evaluate the effect of trinexapac ethyl on maize hybrids response to side-dress nitrogen rates. The experiment was carried out in Lages, Santa Catarina State, South of Brazil, during two growing seasons with two hybrids (P1680 and P30F53), and four nitrogen rates (0, 150, 300 and 450 kg N ha-1) were tested, with and without the presence of trinexapac ethyl. The experimental design was in randomized blocks arranged in split-split plots, with three replications per treatment. The plants height and ear insertion height, plant lodging and breaking, grain yield and yield components were evaluated. Grain yield increased in a quadratic way with increased nitrogen rate. The highest grain yields were 15,784 and 15,257 kg ha-1, in 2014/15 and 2015/16, respectively. Application rates higher than 150 kg of N ha-1, regardless of the use of the plant growth regulator, promoted maximum grain yield increases, ranging from 14.7 to 18.1%. The application of trinexapac-ethyl reduced the upper stem internode length, 1000-grain dry weight and did not affect the percentage of lodged plants and grain yield of both hybrids. Therefore, the use of trinexapac-ethyl did not enhance the maize grain yield response to increased rates of side-dress nitrogen.

Establishment and traffic stress response of tall fescue as affected by Mycorrhiza fungi and Trinexapac-ethyl

Heavy traffic regularly causes damage of substantial aboveground parts to turf grasses. Several factors could affect the traffic stress severity, including the number of occasions per season and the soil moisture content during the traffic stress. Mycorrhiza results in numerous advantages to host plant like improving the turfgrass establishment, root structure and also abiotic stress tolerance of plants. Festuca arundinacea remains green during the playing season and it is the most popular turf grass for football. Trinexapacethyl (TE) might be influence the wear as growth retardant. Accordingly, mycorrhiza infection effect on tall fescue establishment, and TE effect on traffic stress after establishment were studied. The treatments, including traffic stress (traffic and non-traffic stress), TE (0 and 200 g 100 m-2) and mycorrhiza (Control; Glomus mosseae and Glomus intraradices) 50 g m-2 were evaluated on two cultivars of tall fescue in two growing season of 2017 and 2018. Both mycorrhizas were significantly colonized on turfgrass root during establishment. G. intraradices inoculation increased the establishment by passing 60 days from seeding in F. arundinacea cv. Barvado. After establishment, traffic stress reduced the relative water content (RWC) in 2017 and 2018, and also reduced the turf quality and soluble sugar content (SSC). TE improved the RWC, SSC, turf quality and also colonization percentage. Mycorrhiza inoculation enhanced tall fescue establishment. TE application at 200 g 100 m-2 had no influence on traffic stress, however, it improved turf quality, RWC, SSC and mycorrhiza colonization.

Exogenously Applied Trinexapac-ethyl Improves Photosynthetic Pigments, Water Relations, Osmoregulation and Antioxidants Defense Mechanism in Wheat under Salt Stress

The impact of trinexapac-ethyl (TE) on salinity subjected wheat plants was evaluated via pot based experiment. The treatments applied to wheat seedlings included (Ck) control (no NaCl nor TE spray), foliar spray of TE (1.95 ml L−1), only NaCl (50 mM) and NaCl+ TE (50 mM + 1.95 ml L−1). Foliar application of TE was done seven days after imposition of salinity. Growth parameters (root length, shoot length, fresh weight, and dry weight) and photosynthetic pigments content (chlorophyll a, b, a + b and a/b), water relation (water potential, osmotic potential, turgor potential and relative water contents) as well as catalase (CAT) activity exhibited marked reduction in comparison to control. In addition, an increment was noted in organic solutes content (proline, soluble protein and soluble sugar) and enzyme activity of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in stressed seedlings over control seedlings. The foliar applied TE mostly enhanced growth of salt stressed seedlings, accompanied by reinforcement in photosynthetic pigments, organic solutes, and enzyme activity (SOD, CAT, POD, and APX) in comparison to stressed seedlings. It is worthy to mention that, TE has potential to enhance salt tolerance of wheat seedlings. Thus, our findings suggest that seedling treated with TE is an effective strategy that can be used to enhance salt tolerance of wheat crop.

Doses and Times of Trinexapac-ethyl Application in Soybean Development and Yield

The intense vegetative growth is one of the problems faced by soybean producers, causing the lodging, making difficult and damaging the harvest and, even, the efficiency of the application of agricultural defenses. The use of growth regulators is an important tool in the management of growth, in addition, it can favor the transport of photoassimilates for grain filling. Therefore, the objective was to evaluate the best dose and time of trinexapac-ethyl application in the development and yield of soybean varieties. The experiment was conducted in the Selvíria County, Brazil (20°20′53″ S, 51°24′02″ W). The experimental design was used in randomized blocks with treatments arranged in a factorial scheme 5 x 3 (doses x times), with four replications. The varieties used were the BRS Valiosa RR and the BMX Potência RR, the doses of the growth regulator were 0; 50; 100; 200 and 400 g ha-1 of trinexapac-ethyl (Moddus®) and the application times were at the phenological stages V7, V10 and R2. The varieties BRS Valiosa and BMX Potência, respectively, were obtained at the phenological stage V10, with application of 200 g ha-1 of trinexapac-ethyl, greater dry matter accumulation of leaves and pods. Nevertheless, the same did not act on the foliar area of the BRS Valiosa RR variety in the same way that it did not induce changes in the production components of the BMX Potência RR variety. Regardless of the application period (V7, V10 and R2) and the dose (up to 400 g ha-1), the application of trinexapac-ethyl was not a management capable of influencing the agronomic characteristics and the lodging of the plants in both varieties.

Nitrogen supply associated with the application of trinexapac-ethyl in upland rice irrigated by sprinkler

The lodging of rice plants significantly increases the losses of this crop. Lodging is caused by the inadequate management of water and fertilizers, particularly nitrogenous fertilizers. The use of growth regulators causes a reduction in plant height and consequently lodging, and may reduce harvest losses. The objective of this study was to evaluate nitrogen (N) doses with and without application of plant growth regulator in upland rice irrigated by a sprinkler system. The experimental design consisted of randomized blocks arranged in a 4 × 2 factorial design with four replicates. The treatments consisted of four N doses (0, 40, 80, and 120 kg ha-1) combined with the presence or absence of foliar application of a plant growth regulator. The application of 150 g ha-1 of trinexapac-ethyl at the flower differentiation stage reduced plant height and lodging. In addition, this treatment promoted increased 100-grain mass. The use of N doses in topdressing increased plant heights and grain yield. The plant growth regulator did not interfere with the milling yield of upland rice. Nitrogen fertilization in the topdressing did not interfere with the milling yield of upland rice irrigated by a sprinkler system.

Pode o etiltrinexapac estimular o crescimento de mudas de eucalipto?

Reguladores vegetais e herbicidas atuam e modificam diversos processos metabólicos nas plantas. A aplicação de doses sub-letais destes compostos pode ser utilizada de modo a modular o desenvolvimento e o crescimento das plantas, um efeito denominado homesis. Múltiplos estudos tem relatado o efeito promotor de doses sub-letais de etil-trinexapac no acúmulo de biomassa e na expansão da área foliar de plantas de eucalipto. Até o presente momento, não há recomendação acerca de doses promotoras e/ou inibidoras de processos metabólicos para a cultura do eucalipto. Desta forma, este trabalho tem como objetivo investigar o efeito de doses crescentes de etil-trinexapac no estabelecimento e crescimento inicial de mudas de Eucalyptus urograndis. Etil-trinexapac foi aplicado em doses de 15 à 90 g de ingrediente ativo por hectare (g i.a. ha-1) em duas modalidades através da pulverização ou da imersão das raízes em solução. As doses de 15 g i.a. ha-1 via pulverização, e 30 g i.a. ha-1 via imersão de raízes, resultaram em efeito positivo no crescimento no clone GG100 de Eucalptus urograndis, com acréscimos de, respectivamente, 74,6% e 12,8% na massa seca total, em relação à testemunha. As doses de 15 à 90 g i.a. ha-1 via pulverização resultaram em efeito estimulatório no crescimento do eucalipto. As doses de 15 e 30 g i.a. ha-1, na modalidade imersão das raízes, proporcionaram efeito positivo nas características avaliadas do eucalipto. A dose de 90 g i.a. ha-1 apresentou efeito inibitório ao crescimento do eucalipto na modalidade imersão das raízes, aos 35 dias após a aplicação de etil-trinexapac.

Plant Growth Regulator and Irrigation Effects on Physiological and Harvest Maturity of Red Clover in Relation to Seed Quality

Core Ideas Trinexapac‐ethyl, a plant growth regulator, does not affect the quality of red clover seeds if applied at a rate of up to 700 g a.i. ha–1. Seeds reach maximum quality at harvest maturity, when seed moisture content is approximately 140 g kg–1. Visual indicators of physiological maturity of red clover include flower heads contain light brown petals and brownish‐green sepals, whereas seeds are pale green to pale yellow. At harvest maturity, heads contain dark brown petals and sepals, whereas seeds range from yellow to yellow‐dark grayish purple. A single irrigation application of water at the first flowering stage increased yield by approximately 9% in a 2‐yr study. Application of trinexapac‐ethyl at a rate of 560 g a.i. haw in the stem elongation stage increased seed yield by 16% in 1 of a 2‐yr study. Seed moisture content at physiological maturity of red clover ranges from 340 to 540 gkg–1 and approximately 140 g kg–1 at harvest maturity. Plant growth regulators (PGRs) and irrigation affect seed yield of red clover (Trifolium pretense L.). However, the effects of these factors on physiological maturity (PM), harvest maturity (HM), and seed quality are unknown. Therefore, the objectives of this study were to determine the effects of trinexapac‐ethyl (TE) PGR and irrigation on PM, HM, and seed viability and vigor on the most common red clover variety in Oregon over 2 yr. Five TE rates, ranging from 0 to 700 g a.i. ha−1, were applied at stem elongation and bud emergence stages. Irrigation was applied at the first flowering stage. Physiological and visual indicators were recorded to determine PM and HM. Standard germination (SG), tetrazolium (TZ) and cold (CT) tests were conducted to evaluate seed quality at weekly intervals starting from seed formation until HM. Irrigation resulted in a 4‐d delay in PM compared to the non‐irrigated treatment, but TE applications did not affect timing of seed maturation. At PM, flower heads contained light brown petals and brownish‐green sepals, whereas seeds were pale green to pale yellow. At HM, heads contained dark brown petals and sepals, whereas seeds ranged from yellow to yellow‐dark grayish purple. Seed dry weight did not change from PM to HM. Seed moisture content at PM ranged from 340 to 540 g kg−1 and decreased to below 140 g kg−1 at HM. At HM, seeds reached maximum quality as viability ranged from 92 to 98% by TZ and SG, and vigor ranged from 90 to 94% by CT.

Effect of Trinexapac-Ethyl, at Two Application Timings, on the Initial Development of Eucalyptus under Water Deficit

ABSTRACT: Eucalyptus plants are sensitive to stress during their initial development, and water deficit is the most important one. Thus, the hormetic effect caused by the application of chemical products may be a factor that allows plants to tolerate such stresses. The objective of this study was to evaluate the effects of trinexapac-ethyl on the initial growth of Eucalyptus urophylla (Clone I-144), under water deficiency, at two application timings (before planting - BP; and after planting - AP). Two experiments were conducted simultaneously in a greenhouse for 74 days after planting (DAP) eucalyptus in 15 L pots. Treatments consisted of three trinexapac-ethyl doses (0.0, 30, and 60 g a.i. ha-1) and two water conditions (with and without water deficit). A complete randomized block design was used, in a 3 x 2 factorial arrangement, with five replications. At the BP application timing, trinexapac-ethyl was sprayed at 0 DAP, and at the AP timing, at 24 DAP. In both experiments, plant height, diameter, leaf area, dry matter, total relative chlorophyll content and gas-exchange were evaluated. There was a positive effect for the net CO2 assimilation rate at 27 and 40 DAP, for AP and BP, respectively. Eucalyptus plants, without water deficit, presented higher growth, regardless of the application timing. In conclusion, the application of trinexapac-ethyl before planting caused a positive effect on the height and diameter of eucalyptus; and the application timing influenced, in different ways, the evaluated characteristics, not having harmful effects on any of them.

Growing Degree Day Models for Plant Growth Regulator Applications on Ultradwarf Hybrid Bermudagrass Putting Greens

Plant growth regulators (PGRs) are commonly applied to ultradwarf hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy] putting greens during the growing season. Trinexapac‐ethyl (TE) and prohexadione‐Ca (PH) are PGRs that inhibit gibberellic acid biosynthesis and are used to reduce clipping yield and improve turfgrass visual quality. Growing degree day (GDD) models have optimized the timing of PGR reapplications to creeping bentgrass (Agrostis stolonifera L.) putting greens, but no information is available regarding proper PGR reapplication timing on bermudagrass putting greens. The objective of this research was to develop a GDD model to determine optimal TE and PH application frequencies on bermudagrass putting greens. Field research was conducted on three ultradwarf cultivars at separate locations in the southeastern United States: ‘MiniVerde’ in Knoxville, TN, ‘Champion’ in Durham, NC, and ‘TifEagle’ in Starkville, MS. Peak yield suppression was 49 to 65% after TE application at 0.034 kg a.i. ha−1 and 50 to 54% after 0.154 kg PH ha−1. Peak suppression occurred later for TE (166–177 GDD calculated using 10°C as the base temperature [GDD10C]) than for PH (92–97 GDD10C), which resulted in an estimated PGR reapplication interval of 216 to 230 for TE and 120 to 126 GDD10C for PH. Enhanced clipping yield and rebound did not follow clipping yield suppression. The use of a GDD model to schedule PGR applications on bermudagrass putting greens has the potential to maximize PGR benefits; however, season‐long implementation of this GDD model needs comparison with current PGR programs used on ultradwarf putting surfaces.

Responses of Intermediate Wheatgrass to Plant Growth Regulators and Nitrogen Fertilizer

Core Ideas Trinexapac‐ethyl reduces height and lodging in wheatgrass.Trinexapac‐ethyl increased grain yield when lodging risk was high.Prohexanedione calcium had no effect on wheatgrass.Trinexapac‐ethyl can reduce risk of yield losses due to lodging. Intermediate wheatgrass (Thinopyrum intermedium; IWG), a new perennial grain crop, has the potential to provide ecosystem services while producing food‐grade grain; however, productivity is currently limited by high rates of lodging. Trinexapac‐ethyl (TE) and prohexadione‐calcium (PC) are widely used plant growth regulators (PGRs) for mitigating lodging and improving seed yield in other grass crops. Our objectives were to determine the effects of the PGRs PC and TE, PGR application rate, and nitrogen (N) fertilizer rate (0, 40, 80 kg N ha−1) on IWG lodging, height, and grain and biomass yields. Experiments were initiated in first‐ and third‐year stands at St. Paul and Rosemount, MN. Few effects of PC on IWG height, lodging, or yields were observed, while TE consistently reduced plant height by 10 to 20% and lodging by up to 20% in a year with high lodging risk. Application of TE to IWG at the recommended rate (437 g a.i. ha−1) or higher rates increased grain yields by 65 to 100% when lodging incidence was high, but did not affect grain yields in years with lower lodging risk. While a negative correlation between lodging and grain yields was observed, nitrogen fertilizer affected IWG grain and biomass yields in only one of five site‐years, and there was no interaction between N fertilizer and PGR effects on IWG. Nonetheless, the PGR TE demonstrated the potential to reduce plant height and lodging, thereby increasing IWG yield potential.

Phenological Sensitivity of Two Maize Cultivars to Trinexapac-Ethyl

ABSTRACT: In Brazilian agriculture there are few reports on trinexapac-ethyl (TE) effects on maize plant lodging management. This study aimed to evaluate the effects of sequential application of TE sprayed on different plant growth stages of maize using the simple hybrid P30F53HR and the variety SCS 154 Fortuna. Experiments were carried out in a greenhouse in the 2013 and 2014 harvests. Plants were grown singly in 5L pots filled with 75% soil and 25% substrate. The experimental design was a randomized complete block with four replications. The following treatments were performed: (T1) control (no application of growth retardant); (T2) application at V2 (100 g a.i. ha-1); (T3) sequential application of 100 g a.i. ha-1 at V2 plus V3; (T4) sequential application of 100 g a.i. ha-1 at V2+V3+V4; (T5) single application of 300 g a.i. ha-1 at V4; (T6) sequential application of 100 g a.i. ha-1 at V2+V3+V4+V5; (T7) sequential application of 100 g a.i. ha-1 at V2+V3+V4+V5+V6 and (T8) sequential application of 100 g a.i. ha-1 at V2+V3+V4+V5+V6+V7. The some morphological characteristics of the two maize genotypes changed in response to TE treatment. From stage V4 onwards, maize plant height showed signs of sensitivity to the growth retardant. Plants in T8 (TE applied over V2 to V7) were more sensitive to TE with over 45% reduction in plant height compared with application T7 (applied from V2 to V6). This response was similar in both maize genotypes, thus indicating that plants are highly sensitive to TE after the V6 stage.

Physiological quality of seeds of white oat cultivars in response to trinexapac-ethyl application

The aim of this study was to assess the effect of the growth retardant trinexapac-ethyl on the physiological quality of seeds of different grain white oat cultivars in two growing environments. The experiments were carried out in Londrina and Maua da Serra, Parana State, Brazil. The experimental design was a randomized block design in a 4 × 2 factorial scheme with four replications. Treatments consisted of four white oat cultivars (IPR Afrodite, IPR Artemis, URS Corona, and URS Guria), with and without growth retardant application. Trinexapac-ethyl was applied by foliar spraying in a dose of 125 g a.i. ha−1 at the stem elongation stage between the first and second perceptible node. The following parameters were assessed: germination, first germination count, length and dry matter of seedling shoot and root, accelerated aging, electrical conductivity, emergence rate index, seedling emergence in sand, one-thousand-seed weight. At the end of the study, Londrina and Maua da Serra presented a production potential white oat seed with germination above the standards for the species. Trinexapac-ethyl application reduced seed vigor of the cultivars IPR Afrodite and IPR Artemis produced in Londrina and Maua da Serra, respectively.

Chemical composition and physiological quality of wheat seeds with the application of trinexapac-ethyl, a plant growth regulator

This study evaluated the effect of the plant growth regulator trinexapac-ethyl on chemical composition and physiological quality of wheat seeds produced under fertilization for high yield potential. The experiment was performed under completely randomized design with five treatments (0; 200; 400; 600; 800 mL ha-1 of the commercial product Moddus ) and four repetitions. The plant growth regulator was applied at elongation via foliar spraying. Seeds were harvested at the end of crop cycle. Variables evaluated were 1000 seeds weight, germination and first count of germination, speed of germination index, seedling dry matter, electrical conductivity, accelerated ageing and the contents of total soluble sugars, starch, amino acids and proteins. The first count of germination increased until the higher dose. Electrical conductivity after three hours of imbibition reduced at the doses of 600 mL ha-1 and 800 mL ha-1, indicating greater seed physiological quality. Starch showed a trend of increase until the dose of 448 mL ha-1; amino acids until the dose of 243 mL ha-1 and protein until the dose of 417 mL ha-1. The content of total soluble sugars decreased with the increasing dose of the plant growth regulator. Therefore, wheat seeds produced from plants in which trinexapac-ethyl is applied present higher vigor and greater contents of starch, protein and amino acids, but lower content of total soluble sugars. Our results demonstrate that trinexapac-ethyl can be used for wheat management in seed production fields in the recommended dose (400 mL ha-1) with benefits in seed quality and composition.

Development of Different Grass Species with the Use of the Growth Regulator Trinexapac-Ethyl

ABSTRACT: The use of synthetic compounds to retard the growth of lawns aims at reducing the number of operations for their maintenance. Thus, the main goal of the present study was to evaluate the effect of different doses of trinexapac-ethyl on the development and rooting of five different grass species. Bahiagrass, St. Augustine grass, Japanese lawn grass, Bermuda grass and, broadleaf carpetgrass were grown in pots of 20 L. The experimental design was completely randomized, with four replications. Trinexapac-ethyl (g ha-1) was applied at doses of 113+113, 226+113, 226+226, 452+113, 452+226, 452+452 in a sequential spraying, and also at single doses of 678 and 904. The second application was carried out 14 days after the first. On the day prior to applications all species were cut at 3 cm height. The phytotoxicity evaluations were performed weekly, and evaluations on plant height, number and height of inflorescences, biomass of aerial parts and roots were carried out 35 days after the second application. The trinexapac-ethyl application was effective in inhibiting the development of the Japanese lawn grass, Bermuda grass and broadleaf carpetgrass when applied in sequential doses higher than 226 g ha-1, or single doses of 678 or 904 g ha-1 and, the visual appearance of lawns was not affected. In the case of St. Augustine grass and Bahiagrass species, the growth regulator did not promoted reduction in the growth of both grass species.

Growth regulator and maize response to the increase in plant density

Abstract: The objective of this work was to evaluate the effect of application of the growth regulator Trinexapac-ethyl on maize response to the increase in plant density at two sowing dates. A field experiment was carried out in the municipality of Lages, state of Santa Catarina, Brazil, during the 2014/2015 and 2015/2016 growing seasons. Two sowing dates (10/15 - preferential, and 12/5 - late), four plant densities (5, 7, 9, and 11 plants m-2), with and without Trinexapac-ethyl application, were tested. The growth regulator was sprayed at a rate of 150 g a.i. ha-1, when hybrid P30F53YH was at the V5 and V10 growth stages. The spraying of Trinexapac-ethyl decreased the stem length above the ear insertion node at both growing seasons. Grain yield ranged from 11,422 to 14,805 kg ha-1, and increased in a quadratic way with the increment in plant density. The highest yields were reached when maize was sown in October. The spraying of Trinexapac-ethyl did not affect grain yield, but decreased the 1,000 kernels mass at both sowing dates. The use of Trinexapac-ethyl does not enhance grain yield of maize hybrid P30F53YH at crowded stands in response to the densification, regardless of sowing time.

Trinexapac-Ethyl Causes Stimulatory Effect on the Initial Growth of Eucalyptus urograndis Clones

Eucalyptus plants are sensitive to stress factors in the initial growth phase. The plant growth regulator trinexapac-ethyl can provide gains to eucalyptus plants, a phenomenon known as hormesis. Thus, the aim of this work was to evaluate the effect of trinexapac-ethyl on the initial growth of two Eucalyptus urograndis clones (Clone 1 = I-144 and Clone 2 = 1407). The experiment was performed during 90 days after planting (DAP) of eucalyptus, in 100 L pots, with a randomized complete block design. The treatments were arranged in a 2 × 3 factorial scheme, with two eucalyptus clones and three trinexapac-ethyl doses (0, 30 and 60 g i.a. ha-1), with four replications. Fortnightly, plants height and stem diameter were evaluated. At 90 DAP, the leaf area and plants dry matter (DM) were evaluated. Clone 1 obtained leaf area and total DM 53% and 58% larger than Clone 2, respectively. The higher dose of trinexapac-ethyl provided mean gains of 30% in stem DM and total DM in Clone 1. For Clone 2, both doses of the product caused mean gains of 70% in stem DM, leaf DM and total DM. In conclusion, trinexapac-ethyl has a positive effect on the initial growth of E. urograndis, Clones I-144 and 1407. Clone I-144 showed higher growth than Clone 1407, regardless trinexapac-ethyl application. However, the Clone 1407 obtained more expressive gains with the application of trinexapac-ethyl, compared to Clone I-144.

Effects of Trinexapac‐Ethyl and Daconil Action (Acibenzolar‐S‐Methyl and Chlorothalonil) on Heat and Drought Tolerance of Creeping Bentgrass

The plant growth regulator trinexapac‐ethyl (TE) is known for its effects of suppressing shoot vertical growth. Some fungicides are claimed to promote the physiological health of plants in the absence of diseases. The objective of this study was to determine whether acibenzolar‐S‐methyl (one of the active ingredients in Daconil Action), TE alone, or the combination of the two may be most effective in promoting creeping bentgrass (Agrostis stolonifera L.) tolerance to heat and drought stress under field conditions. Daconil Action and TE were foliar applied alone or in combination to creeping bentgrass managed under fairway conditions at Rutgers University in 2014 and 2015. Stress tolerance was measured by evaluating turf quality, leaf membrane stability, relative water content, and canopy characteristics estimated by multispectral radiometry. Foliar application of either Daconil Action or TE alone improved heat and drought tolerance, and the positive effects were more pronounced and consistent during the stress periods with the combined treatment than either treatment alone. The beneficial effects of these compounds were most pronounced during periods of drought or heat when stress induced the most severe physiological damages. Foliar application of these compounds may help creeping bentgrass maintain better quality turf during hot or dry periods in warm climate conditions with limited water resources for irrigation.