Thesis (Ph. D.)--University of Idaho, 2005. / Abstract. "December 2005." Includes bibliographical references (leaves 88-92). Also available online in PDF format.

The effectiveness of 5-bromo-3-sec-butyl-6-methyluracil (bromacil) for the selective removal of orchardgrass (Dactylis glomerata L.) from Kentucky bluegrass (Poa pratensis L.) turf and some physiological responses of the grasses to bromacil were evaluated in field studies. Bromacil reduced photosynthesis to a greater extent in orchardgrass than Kentucky bluegrass turf. Foliage carbohydrates were depressed initially in bluegrass followed by recovery in 2 weeks to 1 1/2 months following bromacil application. Orchardgrass, however, did not recover. Application of 0.56 kg/ha bromacil each summer and fall for 2 years gave the best control of orchardgrass. During the second year, increase in foliage crude protein was observed in treated bluegrass. Bluegrass foliage yields were equal to or greater than the controls. Orchardgrass yields were drastically reduced by bromacil. Effective seedling orchardgrass control was obtained with minimal bluegrass injury at 0.14 to 0.28 kg/ha of bromacil. Bromacil treated areas were effectively fall-seeded with bluegrass approximately 8 weeks after a 0.56 kg/ha application, Rooting of bluegrass sod was not inhibited at the rates used for selective control of orchardgrass in bluegrass turf. In controlled environmental growth chamber studies, bromacil had no effect on germination of Merion Kentucky bluegrass or Virginia Common orchardgrass, but reduced the growth of emerging shoots of orchardgrass more than bluegrass. Fresh weight gain, root growth, and transpiration were reduced in orchardgrass plants at 0.125 ppmw bromacil whereas 1.0 ppmw gave reductions in bluegrass. Photosynthesis was inhibited initially in both grasses, however, bluegrass recovered in 6 days. Foliage carbohydrate content was greater and was affected less by bromacil treatment in bluegrass than orchardgrass. Root absorption and translocation of 2-¹⁴C-bromacil to the shoot was directly related to transpiration in both grasses. Bromacil was absorbed and translocated acropetally in sheath and foliar treatments in both grasses. Higher metabolic conversion of 2-¹⁴C-bromacil occurred in bluegrass as compared to orchardgrass with 1.0 ppmw treatment. The major metabolites were 5-bromo-3-(2-hydroxy-1-methylpropyl)-6-methyluracil and an unknown. Trace amounts of 3-sec-butyl-6-methyluracil and 5-bromo-3-sec-butyl-6- hydroxymethyluracil were also detected. Bluegrass tolerance to bromacil involves high carbohydrate levels in tissues, hydroxylation of bromacil, and rapid recovery of photosynthesis. / Ph. D.

The compatibility of ACP 2100, a member of the imidazolinone family (chemistry not released), imazaquin (2- [4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H̱-imidazol2- yl]-3-quinolinecarboxylic acid) and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid} was investigated for use in a turf management program, including growth regulation and broadleaf weed control. Field and greenhouse results indicated an antagonistic interaction between triclopyr and imazaquin for control of common dandelion (<i>Taraxacum officinale</i> Weber in Wigger). Addition of imazaquin at 276 g ha⁻¹ to triclopyr at 138 g ha⁻¹ resulted in less dandelion control than 138 plus 138 g ha⁻¹, respectively. Greenhouse and laboratory studies indicated a synergistic interaction between ACP 2100 and triclopyr, not apparent in the field. Addition of ACP 2100 to triclopyr at 34 and 69 g ha⁻¹ resulted in less than expected dandelion biomass, indicating increased dandelion control. ACP 2100 initially decreased triclopyr uptake, but resulted in greater uptake 48 hours after treatment. ACP 2100 also increased triclopyr translocation to the crown, root and middle rosette leaves. In the field and greenhouse, triclopyr did not influence growth regulation and decreased turf injury caused by ACP 2100. Studies showed that as the rate of ACP 2100 increased with the rate of triclopyr an antagonism occurred, resulting in decreased turf injury. The low rate of both ACP 2100 and imazaquin in combination resulted in equal turf growth regulation activity to the high rate of either chemical alone or in combination. One greenhouse study indicated that the interaction was synergistic for height suppression with ACP 2100 and imazaquin at rates of 12 plus 17 or 24 g ha⁻¹, respectively. However, field studies showed that ACP 2100/imazaquin combinations resulted in unacceptable injury to ‘l90’ and ‘Glade-Plush-Ram’ Kentucky bluegrass (<i>Poa pratensis</i> L.). The best turf quality, growth regulation and dandelion control was achieved with a combination of ACP 2100 at 96 and 144 g ha⁻¹ plus triclopyr at 276 g ha⁻¹. These results indicate that turf management costs may be reduced without sacrificing dandelion control by incorporating a chemical mowing program into a spring herbicide treatment. / Ph. D.

Cool season perennial grasses are the foundation of equine nutrition in the transition zone. The objective of this study was to evaluate forage quality using ADF, NDF, IVTDMD, CP, WSC, and ESC and changes in vegetative swards seasonally, diurnally, across species (Kentucky bluegrass, tall fescue, orchardgrass, and perennial ryegrass) and cultivar. This study was conducted in 2015 and 2017 and plots were maintained vegetatively with two to four week mowing. Morning and afternoon sample collection occurred monthly during the growing season. Samples were flash frozen; freeze dried, ground, and scanned using Near Infrared Reflectance Spectroscopy (NIRS) to predict forage quality. There was a significant year effect; therefore year was analyzed separately. Generally, ADF and NDF were highest for Kentucky bluegrass (30 and 52%), lowest for perennial ryegrass (25 and 46%), and tall fescue and orchardgrass were inconsistent. Crude protein was variable across species and season, ranging 10 to 25%. ADF and NDF concentrations were higher in the morning; IVTDMD, WSC, and ESC were higher in the afternoon; and CP was similar diurnally. In conclusion, forage quality in vegetative cool season grass pastures was sufficient to meet the nutritional needs of most equines, but varied seasonally, diurnally, across species, and cultivar.

Due to end users irrigating with excess water, water conservation of turfgrass can make a large impact in urban water conservation by reducing water applied while still maintaining visual appearance. This study was conducted to determine if Kentucky bluegrass (Poapratensis L.) can be deficit irrigated to maintain minimum acceptable appearance while conserving water. The study investigated water stress in terms of stomatal conductance, chlorophyll index, leaf temperature and predawn leaf water potential at the point of water stress, or where visual quality no longer meets expectations during dry down conditions. Water use was measured over well established Kentucky bluegrass with an eddy covariance system that was validated with soil water measurements. Turfgrass was irrigated at 80% of reference evapotranspiration based on allowable depletion of 12 mm of soil water during growing season that was considered to be well-watered. Two dry downs were conducted over a two-year period (early and late summer). Turfgrass was allowed to dry down without irrigation until visual quality reached the minimum acceptable points (score ≤ 6). During drying periods, visual rating, chlorophyll index, predawn leaf water potential, and leaf temperature with stomatal conductance rapidly decreased once stomatal conductance fell to approximately half of well-watered levels. Both soil water content and evapotranspiration had weak correlation with stomatal conductance; however, stomatal conductance tended to have higher correlation with the change in soil moisture than with the change in crop evapotranspiration. Soil water use and eddy covariance data in terms of crop evapotranspiration had high correlation. The plant water use factor ranged from around 0.8 to 1.1 under well-watered condition corresponding to visual rating from 7 to 9. At the minimum acceptable point of visual rating, which is 5.5 to 6, the plant factor ranged from 0.65 to 0.87. This value of plant factor is quite high at this point. Even when Kentucky bluegrass went below acceptable visual quality, the grass still used significant amounts of water with the plant factor value ranging from 0.6 to 0.8. The data suggested that deficit irrigation cannot be applied with Kentucky bluegrass in the Intermountain West area.

Billbugs are a serious pest of turfgrass in the Intermountain West. Billbug larvae severely discolor and eventually kill turfgrass by feeding in stems, on roots, and on crowns of the plant. Billbugs are typically managed with preventive, calendar-based applications of insecticides. Most of our knowledge on the biology and management of billbugs comes from research in the eastern U.S, and little is known about billbug biology and best management practices in the Intermountain West. First, I examined the seasonal activity of billbug life stages in Intermountain West turfgrass and developed a predictive degree-day model to better time management strategies against billbugs. I found that compared to the eastern U.S., a regional model that starts earlier (January 13) and has a cooler insect development threshold (3oC) was adequately robust to predict billbugs in Utah and Idaho. Next, I used the Utah-Idaho degree-day model to determine whether preventive and curative timings for billbug management developed in the eastern U.S. were effective in the Intermountain West. Testing four insecticides with the Utah-Idaho model and with eastern U.S. management timings I found that there was support to consider adoption of these same recommendations in Utah and Idaho, particularly for current preventive insecticides such as neonicotinoids and anthranilic diamides. Finally, considering that turf insecticides can negatively impact predatory insects, thought to viisuppress turf pests, I assessed the predatory arthropod community in Intermountain West turf and their impacts on billbugs. I found that the predatory arthropod community consisted primarily of ground beetles and spiders, representing 60% and 28% of all predators, respectively. I found that predators contributed the most by consuming billbug eggs and by changing the behavior of billbug adults with an observed reduction in mating activity. My research not only lays the ground work for development of effective, sustainable integrated management of billbugs in Intermountain West turfgrass, including conservation biocontrol,but also illustrates the necessity of regional predictive models, monitoring, and appropriate timing of management for successful turf pest suppression.

Glasshouse and growth-chamber experiments were conducted to evaluate primisulfuron phytotoxicity and the influence of adjuvants on downy brome and Kentucky bluegrass. GR₅₀ (50% growth reduction) values were 0.97 ± 0.57 and 8.07 ± 1.85 g/ha for downy brome and Kentucky bluegrass, respectively. Primisulfuron was applied to downy brome and Kentucky bluegrass at 3 placement sites; foliar, soil, and foliar plus soil. Foliar or foliar plus soil applications were more effective at reducing downy brome dry weights than the soil application of primisulfuron, while Kentucky bluegrass was injured more from the soil or foliar plus soil applications than from the foliar application of primisulfuron. Primisulfuron at 5 g/ha applied alone reduced downy brome dry weights by 5%, whereas, when an adjuvant was added, dry weights were reduced by 52 to 83%. Primisulfuron was more phytotoxic to downy brome at alternating temperatures of 8-16 C and 16-24 C than at 0-8 C. Phytotoxicity of primisulfuron was less when downy brome plants were stressed for soil moisture after herbicide treatments than when the plants were not stressed or only stressed before treatment. / Graduation date: 1999

A series of studies were initiated to investigate growth responses of Kentucky bluegrass (Poa praetensis L.) and creeping bentgrass (Agrostis palustris Huds.) to foliar applications of two plant growth regulators (PGR) and/or chelated Fe (Na Fe diethylene triamine pentaacetate). Environmental variables considered were N levels, soil moisture regimes, and saline irrigations. The two materials investigated for PGR properties were a commercial product called Roots (a cold-water extract of seaweed and peat humus fortified with "intermediate metabolites" and thiamine) and the systemic fungicide propiconazole, trade name: (Banner) and chemical name: [1- {(2-(2,4-dichlorophenyl)-4-propyl-l,3-dioxolan-2yl}methyl-l H-1,2,4-triazole]. Fortified seaweed extract (FSE) was applied at 9.3 L/ha, and propiconazole (PPC) was applied at 0.93 L a.i/ha. Each was applied alone or in conjunction with chelated Fe at 0.11 kg a.i/ha. Kentucky bluegrass foliage height, root and shoot dry weight, and several foliar nutrients increased following PGR treatments when grown under either limited soil moisture or saline irrigation. Foliar applications of PGR and/or chelated Fe to creeping bentgrass reduced wilting and evapotranspiration, and increased leaf water status, root strength, and shoot dry matter at two levels of N during and after drought stress. / Ph. D.

<p>Germination testing and seedling vigor for Kentucky bluegrass germination. Analyzing growth from Kentucky bluegrass cultivars. </p>

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Turfgrass covers 1.9% of the nation’s surface area and is the largest irrigated crop in the USA. Developed urbanized land is projected to double by 2025, which will increase turf’s environmental impact. Studies were conducted to evaluate environmental impacts by characterizing nitrogen, carbon, and water fluxes in turfgrass ecosystems. Emissions of nitrous oxide (N[subscript]2O), a major greenhouse gas and ozone depleter were measured from bermudagrass (Cynodon dactylon L. Pers. x C. transvaalensis Burtt-Davy) (bermuda), perennial ryegrass, (Lolium perenne L.) (rye), and zoysiagrass, (Zoysia japonica Steud.) (zoysia) under regional N management. In a separate study, N2O fluxes were measured from bermuda fertilized with controlled-release N fertilizers including polymer-coated and organic-N, and quick release urea. Emissions of N2O were measured using static surface chambers and gas chromatography. Zoysia, with less N requirements, had lower emissions than bermuda. Cumulative N[subscript]2O emissions were similar among N types. To measure water and carbon fluxes, a portable non-steady state chamber was designed and tested. The chamber had minimal affects to the canopy during field measurements: leak values averaged <1.5 micromol CO[subscript]2 m[superscript]-2 s[superscript]-1; average chamber pressure was 0.09 Pa ±0.01 Pa; temperature rise inside the chamber averaged 0.74C; and the chamber had 90% photosynthetically active radiation transmittance. Using the chamber, differences were detected in net photosynthesis (Pnet), gross photosynthesis (Pg), evapotranspiration (ET), canopy stomatal conductance (gc), and water use efficiency (WUE) in well-watered tall fescue (Festuca arundinacea Schreb.), Kentucky bluegrass (Poa pratensis L.) (KBG), zoysia, and bermuda. Irrigation requirements, visual quality ratings, and genetic rooting potential of 28 KBG cultivars and 2 Texas bluegrass hybrids (P. pratensis x P. arachnifera Torr.) were quantified in greenhouse and rainout facility studies. Average water applied ranged from 23.4 to 40.0 cm among cultivars. Bedazzled, Preakness, and Bartitia required less water and had higher average quality than other cultivars. Compact America and Mid-Atlantic phenotypes exhibited greatest potential for success in integrating reduced water inputs with maintenance of acceptable visual quality. Results indicated that turfgrass management could mitigate N[subscript]2O emissions and conserve water while maintaining healthy turfgrass, and the new chamber will enhance turfgrass studies by providing rapid measurements of photosynthesis.