Palmer amaranth (Amaranthus palmeri) is a major weed in United States cotton and soybean production systems. Originally native to the Southwest, the species has spread throughout the country. In 2004 a population of A. palmeri was identified with resistance to glyphosate, a herbicide heavily relied on in modern no-tillage and transgenic glyphosate-resistant (GR) crop systems. This project aims to determine the degree of genetic relatedness among eight different populations of GR and glyphosate-susceptible (GS) A. palmeri from various geographic regions in the United States by analyzing patterns of phylogeography and diversity to ascertain whether resistance evolved independently or spread from outside to an Arizona locality (AZ-R). Shikimic acid accumulation and EPSPS genomic copy assays confirmed resistance or susceptibility. With a set of 1,351 single nucleotide polymorphisms (SNPs), discovered by genotyping-by-sequencing (GBS), UPGMA phylogenetic analysis, principal component analysis, Bayesian model-based clustering, and pairwise comparisons of genetic distances were conducted. A GR population from Tennessee and two GS populations from Georgia and Arizona were identified as genetically distinct while the remaining GS populations from Kansas, Arizona, and Nebraska clustered together with two GR populations from Arizona and Georgia. Within the latter group, AZ-R was most closely related to the GS populations from Kansas and Arizona followed by the GR population from Georgia. GR populations from Georgia and Tennessee were genetically distinct from each other. No isolation by distance was detected and A. palmeri was revealed to be a species with high genetic diversity. The data suggest the following two possible scenarios: either glyphosate resistance was introduced to the Arizona locality from the east, or resistance evolved independently in Arizona. Glyphosate resistance in the Georgia and Tennessee localities most likely evolved separately. Thus, modern farmers need to continue to diversify weed management practices and prevent seed dispersal to mitigate herbicide resistance evolution in A. palmeri.

Master of Science / Department of Agronomy / Johanna A. Dille / Corn yield potential is limited by water deficit stress and limited soil nitrogen. Field and greenhouse experiments were conducted near Manhattan, KS in 2005 and 2006. The field experiment evaluated the influence of nitrogen (N) rate and increasing Palmer amaranth (PA) density grown alone and in competition with corn in two moisture environments. In 2006 the dryland environment was very drought stressed, while 2005 had more intermediate conditions. Weed-free corn yields were approximately half in dryland environments compared to the irrigated environment across years. Increasing PA density increased corn yield loss similarly in both 2005 environments and in 2006 dryland environment across all N rates. In the 2006 irrigated environment corn yield loss was increased by decreasing N rate and increasing PA density. Maximum predicted yield loss at high PA densities in both 2005 environments was 20-54% while in 2006 dryland environment, maximum yield loss was 95% and in the irrigated environment was 62%. In general, soil moisture environment was more critical than N rate or PA density when determining potential corn yield. In the greenhouse study a factorial arrangement of two irrigation methods and five crop-weed combinations (corn, PA, GF, corn/PA, and corn/GF) was established with two replications and three runs conducted. Two plants were grown in 25.4 cm diameter PVC pipe cut into 91.5 cm lengths. Irrigation application method included a surface and subsurface application. Plants were harvested at the V10 corn growth stage. No differences were detected between irrigation methods with respect to above- or below ground biomass production. Corn aboveground biomass was decreased by the presence of corn or PA but not GF. Below ground biomass information was presented as column totals because species could not be separated. There was no impact on root to shoot ratio, total below ground biomass, rooting depth, or root area across the crop-weed combinations except for the GF monoculture columns which were lower than all other crop-weed combinations. Future research needs to examine the light interception of corn and PA when grown at different N rates along with examining the influence of surface and subsurface irrigation practices on crop weed interactions and weed seed germination in a field setting.

One of the most influential disturbances for stream fish assemblages is large-scale declines in flow caused by periods of drought. Although stream characteristics are known to influence the response of stream fishes to drought, we asked if ecological traits of stream fishes determine, in part, their population level response to drought. To test for ecological trait-based responses to drought in a stream fish assemblage, we quantified species abundances over a period of 5 years that represented a wet to dry period. We sampled stream fishes in Yellow Creek, Wyoming, USA, a high elevation stream dependent on snow-storage for most of its flow. There were five regularly occurring species in the study site: redside shiner (Richardsonius balteatus), northern leatherside chub (Lepidomeda copei), mottled sculpin (Cottus bairdi), speckled dace (Rhinichthys osculus), and mountain sucker (Catostomus platyrhynchus). We used size class, species, and drought measures as predictors of abundance. Mean Palmer drought severity index over the growing season from the previous year (one year lag) provided the best predictor of stream fish abundances. Four of five species showed strong declines in abundance in response to drought conditions (mountain sucker abundance was not affected), but ecological traits of species were not good predictors of the magnitude of response to drought. Northern leatherside chub are most vulnerable to local extirpation during times of severe drought. Overall, juveniles showed a greater decline in abundance than adults in response to drought. Climate models predict that mountain streams will experience changes in flow regime, which may exacerbate effects of drought. Low flow refuge habitat may need to be incorporated into stream restoration designs to help increase recolonization in streams, especially for stream fishes that are most vulnerable to local extirpation and that have low recolonization rates.

The resistance of Palmer amaranth (PA) and the tolerance (natural resistance) of pitted morningglory (PM) to glyphosate have made these species among the most common and troublesome weeds in the southeastern U.S. since the adoption of glyphosate-resistant (GR) crops. Populations of GR PA (R1 and R2) were identified in Mississippi. The inheritance of glyphosate resistance was examined in reciprocal crosses (RC) between glyphosate-resistant (R) and -susceptible (S) parents (Female-S × Male-R, S/R, and Female-R × Male-S, R/S), and second reciprocal crosses (2RC) (Female-S/R × Male-S/R, S/R//S/R, and Female-R/S × Male-R/S, R/S//R/S). Dose-response assays resulted in 17- to 4old resistance to glyphosate compared with S. Population S accumulated 325- and 8-times more shikimate at the highest glyphosate dose than in R1 and R2, respectively. cDNA sequence analysis of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene indicated no target site mutation. Genomes of R1, R2, RC, and 2RC contained from 1- to 59old more copies of EPSPS gene than S; EPSPS was highly expressed in R1 and R/S, but was poorly expressed in S, S/R, and R2. EPSPS activity was lower in S and S/R than in R and R/S, glyphosate absent; all were inhibited by glyphosate. Western Blot analysis confirmed an increased EPSPS protein level to EPSPS copy number correlation. Thus, the level of resistance was decidedly influenced by the direction of the cross. R and S female plants were reproductively isolated and seed were still produced, suggesting that PA can produce seed both apomictically and sexually (facultative apomixis). This mode of reproduction determined the low copy number inheritance, as well as guaranteeing the GR trait stability in the R populations. Dose-response assays resulted in 2.6old variability in tolerance to glyphosate between the most tolerant (MT) and the least tolerant (LT) PM populations. The level of tolerance positively correlated with the time of exposure to GR-crop system. Less shikimate was recovered in MT as compared to LT. Levels of aminomethylphosphonic acid (AMPA) were not different between populations and sarcosine was not present in either populations. Consequently, metabolism of glyphosate to AMPA or sarcosine is not a common factor in explaining natural resistance levels.

The continued spread of Palmer amaranth (Amaranthus palmeri S. Wats.) throughout the southern and midwestern United States is a result of herbicide-resistant populations. Besides being the most troublesome weed specie in several agronomic crops, Palmer amaranth is also host to economically important pests such as tarnished plant bug (Lygus lineolaris Palisot de Beauvois). Pesticide application methodology that maximizes efficacy while reducing selection pressure is needed to combat herbicide-resistant Palmer amaranth. Pulse width modulation (PWM) sprayers are used for pesticide application with the goal of maintaining product efficacy while mitigating spray drift. Additionally, alternative off-season weed management practices such as flooding could be adopted to optimize soil seedbank depletion. Therefore, evaluation of spray droplet size and flooding period on Palmer amaranth control and seed germination was conducted. The objectives of this research were to: (1) evaluate the influence of spray droplet size on lactofen and acifluorfen efficacy on Palmer amaranth using a PWM sprayer, (2) develop prediction models to determine spray droplet size that provides the greatest level of Palmer amaranth control, (3) evaluate the impact of flooding period and seed burial depth on Palmer amaranth seed germination in different soil textures, and (4) analyze the impact of nitrogen fertilizer application rate on the attractiveness of Palmer amaranth to tarnished plant bug. Results show that spray droplet size does not affect lactofen efficacy on Palmer amaranth, thus, coarser spray droplets are recommended to increase spray drift mitigation efforts. In contrast, acifluorfen applied with 300 μm (medium) spray droplets provided the greatest Palmer amaranth control. Furthermore, prediction models indicated that greater model accuracy was obtained when adopting a location-specific weed management approach. Flooding periods of 3, 4, and 5 months reduced Palmer amaranth seed germination across burial depths and soil textures. Therefore, fall-winter flooding may be adopted as an effective practice for soil seedbank depletion. Results also demonstrated that nitrogen fertilizer application rate does not consistently impact Palmer amaranth attractiveness to tarnished plant bug.

Weeds pose a challenge to cotton production, and herbicides have been the primary means of control. However, there is growing concern over weed resistance to herbicides. To address this issue, we evaluated three cover crop species and six cotton accessions for weed suppression. The study found that hairy vetch, wheat, and B16 cotton CS line effectively suppressed Amaranthus species, while MNTN 4-15, B16, hairy vetch, and wheat were correlated with the highest cotton yield. Cover crops were also analyzed for chlorogenic acid content, with wheat, MNTN 4-15, and hairy vetch producing the highest amounts. The greenhouse tray study showed that wheat and hairy vetch cover crops were among the best treatments for weed suppression. These findings suggest that cover crops may provide effective weed control and improve crop yield.

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This thesis is a study and description of the process of designing the scenic elements of Saying Grace by Robert Smythe, an adaptation and translation of the play Divinas Palabras by Ramón María del Valle-Inclán written for Temple University Theater. The body outlines the process the author took in researching and developing the concept for the play, finalizing the design with the director of the piece, and completing the actual drafting and artwork necessary to realize said design. It also details the actual construction of the scenery, properties, and puppet elements, discusses the final product and offers self-evaluation. Plates of the drawing and drafting, and photographs of the scale model and final production accompany this work. / Theater

Herbicide resistant weeds are driving implementation of integrated weed management (IWM). A new tactic to manage weeds is harvest weed seed control (HWSC), which targets weed seeds retained on the plant at crop harvest and either destroys, removes, or concentrates them. Research is limited on the effectiveness of HWSC in US cropping systems. For HWSC to be effective it is important to know when and how many seed are shed from a weed species in relation to crop harvest. Research was conducted to quantify when weed seed are shattered from 6 economically important weed species, four broadleaf (redroot pigweed, common ragweed, common lambsquarters, and common cocklebur) and two grass species (large crabgrass and giant foxtail). Results indicate that among summer annuals, broadleaf species retain larger proportions of their seed compared to grass species at the first opportunity for soybean harvest. As harvest was delayed, more seeds shattered from all species evaluated, indicating timely harvest is critical to maximizing HWSC effectiveness. Studies were conducted on grower fields in Virginia to evaluate the effectiveness of HWSC (field residue and weed seed removal). Results indicate that HWSC can significantly reduce populations of Italian ryegrass in wheat and common ragweed in soybean in the next growing season, but reductions were not observed for Palmer amaranth in soybean. Investigating IWM system for common ragweed control in soybean, HWSC was found to be less effective than soybean planting date (i.e. double cropping after wheat) at reducing common ragweed populations. However, the effectiveness of HWSC varied by location. If HWSC adoption were to become widespread, weeds could adapt by shedding seed earlier in the season. Research was conducted by growing Palmer amaranth populations from across the eastern US in a common garden. Currently there are differences in flowering time and seed shatter among Palmer amaranth populations based on the location of the maternal population, indicating potential for adaptation. This research demonstrates that HWSC is a viable option for weed management in US cropping systems but needs to be stewarded like any other weed management tool. / Doctor of Philosophy / Herbicide resistance in weeds is a growing problem in the US and around the world. Alternative methods of weed control must be adopted to maintain crop yields in the presence of herbicide-resistant weeds. Researchers and extension specialists strongly advise growers to adopt an integrated weed management (IWM) approach. Integrated weed management involves implementing multiple weed control tactics during a growing season. By using multiple methods of weed control within a given season the chances of weeds becoming resistant or adapting to any single tactic is reduced. Harvest weed seed control (HWSC) is a new tactic developed in Australia in response to herbicide resistance. HWSC targets weed seeds retained on the plant at crop harvest. In a normal crop harvest, the combine removes the grain and spreads crop residues (leaves, stalks, and other plant parts), including weed seeds, back across the field. When HWSC is implemented, weed seeds are destroyed (narrow windrow burning, cage mills) or concentrated and potentially removed from the field (chaff carts, direct bale, chaff lining). Thus, HWSC limits the number of weed seeds returned to the soil seed bank. There is limited research on HWSC and its integration with other tactics, in US cropping systems. For HWSC to be effective it is necessary for weed seeds to be retained on the mother plant in sufficient quantities at crop harvest. Research was conducted in Virginia to determine when weed seeds are shattered during the soybean growing season for 6 economically important weed species, four broadleaf (redroot pigweed, common ragweed, common lambsquarters, and common cocklebur) and two grass species (large crabgrass and giant foxtail). The broadleaf species retained >85% of their seed until the first opportunity for soybean harvest (mid-October). In the grass species, more seed shattered prior to soybean harvest with 50% of large crabgrass and 74% of giant foxtail seed being retained at the first opportunity for soybean harvest. When harvest was delayed seed continued to shatter and less was captured using HWSC. This research indicates broadleaf species are more suitable candidates for HWSC than grass species, among summer annuals. Further research on the ability of seed to germinate in relation to when seeds were shed was conducted on redroot pigweed, common ragweed and common lambsquarters. Results indicate that there are variable effects on germination of these species depending on when they were shed. HWSC was implemented on grower fields to assess the impact on weed populations of 3 weed species (Italian ryegrass, common ragweed, and Palmer amaranth). These experiments compared conventional harvest and HWSC (field residue and weed seed removal) when all other management strategies were the same within that field. Italian ryegrass tiller density in wheat varied by location but was reduced up to 69% in the spring following implementation of HWSC. By wheat harvest, HWSC reduced Italian ryegrass seed head density 67% at one location compared to conventional harvest. In soybean, common ragweed densities were reduced by 22 and 26% prior to field preparation and postemergence herbicide applications, respectively, in the HWSC plots compared to the conventional harvest plots. No differences were observed in common ragweed density by soybean harvest. No differences were observed with Palmer amaranth densities at any point during the soybean growing season. This research show that HWSC can reduce weed populations but is variable and additional research is still needed. IWM experiments were established across Virginia to compare soybean planting date (full season or double cropped), + cover crop (cereal rye/wheat or no cover), and + HWSC (field residue removal) to evaluate the best management strategy for common ragweed in soybean. Across all locations, double cropping soybean behind wheat had the greatest impact on common ragweed densities at the end of the first season. The impact of double cropping soybeans on common ragweed population is due to the emergence pattern of common ragweed; majority of common ragweed emerges prior to planting double cropped soybean (mid-June to early-July). HWSC was variable and only reduced common ragweed density at one of three locations. Widespread adoption of HWSC could place a selection pressure on weeds to shatter seed earlier in the season. A common garden experiment was conducted in Blacksburg, VA to assess Palmer amaranth populations collected from central Florida to southern Pennsylvania for differences in flowering time, time to seed shatter, and other phenotypic traits. Results indicate that latitude of the maternal population influences time to first flower with a 0.53 d reduction in flowering time for every degree north in latitude the maternal population was collected from. The strongest predictor of Palmer amaranth flowering time was emergence date/daylength. For every day emergence was delayed the time to first flower was reduced by 0.31 and 0.24 d for female and male plants, respectively. Time from emergence or first flower to first seed shatter was reduced by 0.48 or 0.17 d, respectively, for each day emergence was delayed. These results indicate that differences exist currently among Palmer amaranth populations and the selection pressure of HWSC could push these populations to flower and shatter seed early.