Theses and Dissertations at Montana State University (MSU)

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Biochemical, physiological, and genetic investigations of multiple herbicide resistant Avena fatua L.
(Montana State University - Bozeman, College of Agriculture, 2023) Wright, Lucas Arlin; Chairperson, Graduate Committee: William Dyer; Barbara K. Keith (co-chair)
Intense herbicide usage has led to the evolution of herbicide resistant weeds, which threaten food production and security. The multiple herbicide resistant (MHR) Avena fatua (wild oat) lines investigated here are resistant to all members of selective herbicide families available for A. fatua control. The research in this thesis is designed to help understand some of the ecological, biochemical, and genetic aspects of MHR. First, MHR lines with elevated volatile organic compound (VOC) levels and herbicide susceptible lines were used to compare the feeding behavior of Spodoptera exigua (beet armyworm), and potential role of VOCs to mitigate herbicide injury. Results for feeding behavior were mixed, possibly being influenced by environmental and genetic changes more than VOCs. Exposing VOCs to A. fatua lines found that linalool reduced flucarbazone injury of HS plants, while a combined VOC treatment generally increased herbicide injury. MHR responded differently than HS plants to some treatments, suggesting that MHR has fundamental VOC perception alterations. Other studies compared plant pigments and energy management capabilities and showed that MHR lines had higher beta-carotene and chlorophyll b concentrations, as well as enhanced photosynthetic and excess energy management capabilities in MHR lines. Finally, two populations of recombinant inbred lines (RILs) were phenotyped for herbicide resistance and used to discover several quantitative trait loci (QTL) associated with resistance. Overall, this work contributes to our understanding of MHR and will lay the groundwork for future studies.
Ventenata (Ventenata dubia) control treatments on the Crow Reservation
(Montana State University - Bozeman, College of Agriculture, 2023) Fighter, Zachariah Zachary Zane; Chairperson, Graduate Committee: Jane M. Mangold; Scott Powell (co-chair)
Ventenata (Ventenata dubia) is a non-native winter annual grass that has been of increasing concern in southeastern Montana. Research has shown that ventenata can increase rapidly, lower forage production, and reduce biodiversity. This project is located in southeastern Montana, in Bighorn County on the Crow Reservation. Two studies were conducted to understand control options and monitoring of those treatments post-treatment. A field study tested two herbicides and a soil amendment for the management of ventenata. At four sites, indaziflam and imazapic at two water carrier rates and two rates of an organic soil nutrient amendment were tested using a split-plot randomized block design. The water carrier rates were meant to mimic aerial and ground applications. Herbicides were applied using a hand-held boom sprayer pressurized by CO 2. Soil amendment was hand-broadcasted. In late June 2022 (first growing season post-treatment), sampling consisted of randomly placing 3, 20 cm x 50 cm frames in each split-plot and estimating cover by species along with litter and bare ground. Imazapic and indaziflam provided the highest reduction of ventenata, regardless of water carrier rate. Across the four sites, imazapic reduced ventenata cover to <1% while indaziflam reduced cover to 4%, compared to the control which was 38%. The soil amendment reduced ventenata to 25% at two sites, suggesting it may not be as promising of a control method as the herbicides. Application rates for all treatments did not differ, suggesting that aerial application of the herbicides may provide just as good of control as ground application. This is encouraging for the prospect of managing ventenata aerially. At one of the sites, a remote sensing time series study using an Unmanned Aerial Vehicle (UAV) with a multispectral sensor was used to understand differences in the Normalized Difference Vegetation Index (NDVI) between herbicide sprayed and non-sprayed plots. Findings indicate that there is a shift in NDVI in late June where sprayed plots peak in NDVI and remain green longer into the season than non-sprayed plots. This study provides control options that land managers in southeastern Montana can consider using for ventenata management.
Hybridization and invasiveness in Eurasian watermilfoil (Myriophyllum spicatum): is prioritizing hybrids in management justified?
(Montana State University - Bozeman, College of Agriculture, 2021) Hoff, Hannah Katherine; Chairperson, Graduate Committee: Ryan Thum; Ryan A. Thum was a co-author of the article, 'Hybridization and invasiveness in Eurasian watermilfoil (Myriophyllum spicatum): is prioritizing hybrids in management justified?' submitted to the journal 'Invasive plant science and management' which is contained within this thesis.
Hybridization can play an important role in the evolution of invasiveness. Eurasian watermilfoil (Myriophyllum spicatum L.) is a widespread aquatic invasive plant species that hybridizes with native northern watermilfoil (Myriophyllum sibiricum Kom.). Previous studies have found mixed evidence for whether hybrid watermilfoil (Myriophyllum spicatum x sibiricum) and pure M. spicatum differ in vegetative growth rate and herbicide response. While several studies have emphasized variation in these traits among M. spicatum x sibiricum genotypes, variation within M. spicatum has not been considered. Therefore, it is unclear how important genetic variation within M. spicatum, versus between M. spicatum and M. spicatum x sibiricum, is in influencing invasive traits and management outcomes. If M. spicatum x sibiricum genotypes are always more invasive than M. spicatum genotypes, simply distinguishing taxa may be sufficient for identifying lake management priorities; however, if significant phenotypic overlap is observed between taxa, distinguishing individual genotypes may be important for tailoring management strategies. We performed replicated trials of a vegetative growth and 2,4-D assay to measure clonal variation in growth rate and herbicide response of M. spicatum and M. spicatum x sibiricum. Our results indicate that M. spicatum x sibiricum exhibits higher average vegetative growth than M. spicatum, whether or not it is treated with 2,4-D. We did not observe interactions between taxon and treatment or between genotype and treatment. Despite differences between M. spicatum and M. spicatum x sibiricum in average vegetative growth, there was substantial overlap between taxa. For example, we found that the fastest-growing genotype of pure M. spicatum did not differ significantly in average growth from the fastest-growing M. spicatum x sibiricum genotype. The potential for overlap between these invasive Myriophyllum taxa suggests that distinguishing and characterizing genotypes may be more informative for management than simply distinguishing between M. spicatum and M. spicatum x sibiricum.
Integrating DNA fingerprinting of invasive watermilfoil strains into aquatic vegetation monitoring and assessment
(Montana State University - Bozeman, College of Agriculture, 2021) Gannon, Kathryn Alta; Chairperson, Graduate Committee: Ryan Thum; Raymond Newman and Ryan Thum were co-authors of the article, 'Integrating DNA fingerprinting of invasive watermilfoil strains into aquatic vegetation monitoring and assessment' submitted to the journal 'Journal of aquatic plant management' which is contained within this thesis.
Eurasian watermilfoil (Myriophyllum spicatum L.) and its hybrids with native northern watermilfoil (Myriophyllum spicatum L. x Myriophyllum sibiricum) (invasive watermilfoils) are among the most heavily managed invasive aquatic plants in the United States. Within invasive watermilfoils there are distinct strains which are produced through sexual reproduction and can be maintained indefinitely by clonal propagation. Different strains can differ in their invasiveness (e.g., growth and potential for spread) and response to herbicides. However, strain identification is not routinely implemented as part of management planning or evaluation. In this thesis, we integrated molecular fingerprinting that can distinguish different Eurasian and hybrid watermilfoil strains into aquatic vegetation monitoring in eight Minnesota lakes over the course of three years. We provide proof of concept that by tracking strain incidence over time it is possible 1) to detect changes in strain composition of invasive watermilfoil populations, and 2) to identify priority strains for future growth and herbicide assays. This study demonstrates that integrating genetic fingerprinting into aquatic vegetation management and evaluation holds promise to inform management decisions by identifying those strains that have the most invasive potential. As far as we are aware, this is the first published study to examine the strain composition of invasive watermilfoil populations over time.
Impacts of a non-native forb, Alyssum desertorum Stapf., and non-target effects of Indaziflam in the sagebrush steppe of Yellowstone National Park
(Montana State University - Bozeman, College of Agriculture, 2021) Meyer-Morey, Jordan; Chairperson, Graduate Committee: Lisa J. Rew
Non-native plants can reduce biodiversity and disrupt essential ecosystem services and functions. For most non-native plant species however, quantitative evidence of negative effects is lacking, as are fundamental demographic details; such information can inform whether and at what growth stage to implement control. Control strategies can also negatively impact non-target native plant communities; therefore, evaluating the tradeoffs of management and understanding the actual impacts of the invader is essential. I sought to understand the life history, and evaluate the competitiveness and impacts of the non-native annual forb, Alyssum desertorum Stapf., as well as non-target effects of management, across an elevation gradient in a cool, mountain sagebrush (Artemisia tridentata ssp. vaseyana (Rydb.) Beetle) steppe plant community. Seed viability, fecundity, overwintering success, and likelihood of reaching reproductive maturity of A. desertorum all declined as elevation increased; all life stage transition rates were high, suggesting that targeting seed production or fall germination would be the most effective means for control of this species. Replacement series experiments revealed that A. desertorum is a weak competitor with functionally similar species. Additionally, in the field, the presence of A. desertorum did not affect species richness nor Shannon's diversity aboveground or in the soil seedbank, and functionally similar native annual forbs were not displaced in invaded areas. I evaluated the efficacy and non-target effects of the pre-emergent herbicide, indaziflam, in diverse sagebrush steppe with localized infestations of A. desertorum across an elevational gradient. While indaziflam effectively controlled A. desertorum for two years, the richness and diversity of the surrounding community was reduced. Indaziflam inhibited recruitment of forbs, both in the field and in the seedbank. As indaziflam provides residual control of the soil seedbank for up to three years, my results suggest the future community composition may be altered, particularly native annual forb populations. Considering the weak competitive ability of A. desertorum, the species' minimal impacts to richness and diversity, and the negative effects of indaziflam to annual native forb species, I conclude that the non-target effects of indaziflam would outweigh any benefits to controlling A. desertorum in intact sagebrush steppe.
Restoring semi-arid lands with microtopography
(Montana State University - Bozeman, College of Agriculture, 2019) Dillard, Shannon Leigh; Chairperson, Graduate Committee: Anthony Hartshorn
Water is often limiting to plant establishment in semi-arid lands, and this limitation can be especially pronounced in restoration contexts where human legacy impacts and/or non-native plants are present. The application of herbicide and mulch can help retain soil moisture by killing unwanted plant species or lowering evaporative losses, respectively. Creation of microtopography, or soil surface variation, is a third technique that could alleviate growing-season water shortages. Here we report findings from a study that explored the effects of these three techniques combined with broadcast seeding a mix of four native grasses, one native shrub, and one native forb for increasing plant canopy cover and density at three sites in northern Yellowstone National Park. One year after treatment, plant cover in control plots averaged 60%. Across plots treated singly with 1.5% glyphosate herbicide, 3 cm of red cedar mulch, or hand-dug microtopography, only mulch and microtopography increased canopy cover relative to control plots, although the increase consisted mostly of non-native species (>97%). Herbicide, not surprisingly, decreased canopy cover, and that decrease also consisted mostly of non-native species. The herbicide treatment was the most effective in encouraging native species canopy cover and density while simultaneously reducing the same measures of non-native species. Microtopography treatments encouraged growth of all plants (native and non-native), particularly in the micro-lows, but for this to be an effective restoration strategy, non-native species must first be controlled. Although herbicide was quite effective at reducing non-native species populations, particularly at the Cinnabar site, spraying must be timed with the phenology of the existing non-native plant community. We learned that reducing competition with non-native plants does not necessarily encourage native plant growth, which may indicate that growing conditions need to be improved at this site before restoration can be successful. Taken together, our results suggest that soil amendments like microtopography and mulch may have beneficial restoration applications in semi-arid lands but may also show little benefit on a short time-scale in a highly disturbed system. Areas plagued by non-native species invasions and legacy agricultural and grazing impacts are likely to require careful planning of restoration approaches in order to claim long-term success.
Restoration of spotted knapweed infested grasslands in Glacier National Park
(Montana State University - Bozeman, College of Agriculture, 2003) Stringer, Lewis Tipton; Chairperson, Graduate Committee: Catherine A. Zabinski
There is an immediate and on-going need in Glacier National Park (GNP), and other public and private lands, to determine effective methods to re-establish and sustain native plant populations following control treatments of Centaurea maculosa. My research was developed in response to GNP concerns regarding annual herbicide treatment of C. maculosa invaded sites. The aim of this study was to determine if herbicide applications, site preparation and revegetation methods would increase the density and percent cover of native species, while reducing spotted knapweed at two sites in and near Glacier National Park. A priori contrast analysis was used to determine differences in treatment effects. The results of my experiment show that spot spray herbicide application reduced C. maculosa cover without significantly reducing existing native forbs. However, a repeat-herbicide application increased exotic graminoid cover. Tillage reduced the density of C. maculosa seedlings, but resulted in an increase in C. maculosa percent cover, and an overall decline in native forbs. Revegetation methods had limited success at increasing native species, and reducing C. maculosa. The only effect was at Swift Current, where the percent cover of native forbs was significantly higher with the planting treatment, and most pronounced in plots with repeat-herbicide application. Additionally, we measured the composition and density of the seed bank in C. maculosa dominated sites using the seedling emergence method. C. maculosa density was 3,900 and 6,714 seeds / m 2 at the two sites, which was 2 and 3 times higher than the sum of all other species. Seed bank composition and density needs to be considered in efforts to restore C. maculosa infested areas.
Genetic surveys in combination with laboratory studies on growth and response to herbicide can help design, evaluate, and optimize Eurasian watermilfoil management plans
(Montana State University - Bozeman, College of Agriculture, 2018) Guastello, Paula Ropp; Chairperson, Graduate Committee: Ryan Thum; Ryan A. Thum was a co-author of the article, 'Mesocosm evaluation of Eurasian and hybrid watermilfoil response to endothall in Jefferson Slough, Montana' in the journal 'Journal of aquatic plant management' which is contained within this thesis.
Eurasian watermilfoil (Myriophyllum spicatum) is a top priority for aquatic plant managers in the United States. Dense mats of Eurasian watermilfoil obstruct irrigation and recreational activities, while drastically reducing property values and potentially providing a habitat for disease-carrying mosquitos. Nuisance populations are generally managed through herbicide use. Eurasian watermilfoil is capable of both sexual and clonal reproduction, creating a unique opportunity for adaptation: sexual reproduction generates genetic variation within a population, then fit genotypes can propagate via clonal reproduction. Pure Eurasian watermilfoil is genetically diverse, and additional genotypes result from frequent hybridization with native northern watermilfoil (Myriophyllum sibiricum). Recent studies have shown that genetic variation in Eurasian watermilfoil populations may affect herbicide efficacy in managed populations. Given the variability in herbicide response, I propose conducting site-specific studies to evaluate the response of genotypes in a waterbody to evaluate and optimize management strategies. In my thesis, I evaluated the potential to control nuisance pure and hybrid Eurasian watermilfoil with endothall in a riverine environment (Jefferson Slough, Montana). Molecular genetic surveys indicated that only one genotype of each taxon was present throughout the slough. I first compared vegetative growth and endothall response of the hybrid and Eurasian genotypes in the greenhouse, where I did not identify a difference in endothall sensitivity. Next, I evaluated the efficacy of an operational endothall treatment in Jefferson Slough. Similar to the greenhouse study results, hybrid and Eurasian watermilfoil were reduced to the same average biomass seven weeks after operational endothall treatment. Taken together, the greenhouse and operational field treatment indicate that the genotypes in Jefferson Slough were similarly susceptible to endothall. However, vegetative growth differences may have important management implications over time. In the greenhouse, Jefferson Slough hybrids grew significantly more than Eurasian watermilfoil in the absence of endothall. Additionally, there was a qualitative shift towards higher frequency of hybrids where the taxa intermixed. These results suggest a relatively higher potential for re-growth of hybrids compared to Eurasian watermilfoil following treatment. Jefferson Slough hybrids may require additional treatment to achieve sufficient long-term control. In conclusion, I discuss integration of genetic surveys into management and research priorities.
Effect of spectral band selection and bandwidth on weed detection in agricultural fields using hyperspectral remote sensing
(Montana State University - Bozeman, College of Agriculture, 2017) Tittle, Samuel Bryant; Chairperson, Graduate Committee: Rick L. Lawrence
Presence of weeds in agricultural fields affects farmers' economic returns by increasing herbicide input. Application of herbicides traditionally consists of uniform application across fields, even though weed locations can be spatially variable within a field. The concept of spot spraying seeks to reduce farmers' costs and chemical inputs to the environment by only applying herbicides to infested areas. Current spot spraying technology relies on broad spectral bands with limited ability to differentiate weed species from crops. Hyperspectral remote sensing (many narrow, contiguous spectral bands) has been shown in previous research to successfully distinguish weeds from other vegetation. Hyperspectral sensor technology, however, might not currently be practical for on-tractor applications. The research objectives were to determine (1) the utility of using a limited number of narrow spectral bands as compared to a full set of hyperspectral bands and (2) the relative accuracy of narrow spectral bands compared to wider spectral bands. Answers to these objectives have the potential for improving on-tractor weed detection sensors. Reference data was provided by field observations of 224 weed infested and 304 uninfested locations within two winter wheat fields in Gallatin County, Montana, USA. Airborne hyperspectral data collected concurrently with the reference data provided 6-nm spectral bands that were used in varying combinations and artificially widened to address the research objectives. Band selection was compared using Euclidean, divergence, transformed divergence, and Jefferies-Matusita signature separability measures. Certain three and four narrow band combinations produced accuracies with no statistical difference from the full set of hyperspectral bands (based on kappa statistic analysis, alpha = 0.05). Bands that were artificially widened to 96 nm also showed no statistically significant difference from the use of 6-nm bands for both all bands and select band combinations. Results indicate the potential for bands that can differentiate weed species from crops and that the narrowest spectral bands available might not be necessary for accurate classification. Further research is needed to determine the robustness of this analysis, including whether a single set of spectral bands can be used effectively across multiple crop/weed systems, or whether band selection is site or system specific.
Evaluating non-native annual brome control with herbicides and facilitating Wyoming big sagebrush establishment in degraded drylands
(Montana State University - Bozeman, College of Agriculture, 2017) Metier, Emily Pierson; Chairperson, Graduate Committee: Lisa J. Rew; Matt Rinella (co-chair)
The degradation of drylands, through resource extraction and non-native annual brome invasion, is a major problem throughout the Intermountain West. Most restoration relies on establishing desired species from seed, but success is limited and establishing Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) is especially failure prone. This study focused on developing methods for controlling annual bromes, specifically cheatgrass (Bromus tectorum L.) and Japanese brome (Bromus japonicus Thunb.), and successfully re-introducing native sagebrush steppe species to degraded drylands. In the greenhouse, I assessed the efficacy of glyphosate and four graminicides (clethodim, sethoxydim, fluazifop, and quizalofop) applied at two rates, to cheatgrass plants of different heights. I also assessed the same five herbicides on three accessions of cheatgrass and Japanese brome. All herbicides reduced cheatgrass biomass, with most effective control on plants less than 11 cm. Overall, glyphosate and sethoxydim treatments were least effective, and quizalofop and fluazifop treatments were most effective. Japanese brome and the disturbed accessions of both species were more susceptible to herbicides than cheatgrass and the undisturbed accessions. My field study targeted the same annual bromes on two Montana coal mines. Four herbicide treatments (control, glyphosate, quizalofop, or glyphosate plus quizalofop) and two seeding treatments (differing in the amount of sagebrush seed) were evaluated for their effectiveness to manage annual bromes and boost seeded species establishment. Half of each herbicide plot was retreated with quizalofop the second year. All herbicide treatments reduced annual brome cover, especially in plots that received glyphosate. Wyoming big sagebrush density and cover of sown species increased in seeded plots with and without herbicides, but there was no difference between seeding treatments. Herbicide effects on seeded species were inconsistent, though generally establishment was greatest in plots receiving glyphosate. Quizalofop retreatment reduced annual brome cover, but did not impact seeded species establishment. These results suggest that targeted herbicide applications can be used to control non-native annual bromes and increase seeded species establishment. Specifically, using glyphosate pre-seeding when plants are small and graminicides post-seeding, can decrease annual brome cover. These treatments can provide a window of opportunity for establishing species from seed, including Wyoming big sagebrush.

Theses and Dissertations at Montana State University (MSU)

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