Theses and Dissertations at Montana State University (MSU)
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Item Overcoming the challenges of tamarix management with Diorhabda carinulata through the identification and application of semiochemicals(Montana State University - Bozeman, College of Agriculture, 2018) Gaffke, Alexander Michael; Chairperson, Graduate Committee: David K. Weaver; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Paul A. Grieco, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Semiochemicals to enhance herbivory by Diorhabda carinulata aggregations in saltcedar (Tamarix spp.) infestations' in the journal 'Pest management science' which is contained within this thesis.; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Field demonstration of a semiochemical treatment that enhances Diorhabda carinulata biological control of Tamarix spp.' submitted to the journal 'BioControl' which is contained within this thesis.; Sharlene E. Sing, Tom L. Dudley, Daniel W. Bean, Justin A. Russak, Agenor Mafra-Neto, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Allee effects and aggregation pheromones: new releases of Diorhabda carinulata remain longer in the presence of pheromone formulations' submitted to the journal 'Biological Invasion' which is contained within this thesis.; Sharlene E. Sing, Jocelyn Millar, Tom L. Dudley, Daniel W. Bean, Robert K. D. Peterson and David K. Weaver were co-authors of the article, 'Behavioral responses of Diorhabda carinulata adults to repellent compounds isolated and identified in volatiles collected from conspecific larvae' submitted to the journal 'Journal of chemical ecology' which is contained within this thesis.The northern tamarisk beetle, Diorhabda carinulata (Desbrochers), is an approved and established classical biological control agent for saltcedars (Tamarix spp.). Adequate control of Tamarix has not yet been achieved in certain areas where D. carinulata has been released. Retaining beetle populations on sites where it has been released is problematic, and accurately monitoring D. carinulata populations to determine successful establishment is difficult. Negative, indirect impacts have also resulted from the agent's establishment outside targeted treatment areas in the southwestern United States. Manipulation of D. carinulata spatial distribution with semiochemicals could potentially resolve or ameliorate these and other operational issues. Lures utilizing a specialized wax based matrix for the controlled release of semiochemicals were impregnated with a previously identified pheromone and/or behaviorally active host plant volatiles known to stimulate aggregation in D. carinulata. Emission of these compounds from the matrix was characterized using a push-pull volatile collection system, and quantified using gas chromatography-mass spectrometry. Observed release rates confirm that semiochemicals lures formulated with this matrix are a viable option for facilitating aggregation of D. carinulata under field conditions. The results of field-based assays indicate saltcedars treated with this semiochemical delivery system attracted and retained higher densities of D. carinulata than Tamarix that received a control (semiochemical free) lure. Higher densities of both adult and larval D. carinulata were recorded on treated plants. Semiochemically treated Tamarix plants also exhibited more damage, resulting in a greater decrease in canopy volume than control trees. The attraction and retention of D. carinulata to these species-specific semiochemicals on treated Tamarix plants also arrested the dispersal of newly released individuals, resulting in greater population growth. Repellent semiochemicals were also investigated for their potential to manipulate spatial distributions of D. carinulata in the field and behavioral assays conducted with reproductive adults demonstrated the ability of larval produced compounds to repel conspecific adults. These results indicate that semiochemical-impregnated media could be useful for detecting, retaining, and directing populations of D. carinulata. The use of semiochemicals could be used to potentiate low density populations, increase monitoring efficacy, retain adults on release sites, and repel D. carinulata from sensitive habitat.Item Olfactory preference and reproductive isolation of two Mecinus species (Coleoptera: curculionidae): implications for biological control of dalmatian, yellow, and hybrid populations of Toadflax, Linaria species(Montana State University - Bozeman, College of Agriculture, 2016) Hubbard, Charles Eli; Chairperson, Graduate Committee: David WeaverClassical biological control of the exotic, invasive toadflaxes Linaria vulgaris (L.) Mill. and Linaria dalmatica Mill. has had both successes and failures. One of the new challenges land managers face is the apparent increase in vigor shown by naturally occurring hybrid populations of the two toadflax species. This has presented practical problems because managers now are unable to decide which weevil species to use on these hybrids: Mecinus janthinus, which is found on L. vulgaris, or M. janthiniformis which has preference for L. dalmatica. This key question was addressed using olfactometer experiments to determine if the volatile profile for each plant establishes host fidelity for the naturally-occurring associated Mecinus species. Adults of both insect species were paired in cages on clones of naturally occurring and synthetic reciprocal cross hybrids and the parent toadflax species to quantify mating events and to determine the number of offspring produced on clones of each plant type of plant in incomplete randomized blocks. We did this using both intraspecific and interspecific pairs of Mecinus species to determine how many offspring are produced by intraspecific adults and also to explore the possibility of establishing a hybrid weevil population using clones of each plant type. Host plant preference for both Mecinus species is influenced by olfactory responses, but this was only evident for adult females. Our first series of no-choice experiments with intraspecific mating pairs indicated that M. janthiniformis is more successful in terms of offspring produced for all types of hybrid toadflax tested. The results also showed that M. janthinus had a higher percentage of survival on all types of hybrids. As expected each Mecinus species performed best on its natural host plant. The results of our second series of no-choice experiments suggest that these two weevil species can produce viable interspecific offspring on clones of most of the plant types evaluated. This suggests that the newly described M. janthiniformis is very similar to M. janthinus and the separation between the two species is controlled at least in part, by olfactory cues from the favored host. In the future, land managers can better decide which Mecinus species to use based on whether the hybrid weed species is influenced more by L. vulgaris, or L. dalmatica.Item Soil nutrient availability as a mechanistic assessment of carbon addition and biological control of spotted knapweed (Centaurea maculosa Lam.)(Montana State University - Bozeman, College of Agriculture, 2003) Brockington, Michel Rene; Chairperson, Graduate Committee: Roger L. Sheley.Item Factors involved in the success and establishment of the field bindweed gall mite Aceria malherbae Nuzzaci (Acari: eriophyidae)(Montana State University - Bozeman, College of Agriculture, 2014) Konigsberg, Evelyn Rivka; Co-chairs, Graduate Committee: Jeffrey Littlefield and Tracy M. SterlingDespite years of study and management, field bindweed (Convolvulus arvensis L., Fam.: Convolvulaceae) remains a problematic invasive species across the United States and is in need of better management options. Studies were conducted to determine factors affecting the establishment and performance of the biological control agent Aceria malherbae Nuzzaci. To determine the effects of sub-lethal herbicide applications on gall induction and development of A. malherbae, a bioassay was conducted with four herbicides, each having different modes of action. Atrazine, glyphosate, imazapic, and picloram were applied at 25% of their recommended dosages on plants infested and not infested with A. malherbae. Sub-lethal herbicide applications had an adverse effect on plant stem height, total stem length, numbers of leaves or branches, or on above-ground or below-ground biomass; whereas A. malherbae did not. Synergistic impacts of herbicide applications and A. malherbae on growth parameters of field bindweed were not observed. Pre- and post-spray gall counts were not significantly different, indicating that gall induction and development was not altered by these sub-lethal dosages. The establishment and effectiveness of A. malherbae has been reported to vary across western North America, with genetic variation of field bindweed as a possible contributing factor. Four field bindweed populations, collected from Montana, California, Oregon, and New Mexico, were exposed to A. malherbae to determine if growth parameters conducive or detrimental to the development of the mite vary among plant populations. When grown in a common environment, plant height, stem length, and number of branches and leaves significantly varied among populations although biomass did not differ. Galling by A. malherbae did not impact field bindweed growth, except for slight reduction in root biomass of infested plants. Gall induction was lower on plants from New Mexico than Oregon. Field studies assessed the relationship between habitat characteristics and plant cover and the presence and abundance of the mite. Multidimensional scaling of site characteristics indicated a spatial relationship, though no habitat relationship, among established A. malherbae populations. In within-field studies, a significant positive relationship was observed between percent grass cover and mite abundance and a negative relationship between field bindweed and mite abundance.Item Enhancing efficacy of herbicides to control cheatgrass on Montana range, pasture, and Conservation Reserve Program (CRP)(Montana State University - Bozeman, College of Agriculture, 2013) Ehlert, Krista Ann; Co-chairs, Graduate Committee: Jane M. Mangold and Richard E. EngelChemical control of cheatgrass has recently focused on imazapic; factors such as application rate and timing and the presence of plant litter can influence imazapic's efficacy. Herbicides minimally impact the seedbank so integrating a seed-killing pathogen like Pyrenophora semeniperda may result in more effective and sustainable control. My research objectives were to 1) test the effect of imazapic application rate and timing and plant litter on cheatgrass and desired plant species in range and Conservation Reserve Program (CRP) lands, 2) conduct a soil bioassay to determine imazapic persistence as affected by imazapic rate, presence of plant litter, and time after herbicide application, and 3) determine whether the fungal pathogen P. semeniperda combined with a single imazapic application would provide greater control of cheatgrass than either strategy used alone. Objective 1 was carried out in range and CRP lands over two years with a factorial combination of four imazapic rates, two litter manipulation treatments and/or two application timings. In general, all three imazapic rates were equally effective in controlling cheatgrass compared to the non-sprayed control. Litter manipulation treatments had little effect on imazapic efficacy, but early application of imazapic resulted in more consistent cheatgrass control. Objective 2 was conducted in the greenhouse using soil samples collected over a six month period from the field study for Objective 1. Cucumber and cheatgrass were used as indicator species. All three herbicide rates reduced both species' biomass below that of the control. Again, litter manipulation had a minimal effect, and imazapic was found to persist through the following spring after spraying. Objective 3 was explored in a greenhouse experiment using a factorial combination of two imazapic treatments, two P. semeniperda treatments, and three seeding depths. Pyrenophora semeniperda reduced cheatgrass emergence, while cheatgrass biomass and density were affected by imazapic and the integration of imazapic and P. semeniperda. Imazapic and P. semeniperda did not favorably interact to reduce biomass and density; however, integrating these two tools holds promise as P. semeniperda can reduce the seedbank, and imazapic can control seedlings that escape pathogen-caused mortality.Item Vegetative reproduction and the integrated management of Canada thistle(Montana State University - Bozeman, College of Agriculture, 2009) Sciegienka, Joanna Katarzyna; Chairperson, Graduate Committee: Fabian D. Menalled.Canada thistle (Cirsium arvense (L.) Scop.) is an aggressive, introduced creeping perennial weed that flourishes in a wide variety of environments. Its deep, creeping root system and colony forming tendencies make it one of the most difficult weeds to control. A strategy that incorporates a better understanding of the biology of Canada thistle into the development of an integrated management plan that includes herbicides and biological control could help reduce the dispersal and impact of this species. The objectives of this work were to: 1) determine how Canada thistle emergence and growth are affected by changes in root size, biomass, burial depth, and soil moisture and 2) compare single and joint impacts of herbicides and biological control agents on Canada thistle growth. Objective 1 was carried out in a greenhouse and in field conditions. To monitor Canada thistle emergence and growth responses, a completely randomized factorial design was used in the greenhouse, and a randomized complete block design was used in the field. Models were developed to predict emergence and growth patterns based on available water, burial depth, and various root metrics. For the exception of available water, the same predictors were used in field conditions to predict Canada thistle emergence and growth. The variables that were manipulated were able to significantly predict the responses measured, and we concluded that available water, root burial depth, and root weight, length, diameter, and volume are indicators of emergence likelihood, emergence time, shoot and root growth, and shoot number. Objective 2 was carried out in greenhouses and field settings. Three herbicides were evaluated with and without insects to determine reduction in Canada thistle root and shoot biomass in the greenhouse. One herbicide was also used at a low rate and evaluated singly and in combination with a stem-boring weevil (Hadroplontus litura (F.)) and a pathogen (Pseudomonas syringae pv. tagetis) to determine effect on Canada thistle response in the greenhouse and field. We failed to reject our null hypothesis of additivity between control agents, and concluded that integrating individual control methods yields greater Canada thistle control than any singular method.