Theses and Dissertations at Montana State University (MSU)
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Item Exploring the potential of entomopathogenic nematodes against wireworms in Montana(Montana State University - Bozeman, College of Agriculture, 2020) Sandhi, Ramandeep Kaur; Chairperson, Graduate Committee: Michael A. Ivie; David Shapiro-Ilan, Anamika Sharma Gadi V P Reddy were co-authors of the article, 'Efficacy of available entomopathogenic nematode strains against Limonius californicus (Mannerheim)' in the journal 'Biological control' which is contained within this dissertation.; Ratnasri Pothula, Satyendra K. Pothula, Byron J. Adams, Gadi V.P. Reddy were co-authors of the article, 'First record of native entomopathogenic nematodes from Montana agroecosystems' in the journal 'Journal of nematology' which is contained within this dissertation.; David Shapiro-Ilan and Gadi V.P. Reddy were co-authors of the article, 'Montana native entomopathogenic nematode species against Limonius californicus (Coleoptera: Elateridae)' in the journal 'Journal of economic entomology' which is contained within this dissertation.; David Shapiro-Ilan, Gadi V P Reddy and Michael A. Ivie were co-authors of the article, 'Efficacy of entomopathogenic nematode infected insect cadavers against wireworms in greenhouse and field' submitted to the journal 'Pest management science' which is contained within this dissertation.; Gadi V P Reddy, David Shapiro-Ilan and Michael A. Ivie were co-authors of the article, 'Effect of soil texture, soil moisture, and soil temperature on efficacy of entomopathogenic nematode strains against wireworms under laboratory conditions' submitted to the journal 'Journal of applied entomology' which is contained within this dissertation.Wireworms (Coleoptera: Elateridae), are important soil-dwelling pests and have become a serious threat to spring wheat in the Northern Great Plains because of lack of effective control measures, creating a need for alternative control methods such as biological control with entomopathogenic nematodes (EPNs). Ten EPN strains were tested against sugarbeet wireworm, Limonius californicus (Mannerheim) in laboratory bioassay. Out of these ten strains, Steinernema carpocapsae (Weiser) (All and Cxrd strains) and S. riobrave Cabanillas, Poinar, and Raulston (355 and 7-12 strains) were found effective in laboratory and shade house. However, the dose required to kill at least 50% of the treated L. californicus larvae was 200 infective juveniles/cm 2. Two Montana native EPN species (S. feltiae and Heterorhabditis bacteriophora) were extracted and were evaluated against L. californicus in laboratory and shade house. Although, 50% mortality was observed due to S. feltiae isolates in laboratory conditions, none of the two isolates of S. feltiae performed well against L. californicus in shade house. Steinernema carpocapsae and S. riobrave in the form of infected Galleria mellonella L. cadavers were evaluated against wireworms (L. californicus and H. bicolor) in field and greenhouse. In field, none of the four EPN strains were found effective in reducing wireworm populations or protecting crop yield in both spring wheat and barley fields. However, only one infected Galleria cadaver of S. carpocapsae (All and Cxrd) and S. riobrave 355 was able to kill wireworm larvae as well as reduce wheat plant damage in greenhouse. The imidacloprid treatment enhanced the infection and killing ability of EPNs against L. californicus. Steinernema carpocapsae All and Cxrd were able to kill 30-46% of L. californicus larvae in all four soil types tested as compared to S. riobrave 355 and 7-12 strains, when maintained at field capacity moisture levels. However, S. carpocapsae All and Cxrd strains were able to infect 35-50% wireworm larvae in sandy loam and clay loam soil type at standardized moisture (18%). Steinernema carpocapsae All and Cxrd killed greater wireworm numbers at 16% moisture level and 25 °C as compared to other moisture and temperature levels in sandy clay loam soil. These results indicate that EPN based strategies could be useful for wireworm management but need to be explored further under field conditions. This strategy can at least be part of a large Integrated Pest Management system for wireworm control in Montana.Item Elucidating the effect of anthropogenic land management on soil nematode community structure(Montana State University - Bozeman, College of Agriculture, 2019) Burkhardt, Andy; Chairperson, Graduate Committee: Jamie Sherman; Shabeg S. Briar, John M. Martin, Patrick M. Carr, Jennifer Lachowiec, Cathy Zabinski, David W. Roberts, Perry Miller and Jamie Sherman were co-authors of the article, 'Perennial crop legacy effects on nematode community structure in semi-arid wheat systems' in the journal 'Applied soil ecology' which is contained within this thesis.; Shabeg S. Briar, John M. Martin, Patrick M. Carr and Jamie Sherman were co-authors of the article, 'Characterization of soil nematode community structure in semi-arid dryland barley (Hordeum vulgare L.) systems' which is contained within this thesis.Nematodes as a taxonomic phylum are incredibly diverse and play an important role in soil biology, nutrient cycling, and soil food web function. Nematodes can be categorized into five major trophic groups including bacterivores, fungivores, herbivores, predators, and omnivores. Plant-parasitic nematodes (PPNs) affect soil food web resources through direct herbivory, while free-living (non-pathogenic) bacterivores and fungivores graze on microbes and contribute significantly to soil nutrient pools. Predatory nematodes regulate the soil food web by preying on other nematodes and invertebrates in the soil. An unbalanced soil food web community can lead to unintended impacts to other species and create a cascading effect. In agriculture, this impact can lead to low crop production and reduced revenue by means of soil ecological degradation. The goal of this project was to elucidate the nematode community structure changes under different management strategies in both agricultural and range settings. The hypotheses we tested were 1) that crop rotations eliminating fallow would positively and significantly impact the soil nematode community that would in turn self-regulate the PPN population and 2) native sagebrush steppe would have a more diverse nematode community than converted sagebrush steppe managed for livestock grazing or other uses. We did so with the following studies: 1. Quantitatively assessed nematode community structure under barley monoculture and barley-fallow vs. barley-pea rotations using multiple ecological measures and indices and correlated those measures and indices with soil chemical and physical properties as well as agronomic parameters of each system. 2. Quantitatively assessed nematode community structure under wheat-tilled fallow, wheat-no-till fallow, and no-till wheat monoculture vs. several no-till wheat-pulse rotations using multiple ecological measures and indices to evaluate long term impacts of cropping system to the nematode community. 3. Quantified taxonomic diversity and ecological indices of disturbed and undisturbed sagebrush steppe in the Bangtail Mountains west of Wilsall, Montana to evaluate disturbance regimes in a reclaimed environment.Item An assessment of nematodes affecting wheat in Montana(Montana State University - Bozeman, College of Agriculture, 2018) Al-Khafaji, Riyadh Talib; Chairperson, Graduate Committee: Alan T. DyerNematodes represent a major biological constraint on wheat and barley production worldwide, and yet no comprehensive assessment of plant parasitic nematodes associated with cereals has been conducted for Montana. To address this shortcoming, a survey was conducted to determine the species of plant parasitic nematodes associated with small grains, and an assessment of variation in virulence across 4 crops and 8 resistant wheat lines was conducted for Pratylenchus neglectus populations collected from across Montana. The survey, conducted across 11 counties, and found widespread distribution of P. neglectus, Tylenchorhynchus spp., and Tylenchus spp. within the state. Populations of P. neglectus were generally low (268 to 363 nematodes/kg of dry soil for 2015 and 2016, respectively). However, destructive populations were detected in 9 fields in both 2015 and 2016. In addition, populations of the cereal cyst nematode Heterodera avenae were detected. Cereal cyst nematode Heterodera filipjevi, a regulated pest, was detected in only one field. Additional species of parasitic nematode were detected, but rare. To assess the applicability of resistant crops and wheat lines for management of P. neglectus, greenhouse trials were conducted using nematode populations from within the state. In two trials conducted with resistant crops, significant interaction was detected between crops and populations of nematodes (ANOVA P< 0.001 and P= 0.01). In the first trial, populations from 3 counties were virulent on barley (mean reproductive factor = 10.9). Populations from other counties were either non-virulent on barley, or their inoculations were ineffective. In the second trial, 2 of the 3 populations were again virulent on barley (mean Rf = 4.4 and Rf = 10.7). Trials examining virulence across resistant wheat lines found no interactions between populations and wheat lines (ANOVA P= 0.60 and P= 0.93). While significant variation in reactions to the resistant lines were detected, none of the lines appeared particularly resistant to Montana populations, with mean Rf values of 13.1 and 15.4 for trials 1 and trials 2, respectively. Results suggest plant parasitic nematodes are localized problems, with P. neglectus and Heterodera species of particular concern, and that "resistant" wheat lines and barley may ineffective in managing P. neglectus in some regions of the state.Item Discovery and distribution of root lesion nematode, Pratylenchus neglectus, in Montana(Montana State University - Bozeman, College of Agriculture, 2007) Johnson, Wendy Ann; Chairperson, Graduate Committee: Alan T. Dyer.Root lesion nematodes (Pratylenchus neglectus and P. thornei) cause significant yield losses for wheat worldwide. To assess the prevalence of root lesion nematodes in Montana, soil samples were collected statewide in 2006 and 2007. In 2006, P. neglectus was found in 12 of the 17 counties and in 41% of all field samples surveyed. In 2007, P. neglectus was found in 11 of 15 counties and in 37% of all field samples surveyed. No P. thornei was found. For fields having root lesion nematode in 2006, P. neglectus mean population densities were 1213 nematodes/kg soil with population densities exceeding the damage threshold of 2500 nematodes/kg soil in 14% of the sampled fields. For fields having root lesion nematodes in 2007, P. neglectus mean population densities were 1303 nematodes/kg dry soil with densities exceeding the damage threshold of 2500 nematodes/kg dry soil in 13% of the samples. Damaging populations were restricted to the north central part of the state and were generally found in fields following a crop of winter wheat (p= 0.02). Stunt nematodes (Tylenchorynchus spp.) were detected in 93% and 85% of sampled fields for 2006 and 2007, respectively.