Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Jan. 13, 2009). PDF text: vii, 132 p. : ill. (some col.) ; 4.76 Mb. UMI publication number: AAT 3315331. Includes bibliographical references. Also available in microfilm and microfiche formats.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 31, 2007). Includes bibliographical references.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Georgia Davis. Vita Includes bibliographical references.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 86-87). Also available via the Internet.

Thesis (Ph.D.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 1, 2009) Vita. Includes bibliographical references.

No description available.

The thesis aims to optimize the methods of laboratory culture and to fill in the gaps in knowledge of D. virgifera virgifera ecophysiology. The experiments on embryology and development proved that the diapause of D. virgifera virgifera is of obligatory type and can be terminated by exposure to long-day conditions (20:4; photo : scotophase) and constant temperature of 25 °C. Approximately 10% of eggs completed the development to adults within 4 months. Besides numerous other environmental conditions that are discussed, temperature seems to be a key factor influencing longevity in this pest. Higher temperature of 25 °C prolonged survival by more than 20 days in 2015, compared to 22 °C in 2014.

<p>The western corn rootworm (WCR) <i>Diabrotica virgifera virgifera</i> Leconte is a major pest of maize in the United States. Currently, it is principally managed using Bt maize hybrids and neonicotinoid seed treatments (NSTs), which were concurrently introduced in the early 2000s. This simultaneous release, and subsequent rapid adoption, created a situation in which Bt maize hybrids were never assessed in the absence of NSTs, and vice versa. Consequently, neonicotinoids’ influence on refuge function, primarily whether these insecticides aid or hinder the production of a sufficient population of susceptible beetles to delay resistance, has not been assessed. Moreover, a mounting suite of detrimental environmental effects of NSTs have been documented, lending some urgency to questions about their necessity.</p><p>To determine the influence of NSTs on refuge function, untreated and treated Bt maize fields were planted with 5% untreated refuge marked with ¹⁵N. Throughout the field seasons of 2019 and 2020, adults were collected from these fields and analyzed to determine their natal host plant. Results documented that the numbers of refuge beetles produced by the 5% seed blend are likely insufficient to result in rates of mating to delay resistance development.</p><p>To determine if the effect of using NSTs in combination with Bt maize hybrids is additive, synergistic, or neutral at managing secondary soil pests in the Midwest, four 16 block fields were planted in 2018, 2019 and 2020 comparing four treatments (1. Untreated, Bt seed; 2. NST, Bt seed; 3. Untreated, non-Bt seed; 4. NST, non-Bt seed). Compact method sampling, root rating, and yield were used to document the presence of secondary soil pests. All three sampling years documented low abundance of white grubs and wireworms. There was minimal influence of NSTs on maize yield (2018: p = 0.07; 2019: p = 0.62; 2020: p = 0.056) and root damage (0-3 scale) (2018: M = 0.0092; 2019: M = 0.0091; 2020: M = 0.0361). These same fields were used to document the presence of NSTs in soil, as well as residues in nearby waterways. Results documented greatest soil and water clothianidin levels earlier in the season and declined as the season progressed.</p><p><br></p>

<p>Root phenotyping technology is an essential component of modern agriculture and plant science research. Conducting root-related research in a non-destructive manner is crucial for studying plant roots without damaging the plants themselves and allowing for time-series studies. The research aims to validate the efficacy of MISIRoot, an innovative root phenotyping technology, through the implementation of two projects. The first project focuses on the early detection of western corn rootworm, one of the most devastating corn rootworm species in North America, particularly in midwestern corn-growing areas. The second project focuses on the assessment of the soybean nodulation process, which is crucial for nitrogen fixation by Rhizobia living in the nodules on the soybean roots. The current state-of-the-art methods for western corn rootworm and soybean nodulation assessments still require the whole plant to be dug up, which causes irreversible destruction to the plant itself. Although recently developed root phenotyping methods such as minirhizotron, CT, and MRI scanners offer unique advantages in observing plant roots, their potential for field applications is currently limited.</p> <p>Data collection for both projects was carried out using MISIRoot, a minimally invasive plant root phenotyping robot that works in situ within natural soil. The MISIRoot system mainly consists of an industrial-level robotic arm, a mini-size camera with a lighting set, a plant pot holding platform, and image processing software for root recognition and feature extraction. MISIRoot can take high-resolution color images of the roots in soil with minimal disturbance to the root and reconstruct the plant roots' three-dimensional (3D) structure at an accuracy of 0.1 mm.</p> <p>For the first project, the MISIRoot system successfully distinguished the corn plants inoculated with western corn rootworm larvae from the healthy plants before the shoot section of the corn plants revealed significant differences. For the second project, the MISIRoot system successfully demonstrated its ability to differentiate soybean plants with and without nodules.</p>

Studies were conducted in 1990 and 1991 to investigate two kinds of soil insects that attack field corn in Virginia. Corn rootworms, the most important of which is the western corn rootworm (WCR), feed on corn roots and have been sampled effectively using yellow sticky traps. The spatial distribution of weekly counts of WCR on yellow sticky traps was investigated over three consecutive weeks in July of each year using Pherocon A.M. traps. The traps were cut in half, placed in a seven by seven grid, and separated by an average distance of 18.3 m. Data were collected in a total of 24 corn fields. Dispersion indices showed that the trap counts of WCR were aggregated. Further analysis using geostatistics revealed that the trap counts were nonrandomly distributed at least half the time at all population densities; however, the presence and type of spatial pattern was density-independent. Pests of germinating corn seeds comprise a guild of insects including seedcorn maggots, wireworms, and white grubs. No one method has yet been developed to sample all of the insects in the guild. A new method, the baited wire trap (BWT), was evaluated in 47 fields in 1990 and 1991. No significant differences were found between the proportion of seeds damaged by pests of germinating seeds in the BWT and seeds planted by hand at conventional plant spacings. The proportion of damaged seeds in the BWT was significantly less than that in the commercially-planted fields; however, the proportion of damaged seeds in the BWT was significantly greater than the stand loss in these same fields. Linear regression revealed a significant relationship between the proportion of damaged seeds in the BWT and simulated plantings, and the conventionally planted fields. Because of low coefficients of determination (R²), the BWT could not be used to accurately predict damage by the germinating seed pest guild. However, the BWT detected damage by all three members of the pest guild and was found to be significantly faster to use than the bait station method. / Master of Science