Browsing by Author "Clyde Sorenson, Committee Member"

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Advances in resistance monitoring of agricultural pests and in the elucidation of mite reproductive physiology
(2010-03-31) Cabrera, Ana Rosa; Christina Grozinger, Committee Member; James Harper, Committee Member; R. Michael Roe, Committee Chair; Clyde Sorenson, Committee Member
The work conducted for this dissertation aimed to contribute in our knowledge regarding resistance monitoring of agricultural pests and mite reproduction. Resistance monitoring of lepidopteran pests exposed to transgenic cotton expressing Bacillus thuringiensis (Bt) toxins is necessary and required to prevent the development of insect resistance. A bioassay was developed using Bt cotton plant extracts to rehydrate a heliothine diet and observe feeding disruption of the cotton pest Heliothis virescens. A diagnostic dose was estimated for two different pyramided Bt cotton varieties. The bioassay was evaluated with field H. virescens populations from North Carolina and two Bt resistant, laboratory strains. Ready to use meal pads containing Bt from cotton plants can be stored for up to 5 months. This bioassay is practical, lower cost and can be adapted for other Bt cotton varieties and Bt crops. This work is described in chapter 1. Mites are important medical and agricultural pests. Currently, there is limited information regarding the regulation of female reproduction in mites and few studies have study mite yolk proteins. A review of the literature was conducted regarding the regulation of female reproduction in mites and a new model for the regulation of vitellogenesis in the Acari was proposed. Relevant work on the regulation of vitellogenesis in insects, crustaceans and ticks, as well as observations on the effects of some insect hormones and their analogs on mite reproduction, leads us to conclude that the prevailing assumption that mites regulate vitellogenesis with high levels of juvenile hormone (JH) may not be correct. As a result of this review a new unifying model for the Acari was developed where ecdysteroids, and no JH, regulate vitellogenesis in mites. This review was published in 2009 in the Journal of Insect Physiology and is presented in chapter 2. In chapter 3, the characterization of the major yolk protein vitellin of the twospotted spider mite, Tetranychus urticae, is presented. This work determined T. urticae vitellin is a glycolipoprotein, although the carbohydrate and lipid content appears to be lower than that of the American dog tick, Dermacentor variabilis. It was clear that spider mite vitellin does not carry heme, a fundamental difference with the tick yolk protein. Finally, T. urticae vitellin migrated as a single band under native-PAGE conditions, but five different bands were observed with isoelectric focusing analysis, indicating that multiple Vgs may be expressed. This conclusion is also supported by the recent evidence that T. urticae ovipositing females express at least 4 vitellogenin (Vg) genes. This work was published in the Journal of Insect Physiology in 2009. Finally, the transcriptome analysis of the predatory mite, Phytoseiulus persimilis, is presented in chapter 4. This is the first transcriptome analysis of a mite and as a result of a 454 pyrosequencing project that yielded 12,556 sequences of transcripts. From those, 11 contigs were similar to arthropod Vgs and 6 to Vg-receptors (VgR). These contigs were further studied with available tools such as the open reading frame finder in Genbank and alignments with ClustalW and stage-specific expression studies were conducted with selected Vg (6) and VgR (3) contigs. Two Vg contigs (11791 and 12365) are likely to correspond to two different Vg genes. Obtaining DNA-sequence information of mite Vg and VgR genes will facilitate the study of the regulation of female reproduction in mites, which can lead to new ways of mite pest control.
Arthopod Fauna Associated With Kudzu (Pueraria montana var. lobata Willd) In North Carolina
(2004-12-02) Thornton, Melissa Rose; Clyde Sorenson, Committee Member; George Kennedy, Committee Member; David Orr, Committee Chair
The purpose of this research was to obtain background information to aid the implementation of a biological control program against the weed, kudzu (Pueraria montana var. lobata Willd). This research had several specific objectives that examined: 1) potential insect pollinators and seed production of kudzu in NC; 2) phytophagous insects and insect herbivory of kudzu foliage, seeds, vines and roots in NC; 3) abundance and diversity of foliar, vine, and root feeding insect communities on kudzu in comparison with those found on soybeans, the closest North American relative of kudzu in the United States. Kudzu is pollinated by native and naturalized insects in NC, in a pattern that varies by flower apparency rather than density. Arthropod herbivory by native generalists almost eliminated kudzu seed viability, while a naturalized Asian specialist consumed a nominal proportion of seeds. These data indicate that seed feeding arthropods would be poor candidates for importation biological control. Kudzu and soybeans shared the same foliar feeding insect communities and levels of defoliation, suggesting that foliage feeders are also poor choices for importation. No kudzu vine or root feeding insects or damage were found during the two years of this study, suggesting that future importation biological control research should focus on such feeders from Asia.
The Biology and Ecology of Hunting Billbug in North Carolina Turfgrass.
(2010-03-31) Doskocil, Joseph; Rick Brandenburg, Committee Chair; Clyde Sorenson, Committee Member; Yasmin Cardoza, Committee Member; William Hunt, Committee Member; Lane Tredway, Committee Member; Nicholas Hamon, Committee Member
The Dance Flies (Diptera: Empidoidea) of Madagascar
(2009-12-02) Swink, Whitney Garland; Brian Wiegmann, Committee Chair; Andrew Deans, Committee Member; Clyde Sorenson, Committee Member
The Empidoidea are a monophyletic superfamily of flies that includes dance flies (Empididae), long-legged flies (Dolichopodidae), and several small families (Atelestidae, Hybotidae, and Brachystomatidae). Empidoids are found worldwide and contain many thousands of species, but none have ever been described from Madagascar. An ongoing biodiversity survey by the California Academy of Sciences has brought to light many hundreds of undescribed empidoids from the island. This research project involves description, databasing, and DNA barcoding to establish the first estimates of empidoid species diversity in Madagascar. This study will contribute to critical surveys of species richness for rapidly degrading habitats in this important biodiversity hotspot. Representatives from two empidoid families, Empididae and Hybotidae were collected from Madagascar. There are eight new species of Hybos (Hybotidae: Hybotinae) from Madagascar: H. gardneri sp. nov., H. flaviarticulus sp. nov., H. verykoukis sp. nov., H. fianarantsoensis sp. nov., H. exastis sp. nov., H. triangulus sp. nov., H. angustifacies sp. nov., and H. ignotopalpus sp. nov. All species are described and male genitalia are illustrated. DNA barcoding was performed on the flies from the subfamily Hybotinae in order to infer species limits, but due to poorly preserved or degraded DNA, no definitive conclusions could be drawn. To aid identification, eight new barcodes were obtained that will be submitted to the barcode library upon publication of the new species. All data collected for the Madagascar empidoids have been recorded in a Mandala database and all images have been uploaded into Morphbank. Additionally, a LucID key is available on the Internet for species identification.
Data Generation and Utilization for Evaluating Helicoverpa zea (Lepidoptera: Noctuidae) Resistance Management in Bt Field Corn and Cotton through Computer Modeling
(2005-12-02) Kurtz, Ryan Warner; Fred Gould, Committee Member; J. R. Bradley, Jr., Committee Co-Chair; Clyde Sorenson, Committee Member; John W. Van Duyn, Committee Co-Chair
To mitigate resistance development in pest insects to transgenic field corn and cotton expressing Bacillus thuringiensis (Bt) proteins, the USDA and EPA have indicated that a high dose/refuge strategy is most effective, but single toxin Bt crops which predominate the transgenic crop acreage provide only a moderately high dose for one target pest in North Carolina, Helicoverpa zea (Boddie), or bollworm. When a source of susceptible insects is present, moderately high insecticide doses are expected to result in resistance development more quickly than high doses. In theory, introducing a pyramided genotype expressing two different Bt proteins in the presence of a source of susceptible insects can more substantially delay resistance development than a single Bt genotype expressing a high or moderately high Bt dose. Herein, we determine the effects of transgenic field corn (2001 & 2002) and cotton (2003 — 2005) genotypes expressing Bt proteins Cry1Ab/Ac & Cry2Ab, both singly and pyramided, on the development and survival of H. zea. Effects were documented by quantifying larval, pupal, and adult populations for each Bt crop genotype and a conventional sister genotype over time in eastern North Carolina. Each year all Bt field corn genotypes significantly reduced larval populations and production of pupae and adults below that of the non-Bt genotype with the pyramided Bt genotype significantly reducing these populations below each single toxin Bt genotype. Additionally, larval growth rate, pupal weight, and pupal length were reduced and adult eclosion date delayed by Bt field corn genotypes. Adverse weather conditions resulted in no useful data collected from cotton in 2003 & 2004, thus all cotton data reported are from two locations in 2005. All three Bt cotton genotypes significantly reduced the percentage of terminal regions and bolls containing live heliothine larvae and feeding damage compared to the non-Bt genotype with no significant differences among Bt genotypes. All three Bt genotypes also significantly lowered bollworm pupal and adult production per hectare compared to the non-Bt genotype; moreover, the Bollgard II and Cry2Ab significantly lowered pupal and adult production compared to the Bollgard genotype. Adults from the non-Bt genotype eclosed significantly earlier than adults from all three Bt genotypes, but there were no statistical differences between any Bt genotypes. We then use the simulation model originally described in Storer et al. 2003 to evaluate the role of pyramided Bt cotton and corn cultivars, EPA mandated non-Bt refuges, and soybean as a host in H. zea resistance development to Bt. With at least one pyramided Bt cultivar, the model predicts that the 20% sprayed non-Bt cotton refuge's contribution to delaying resistance evolution is greatly supplemented by other non-Bt sources of susceptible moths (i.e. soybean and other non-Bt alternate hosts) and has less of an effect on Bt resistance management than the non-Bt corn refuge. A field study was also conducted in eastern North Carolina to determine what effect seed mixtures of Bt and non-Bt cotton containing greater than 90% Bollgard II cotton have on fruit damage by H. zea and cotton yield. A lab study determined the efficacy of Bollgard II bolls against feral H. zea larvae (≥ 3rd instar) that initially fed on non-Bt cotton. Averaged over years, there were no significant yield differences between any seed mixture despite the 8% non-Bt mixture having significantly higher boll damage than all other treatments; however, when analyzed by year, the 100% Bollgard II treatment had significantly higher seed cotton yield than all seed mixture treatments. In our lab study, H. zea larvae (≥ 3rd instar) were able to survive to adulthood on Bollgard II cotton bolls after initially feeding on non-Bt cotton but at significantly lower percentages than larvae that remained on non-Bt cotton.
Novel Insecticide Resistance-Monitoring Bioassays for Lepidopteran and Hemipteran Cotton Pests and 454 Pyrosequencing To Identify Potential Gene Targets for RNAi Silencing in Hemipteran Cotton Pests.
(2010-08-17) Van Kretschmar, Jacob; Richard Roe, Committee Chair; Fred Gould, Committee Member; Clyde Sorenson, Committee Member; Gail Wilkerson, Committee Member; Jack Bacheler, Committee Member
Response of the Tawny Mole Cricket (Orthoptera: Gryllotalpidae) to Synthetic Insecticides and Their Residues.
(2011-01-10) Silcox, Diane; Rick Brandenburg, Committee Chair; Sarah Thompson, Committee Member; Clyde Sorenson, Committee Member; Fred Yelverton, Committee Member