During the summer of 1957 the writer became interested in water mites while collecting insects in an unnamed pond (see map in appendix) near Tomales, California. It was noted during that period that specimens of a giant water-bug, Lethocerus americanus Leidy (1847) had many larval mites attached to their ventral sides, and the lack of information concerning these animals and their life histories stimulated interest in investigating the problem detailed in this thesis. This work was begun in the summer of 1957 and has continued through the summer of 1959 and 1960. Due to the lack of information and lack of agreement by other investigators concerning the morphology of the adult Hydrachna miliaria Berlese (1888) [bilunata Marshall (1931)], the problem of this thesis is to redescribe it and to describe the stages of its life history. Stages of the life history of H. miliaria have not been described previously by other investigators.

The overwintering habitats and winter mortality rates of predaceous mites (Phytoseiidae: Typhlodromus) were investigated during three successive winters, 1965-66, 1966-67, and 1967-68. Three species were predominant in derelict apple orchards, Typhlodromus mcgregori Chant on twigs and spurs and rough bark of scaffold limbs and trunk, Typhlodromus occidentalis Nesbitt on rough bark of scaffold limbs and trunk, and Amblyseius cucumeris Oudemans in ground cover. Other species (Typhlodromus columbiensis Chant, Typhlodromus caudiglans Schuster, Amblyseius fallacis (Garman), Amblyseius ovatus (Garman), Amblyseius floridanus (Muma), and Amblyseius rosellus Chant) were collected only incidentally. Substantial numbers of T. mcgregori and T. occidentalis were found to fall with yellowed falling leaves during the autumn leaf drop; however, a majority of the mites stayed on the trees, overwintering on twigs and spurs (T. mcgregori) and bark (T. occidentalis). Typhlodromus mcgregori was found overwintering primarily under old corky abscission layers of leaf petioles and fruit stalks on the 1-5 year old section of twigs and spurs. No significant winter mortality of T. mcgregori was found during the five month period from December to April. The importance of overwintering sites and winter mortality rates to biological and integrated control programs is discussed.

Recent efforts to integrate certain Phytoseiid predators in pest (mite) management programs for apples have been somewhat successful and economical in many fruit growing areas. Convenient descriptions and reviews of the literature for species which have been collected from the state are provided to stimulate further work with Utah Phytoseiids. Seven species of Amblyseius and five Typhlodromus are described and notes provided concerning their respective geographic distributions and biologies.

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Mites are endemic and allergy to mite excreta and parts is one of the most common allergies. Health care practitioners have recommended the removal of carpets from homes of people with mite allergies. Little, if any, consideration is given to the fact that some persons may benefit directly from the presence of carpet in their homes. In the allergen and mite research literature, carpets are rarely described as having unique characteristics and are generally referred to as a generic entity. Carpets, however, do have unique characteristics that define their construction, appearance, wearability, and cleanability. Seventy-two pieces of commercially available, residential flooring materials were inoculated with identical numbers of mites, Dermatophagiodes farinae, and placed in the Textiles Conditioning Lab at Virginia Tech. The mites and carpet pieces were maintained in the lab, under identical, environmentally controlled conditions for 6 weeks, then the mites were extracted and counted. On the basis of the results of statistical tests run on the study data, the null hypothesis, that there is no difference between the numbers of mites grown on the different flooring conditions, was rejected. Statistically significant differences exist between the hard floor and the nylon carpet, between hard floor and olefin carpets, but no difference between hard floor and wool carpet. Nylon was the carpet fiber that was most supportive of the growth of house dust mites, olefin was the second most supportive, and wool carpet and hard floor were similar in being the least supportive. / Master of Science

Laboratory experiments were conducted to evaluate Tetranychus urticae Koch dispersal response to fenvalerate and permethrin. A petri dish spider mite trap which allows the partitioning of the dispersal response into spindown and walkoff categories was developed. Fenvalerate induced the more severe dispersal response. A greenhouse experiment was conducted to evaluate Tetranychus urticae oviposition site selection in response to residues of fenvalerate and permethrin, at two levels of residue deposition. When pyrethroid-free leaf surface was available, nearly all eggs were found on the untreated surface, away from the pyrethroid residues. When pyrethroid-free leaf surface was not available, a substantial number of eggs were found suspended by silk threads above the treated surface. The results were found to be in agreement with the general pyrethroid avoidance hypothesis. A series of greenhouse experiments were conducted to evaluate Tetranychus urticae oviposition response following impingement, and contact with residues of fenvalerate and permethrin. In all instances the pyrethroids were found to reduce the number of eggs oviposited. Mites recovered after several days, and oviposition returned to normal. The results did not lend support to the hormoligosis hypothesis of insecticide induced mite outbreaks. Field and greenhouse experiments were conducted to evaluate Tetranychus urticae oviposition response, over time, to soybeans which have received an application of fenvalerate of permethrin. The pyrethroids did not alter the soybeans in a way which improved the quality of the plant as a resource for increased levels of spider mite oviposition. / Master of Science / incomplete_metadata

Three densities of European red mite (ERM) (<i>Panonychus ulmi</i> Koch) and twospotted spider mite (TSM) (<i>Tetranychus urticae</i> (Koch)) were maintained on greenhouse-grown 'Imperial Delicious' apple (<i>Malus domestica</i>) and 'Redhaven' peach (<i>Prunus persica</i>) leaves. As ERM- and TSM-days increased, apple leaf net photosynthesis (Pn), transpiration (Tr) , and chlorophyll content (TCHL) decreased linearly. TSM was more damaging to apple leaf gas exchange than ERM. Apple water use efficiency (WUE) declined similarly with increasing mite-days for both mite species. Apple specific leaf weight (SLW) decreased with ERM-days and increased with TSM-days. Peach Pn, Tr, and TCHL declined linearly for both ERM and TSM. Both mite species were equally damaging to peach leaf gas exchange. Peach WUE decreased with increasing ERM and TSM-days. There was no mite effect on peach SLW. The results from separate apple and peach studies indicate that peach may be more tolerant to mite feeding than apple. / Master of Science

Investigations of potato (Solanum tuberosum) have been hampered by its complicated genetics and high genetic load. This dissertation applies genome reduction techniques to investigate a broad swath of genomic and physiological phenomena. It begins with the presentation and evaluation of a protocol to characterize endoreduplication within potato tubers, demonstrating substantial variation between tissue types and among wild species which may facilitate research into the genesis and growth of these starchy underground stems. Next, we transitioned to explore the distribution and consequences of a specific class of transposable element, Miniature Inverted Transposable Elements (MITEs), showing that they comprise approximately 5% of the potato genome, occur more frequently in genes with stress-related functions, and may be associated with changes, especially decreases, in gene expression. We then combined homology and sparsity based approaches to predict recent MITE activity, identifying five families as especially active. Finally, we expose the gene underlying the potato flower color locus, a homolog of AN2, while showing the effects it exerts on the flavonoid biosynthesis and fruit ripening pathways. This region was shown to be particularly dynamic, replete with MITEs and structural variants which we hypothesize to be the ultimate cause of differences in AN2 expression within the germplasm we examined. While the separate topics of this dissertation are quite disparate, each addresses an important topic in potato genetics, the in-depth study of which is only possible through the utilization of genomic reduction approaches to acquire homozygous genotypes for study and currently available genomic resources. / Ph. D. / Despite their humble appearance and routine consumption, potatoes have a complex genetic structure and a life cycle capable of both sexual reproduction through flowers, fruit and seed, and asexual reproduction through the tubers which also comprise the edible product. From an agronomic perspective, one of the most important qualities of a potato tuber is size, a feature influenced by genetics and environment. Cell-to-cell variation for the amount of DNA per cell, one component that influences tuber size, is known to occur, yet our ability to measure DNA content in starchy tuber cells has been obscured by debris generated through routine preparation techniques. We present and evaluate a new method for measuring the DNA content of potato tuber cells, which provides reliable results across a range of different potato varieties and species. ‘Jumping genes’ also known as transposons, first reported in maize but now known to occur in most advanced plant and animal species, have been found to comprise ~5% of the recently sequenced potato genome. We show that a particular class of transposons is more likely to occur adjacent or actually in certain types of genes, such as those which confer resistance to disease, where they may have meaningful effects on how those genes operate. We then proceed to predict the current activity of the various families of these jumping genes to understand how they continue to alter the genetic landscape of potato. Finally we identify a particular gene which dictates flower color in potato (purple vs. white). We demonstrate that several transposons occur in some forms of the flower color gene. Originally we hypothesized that transposons were associated with the turning off of the purple flower color form; however, on closer examination, we could express the white flower form in transgenic plants that were originally white-flowered and convert them to have purple flowers, demonstrating that even the white flower form was functional. While the separate topics of this dissertation are quite disparate, each addresses an important topic in potato genetics, the in-depth study of which is only possible through the availability of the special strains of potatoes with reduced chromosome number and the publication of the potato genome.