The need for an improved control strategy for the operation of a wind-powered refrigeration system for the storage of apples was investigated. The results are applicable to other systems which employ intermittently available power sources, battery and thermal storage, and an auxiliary, direct current power supply. Tests were conducted on the wind-powered refrigeration system at the Virginia Polytechnic Institute and State University Horticulture Research Farm in Blacksburg, Virginia. Tests were conducted on the individual components of the system. In situ windmill performance were also conducted. The results of these tests have been presented. An improved control strategy was developed to improve the utilization of available wind energy and to reduce the need for electrical energy from an external source while maintaining an adequate apple storage environment. / Ph. D.

Chronic oxidation linked diseases are on a rise and are one of the leading causes of death globally. Epidemiological evidence increasingly points towards consumption of fruits and vegetables as a preventive way to manage early stages of chronic oxidation linked diseases. Oxidation linked diseases are caused by excessive reactive oxygen species (ROS) generated by a disruption in cellular antioxidant homeostasis due to an overload of calories combined with stress, no excerise and a diet low in antioxidants. Phenolic compounds can not only act as antioxidants but also stimulate the activities of antioxidants enzyme through protective pathways which can help modulate cellular protection. The aim of this dissertation was to use probiotic fermentation to enhance the phenolic and antioxidant compounds in fruit systems which can form the basis of functional food design. The potential of these food systems for disease prevention was investigated in eukaryotic systems through understanding the role of critical metabolic pathways involed in prevention of oxidation linked chronic diseases. Based on structure-function rationale, antioxidant, anti-hyperglycemia and anti-hypertensive potential of phenolic compounds in tea and the effect of extraction time and different degrees of fermentation were investigated in in vitro models. Results indicated that the most fermented teas and a longer extraction time had the highest potential. Further these extracts also had higher H. pylori inhibition potential. Probiotic fermentation of fruit juices with L. helveticus was used to mobilize phenolics and improve biological functionality by maintaining a consistent phytochemical profile. Results indicated that total phenolic and antioxidant potential decreased with feremnetation. However α-glucosidase inhibitory activity and H. pylori inhibitory potential increased with fermentation. Investigation into the mechanism of H. pylori inhibition with fermented cherry extracts revealed inhibition of proline dehydrogenase as the likely mode of action. The potential of fermented apple extracts was further investigated as a phytochemical elicitor in eliciting phenolic and antioxidant response in germinating fava bean. The results indicated a stimulation of phenolic and antioxidant response likely through the stimulation of carbon flux through glycolytic pathways. In yeast, fermented apple extracts accelerated cell death in the presence of peroxide stress in pretreatment model whereas it provided protection against oxidative stress and prevented cell death in concurrent model. Chitosan oligosachharide treatment was investigated as a potential replacement of cancer causing diphenylamine treatment for scald reduction in Cortland apples. Although the treatment did not have any effect on scald reduction, it provides better protection in storage by stimulating phenolic and antioxidant response which related to better health relevant functionality.

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.

Mature field-grown apple trees were used to gain a better understanding of the influences of light and fruit on leaf physiology. Light effects on net photosynthesis (Pn), specific leaf weight (SLW), leaf N content (Weight/area) (Nw), and leaf N concentration (% dry weight) (Np) of spur leaves from two canopy locations were evaluated on four dates in 1987. Interior leaves had lower Pn, SLW, Nw, and Np than exterior leaves. In 1988 the influence of %available photosynthetic photon flux (PPF) on the same parameters was examined throughout the season. On most measurement dates both Pn and SLW increased quadratically while Nw increased linearly with increasing PPF. In both years positive linear relationships existed between Pn and Nw, SLW and Nw, and Pn and SLW. / Ph. D.

The overall goal of this research was to determine the effects of spirea aphid, Aphis spiraecola Patch, feeding and nitrogen fertilization on net photosynthesis (Pn), leaf chlorophyll content and greenneess, growth, dry matter accumulation, and carbohydrate concentrations of young apple trees, with comparisons to apple aphid, Aphis pomi DeGeer. Trees were artificially infested and grown in an unheated greenhouse with screened ends. The spirea aphid responded differently to various nitrogen treatments. Aphid density increased at a faster rate on trees receiving higher nitrogen application. The leaf nitrogen concentration increased significantly and linearly with increasing amount of urea application in both infested and control leaves. Also, a significant difference in leaf nitrogen concentration was found at each urea application rate between infested and control leaves. Spirea aphid feeding and sooty mold accumulations caused significant reductions in photosynthetic rates, leaf chlorophyll content, and greenness. Pn increased linearly with increasing chlorophyll content and greenness; nitrogen rates caused an increase in Pn and leaf greenness. Aphid-days accumulations were strongly correlated to Pn and greenness at each nitrogen rate applied. Accumulation of callose at the phloem sieve plates in response to spirea aphid feeding occurred but to a lesser degree than from other aphids reported on apple and pecan leaves. Accumulation of fresh and dry weights in all tree parts (leaves, lateral shoots, trunk, rootstock, and roots) during the growing season were affected by both spirea aphid and nitrogen fertilization. The spirea aphid reduced accumulation of fresh and dry weights in all tree partitions when trees were harvested at the end of the first growing season. These reductions were still lower than the control when trees were harvested at the ten-leaf stage the following spring. The spirea aphid caused a significant reduction in lateral shoot growth at the end of the growing season and at the ten-leaf stage. Fresh and dry weights of all tree partitions tended to increase with increasing rates of nitrogen. The percentage and the amount of nonstructural carbohydrates (NSC) in all tree partitions were reduced by spirea aphid feeding and were positively related to nitrogen rate. At the ten-leaf stage in the second season, similar results were obtained. Development of spirea aphid and apple aphid was similar on trees fertilized with a moderate rate of nitrogen. Pn and leaf greenness declined to a similar extent with accumulated aphid-days, for both aphid species. Aphid species did not affect any of tree growth or NSC accumulation. / Ph. D.

Population dynamics of selected pests (Panonychus ulmi, Aculus schlechtendali, Aphis citricola, Dysaphis plantaginea spp.) in Virginia apple orchards and predators (Leptothrips mali, Haplothrips subtilissimus, Orius insidiosus, Stethorus punctum, Dereacoris nebulosus, Chrysopa spp.) were monitored during 1977-78 under 3 reduced pesticide programs. The pesticide program with phosalone and Dikarᴿ as its principal components allowed the largest number of predators to remain in the orchard and controlled most pests. L. mali and H. subtilissimus were the most abundant predators and appeared to respond numerically to densities of A. schlechtendali. O. insidiosus and D. nebulosus usually increased late in the season and S. punctum responded to densities of P. ulmi inconsistently but together with thrips may have had an important role in reducing P. ulmi populations. Chrysopa spp. remained at consistently low levels throughout the study. Laboratory studies indicated that phosalone and Dikar were the least toxic to L. mali among the pesticides tested. Benomyl can probably be substituted for Dikar in order to lessen mortality of A. schlechtendali in the field. L. mali was studied in the laboratory to determine aspects of its development, biology and prey relationships. Mean development time (days) for each stage at 23.9°C was: egg, 7.5; Ist larva, 5.7; 2nd larva, 5.4; prepupa, 1.0; pupa I, 1.5; pupa II, 4.0 and total (eggadult), 25.6. The preoviposition period ranged 5-7 days and the mean no. eggs/lab-reared (LR) and field collected (FC) females were: mated - LR, 13.0; FC, 28.0 and unmated - LR, 11.7; FC, 45.1. Mean longevity (days) of unmated females (LR, 50.1 and FC, 54.2, respectively) was greater than that for males and mated females. L. mali completed development on Golden Delicious apple pollen in 23 days (1st stage larva - adult). This thrips fed on the following orchard pests: A. schlechtendali, Tetranychus urticae, Lecanium corni, and on the eggs of Laspeyresia pomonella and Platynota flavedana. No feeding was observed on S. punctum, but L. mali fed on the phytoseiid mite, Proprioseius oudemansi. The functional response of all feeding stages of L. mali to densities of P. ulmi was determined at 18.3, 23.9, and 29.4°C and the numerical response of adult female L. mali to this mite species was investigated. The greatest effect of temperature on the functional response curve was observed with field collected adult female L mali. The numerical response of L. mali reached a maximum of 0.70 eggs/ female/48 h. The individual or joint potential impact of L. mali with S. punctum or O. insidiosus on P. ulmi was evaluated in the laboratory. At a mite density of 45/arena, L. mali with S. punctum killed significantly more P. ulmi than L. mali or S. punctum alone. In 75% of the replicates where L. mali was combined with O. insidiosus, the latter killed and consumed the thrips. A simple, non-destructive, but inefficient visual sampling method for L. mali on apple foliage was compared to a destructive, time-consuming, efficient limb-tapping sampling technique. With this comparison the usefulness of the visual sampling method was improved, thus increasing the potential of this sampling technique. / Ph. D.

Several experiments were conducted to determine: the influence of canopy position, girdling, and defoliation on nectar production; whether instantaneous light measurements yield reliable estimates of cumulative seasonal light levels within the canopy; and the effect of the canopy light environment on spur leaf physiology and fruit quality. Defoliation of nongirdled flowering spurs had no effect on nectar production or composition, while defoliation of girdled spurs induced nectar sugar concentration by 24%. Canopy position had no influence on nectar production or composition. At full bloom there were differences in photosynthetic potential of spur leaves from different canopy positions. Exterior leaves had a greater maximum photosynthetic rate and an unique photosynthetic light response curve compared to the intermediate and interior leaves. Differences among positions persisted throughout the season. Stomatal conductance, specific leaf weight, dark respiration, and light levels were greater for the exterior leaves throughout the season. Instantaneous light measurements made on a single uniformly overcast day after the canopy was fully-developed (average of four times during the day) provided reliable estimates (predictive R2 > 0.90, n = 30) of total cumulative seasonal photosynthetic photon density (PPD). There was a I-to-l relationship between instantaneous and cumulative PPD after canopy development was complete providing both measures were expressed as a percentage. The relationships were equal over multiple dates for two consecutive years. Cloudless conditions provided poor estimates (predictive R2 = 0.49 to 0.80, n = 30). Light environment and harvest date influenced fruit quality characteristics within the canopy. Fruit red color, intensity of red color, and soluble solids concentration were all positively related to light level, with the highest R 2 on the early harvest dates. Fruit weight, firmness, length/ diameter ratio, starch index, and seed number were not consistently influenced by the light environment. The number of hours above an average photosynthetic photon flux density threshold of 250 I-£mol. m-2• sec'! explained slightly more of the variation in fruit quality characteristics than any other expressions of light. / Ph. D.

The theory that fruit abscission may be the result of a reduction in metabolites available to the young fruit was addressed by this study. Shade cloth or terbacil, a photosynthetic inhibitor, were applied to limbs and whole trees to examine the influence of treatment and time of application on fruit nonstructural carbohydrates and abscission. 'Stayman' apple limbs shaded with 92% shade material from 5-15, 10-20, 15-25, 20-30, and 25-35 days after full bloom (April 22) had lower fruit retention than unshaded controls on 11 June. On 18 June, fruit diameter was greater on limbs shaded between 5-25 days after full bloom (DAFB) than on unshaded limbs. At 15, 20, 25, and 30 DAFB, fruit from limbs shaded for 10 days had lower total nonstructural carbohydrates (TNC), total sugars, and reducing sugars (% dry wt) than fruit from limbs shaded for 0 or 5 days. Terbacil (3-tert-butyl-5-chloro-6-methyluracil) was applied at 0, 50, 100, and 200 ppm to whole nine-year-old 'Redchief Delicious' apple trees at 15 DAFB. Terbacil markedly inhibited Pn; recovery occurred by 9 and 26 DAA for the 50 and 100 ppm rates, respectively. Phytotoxicity prevented the determination of Pn in the 200 ppm treated trees. Fruit dry weight, TNC, total sugars, and reducing sugars (% dry wt and mg/fruit) declined with increasing rates of terbacil. Total fruit abscission was observed 12 DAA for the 100 and 200 ppm treatments, while the 0 and 50 ppm applications retained 4.6 and 1.4 fruit per cm² limb cross sectional area (LCSA) at 35 DAA, respectively. Compared to the control, 50 ppm terbacil decreased fruit number and weight at harvest, but increased fruit weight. Terbacil at 75 ppm and 92% shade material were applied to whole, 3-year-old 'Redchief Delicious' trees at 18, 23, and 28 DAFB. Generally, fruit dry weight, total sugars, and reducing sugars were lowered by both shade and terbacil treatments. In most cases, fruit from shaded trees were lower in dry weight and measured nonstructural carbohydrates than fruit from terbacil-treated trees after 5 or 10 days of treatment. Shading for 5 or 10 days resulted in total fruit drop. Terbacil at 75 ppm resulted in 0.8 as opposed to 2.9 fruit per cm² LCSA on the controls at 54 DAFB. / M.S.

M.S.