The species complex and population dynamics of spiders were studied in an abandoned and several commercial apple orchards in Virginia. There were 68 and 45 species found in the abandoned and combined commercial orchards respectively. Species numbers in individual commercial orchards ranged from 18-28. There were 16 species common to all sprayed orchards. Members of the Salticidae, Philodromidae, Thomisidae, Theridiidae, Anyphaenidae, and Dictynidae, together comprised about 90% of the total spiders collected in the abandoned orchard during a one year study. Results from commercial orchards reflected similar findings. Two peaks of spider abundance were usually observed in all orchards; a small one in the spring and a larger one in the late summer-fall. Spiders often represented over 50% of the total predators collected in commercial orchards during the spring and fall. Studies of the association of spiders and various pest-prey indicate that spiders may be important suppressive or regulatory agents especially with regards to aphid and tortricid leafroller populations. Results of an evaluation of the seasonal efficiency of the limb beating sampling technique indicated that the sampling method was acceptable for quantitative spider population estimates. The time of sampling did not effect the population estimates of spiders during the normal sampling periods of 6 a.m. - 6 p.m. Spider feeding tests on insect pests-prey and beneficials showed that one pest species could be preyed upon by a complex of spider species. Beneficial insects such as Lepthothrips mali (Fitch) also were susceptible to capture by several spider species. / Master of Science

Herdmate comparison used currently by Holstein-Friesian Association of America to calculate predicted difference type was compared to two iterative procedures, adjusting for average PDT of herdmates' sires and average cow index of herdmates respectively, and a mixed model method. PDTs were calculated using the different methods for 6816 bulls with ten or more daughters. Mean PDT for the herdmate comparison was -.18 while means for the two respective iterative procedures were -.24 and -.19. Mixed model proofs sum to zero. Adjustments for average PDT of herdmates' sires increased variance of proofs compared to the other systems. Mixed model PDTs were least variable. Correlations between herdmate average and two measures of genetic merit of herdmates, average PDT of herdmates' sires and average cow index of herdmates, were .48 and .45. Positive regression coefficients of final score and herdmate average on two measures of genetic merit of herdmates also indicated a positive association between herd average and level of competition. The effects of failure to account for genetic merit of herdmates under present system was examined. Progeny were divided into low, middle, and high herdmate average groups and ·summaries were calculated for 778 sires with at least 20 daughters in each of three groups. Mean PDTs calculated by the herdmate comparison were .12, -.28, and -.45 for the low, middle, and high groups respectively. Eighty-three percent of the low herdmate comparison PDTs exceeded summaries in high group and 70% of low group evaluations were greater than respective middle group PDTs indicating biases in present sire summaries due to failure to account for genetic level of competition. Adjustment for average PDT of herdmates' sires and average cow index of herdmates reduced the advantage of PDTs calculated in low levels. The mixed model method appeared to be most effective in reducing biases in favor of bulls proven in below average herds. Summaries in low group were consistently higher than PDTs calculated in the other levels due to inability to completely remove differences in selection intensities among herds. PDTs calculated in high group were consistently less variable than those calculated in low herd levels. Means of final score, average PDT of herdmates' sires, and average cow index of herdmates were larger and less variable than corresponding means in low group demonstrating increased selection for type in high scoring herds. Accuracy in sire evaluation for type will be improved by adjusting for genetic merit of herdmates, however bulls proven primarily in low scoring herds will continue to be favored slightly. / Master of Science

Water, sediment, detritus, caddisflies, snails, and crayfish were collected from Bull Run between July 31 and October 2, 1977 and analyzed for Fe, Mn, Ni, Pb, Cd, Zn, Cr, and Cu by atomic absorption spectrophotometry after appropriate digestion and extraction procedures. The samples were collected from six sampling stations along Bull Run which received sewage effluent, urban runoff, and stormwater drainage from the Manassas area. Sampling stations included an upstream control located well above the urban area, four stations located immediately above and below suspected stormwater inputs, and a station sufficiently removed from direct stormwater input. Concentrations of Pb and Cu in water, sediment, detritus, and caddisflies increased with increasing distance downstream and were significantly (0.95 level) greater in these components immediately below the stormwater input than at the upstream control. Concentrations of Pb in sediment collected at a downstream station were significantly greater than those at the control station even though the control sediment characteristics favored metal retention more than the downstream sediment characteristics. Mean Cu concentrations in sediments at this station were greater (but not significantly) than at the upstream control station while all other metals were concentrated the least in sediment at the downstream station. Significant (0.95 and 0.99 level) linear correlation coefficients among a majority of stream components were found for Pb and Cu. It appears that urban runoff and stormwater drainage contributed sufficient quantities of Pb and Cu into Bull Run such that these metals accumulated greater in stream components below the Manassas urban area. / Master of Science

Modal analysis is a tool widely used to describe mathematically the vibratory behavior of structures. In modal analysis, the response of a structure at a given frequency of excitation is represented as the summation of the contributions of a 11 the modes of vibration. Although continuous structures have an infinite number of modes, only a few of them are present to a significant degree in the response at any frequency of excitation. These modes are the dominant modes at the given frequency. A vector fit method was developed to determine the number of dominant modes. This method uses only the transfer function matrix (or some part of it) as input, and it approximates each column vector of the matrix as a linear sum, using as a basis a set of orthogonal unit vectors. The errors resulting from these approximations, defined in a least squares sense, are the plotted versus frequency. The relative magnitudes of the error curves indicate the number of dominant modes in the frequency band in question. The method was tested numerically on three models with known modal parameters. These models were designed to have regions of high modal density. It was found that interpretation of the error curves required a certain amount of qualitative judgement based upon criteria other than simply the relative error magnitudes. With these criteria. identified, it was concluded that the vector fit method reliably predicts the correct number of dominant modes provided only that a sufficiently large transfer function matrix is: employed. Specifically, both the number of rows and the number of columns must be greater than the number of dominant mopes. / Master of Science

Horsenettle is a persistent, native, perennial weed of pastures and cornfields in southwest Virginia. A survey of insects associated with the weed revealed a number of general feeders, several insect pests of economic plants related to horsenettle, and a few lesser known species. The moth, Frumenta nundinella, demonstrated a high degree of host specificity in the tests conducted The larvae attack the plant in two ways: first instars web the terminal leaves together and form a round hollow chamber within which they feed on the growth tip of the plant, or they enter berries and consume all of the seeds. There are two generations per year, each being about 50 days. The insects overwinter as adults. Females oviposit in the spring and mid-summer. Normally first generation larvae occupy leaf chambers and second generation larvae occupy berries. In the absence of berries, leaf chambers will be formed. Predation, desiccation and interspecific competition with first instars appear to be important mortality factors. Four Hymenopterous parasites were reared from the larval or pupal stages. First generation larvae in leaf chambers significantly reduce (P < .05) dry weight of horsenettle regardless of the number of larvae on the plant. The second generation reduces seed production. E· nundinella was found to be present in 9 counties in western and northern Virginia but population levels were low in all the survey areas. / Master of Science

Brassaia actinophylla and Dieffenbachia maculata "Lodd" G.Don were grown in two organic media and treated with five salt solutions to determine the effect of soluble salt concentration on growth and quality. The soluble salt concentration was determined using the saturated paste extract method. Dieffenbachia growth and quality were better when 0.45 g/l 15-30-15 fertilizer was applied than when 0.225 g/l 15-30-15 plus 1.5 g/l NaCl was applied, regardless of medium considered. Dieffenbachia growth and quality were significantly reduced at a conductivity of 4.5 nunho/cm in the peat and sand medium and at 4.1 mmho/cm in the medium containing pine bark. The maximum Dieffenbachia growth and quality occurred at a conductivity of 0.8 to 1.3 mmho/cm. Brassaia growth and quality in medium 1 were poorest with application of 0.225 g/l 15-30-15 plus 1.5 g/l NaCl, and were more favorable with application of 0.225 g/l 15-30-15 plus 0.5 g/l NaCl. The more favorable conductivity range was 2.2 to 2.4 mmho/cm in the peat and sand medium. The growth of Brassaia in the medium containing pine bark was more favorable under application of 1) the low rate of complete fertilizer (0.225 g/l of 15-30-15), 2) the high rate of complete fertilizer (0.45 g/l 15-30-15), and 3) 0.225 g/l 15-30-15 plus 0.5 g/l NaCl than under application of 0.225 g/l 15-30-15 plus 1.5 g/l NaCl. The mean conductivity of the pine bark bearing medium under the three more ' beneficial treatments ranged from 0.7 to 2.4 mmho/cm. Brassaia and Dieffenbachia were shown to be less tolerant of salinity than was determined previously. / Master of Science

An investigation was made of the relationship between the achievement, designated as success or failure; of MSFA participant families and their MMPI scores obtained during basic orienta..tion procedures. Subjects were twenty-eight families enrolled at the MSFA Training Center in vocational and educational classes for an average of 4.9 months. For each family it was determined that both husband and wife had a valid MMPI profile. Husband and wife profiles were paired for each family and the family was considered to have scored high if either spouse scored 70 or above on a given scale. If official MSFA records indicated that the family completed training and at least one spouse remained employed for.three months after placement, the family was defined as a success. A family who dropped ou:t of training before comp~etion or in which neither spouse remained employed for thr~e months was defined as a failure. A chi square analysis revealed no significant relationships between Training Center achievement and scores on any of the ten MMPI clinical scales. Therefore, it cannot be said that there is an association between MMPI scores and Training Center achievement. Another finding of this study was that families classified as migrants are significantly less likely to be successful than are families classified as seasonal farmworkers. A need was perceived for further research investigating the differences between migrants and seasonal farmworkers and for further development and testing of paired spouse MMPI profiles as an approach to measuring family characteristics. / Master of Science

The Gluconobacter phage GW6210, infects the ATCC strain 621 of G. oxydans. This phage possesses a polygonal head and contractile tail; therefore, it can be placed morphologically into Bradley's group A and tentatively placed in the virus family Myoviridae. This intensive electron microscopic study shows phage GW6210 to have a polygonal head, collar, tail sheath, baseplate, and tail pins. This phage is primarily unusual because of its large size. Using Tobacco Mosaic Virus as an internal standard, the head was found to be 170 nm in diameter and the tail was 136 nm long and 34 nm wide. The phage preparation seemed to consist of two plaque types: a small clear plaque having a 0.3 ± 0.1 mm diameter surrounded by a large turbid region that measured 3.5 ± 0.7 mm wide, and a small turbid plaque that varied greatly in size (1.4 ± 0.8 mm). However, subsequent data indicated that these types represented size variation of a single plaque type. In addition to the normal host of GW6210, G. oxydans subspecies suboxydans ATCC 621, the host range of this phage includes: G. suboxydans var. α, IFO 12528; A. melanogenus, ICPB 2096; G. rubiginosis, IFO 3244. Fifty strains of Gluconobacter and 52 strains of Acetobacter were unaffected by the phage as weel as 3 strains of Pseudomonas tested. / Master of Science

The purpose of this study was to investigate the extent to which algal-produced organic matter may react with chlorine in aqueous solution to form trihalogenated methanes. Two species each of green and blue-green algae were cultured in an inorganic medium and harvested on several days throughout the growth cycle. Media filtrates and cell suspensions were analyzed for total organic carbon and chloroform produced after chlorination. Pure solutions of representative algal extracellular metabolites were analyzed in a similar manner. The highest-yielding (chloroform-carbon per total organic carbon) compounds were released during the late exponential growth phase. More organic carbon was accumulated in the external medium through the stationary growth phase by the blue-green species, but higher yields were obtained in the green algae cultures during these later stages of growth. The results indicate that the differences in the total chloroform production potential may be more significant among individual algal strains than between larger taxonomic divisions, such as the green and blue-green algae. None of the model compounds studied produced chloroform yields comparable to those of the. media filtrates or biomass. The chloroform-carbon yields of the culture filtrates were in the same range as those reported for the humic and fulvic acids, and in some cases much higher. Therefore, the algal extracellular products may be important as precursors in the formation of trihalomethanes during water treatment. / Master of Science

The demand for potable water may be culminating in a compromise on what constitutes a "safe" drinking water due to the rapidly approaching need to utilize recycled waters. The elimination of viruses pathogenic to humans from recycled waters will depend on the removal efficiencies of treatment processes and the sensitivity of detection methodologies. Enteric viruses can survive current wastewater treatment practices, and some even persist for long periods of time in natural waters. The objectives of this investigation were threefold: first, to construct a virus concentrator suitable for sampling secondary sewage treatment plant effluents; second, to sample the effluent of trickling filter sewage treatment plants prior to chlorination to determine the remaining amount of enteric viruses; third, to determine the virus removal efficiencies of a final settling and chlorination operation by using bench-scale simulations of the two units. Viruses were not detected in any of the secondary effluents of three trickling filter plants samples. However, these results may have been obtained because the level of viruses was below the minimum detection limits of the virus concentrator that was constructed. Also, if viruses were present, the high pH elution process may have been deleterious, or the BGM host cell was incompatible. Detention times in the model system studies of a final sedimentation basin and chlorine contact chamber were based on Rhodamine WT dye studies of plant-scale units. These studies suggested that 98.5 to 100 percent of the enteric viruses contained in the actual plant effluent would be removed or inactivated by the combination of final settling and chlorination. / Master of Science