M.S.

Thrips are major agricultural pests throughout much of the United States. More information is needed about sampling methods, management practices, and insecticide susceptibility to help better control this pest. A two year survey was conducted to determine the species present in southeast Virginia and the population characteristics of those species. Thrips were monitored using yellow sticky traps. Tobacco thrips, Frankliniella fusca, were the most abundant species. In general thrips populations began to build up beginning in April, peaked in August, and then started to decline. Differences in this trend were observed between species. A study was conducted in seedling soybean to evaluate the within-plant location of thrips, whether a plant subsample could be used for thrips monitoring, and to determine the thrips species complex present. Soybean thrips, Neohydatothrips variabilis, were the most prominent species present. The greatest density of thrips larvae was located in the terminal bud of the seedling and suggests that immature thrips aggregate. Neither of the proposed subsamples of plant material explained the variability in immature thrips numbers and at this time we recommend whole-plant sampling for obtaining the most accurate estimate of thrips populations in seedling soybean. Tobacco thrips, F. fusca, as well as a complex of other thrips species attack cotton and peanut seedlings and can cause significant yield loss to these crops in the mid-Atlantic U.S. Experiments were conducted in these two crops to assess the efficacy of a novel diamide insecticide cyantraniliprole applied as a liquid in-furrow at planting and post-plant emergence broadcast spray treatment to control thrips. In both cropping systems cyantraniliprole significantly reduced the number of immature thrips and reduced thrips feeding injury to the plants. In several instances cyantraniliprole treatments resulted in increased yield as compared to the non-insecticide treated control and yields which were statistically similar to those obtained with standard thrips control insecticides. Laboratory bioassays were conducted to evaluate the toxicity (LC50 values) of cyantraniliprole and two conventional insecticides against F. fusca adults. Results of these assays were inconclusive. At times F. fusca adults were susceptible to the insecticides, but the results could not be replicated consistently. / Master of Science

The annual national production of peanut hulls averages about two hundred million pounds. These hulls are generally disposed of as fuel in the plante processing the nuts or discarded as waste material. Similar cellulosic wastes have been profitably utilized in the past as activated ohars. It was the purpose of this work to determine the conditions by which peanut hulls could be converted to liquid adsorbent chars. / Master of Science

The commercial peanut dryers used today were first conceived when energy was relatively inexpensive. Since then, energy costs have increased significantly, and more efficient peanuts dryers are desirable. To evaluate dryer efficiency, a mobile fan test facility was designed, built and calibrated for on-site fan airflow and energy measurements. Four-, six-, and eight-trailer peanut dryers were tested for performance. The characteristics observed were delivery of fan airflow as compared to manufacturers' ratings, air distribution to each of the trailer supply ports, plenum leaks, and energy savings achieved by the use of flow controls. For testing, air to the dryer fan was provided by a centrifugal supply fan, where the flowrate was determined by measuring the pressure drop across calibrated perforated plate positioned between the two fans. Airflow through each of the trailer supply ports was determined in a similar manner by measuring the pressure drop across calibrated resistance plates. Measured airflow to the trailers from dryer fans was found to be 75 to 100% of the airflow given by the manufacturers' ratings. Air distribution was poor in dryers with no baffle. However, the installation of a baffle resulted in significant improvement in air distribution. The baffle a pressure rise which reduced total airflow up to 5%. Based on a recommended airflow of 0.167 m³/s per m³ of peanuts, fan inlets were restricted to reduce airflow, and energy savings as high as 35% were achieved. Repairs on poorly maintained dryers increased flowrate from 3 to 7%. / Master of Science

The effect of kinetin concentrations (10⁻⁶M and 10⁻⁴M) on distribution of free fatty acids and sterols in plant parts and root exudates of 57-day-old peanut plants grown in nutrient solutions under gnotobiotic conditions was studied. Kinetin was applied to the roots in the culture medium five days before harvest. Upon harvesting root exudates were collected and plants divided into leaves, stems, and roots. The extracted lipid fraction was partitioned using silica gel thin-layer chromatography. Quantitation and identification of free fatty acids and sterols were accomplished by isothermal gas-liquid chromatography. On the basis of ug fatty acid/mg tissue and ug fatty acid/mg lipid kinetin caused no significant changes in total fatty acid concentration. The only significant increase in total sterol concentration was observed in the 10⁻⁴M treatment (ug sterol/mg lipid) in the stems. Use of individual component concentrations, relative percentages, and ratios helped distinguish trends. Shifts in quantity and quality of the free fatty acids and sterols may have been a result of one or a combination of effects attributed to kinetin. Decrease in root exudation in the 10⁻⁶M treatment may have been due to altered membrane integrity. Increase in the sitosterol/ stigmasterol ratio in stems of treated plants may have been a result of delayed senescence. Trends showed transport of free fatty acids and sterols to the roots in 10⁻⁶M treated plants. Kinetin may have effected sterol concentration through changes in HMGCoA reductase activity by unsaturated fatty acids. / Master of Science

The purpose of this research was to obtain information on the requirements for successfully drying mechanically harvested Virginia peanuts by artificial means. The work was performed at the Tidewater Research Station, Holland, Virginia. It was performed in bulk-type bins which were seven feet deep. Two tests, which consisted of four treatments and four replications each, were conducted. One of the replication bins in each treatment was divided into one-foot depth sections. The drying tests were conducted using intermittent heat which was designed to give the prescribed temperature rise when the ambient relative humidity was above 75 percent. The drying potential ranged from 12 cfm/ft³ and a 10 F temperature rise to 9 cfm/ft³ and a 3 F temperature rise. Original moisture contents of the peanuts tested were 43 percent and 31 percent. Weights of the bins were taken during the tests, thereby permitting the calculation of the moisture contents at any time. Drying rate curves were obtained from this. Quality analyses of the peanuts after drying were performed in order to determine the best drying treatment. These included: Fat Acidity, Shelling Damage, and Damaged Kernels from Commercial Grade. The Shelling Damage Tests showed that the lowest drying potential was best. The Fat Acidity Test indicated that the drying potential in all of the treatments was satisfactory when drying Virginia peanuts with an original moisture of 31 percent in a seven-foot depth. However, it appeared that the potential was not adequate to dry peanuts with a 43 percent moisture content in a depth greater than five feet. No information was obtained from the damaged kernels in the commercial grade. The resistance to air flow and the analyses of quality of the end product gave no indication that the sectioning of the bins had any effect on drying as compared with the full depth bins. This can be important in later research from the standpoint of obtaining additional data on drying rates and progression of the drying layer through bulk type bins of Virginia peanuts. / Master of Science

To determine the energy saving potential available from recirculating air in peanut drying, a thin layer drying simulation model was adapted to incorporate recirculation. A heat and mass balance computer model was developed to enable the determination of heat energy input. Laboratory crop dryers were designed and constructed to conduct experiments to verify the simulation models. Five batches of peanuts were dried using different recirculation strategies and the model successfully predicted the experimental results, including moisture content and wet and dry bulb temperatures. Energy savings of up to 20 percent were realized in the experimental runs. The simulation model was also used to evaluate and compare several recirculation strategies in order to determine successful strategies. / Master of Science

M. S.

Two isolates of peanut stripe virus (PStV), stripe and blotch, were compared ultrastructurally in peanut (Arachis hypogaea L. 'Florigiant') at several stages of leaf expansion. Ultrathin sections of young leaves infected with either isolate of PStV revealed pinwheel inclusions attached to the cell wall near plasmodesmata. The cytoplasm of infected cells were highly vesiculated. Virus particles amassed in crystalline arrays were observed in blotch infected cells. Virus particles were observed along the arms of pinwheel inclusions. Scroll inclusions appeared in PStV infected cells at a later stage of leaf expansion. In more mature leaves, pinwheel and scroll inclusions occurred in the cytoplasm in association with mitochondria. Virus particles were observed free in the cytoplasm as well as concentrated in linear arrays along the inner surface of the tonoplast. Membrane and organelle degradation was evident in cells infected with either isolate of the virus. Numerous cytoplasmic inclusions and virus particles were observed in cells from light green areas of the leaf. Cells from dark green areas did not contain cytoplasmic inclusions and contained few if any virus particles. Particle measurements show stripe and blotch isolates to have a mean length of 753 nm and 747 nm for leaf dip preparations and 746 nm and 745 nm for partially purified preparations, respectively. Both isolates had a modal length of 750 nm, regardless of the extraction procedure. The relative virus titer of each isolate was determined in peanut leaves at five stages of leaf expansion and in dark green and light green areas of infected leaves. Virus titer increased significantly from the closed to the fully expanded stage, at which time the virus titer peaked and then decreased slightly. Virus titer was consistently higher in leaves infected with the blotch isolate at all expansion stages. Virus titer was also higher in cells from light green areas of the leaf than from dark green areas of the leaf, regardless of isolate. / M.S.

The Eastern Cape Province of South Africa has climatic conditions which differ from region to region. The groundnut (Arachis hypogaea L.) cultivars, as it is the case with other crops, do not always perform equally well in the varying conditions. Abiotic stresses such as drought, extreme temperatures, and high soil acidity restrict plant growth. Lack of studies on adaptability of commercial groundnut cultivars in the Eastern Cape necessitated this study. Abiotic and biotic factors are not the only limiting factors: calcium availability in the soil is also a limiting factor in groundnut production. The aim of the study was to identify best suited cultivars for climatic conditions of Mthatha and Lusikisiki regions of the Eastern Cape. Two similar field experiments were conducted in the two locations with different climatic conditions. The results showed significant differences (P<0.05) in genotypes with respect to seed yield in both locations. Kwarts produced higher seed yield of 1155 kg ha-1 in Mthatha, while the same genotype produced low seed yield of 630 kg ha-1 in Lusikisiki location. In Lusikisiki the highest seed yield was recorded in Anel (936 kg ha-1) which produced low yield of 692 kg ha-1 in Mthatha. The genotypes that performed well in Mthatha in 2010/11 season included Kwarts, Nyanda, ICGV-SM 95714 and Mwenje. These genotypes were further used to investigate their response to calcium supplementation at flowering stage under conditions of Mthatha in the 2011/12 season. The results were significantly different for calcium absorption (P<0.05). Nyanda, Kwarts and Mwenje responded positively to calcium application at flowering stage producing relatively high yield of 153, 150 and 110 kg ha-1, respectively. Oil content was significantly increased by calcium application at flowering in Nyanda with 27.28% compared to 20.7% without Ca.