This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The synthesis of p-menthane-3,8-diol via the acid-catalyzed cyclization of citronellal in a dilute aqueous sulphuric acid medium was investigated using conventional batch and continuous systems in order to develop a commercial production process for said p-menthane-3,8-diol (PMD). The batch studies conducted during the first part of this study showed that the formation of PMD from citronellal occurs via an intra-molecular Prins reaction that results in the formation of both the desired PMD product, as well as the partially hydrated isopulegol. It was shown that the formationof the by- product, PMD-acetal, results from the reaction between an intermediate, 5-methyl-2- isopropylcyclohexanol, and the citronellal starting material, and not from the reaction between PMD and citronellal as previously reported. Kinetic studies confirmed the existence of a complicated kinetic model. The formation of PMD from citronellal displayed typical pseudo first order kinetics up to conversions of 70 after which the kinetic model becomes complicated as the result of the establishment of quasi equilibrium reactions between PMD and isopulegol (dehydration of PMD and hydration of isopulegol) and between PMD the PMD-acetal, both systems being acid catalysed. The PMD-acetal formation reaction appears to be second order with respect to PMD. Scale-up studies of the batch process to 30L and 50L scales showed that it would be extremely difficult to limit the level of PMD-acetal formation below the desired level of 1 percent, even if citronellal conversions are restricted to about 50 percent. During studies conducted on a commercially availablemicro-structured organic synthesis plant (OSP) it was shown that it is possible to perform the PMD reaction as a continuous process. The results obtained showed that the use of a micro-mixer such as the caterpillar micro-mixer did not provide enough residence time in order for desirable conversions (- 40 percent) to be obtained. By combining themicro-mixer with delay-loops of different thicknesses and lengths, and using increasing reaction temperatures, it was shown that the conversion of citronellal could be improved to some extent, but compared poorly to the expected conversions for a well-stirred batch reactor. By packing selected delay loops with inert SiC particles, improved mass transfer was observed between the organic and aqueous phases as reflected in the increased conversion of citronellal. Using the observations that were made during the use of the OSP, a continuous-flow, tubular reactor system was designed and constructed. Advanced statistical techniques were used to investigate the effect of variables such as temperature, acid concentration, reactor length, flow rate and the organic to aqueous ratio on the rate and selectivity of the reaction. Mathematical models were derived for citronellal conversion, yield of PMD and yield of PMD- acetals, and used to predict the concentrations of citronellal, PMD and PMD-acetals at set experimental conditions. The results obtained showed that it was possible to obtain a product which approached desired specifications.Downstream processing of the PMD reaction mixture as it exits the reactor requires phase separation and neutralization of the acid catalyst solution, followed by further work-up to recover unreacted starting material and intermediates for recycle back to the synthesis reactor, followed by purification of crude PMD to the desired specification. The study showed that neutralization, prior or after phase separation, does not affect the selectivity of the PMD to such a great extent, but does influence the relative conversion due to extended contact of the catalyst with the organic phase after the reaction is terminated. Recovery of unreacted citronellal and isopulegol could be achieved by a simple vacuum evaporation step, which may either be carried out in a batch manner using traditional distillation equipment, or in a continuous process using wiped-film (short path) techniques. It was also shown that selective crystallization of PMD from the crude product mixture by addition of a solvent, such as heptanes or hexane proved to be the best way of achieving the desired product specification.

Field experiments were conducted in two different growing environments to evaluate the spread and movement of Dickeya dadantii. A procedure to inoculate seed potatoes with Dickeya dadantii was developed to use during this study. Spread of Dickeya dadantii from inoculated potato seed to healthy potato seed during the handling, cutting and planting procedures was not detected at either location. Spread of Dickeya dadantii from inoculated seed to surrounding progeny tubers in the field was documented in both locations. In Florida, 33% of progeny tubers tested positive for Dickeya using PCR, and in North Dakota, 13% of the progeny tubers tested positive. Stunting was observed in plants grown from Dickeya dadantii inoculated seed tubers in North Dakota, but not in Florida. These results indicate that Dickeya dadantii may spread during the seed handling and cutting processes and can spread in the field from infected seed tubers to progeny tubers.

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No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Master of Science, 2017 / The African wild dog (Lycaon pictus) is one of South Africa’s most endangered carnivores. The species has suffered massive range shrinkages in the past few decades and population numbers have dropped significantly. Along with other factors responsible for its decline, one of the most notable threats to the African wild dog is conflict with humans. These carnivores are often persecuted by farmers for their alleged depredation of livestock and captive-bred game species, although doubt exists as to whether wild dogs are the avid depredators as suggested. My research therefore aimed to investigate the conflict between people and African wild dog, focussing on livestock depredation. Due to heterogeneous farming landscapes, the history and location of protected areas and the endangered status of the African wild dog, South Africa provides many opportunities to study this particular type of human-carnivore conflict. Firstly, I conducted a meta-analysis of human-carnivore conflict using published literature about African wild dog depredation of livestock and game and compared these to other African carnivores as well as non-African carnivores. Results indicated that African wild dog were less avid depredators than other African species such as lion (Panthera leo) and spotted hyena (Crocuta crocuta). Also evident was that high carnivore and livestock densities, coupled with poor communities with poor livestock husbandry practices, make people and carnivores in developing regions more vulnerable to human-carnivore conflicts. Secondly, I assessed actual African wild dog occurrence in relation to the location of farms, livestock density and several other anthropogenic and natural landscape features. This was achieved using GPS data from four collared African wild dog individuals from packs residing in the northeastern part of South Africa and resource selection functions. Results from these analyses suggested that, whilst African wild dog may occur in close proximity to farms, they established home ranges in areas of low livestock density and few farms, indicating predictive avoidance of areas where mortality may occur. Major roads were highlighted as a vulnerability for the African wild dog, whilst nature reserves and vegetation were also important predictors of wild dog occurrence. Other anthropogenic and natural landscape features varied in importance in determining wild dog occurrence. Knowledge about how the African wild dog selects its resources will enable us to identify vulnerabilities for these carnivores as well as areas where they are likely to occur, aiding in conservation planning. Though African wild dog have historically been reported to kill livestock such goats and cattle, my study seems to indicate that these carnivores are not avid stock-killers. Given the precarious survival status of the African wild dog and the food security needs of people in a developing region strongly suggests the need for cooperation of farmers and the education of communities to aid the recovery of this uniquely African carnivore. / XL2018

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfilment of the requirements for the degree of Master of Science. May 2013 / The purpose of the study was to isolate and identify indigenous nematode species and use them as model organisms for studying the responses of indigenous entomopathogenic nematodes (EPNs) to soil desiccation, soil rehydration, and also to study their behaviour with regards to the infection and location of insect larvae, Galleria mellonella in an 18cm column filled with sterilised sandy loamy soil. Two unknown nematodes were isolated from soil samples collected in Walkerville, South of Johannesburg and their sequences were found to have high affinity to Steinernema australe (accession number FJ235125) and Heterorhabditis bacteriophora isolate 56-C (FJ217351) when aligned with existing sequences in the NCBI database. Furthermore, a polymerase chain reaction was used to amplify the 16S rDNA region in order to identify bacterial symbiots of these EPNs. Symbiotic bacteria isolated from the Heterorhabditis spp had high affinity to Photorhabdus sp carborca (JF12345). Desiccation tolerance studies revealed that EPN5T and EPN3T were able to withstand desiccated conditions or continuous dehydration for 20 days. EPN5T caused 80% larval mortality after day 20 when the last row of Petri dishes was rehydrated. EPN3T caused only 60% larval mortality. All of the sandy controls gave 0% larval mortality by day 20. Comparative dose-response assays involved exposing G. mellonella insect larvae to different IJs concentrations (0, 5, 25, 100, 300 and 500 IJs/ml) were carried for both EPN5T and EPN3T. Larval mortality was recorded daily over a week. Insect mortality was high for both S. australe and H. bacteriphora, at 100IJs\ml, 300 IJs\ml and 500 IJs\ml. Mortality was observed within 48 to 96 hours and insects larvae showed signs of infection after 48hours. Significant differences were observed at EPN concentrations containing 5 IJs/ml and 25 IJs/ml. At these low IJ concentrations H. bacteriphora was able to kill 20% of the larvae by day 3 while S. australe displayed mortality only after day 4 and 5 for the two respective IJ concentrations. The significance of this observation was supported by the two-way Post-hoc analysis. Further studies were conducted to investigate the effect of soil humidity on EPNs behaviour in a column of soil. Results supported that humidity was crucial for EPNs locomotion or mobility and infection efficiency, as 100% mortality was observed in all columns by day 4. The study also investigated different IJ application concentrations in order to determine suitable field application doses. Even at the lowest IJ concentration of both EPNs 33.3% mortality was observed in each column. H. bacteriophora displayed increased mobility because high mortality percentage was obtained within 48hours in almost all three arenas of the column, proving that this species is an effective cruiser foraging deeper into the soil. S. australe was capable of cruising further down to 18cm searching for host as high mortality was observed even at the deeper or the bottom arena near the bottom of the soil column. Lastly field capacity was determined where the sandy loamy soil was saturated with water and allowed to drain so as to remove excess water from the 8 vertical columns for 48hours, resulting in a soil moisture content associated with the soil’s field capacity for water. Overall results of this study gave ideas for IJ formulation IJ storage and IJ application strategies of the identified EPNs which proved to have promising potential as biological control agents.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.