Theses
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A long essay or dissertation or thesis involving personal research, written by postgraduates of University of Ghana for a university degree.
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Item The Potential of Beauveria Bassiana for the Management of Cosmopolites Sordidus (Germar, 1824) On Plantain {Musa, Aab)(University of Ghana, 1999-10) Godonou, I.; Oduro, K. A.; Afreh-Nuamah, K.; Green, K. R.; University of Ghana, College of Basic and Applied Sciences, School of Agriculture, Department of Crop ScienceThe banana weevil, Cosmopolites sordidus (Germar) in association with other pests and diseases, represents a threat to the production of plantain (Musa spp., AAB), the preferred staple food in Ghana. Biological control of the banana weevil was considered the most promising management option for small-scale plantain production and studies were, therefore, undertaken to determine the efficacy of the entomopathogenic fungus, Beauveria bassiana (Balsamo) Vuillemin in the management of C. sordidus. The duration and spatial distribution of the different developmental stages of C. sordidus within plantain plants were determined to provide background information for evaluation of B. bassiana against the banana weevil. The mean egg incubation period and the mean developmental period from larva to pupa and pupa to adult were 6.3 + 0.2, 28 } 0.6 and 7.1 } 0.3 days respectively. The developmental period from egg to adult ranged from 33 to 51 days with a mean of 40.4 } 0.7 days. Within the plantain plant, approximately 80% of the eggs were located in the rhizome, >80% of the larvae were found at the rhizome level and all of the pupated larvae were located in the rhizome, suggesting that this is where a biocontrol agent should be targeted, rather than the pseudostem. Three strains of B. bassiana were obtained and evaluated on the basis of virulence tests and potential for mass production. From the results of these tests, strain 1MI330194 o f B. bassiana was selected for subsequent studies. Laboratory studies using a water-based inoculum applied to corm pieces or pseudostem traps, showed that B. bassiana could control all stages of C. sordidus, with up to 21.3%, 36.4% and 42.3% of eggs, larvae and adults respectively showing signs of fungal disease. Pot experiments to compare different formulations of the strain IMI330194 against adult weevils showed that the highest mortality (>60%) was obtained with groundnut oil plus kerosene-based formulation of conidial powder (GOK-CP), groundnut oil-based formulation of conidial powder (GO-CP) and oil palm kernel cake-based formulation of conidia (OPKC-C). A persistence trial showed that OPKC-C o f IMI330194 still gave 61.0% weevil mortality one month after application, compared with only 12.3% for conidial powder (CP) of IMI330194 and 3.9% for the control with no conidia. In field trials with artificial weevil release, mortality of adult weevils exposed to CP and OPKC-C of IMI330194 ranged from 53.4 to 75.5%, compared to <8% in the control with no conidia. Under natural weevil infestation, 16.7% of plantain suckers treated with CP of IMI330194 and 19.4% of untreated suckers were killed by weevil attack. In contrast, none of the suckers planted with OPKC-C of IMI330194 were killed. A study on the spread of fungal conidia using artificially infected and non-infected adult weevils showed a possible dissemination of B. bassiana conidia from infected weevils up to 18m from the release point. On the basis of results from the present study, the strain IMI330194 of B. bassiana could clearly play a key role in the management of C. sordidus adults on plantain.Item Studies on the Use of Bioactive Materials In Molluscan Traps for the Control of Schistosome Host Snails(University of Ghana, 1999-07) Baidoo, I. A.; Kpikpi, J. E. K.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS)As an aid to the control of the schistosome host snails, effective bioactive materials namely cassava, cocoyam, and sweet potato (Domeh, 1998), sugarcane and peels, all in their raw and processed states were tested in simulated natural environment experiments. The experiments were conducted using ‘biopots’ traps designed using a pot with few small windows created on the sides to allow easy diffusion of test materials to reach the water body to attract the snails It was observed that the materials retained their effectiveness for both Bulinus truncatus and Biomphalaria pfeifferi snails in the following order: cocoyam (1 day fermented) > sweet potato (7 days fermented) > cassava (7 days fermented) > cassava (1 day fermented) > sweet potato (1 day fermented) The effectiveness of one of the top attractants for the snails (i.e. sugarcane) was found to be unaffected by the addition of small quantities of the toxicant bayluscide (< 1 0 0 ^.1, 300(j.l, 500|o.l, and 700|j.l o f 0.6ppm bayluscide per 6.495gm of sugarcane) when tested under laboratory conditions. Higher quantities, however, reduced the attractant effects of the bioactive material. Similar findings were obtained when the tests were conducted under field conditions (i.e. < 1,424.5(4.1, 4,274.5^1, 7,124.5j4l 0.6ppm bayluscide per 92.579gm of sugarcane (an attractant) with bayluscide (a toxicant) in the newly developed ‘biopots traps’. The duration of the traps is a factor to be considered. The details of the experiments leading to these discoveries and the results are presented in this thesis.Item An Evaluation of a Non-Vector Snail Melanoides Tuberculata ( Muller) as An Agent for the Biological Control Of Bulinus Trunca Tus ( Audouin ) A Snail Host Of Urinary Schistosomiasis(University of Ghana, 1996-07) Ayeh-Kumi, P. F.; Kpikpi, J. E. K.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS)Preliminary studies earned out in the Weija Lake in Ghana gave indications of competitive interactions between Melanoides tuberculata and three snail hosts of schistosomiasis ie Bulinus truncatus, Bulinus globosus and Biomphalaria pfeifferi. Subsequent laboratory investigations involving Melanoides tuberculata and Bulinus truncatus carried out under four different conditions ie sandy gravel ( Normal and Heat treated) and sandy clay loam ( Normal and Heat treated) showed that Melanoides tuberculata is able to suppress the growth rate of Bulinus truncatus to varying extents depending on the type and condition of the sediment. Of the two sediments used, it was noted that Melanoides tuberculata competes more effectively on sandy gravel than on sandy clay loam mixture as the adverse effects of the presence of this snail on the rate of weight of Bulinus truncatus using sandy gravel sediment was found to be more severe than the results obtained when the sandy clay loam was used. Normal sediments were found to enhance the competitive advantage of Melanoides tuberculata over Bulinus truncatus more than the Heat treated sediments. In fact Heat treated sediments tended to reverse the competitive interactions in favour of Bulinus truncatus at least in some cases. The intensity of the competitive effects of Melanoides tuberculata over Bulinus truncatuswas also found to be directly proportional to the ratio of Melanoides tuberculata to Bulinus truncatus. Thus M15B5 (ie 15 M. tuberculata to 5 Bulinus truncatus) combination had a greater effects on Bulinus truncatus than M10B10 (ie 10 M. tuberculata to 10 Bulinus truncatus) and M5B15 (ie 5 M. tuberculata to 15 Bulinus truncatus) respectively. When the feeding behaviour and apparatus of the two snails were considered critically, to ascertain the possible influence of food on this ecological interaction it was established that, the radula of the two snails are different morphologically and also function differently. Food selection or preference among the two snail species was also found to be different (P(T=t)=0.001), though some similarities do exist . This suggests that, the basis of the observed competition between Melanoides tuberculata and Bulinus truncatus might not under normal circumstances be due to food However, the competitive ability of Melanoides tuberculata is directly or indirectly linked under normal circumstances to food stress. The findings from these studies suggest the need to extend our biological control studies to include other environmental factors which might be critical in determining the outcome of the competitive interactions between the host and the non host snails of schistosomiasis