College of Agriculture & Natural Resources

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    Effect of ore type on the leaching and biosorption characteristics of lead from waste cupels using spent tea leaves (camellia sinensis)
    (KNUST, 2019-06) Pearl Anne Narkie Korli
    Waste cupel samples from two commercial gold fire assay laboratories in Ghana were sampled and characterized. The selection of the fire assay laboratories was based on the type of ore being processed. Comparative study of the effect of ore type (oxide and sulphide) on the leaching and biosorption characteristics of lead from waste cupels using spent tea leaves (Camellia sinensis) was investigated. Both laboratories use magnesia (MgO) cupels. Waste cupel samples were collected, pulverised and characterized prior to acid digestion. The mineralogical and chemical compositions were determined using X-ray Diffraction and Inductively Coupled Plasma Optical Emission Spectroscopy / Mass Spectroscopy, respectively. Leachates from the waste cupels were contacted with spent tea leaves and the biosorption efficiency and specific metal uptake determined. Results show that lead concentrations in waste cupels from oxide ore (CWO) increased as particle sizes increased whilst lead concentration from sulphide ore (CWS) decreased with increased particle sizes. The biosorption efficiency of lead was higher in CWO leachate ( > 99 %) than in CWS leachate ( < 98 %). For a given biomass concentration, CWO recorded a higher specific metal uptake as compared to CWS. The specific metal uptake in both samples were affected by the volume of leachate and lead concentration in leachate. In both samples, the adsorption isotherms fitted well in Langmuir model. The results from this study indicate that spent tea leaves can be used as an adsorbent to render waste cupels non-toxic before disposal.
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    Prevalence and identification of yam viruses responsible for seed yam degeneration in the Ejura-Sekyedumase and Atebubu-Amantin Districts of Ghana
    (KNUST, 2018-11) Agyemang Marfo,Esther
    ii ABSTRACT Yam viruses are reported to be widespread in all areas where yam is grown. In Ghana, viral diseases are known to cause about 50% of yield reduction on yam. It was for this reason that this research was carried out to manage yam viruses in Ghana. Surveys were conducted in the 2015 and 2016 cropping seasons in two major growing districts, Ejura-Sekyedumase and AtebubuAmantin of Ghana to determine the prevalence of yam virus. There was the need to identify the specific viruses producing the symptoms that were observed during the survey, as such symptomatic leaf samples were taken for analysis at the laboratory using RT-PCR. Out of the 40 leaf samples collected from each district, Ejura-Sekyedumase District had six mixed infections for both Yam mosaic virus (YMV) and Yam mild mosaic virus (YMMV) while eight single infections were recorded for YMMV. Atebubu-Amantin District had 10 mixed infections for both viruses and eight single infections for YMV. Molecular-based diagnostics techniques were also employed to monitor the health status of seven plants (Diosecorea rotundata Poir) established from positive selection, of which five of them did not amplify for any of the two viruses tested while two amplified for both viruses that were tested. Seed yams (‘Dente’, ‘Pona’ and ‘Laribako’) selected in 2015 from symptomless or mildly infected plants (positive selection), as well as those purchased from the Ejura market (farmer practice) and those selected from field diseased plants were established in field experiments in 2016 and 2017 cropping seasons at Ejura and Fumesua using a 3 x 3 factorial in randomized complete block design. The performances of the three seed yam sources were compared for their reaction to yam mosaic virus infection and tuber yield. The three white yam (D. rotundata) varieties used were; ‘Dente’, ‘Pona’ and ‘Laribako’. Plants raised from positive selection performed significantly (P<0.05) better with least virus percentage infection and disease severity scores irrespective of the variety. Positive selection Dente out-yielded farmer practice iii Dente and diseased Dente by 35 and 66.7% respectively in the 2016 cropping season at Ejura. Similar result was obtained at Fumesua with positive selection Dente out-yielding farmer practice and diseased seed yams by 32.6 and 60.7% respectively. In the 2017 cropping season, even though there was general yield reduction indicating loss of seed yam quality with time, similar trend occurred with positive selection plants performing significantly (P<0.05) better with least virus incidence and severity scores at both locations. Positive selection Laribako produced the highest yield at both locations. With farmers’ current practice of recycling seed yams from one season to another, this study showed that positive selection was a good approach to reducing virus load in farmers’ farms as well as reducing seed yam degeneration while maintaining fairly good yields.
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    The efficacy of neem seed oil extract and vegetable oil as insecticides for cowpea–weevil (callosobruchus maculatus) control
    (KNUST, 2019-02) Abanga Paul
    Callosobruchus maculatus, a major storage insect pest of cowpea, lays its eggs on the pods or sometimes on the seeds both in the field and in storage. The larva perforates the seeds and completes its life cycle there. It can cause loss, if not controlled in time. Other pests are Maruna spp and Laspeyresis spp. Storage pests are controlled by the use of recommended ii insecticides, vegetable oils, fumigation or heat treatment to the stored seeds. The objective of this project was to examine the effect of neem oil treatment on cowpea weevils as an alternative for preserving cowpea at storage. The experimental design for the study was Completely Randomized Design with three replications. Data collected included; grain damage, insect mortality; weight loss and number of survived insects. From the results, insect mortality was 100% for treated cowpea seed samples compared to the untreated sample; the control. The results indicated that the control treatment recorded high weight loss of 110 g, 240 g and 350 g for storage months of 1, 2, and 3 compared to the neem oil treatment [100:0] recording the lowest of 10 g, 20 g and 30 g for storage months 1, 2, and 3. The control treatment had the significantly highest percentage of seeds with holes of 36.87 %, 69.54 % and 94.67 % for storage months 1, 2, and 3 compared to the neem oil treatment which recorded 11.09 % 11.10 % and 11.16 % for storage months 1, 2, and 3 respectively. Study concluded that neem seed oil should be used to store cowpea grains to reduce weevil infestation.
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    DYNAMICS OF MULTI INFECTIONS DISEASE (MALARIA-ELEPHANTIASIS-ZIKA VIRUS) TRANSMISSION IN MOSQUITO ENDEMIC REGIONS
    (KNUST, 2019-10) MENSAH, JOHN-AMOAH
    Mosquitoes are one of the deadliest insects in the world. Their ability to carry and spread disease to humans cause millions of deaths every year. The worldwide incidence of diseases caused by mosquitoes has risen 30-fold in the past 30 years, and more countries are reporting their first outbreaks of the mosquito caused diseases. Zika, Malaria, and Elephantiasis are all transmitted to humans by the Aedes aegypti mosquito. More than half of the world’s population live in areas where this mosquito species are present. Sustained mosquito control efforts are important to prevent outbreaks from these diseases. There are several different types of mosquitoes and some have the ability to carry many different diseases. The study presents a multi-infections system model to study the transmission dynamics of Malaria, Zika-Virus and Elephantiasis in an endemic region such as Kedougou in the South Eastern part of Senegal and other parts of the world. This makes it possible to have multi￾infections of the three diseases simultaneously. The main objective of this work was to study the dynamics of multi-infections (Malaria-Elephantiasis-Zika virus) and transmission through the use of mathematical model, to determine the stability of the multi-infections model, the co-infections model and also study the single models for individual diseases including Malaria, Zika and Elephantiasis. The disease-free equilibrium is performed and it was shown to be globally asymptotically stable when the associated threshold number known as the basic reproduction number for the model is R0 < 1. Investigation on the existence and stability of equilibria was also derived, the model was found to exhibit backward bifurcation. Thus, R0 less than unity is not sufficient to eradicate the disease from the population and there was the need to lower R0 below a certain threshold for effective disease control. Sensitivity analysis was performed to determine parameters that have high influence on the basic reproduction number. Optimal control policies was also used as measures to eradicate the diseases from the system.