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BIOEFFICACY OF ORGANIC EXTRACTS OF FISH POISON BUSH (GNIDIA GLAUCA, FRESEN) AGAINST COWPEA WEAVIL (CALLOSOBRUCHUS MACULATUS, FABRICIUS)
(2018-11) WILHELMY MARION JEBET
Cowpea weevil (Callosobruchus maculatus) is a major pests of stored cowpea in the
tropical region of the world. In Kenya, the damage caused by C. maculatus impacts
negatively on its economic and nutritional values and contributes to food insecurity. The
widely adopted use of chemical pesticides is marred with health and environmental
hazards. Global concern on synthetic chemicals has led to heightened restrictions and
limitations on their use. This, therefore, has prompted the search for alternatives to
synthetic pesticides. New studies are focusing on the use of botanicals as a novel approach
to the management of pests. Gnidia glauca has been exploited by local people in control
of post-harvest pests. However, no scientific research has been undertaken to evaluate its
potential anti-insect properties. In this study, four organic leaf extracts of G. glauca
(methanol, ethyl acetate, DCM and blend) were evaluated for contact toxicity, oviposition
deterrence, inhibition of progeny emergence and repellency against cowpea weevil. The
plant leaves were collected from Embu County, Kenya. The samples were prepared,
extracted and investigation carried out under ambient laboratory conditions. The
experimental design entailed five test concentrations (2g/100ml, 4g/100m, 6g/100ml,
8g/100ml, and 10g/100ml) of each extract, the untreated control, the solvent control and
the positive control-Actellic. Each bioassay had four replications. Adult weevils (1-3 days
old) were exposed to the extracts and mortality was monitored daily for the first four days.
Subsequently, oviposition deterrence was assessed on the 15th day while inhibition of
progeny emergence was evaluated on the 49th-day post-treatment. Extract repellency was
assessed for the first 6 hours after treatment. Screening for plants phytochemicals was
conducted using the standard recommended procedures. The results of this study revealed
all G. glauca extracts, to a varied extent, induced mortality on C. maculatus. Mortality
was concentration and exposure time dependent. Highest mortality of 89.74% was
recorded with 10g/100ml ethyl acetate extract 96 hours post-treatment. The extracts
significantly deterred oviposition with the 10g/100ml concentration of ethyl acetate, DCMand blend statistically (p>0.05) comparable to the activity of synthetic pesticide. All the
extracts were found effective in inhibition of progeny emergence. Ethyl acetate extract at
the test dose of 10g/100ml demonstrated the highest inhibition of 99.3% while the least
inhibition of 9.03% was exhibited by 2g/100ml methanol extract. G. glauca extracts
proved to be attractant of C. maculatus rather than repellant, none of the extract
concentration attained repellency greater than 50%. Results also showed that the extracts
had tannins, phenols, flavonoids, terpenoids, saponins, alkaloids, cardiac glycosides and
steroids which have been associated with insect control properties. It was therefore
concluded that the plant extracts, possess bioactivities against Callosobruchus maculatus
on the tested parameters of contact toxicity, oviposition deterrence, inhibition of progeny
emergence and repellency. Hence the studied extracts can further be purified and
developed into the plant-derived bio-pesticides to control C. maculatus.
Upscaling African Indigenous Vegetables Climate Smart Technologies for Food & Nutrition security in Kenya
(2025-11-27) Prof Mary Abukutsa-Onyango, Prof Anselimo Makokha, Dr Eucabeth Majiwa, Mr Patrick Amunavi, Ms Joyce Liti Njenga, Mr James Shikwati, Ms. Esperance Chesoli, Mr Muchiri Nyaggah, and Dr Anne Aswani
Goal:
To contribute to achieving food and nutrition security in the context of climate change challenges facing Kenya by promoting the sustainable production, commercialization and utilization of African Indigenous Vegetables (AIVs).
Overall Objective:
To upscale the production, preservation and utilization technologies of African indigenous vegetables for food and nutrition Security in Kenya.
Potential use of Kenyan Entomopathogenic Nematodes and Neem (Azadirachta indica) for the Sustainable Management of Tomato Leaf Miner (Tuta absoluta)
(2018-06) DAVID MUNYUA MUTEGI
The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was reported in
Kenya in 2014 and has become a devastating pest of tomato crop in both the field and in the
greenhouse. The objectives of this study were; to determine the pathogenicity of Heterorhabdities
species and Steinernema karii nematodes against tomato leaf miner in laboratory conditions; to
evaluate the insecticidal effects of neem biopesticide against tomato leaf miner in the greenhouse
and to evaluate the effectiveness of entomopathogenic nematodes and neem combined with
entomopathogenic nematodes as management options for tomato leaf miner in the greenhouse
conditions. Entomopathogenic nematodes (EPNs) used in the study were obtained from Kenya
Agricultural and Livestock Research Organization (KALRO) entomopathogenic nematodes
laboratories and Tuta absoluta larvae were obtained from a colony reared and maintained in a
greenhouse at Kabete Campus Field Station, Nairobi. Multiplication of the EPNs was done by invivo method or the insect-bait technique with the third instar of greater wax moth (Galleria
mellonella). Bioassays were conducted in petri dishes where the effects of EPNs concentrations;
at 100, 300and 500Ijs/ml on Tuta absoluta larvae exposed for 24-72 hours were evaluated.
Secondly, three different concentrations namely; 20ml/20L, 40ml/20L and 60ml/20L of
Nimbecidine® (Azadirachtin) were evaluated against Tuta absoluta populations in the greenhouse.
Thirdly, the following management options; Steinernema karii nematodes alone applied at a rate
of 1000 Ijs/ml with oil adjuvant Addit® as a wetting agent in water, Steinernema karii nematodes
and neem (Azadirachtin 0.03%) applied sequentially after one hour at a rate of 40ml/20L were
evaluated against Tuta absoluta populations. These were compared with Coragen® SC (20%
Chlorantraniliprole) synthetic pesticide applied at the rate of 3ml/20L and control where only water
was applied. A delta sticky trap supplied with Tuta absoluta pheromone was hanged at the centre
xiii
of the greenhouse at a height of one metre for monitoring Tuta absoluta numbers to enable the
initiation of treatments. The results obtained showed that, the evaluated concentration rates of
Heterorhabditis species and Steinernema karii at 100Ijs/ml, 300 Ijs/ml and 500 Ijs/ml significantly
caused (p < 0.05) mortality to the Tuta absoluta larvae and the highest mortality was recorded at
500 Ijs/ml concentrations with an exposure period of 72 hours. Steinernema karii was more
pathogenic compared to Heterorhabditis species with respect to exposure time, having shown
100% and 91.5% larval mortality, respectively. Secondly, the evaluated neem concentrations
20ml/20L, 40ml/20L and 60ml/20L significantly (p < 0.05) reduced Tuta absoluta population in
the greenhouse tomato. The high concentration (60ml/20L) was more effective in reducing Tuta
absoluta population and fruit damage compared to the lower concentrations and control. High fruit
damage of 96.2% was recorded in the control compared to 30.0%, 23.4% and 20.0% for 20ml/20L,
40ml/20L and 60ml/20L dose rates, respectively. Lastly, EPNs alone and EPNs combined with
neem significantly (p < 0.05) reduced the population of Tuta absoluta. The number reduction of
Tuta absolutaby EPNs combined with neem did not differ with that which was achieved in
Coragen®. Tomato fruit damage was highest in the control with 91.5% compared to 10.8%, 7.9%
and 3.0% for EPNs alone, EPNs combined with neem and Coragen®, respectively. This study
demonstrates the potential of EPNs alone or in combination with neem applied successively at a
one hour interval, as an alternative strategy for the sustainable management of Tuta absoluta in
the greenhouse conditions.
DETERMINATION OF FECAL CONTAMINATION STATUS OF SHALLOW WELLS IN DEDE DIVISION, MIGORI COUNTY, KENYA
(2018-12) OLUOCH EVANCE ODIWUOR
A shallow well is a hole dug, bored or drilled less than 50M deep to extract water.
Contamination of shallow wells with fecal matter presents a grave public health threat
in developing countries, such as Kenya, where large numbers of households lack
access to clean and safe water supplies and rely on untreated surface water sources or
shallow unprotected groundwater for domestic utilization. A report by WHO shows
that 1 billion people practice open defecation with nine out of ten of them in rural
areas and it is estimated that 1.8 billion people use a source of drinking water that is
fecally contaminated. In Kenya unsafe water, sanitation and hygiene are the 2nd
leading risk factors causing morbidity and mortality at the national and county levels
respectively. In Dede Division, 65.5% of households depend on shallow wells for
domestic needs and there are rising trends of confirmed cases of fecal-related
diseases. The study sought to assess human and technical determinants of fecal
contamination status of shallow wells in Dede Division. A cross-sectional study of
households using the wells was conducted. Fisher’s formula was then used to
calculate the sample size of the heads of households. Since the approximated number
of households using shallow wells was <10,000 (4008), the two stages of the formula
were adopted, giving a sample size of 386 heads of households. Out of the 180
shallow wells, 54 (30% of 180) were proportionately sampled and grab sampling
technique adopted while sampling water from each of the sampled shallow wells.
Basic physical parameters like temperature, turbidity and pH were analysed by a
portable turbidity meter and pH meter while H2S rapid field test was employed for
total corliforms analysis of grab samples in the field. Fecal contamination status of
each well was determined by Membrane Filter Technique in kisumu government
labaratory. Chi-square test was used to measure associations between variables while
Multi-variate logistic regression analysis applied to test the hypotheses. The study
reported significant relationship between level of knowledge of respondents on a well
being too close to a latrine as a potential route (risk factor), a well located downhill a
latrine, an open/uncovered well, surface run-offs into wells, dropping objects in
shallow wells, using a dirty drawer, people/animals dropping in wells, doing laundry
next to a well, and human/animal feces dropping in the well as potential routes of
fecal contamination. It further revealed significant associations between several
technical determinants and fecal contamination status of shallow wells e.g distance
(M) from a latrine to a well, with majority of wells within safe distances of
contamination (>10M) but still tested positive for fecal corliforms, distance (M) from
the nearest cattle pen if any with a significant majority of shallow wells testing
positive for fecal corliforms, damage or lack of concrete plinth, breaks/cracks on the
parapet walls, breaks/cracks in the cover/top slab, breaks in the drainage channels,
shallow well covered while not in use and shallow well fenced out respectively.
Majority of shallow wells (69%) tested positive for E. Coli, a strong indicator for
presence of fecal matter in water, with only 31% testing negative. Common human
and technical determinants (risk factors) by and large are functions of fecal
contamination status of shallow wells in Dede Division. Efficient protection of
shallow wells is a critical pointer to their ground water quality. Households in Dede
Division should ensure adequate treatment of shallow wells for fecal contamination
before utilization of water from these sources. This can be both at source or
household level. They should be sensitized by the relevant authorities on common
routes of fecal contamination of shallow well water and safe hygiene and sanitation
practices around shallow wells to prevent fecal contamination of the wells.
Households using shallow wells in Dede Division should ensure proper sighting and
location of latrines in relation to shallow wells to avoid fecal contamination of the
wells through leaching. The pit latrines should be sighted down hill the shallow wells
and located atleast 10 meters apart.
ELECTRON IMPACT ELASTIC SCATTERING OF STRONTIUM USING DISTORTED WAVE METHOD
(2018-11) KIMANI MARTIN KIRUGU
Differential and integral cross sections for electron-atom are useful for interpretation
and understanding of electron contact with the targets and for determining dynamics of
the collision processes. They are useful in X-ray photoelectron spectroscopy (XPS),
upper atmosphere dynamics, Monte-Carlo simulation (MCS), Auger-electron
spectroscopy (AES), in gaseous-exchange, laser development, plasma physics and
fluorescent lighting. For elastic scattering of strontium very few calculations have been
performed and currently there are no known results using the present method. Also the
available theoretical results do not have other results to be compared with so it makes it
important to obtain results to compare them and to be compared with future
experimental results. In calculation of differential and integral cross section for elastic
scattering of electron by strontium atom, first-order distorted wave born approximation
method has been used to determine DCS and ICS at impact energies of 10eV to 200eV
and scattering angles ranging from 00 to 1800
. Also in this study at the initial state, both
initial and final channel distortion potential of elastic scattering of electron by a
strontium atom are taken as the static potentials since it is an elastic scattering. The
distorted waves are expanded in terms of radial wavefunctions and spherical harmonics,
Numerov method was then used to solve the radial equations to obtain the radial
wavefunctions. The Madison and Bartschat computer program DWBA1 for e-
- H
scattering was modified to perform the mathematical computations for e -
- Sr scattering
and the results for differential and integral cross sections are calculated and compared
with the available results. The integral cross sections (ICS) results agree well
qualitatively with the other theoretical results. At lower incident energies (10-30 eV),
the present differential cross section (DCS) results disagree with results obtained from
optical potential method. This is because the first order distorted wave method gives
poor results at low impact energies and also the nature of the distortion potential used.
At intermediate and higher energies (60-200 eV), the present DCS results agree well
with the results obtained from optical potential method. In conclusion, the DWBA was
developed and applied to 𝑒− - Sr scattering, changes on the DWBA1 computer program
were made for strontium, differential cross section (DCS) and integral cross section
(ICS) at impact energies 10-200eV for elastic scattering of electron-strontium were
determined using DWBA at intermediate and high energies and the results compared
with the other available results. From this work it was recommended that some
experimental studies on electron impact elastic scattering of strontium should be made
to give results for comparison with the calculated results, more theoretical studies using
other methods should be conducted on DCS and ICS for purposes of comparison with
the present results, a distortion potential that incorporates the polarization potential,
exchange potential and absorption potential should be used in the calculation and the
present method incorporating all the distortion potentials should be extended further for
electron impact elastic scattering of other alkaline earth metals such as beryllium,
cesium, ytterbium, and radium.
