Browsing by Author "Githae, Eunice W."

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Biological control of desert locust (Schistocerca gregaria Forskål)
(CAB International, 2021) Githae, Eunice W.; Kuria, Erick K.
Desert locust (Schistocerca gregaria Forskål) is one of the most serious agricultural pests in the world due to its voracity, speed of reproduction, and range of flight. We discuss the current state of knowledge on its biological control using microorganisms and botanical extracts. Metarhizium flavoviride was among the first fungus to be recognized as a bio-control agent against desert locust in the laboratory and field conditions. Nevertheless, its oil formulation adversely affected nontarget organisms, hence led to further research on other microorganisms. Metarhizium anisopliae var. acridum (syn. Metarhizium acridum) is an environmentally safer bio-pesticide that has no measurable impact on non-target organisms. However, there are various shortcomings associated with its use in desert locust control as highlighted in this review. Bacterial pathogens studied were from species of Bacillus, Pseudomonas, and Serratia. Botanical extracts of 27 plant species were tested against the locust but showed varied results. Azadirachta indica and Melia volkensii were the most studied plant species, both belonging to family Meliaceae, which is known to have biologically active limonoids. Out of the 20 plant families identified, Apiaceae was the most represented with a frequency of 21%. However, only crude botanical extracts were used and therefore, the active ingredients against desert locust were not identified. Through a comprehensive research, an integrated pest management strategy that incorporates these bio-controls would be a realistic option to control desert locust infestations.
An Inventory and Assessment of Exotic and Native Plant Species Diversity in the Kenyan Rangelands:-Case Study of Narok North Sub-County.
(2015) Cheche, Winnie W.; Githae, Eunice W.; Magana, Adiel E. M.
A botanical inventory and diversity of exotic and native species was assessed in the rangeland of Narok North sub-County, Kenya. A total of 72 species were recorded, composed of 64 species of trees and shrubs and eight species of herbs. They belonged to 34 families and 52 genera. Fabaceae was the richest family with 16 species, followed by Euphorbiaceae (five), Moraceae and Myrtaceae (four each). In total, 48 species were native and 24 exotics with a diversity index H of 1.082 and 0.604, respectively. Hypericum revolutum, a native shrub, was the most dominant with an importance value of 3.81, followed by three exotic species; Datura suaveolens (an invasive species), Dovyalis caffra and Hibiscus rosa-sinesis with importance values of 3.40, 3.35 and 3.23, respectively. The native species were abundant in undisturbed areas while the exotics were most common in areas with vegetation cover less than 60%. Four invasive alien species were encountered namely; D. suaveolens, Lantana camara, L. trifolia and Opuntia ficus-indica. They all had a high density that indicated greater establishment success. This inventory affirms that the rangelands of Narok North are undergoing serious changes in vegetation structure and composition due to human activities and requires urgent attention to conserve biodiversity and genetic resources.
Nitrogen Fixation by Natural Populations of Acacia Senegal in the Drylands of Kenya Using 15N Natural Abundance
(Taylor and Francis Online, 2013-06-24) Githae, Eunice W.; Gachene, Charles K.K.; Njoka, Jesse T.; Omondi, Stephene F.
Nitrogen (N) fixation was estimated for three Acacia senegal (L.) (A. senegal) Willd. varieties (A. senegal var. senegal, kerensis, and leiorhachis) growing naturally in different sites in the dryland areas of Kenya. The quantities of N2 fixed were estimated by the 15N natural abundance method, using leaves as the sampling material. Balanites aegyptiaca (B. aegyptiaca) was selected as the reference species growing in the same area. Soil samples were also collected under A. senegal trees for nodule assessment. Leaf 15N natural abundance values (δ15N) were significantly different between A. senegal and B. aegyptiaca. These values averaged 6.35, 4.67, and 3.03% for A. senegal var. kerensis, leiorhachis, and senegal, respectively, and were lower than those of the adjacent reference species. There were also significant differences in the amount of N2 fixed (% Ndfa) among the varieties. A. senegal var. senegal showed the highest levels of N2 fixation with a mean of 36% while A. senegal var. kerensis and leiorhachis had equal estimates of 25%. However, no nodules were observed in the collected soil samples. Leaf N values were significantly different among the varieties with a mean of 2.73, 2.46, and 4.03% for A. senegal var. kerensis, leiorhachis, and senegal, respectively. This study shows that the three varieties of A. senegal are able to fix N2 in their natural ecosystems and the differences could probably be due to soil properties and nutrient availability under the different environments. The species can hence be utilized as plantations in agriculture and land rehabilitation programs.
Status of Opuntia invasions in the arid and semi-arid lands of Kenya
(CAB International 2018, 2018-03-21) Githae, Eunice W.
Invasive alien species (IAS) are among the leading threats to biodiversity, food security and human well-being. Opuntia (prickly pear cactus) is one of the most widespread and naturalized in the arid and semi-arid areas of Kenya, with extreme effects on rural livelihoods and the environment. However, comprehensive information on the status of invasion in the country is lacking, which is crucial for developing strategies for prevention and management. This paper, therefore, provides an overview of the interacting factors that influence its invasion in Kenya in terms of species diversity, pathways of introduction, negative impacts and the effectiveness of regulations and control measures. Seven invasive species of Opuntia are present in the country with the most abundant (O. stricta) being under biocontrol trial. These species have the same habitat preferences, physiological traits, negative impacts, introduction pathways and management options. Invasion is mainly attributed to changes in land use and consequent land degradation. Introduction pathways are largely intentional for ornamental purposes but unintentional at a local scale through escape from gardens and natural dispersal. The most applied methods of managing Opuntia are mechanical and chemical methods that are unsustainable and labour-intensive at large scale. Effective policies are therefore needed to prevent an increase in the significant negative impacts caused by IAS including those that have a limited distribution.