Browsing by Author "Namikoye, Everlyne Samita"

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    Can Fungal Endophytes Suppress Trialeurodes Vaporariorum and the Transmission of Tomato Infectious Chlorosis and Chlorosis Viruses in Field Conditions?
    (Frontiers in Cellular and Infection Microbiology, 2025-02) Paweer, Marial Makur Zechariah; Namikoye, Everlyne Samita; Nchore, Shem Bonuke; Akutse, Komivi Senyo
    Field trials were conducted for two seasons in two experimental sites (Mwea in Kirinyaga and Ngoliba in Kiambu counties of Kenya) to assess the efficacy of fungal endophytes Hypocrea lixii F3ST1 and Trichoderma asperellum M2RT4 in the control of Trialeurodes vaporariorum vector of tomato infectious chlorosis virus (TICV) and tomato chlorosis virus (ToCV) through seeds inoculation. TICV and ToCV’s disease incidence, severity and the yield were also evaluated. All the fungal endophytes successfully colonized all the tomato plant parts, but the highest root colonization was observed in H. lixii F3ST1 compared to the T. asperellum M2RT4 in both seasons. The number of nymphs was significantly lower in the endophytically colonized tomato plants than the control treatments in all the seasons and at both sites. However, the lowest number of nymphs was recorded in H. lixii F3ST1 compared to T. asperellum M2RT4. On the other hand, the TICV and ToCV disease incidence and severity rates were lower in endophytically colonized tomato crops compared to the control plots. This could be attributed to the reduction in the virus replication and lower feeding ability of T. vaporariorum that was characterized by less excretion of honeydew causing sooty mold. However, no significant difference was observed in ToCV disease severity rates among the treatments and across the seasons. The yield was significantly higher in endophyte plots than the control treatments in both sites and across the two seasons. This study demonstrates that H. lixii F3ST1 and T. asperellum M2RT4 endophytically colonized tomato plants and conferred systemic resistance against T. vaporariorum vector, and significantly reduced the transmission of TICV and ToCV, contributing to high reduction of both diseases’ incidence and severity in the field. However, further studies are warranted to confirm these results at large scale trials
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    Introduction to Crop Protection: Homoptera
    (2020) Namikoye, Everlyne Samita
    Order Homoptera include aphids, whitefly, scales, leafhoppers, and mealybugs. They are plant-sucking, and many excrete honeydew, a liquid high in sugar, which attracts ants and is used as a substrate for sooty mold fungus, which interferes with plant photosynthesis. Some are soft bodied, slow moving, or sedentary, forming colonies with wingless forms. Others are active. Adults have wings held roof-like over the body; the antennae are often short and bristle-like (as with leafhoppers). With sucking piercing mouthparts, many are vectors of plant viruses.Some secrete molted skins or a waxy, powdery substance that covers the body. Many are spread by the wind or carried by ants that feed on the honeydew and protect the insects from natural enemies.
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    Introduction to Crop Protection: Major Insect Pests
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    The major quarantine pests identified recently on cut flowers include bollworms (Helicoverpa armigera, Spodoptera spp.), leaf miner (Liriomyza sp.), white flies (mainly Bemisia tabaci), thrips (mainly western flower thrips – Frankliniella spp.), and fruit flies (Otieno, unpubl.). The greenhouse provides a modified environment which, in many ways, favours the proliferation of cut flower pests and diseases. During certain times of the year, day temperatures in the greenhouse may soar upto 26° -33°C which reduces the regeneration cycle for many pests.
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    Introduction to Crop Protection: Plant Diseases
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Plants, whether cultivated or wild, grow and produce well as long as the soil provides them with sufficient nutrients and moisture, sufficient light reaches their leaves, and the temperature remains within a certain “normal” range. Plants, however, also get sick. Sick plants grow and produce poorly, they exhibit various types of symptoms, and, often, parts of plants or whole plants diet. The agents that cause disease in plants are the same or very similar to those causing disease in humans and animals. They include pathogenic microorganisms, such as viruses, bacteria, fungi, protozoa, and nematodes, and unfavorable environmental conditions, such as lack or excess of nutrients, moisture, and light, and the presence of toxic chemicals in air or soil. Plants also suffer from competition with other, unwanted plants (weeds), and, of course, they are often damaged by attacks of insects. Plant pathology is the study of the organisms and of the environmental factors that cause disease in plants; of the mechanisms by which these factors induce disease in plants; and of the methods of preventing or controlling disease and reducing the damage it causes. Each discipline studies the causes, mechanisms, and control of diseases affecting the organisms with which it deals. Plant pathology is an integrative science and profession that uses and combines the basic knowledge of botany, mycology, bacteriology, virology, nematology, plant anatomy, plant physiology, genetics, molecular biology and genetic engineering, biochemistry, horticulture, agronomy, tissue culture, soil science, forestry, chemistry, physics, meteorology, and many other branches of science.
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    Management of Plant Diseases
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Most serious diseases of crop plants appear on a few plants in an area year after year, spread rapidly, and are difficult to cure after they have begun to develop. Therefore, almost all control methods are aimed at protecting plants from becoming diseased rather than at curing them after they have become diseased. Few infectious plant diseases can be controlled satisfactorily in the field by therapeutic means. The various control methods can be classified as regulatory, cultural, biological, physical, and chemical, depending on the nature of the agents employed. Regulatory control measures aim at excluding a pathogen from a host or from a certain geographic area. Most cultural control methods aim at helping plants avoid contact with a pathogen, creating environmental conditions unfavorable to the pathogen or avoiding favorable ones, and eradicating or reducing the amount of a pathogen in a plant, a field, or an area. Most biological and some cultural control methods aim at improving the resistance of the host or favoring microorganisms antagonistic to the pathogen. A new type of biological control involves the transfer of genetic material (DNA) into plants and the generation of transgenic plants that exhibit resistance to a certain disease(s). Finally, physical and chemical methods aim at protecting the plants from pathogen inoculum that has arrived, or is likely to arrive, or curing an infection that is already in progress.
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    Plant Diseases Caused by Bacteria
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Diseases caused by bacterial plant pathogens are one of the most severe constraints to agricultural productivity. Many types of crops are attacked by these pathogens every season with substantial losses occurring. Diseases caused by bacteria are important because they generally have fewer means of management compared to other types of pathogens, and therefore can pose a more serious threat to crop production. Bacterial pathogens are capable of spreading rapidly and are often detected late when plants have already been invaded and considerable harm already done. Infection may also be latent and is only detected after seedlings have been transplanted or crop produce already delivered to markets. Therefore, strengthening the capacity of farmers to identify and effectively manage bacterial plant pathogens is essential to successful and profitable farming. 3.2 Lecture
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    Plant Diseases Caused by Fungi
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Fungi are microscopic organisms that reproduce by means of spores. Only those with cell wall containing chitin are classified as true fungi. Most plant diseases are caused by fungi and most of them tend to become a problem, especially during the wet weather season. Some of fungal diseases can cause up to 100% loss in crops.
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    Plant Diseases Caused by Nematodes
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Nematodes are lower invertebrate animals and are perhaps the most numerous multicellular animals on the earth. They are generally free-living in marine, freshwater or soil environments, but a large number of species are parasitic to different kinds of plants and animals. The parasitic species are of considerable agricultural, clinical and veterinary importance as pests of plants and parasites of man and livestock respectively. Plant parasitic nematodes (PPN) are eel worms which are essentially aquatic and spend a greater part of their life cycle in the soil. They feed on the surface or the peripheral layers of the root or enter the root and feed from within with the help of a feeding structure called the stylet. Infected plants in general exhibit stunting, yellowing of leaves, wilting and reduced yield, in addition to several below-ground symptoms. Plant parasitic nematodes lay eggs singly or in masses either in the soil or within plant tissues. Most PPN have four larval stages between the egg and adult, with intervening moults. A life cycle from egg to egg can be completed within 3-4 weeks under optimum environmental conditions; temperature being the key factor in determining the duration of the life cycle. This topic deals with how nematodes cause diseases in plants, the symptoms they induce, their lifecycle an interaction with other disease causing agents, their life cycle, dispersal and survival. The above components are discussed in relationship to the control and management of diseases.
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    Plant Diseases Caused by Viruses
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Plant viruses have a huge impact on crop production throughout the world. Consequently, there has been a considerable effort and resources directed towards managing virus diseases. Crop failure due to debilitating viruses creates significant financial hardship and food insecurity in developing countries. Insect-transmitted viruses cross national boundaries into new geographic areas, resulting in negative social and economic impacts on subsistence agriculture. To be successful, virus management strategies must have the capacity to deal with these challenges. Furthermore, such strategies require a good understanding of how viruses spread between crops and across seasons. In addition, accurate diagnosis backed up by reliable detection techniques is the critical first step in virus disease management. Generally, virus management is guided by a number of principles....
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    Population dynamics and management of vectors of viruses causing maize lethal necrosis disease in Bomet County Kenya
    (Kenyatta University, 2018-04) Namikoye, Everlyne Samita
    Maize production in Kenya is under threat due to infection by maize lethal necrosis disease (MLND). The disease is known to cause intensive complete yield loss. It is caused by a synergistic infection of maize by maize chlorotic mottle virus and sugarcane mosaic virus which are mainly vectored by corn thrips (Frankliniella williamsi, Hood) and corn leaf aphids (Rhopalosiphum maidis, Fitch) respectively. This study was carried out with the aim of investigating the following aspects; farmer‘s knowledge and practices on vectors of MLND causing viruses, movement and dispersal of the two vectors in a maize farm and various management strategies through sticky roll trapping, varietal tolerance, action threshold levels, polycropping systems and biocontrol strategies towards the control of the disease and vectors. Field trials were carried out in Bomet County for two seasons from November 2014 to September 2016 using a randomized complete block design. Data was collected by counting vectors, scoring for MLND severity and disease incidence. Presence of MCMV, SCMV virus was also carried out using ELISA tests. Data was analyzed using Genstat version 17 to get mean and significant means were there after separated using LSD. Survey results indicated majority of respondents in Bomet as being youths aged between 21 to 30 years while 58% of the farmers had attained education up to upper primary level. Only 23% were high school graduates. Majority of the farmers were aware of MLND but only 3% knew about the vectors of MLND.The use of vertically positioned blue sticky traps were more attractive to corn thrips compared to the yellow ones (P = 0.023). Similarly, blue sticky rolls trapped more corn thrips and prevented maize from MCMV infection (P<0.001) while the yellow sticky rolls trapped more corn leaf aphids and prevented maize from SCMV infection (P<0.001). Sampling of maize along the rows gave the best prediction for the vector infestations (P<0.001) while the upper plant region proved most effective for vector sampling.The most appropriate time for vector sampling was from 8.30 am to 10. 30 am as well as from 3.30 pm to 5.30 pm. The monthly spray regime had the highest net returns as compared to all the other spray regimes. More over, maize from the entire thunder sprayed plots tested MLND negative compared to the control that received no spray (P<.001). Results showed variety Pannar as the most resistant to MLND (P<.001) as well as landraces MLR1 and MLR 15 (P = 0.002). The companion crops used in the polycropping system showed coriander harboring significantly more corn leaf aphids compared with other companions (P = 0.04). Furthermore, maize planted with coriander tested negative for SCMV and hence MLND negative. Findings from this study provide scouting and monitoring strategies for both vectors as well as various successful management and control methods for the disease and its vectors. Adoption of techniques such as sampling patterns, sampling time, scouting methods, use of sticky cards and sticky rolls will give an indication of the vector status in the field as well as offer control mitigation measures. Varietal resistance coupled with action thresholds of the vectors and the use of companion crops was able to result into minimal disease spread and reduced chances of MLND occurance. This information can be used to formulate a management strategy for the vectors of MLND causing viruses as well as develop a national vector and disease monitoring plan for both the vectors and the disease. This will culminate into improved maize production and food security.
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    Taxonomy and Classification of Insects
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Classification refers to the arrangement of the kinds of individuals living organisms into groups and the groups into systems called classification. TAXONOMY: This is the science of identifying, naming and classifying organisms. Taxonomy is the day today practice dealing with organism kinds, handling and identification of specimen, publication of data, study of literature and analysis of variations shown by specimens. The taxonomists assign the names to plants and animals.
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    Weeds and Weed Management
    (Kenyatta University, 2020) Namikoye, Everlyne Samita
    Weeds are undesirable plants that may grow naturally along with crops. They affect the growth of plants, products desirability, decreased production efficiency and the yields. Weeds usually grow very fast, compete for the some resources and hinder plants growth by producing alellochemical. Weeding is necessary since weeds compete with the crop plants for water, nutrients, space and light. Farmers adopt many ways to remove weeds and control their growth. Tilling before sowing of crops helps in uprooting and removing of weeds, which may then dry up and get mixed up with soil. The best time for removal of weeds is before they produce flowers and seeds. The manual removal includes physical removal of weeds by uprooting or cutting them close to the ground, from time to time. Weeds are also controlled by using certain herbicides; these are sprayed in the fields to kill the weeds. They do not damage the crops.