BC-Department of Agricultural Science and Technology

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Browsing BC-Department of Agricultural Science and Technology by Author "Namikoye, Everlyne Samita"

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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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    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.