Nematolgy Midterm PDF

1 NEMATOLOGY MIDTERM 2  INTESTINAL – TISSUE NEMATODES 1. Trichinela spiralis Common name: Trichina worm Common associated disease: Trichinosis, trichinellosis Morphology: Encysted larva, Adult EPIDEMIOLOGY: found worldwide particularly in members of the...

1 NEMATOLOGY MIDTERM 2  INTESTINAL – TISSUE NEMATODES 1. Trichinela spiralis Common name: Trichina worm Common associated disease: Trichinosis, trichinellosis Morphology: Encysted larva, Adult EPIDEMIOLOGY: found worldwide particularly in members of the meat-eating population. This organism may be found in a number of different animals, including the pig, deer, bear, walrus and rat. 3 LIFE CYCLE: 1. Ingest undercooked meat (striated muscles) 2. Larvae released and mature in intestine 3. Adult male and female copulate. 4. Gravid female migrates to intestinal submucosa and lay larvae 5. Infant larvae migrate to striated muscles to encyst nurse cells and form granuloma. 6. Life cycle will not be completed. (as human is not traditional host) 4 CLINICAL SYMPTOMS: Persons with light infection typically experience: - Diarrhea and possibly a slight fever (usually asymptomatic) Heavily infected patients complain: (during the intestinal phase of infection) - Vomiting - Diarrhea - Nausea - Headache and perhaps a fever - Abdominal Pain As the larvae begin their migration through the body: - Eosinophilia - Blurred vision (periorbital and facial swellings, retinal - Pain in the pleural area (lungs) and conjunctival hemorrhaging) and subungual splinter - Fever - Edema, and cough. - Death may also result during this phase Once the larvae settle into the striated muscle and begin the encystation process: - Muscular discomfort - Edema, local inflammation - Overall fatigue, and weakness The striated muscle of the face and limbs, as well as that of other parts of the body, may become infected LABORATORY DIAGNOSIS: - Examination of the affected skeletal - Antibody testing > using the biopsy muscle > method of choice for recovery of specimen the encysted larvae - Elevated serum muscle enzyme levels - Serologic methods are also available (lactate dehydrogenase, aldolase, and creatinine phosphokinase) 5 TREATMENT: - No medications are indicated if the infected person has a non-life-threatening strain of the disease. >These patients are instructed to get plenty of rest, supplemented by adequate fluid intake, fever reducers, and pain relievers - Patients with severe infections that may be potentially life-threatening are usually treated with prednisone. PREVENTION AND CONTROL: - Thorough cooking of meats, especially from animals known to harbor T. spiralis -------------------------------------------------------------------------------------------------------------- 2. Dracunculus medinensis Common Name: Guinea worm Common Associated Disease: - Dracunculosis - Dracunculiasis - Guinea worm infection Morphology: Larva and Adult EPIDEMIOLOGY: - Found in parts of Africa, India, Asia, Pakistan, and the Middle East - Copepods reside in freshwater, located particularly in areas called steep wells, from which people obtain drinking water and bathe 6 LIFE CYCLE: 1. Ingestion of contaminated aquatic animals or water (copepods) L3 2. Maturation of larva into adult in the small intestine 3. Penetrate to intestinal wall and proceed to connective tissues or body cavities for mating 4. Gravid female lay larvae on subcutaneous tissues (extremities) L1 which results to infected ulcer 5. Contact to freshwater can result to release of larvae 6. Copepods ingest L1 and mature to L3 7. Ingested by the freshwater animals/copepods CLINICAL SYMPTOMS: - Allergic reactions (migration of the - Intense itching and a burning pain at the organism occurs) site of skin lesion (ulcer) - Urticaria - Secondary bacterial infections (ulcers) - Eosinophilia may also develop -> disability or death - Erythema - Dyspnea - Vomiting - Pruritus LABORATORY DIAGNOSIS: - Induced rupture of the infected ulcers by - Serologic tests - antibody screening immersing in cool water reveals the first- - Skin test -> wheal and flare stage larvae -> microscopic examination 7 TREATMENT: - Total removal of the adult worm -> Use stick - Application of topical antibiotics to the area PREVENTION AND CONTROL: - Filtering drinking water through a piece of - Infected people are instructed not to enter fine-mesh cheesecloth sources of drinking water, such as open - Boiling water wells or reservoirs, so that these sources do - Drinking only chlorinated water not become contaminated NEMATODE ADAPTATION AND SURVIVAL 1. Cryptobiosis -is a state of extreme inactivity in response to adverse environmental conditions. (HIGH TEMP, FREEZING TEMP) -describes the state of an organism whose body water is completely dehydrated and metabolic activity has become - ametabolic state of life entered by an organism in response to adverse environmental conditions undetectable 2. Cuticle Structure -The outermost layer of the body wall -permits locomotion via attachment to muscle, confers environmental protection and allows growth by molting. 3. Parasitic lifestyle Adaptations Ex. Endoparasites - parasites that live in tissues and organs or their host Ectoparasites - parasites that lives outside of the host's body ex: ticks, fleas, lice, mites 8 4. High reproductive rate -Significant in population survival How quickly do nematodes reproduce? - It takes approximately 2-4 weeks for one lifecycle from egg to egg. Females can produce 50-500 eggs per cycle depending on the species 5. Environmental sensing and behavior ex. Using of aphids (chemosensory organ on the lips) During feeding, aphids simultaneously ingest sap contents and inject saliva, which can contain viruses if the amphid has previously fed on an infected plant. 6. Temperature Tolerance Adapting to survive to extreme temperatures Ex: Pompeii worm 7. Feeding mechanism Use of specialized feeding structures ex: stylet 8. Resistance to host immune responses. Some parasites can reside within the host's body Helminthic worms are able to avoid the immune system by coating their exteriors with glycan molecules that make them look like host cells. 9  NEMATODE SYMBIOTIC ASSOCIATION Involves relationships between Nematodes that can either be: Mutualistic - Beneficial to both Commensal - Beneficial to one, Neutral to the other Parasitic - Harmful to one A. Ectosymbiosis and Endosymbiosis Endosymbiosis and ectosymbiosis are two types of symbiotic relationships in which organisms interact closely, but they differ in the nature of their interactions. ENDOSYMBIOSIS Endosymbiosis is a term used to describe two organisms living together with one inside the other. The word endosymbiont comes from two Greek root words: endo, meaning within, and symbios meaning, living together. ECTOSYMBIOSIS Ectosymbiosis is a term used to describe two organisms living together, with one residing on the surface of the other. The word ectosymbiont is derived from two Greek root words: ecto, meaning outside, and symbios, meaning living together. B. Obligate and Facultative Symbiosis OBLIGATE SYMBIOSIS Obligate symbiosis in terms of its human host - is the reliance of nematodes to the human host for survival and reproduction. Moreover, this includes the completion of its life cycle in the expense of the definitive host. ex. Meloidogyne spp. & Radopholus similis FACULTATIVE SYMBIOSIS Does not rely completely to the definitive host for survival. Even though parasites can and will infect if given the opportunity, resulting in a variety of complications, they also have the potential to exist in a free-living form that can survive in certain environmental conditions in the absence of a host. ex. Strongyloides stercoralis (Rhabditiform larvae - the free-living larvae of the species that develops outside the definitive host.) 10  C. Mutualism and Commensalism Symbiosis MUTUALISM A type of symbiotic relationship wherein both organisms involved benefit from the interactions ex. nematodes and bacteria - habitat for the bacteria and feeding for the nematodes. COMMENSALISM A type of symbiotic relationship in which just one-party benefits while the other remains unharmed ex. nematodes and millipedes - nematodes resides on the intestines of the millipedes benefiting on the available nutrients. D. Nematode - Fungi Interaction Two of the most prevalent species in soil habitats, nematodes and fungi, interact intricately to influence the dynamics of terrestrial ecosystems. Their interactions are important for enabling the cycling of nutrients, preserving the stability of food webs, and affecting agricultural productivity. Nematode - fungus interaction was first observed by Atkinson (1892) in cotton. Fusarium wilt was more severe in the presence of Meloidogyne spp. Since then, the nematode fungus interaction had received considerable attention on important crop like banana, cotton, cowpea, brinjal, tobacco and tomato Fusarium Wilt Meloidogyne spp 1. Antagonistic Interactions: (A Battle for Resources) in which one organism gains an advantage over the other, are the most common between nematodes and fungi. These exchanges fall into two primary categories: Nematodes Feeding on Fungi: - known as fungivorous nematodes, have fungi as a primary food source. Such as Aphelenchus, Aphelenchoides, Ditylenchus, and Tylenchus, feed on a diverse range of fungi. 11  Fungi Preying on Nematodes: The Rise of Nematophagous Fungi - Nematophagous fungi are those that have adapted to feed on nematodes in their evolutionary history. These fungi use a range of techniques to attract and eat worms. - Such as: Paecilomyces Include techniques: Nematode-trapping devices: Some fungi produce specialized structures like adhesive networks or constricting rings that trap nematodes. 2. Mutualistic Interactions: A Symbiotic Partnership - Nematodes and fungi can also engage in mutualistic relationships, where both organisms benefit from the interaction. Nematodes Facilitating Fungal Growth Fungi Enhancing Nematode Reproduction Example of beneficial fungi is Trichoderma sp. E. Nematode- Bacteria Interaction Can be beneficial (mutualistic) or harmful (parasitic) and can range from facultative, temporary interactions to stably maintained, long-term symbioses. Bacteria can be a potential food source for nematodes Ex: Caenorhabditis elegans 12  F. Nematode-Virus Interaction Relatively rare but primarily involves viruses that infect plants and use nematodes as vectors, or carriers, to spread the virus from one plant to another. These interactions usually involve soil-dwelling nematodes that feed on plant roots, allowing the virus to move into new hosts as the nematode migrates. Ex: Grapevine fanleaf virus and Xiphinema index STEM AND BULB NEMATODE STEM NEMATODES - It is a very destructive pest of bulb onions and garlic. - Feed within the plants on the stems, leaves, and bulbs by injecting enzymes into the cells via their stylets. Ditylenchus dipsaci Common Name: - Stem Nematodes - The stem and bulb eelworm - Onion and garlic bloat nematodes. Common Associated Disease: - Stem nematode disease - Bulb nematode disease Morphology: - Egg - Larvae - Adult Form Epidemiology: - Stem and bulb nematodes, particularly Ditylenchus dipsaci are significant plant parasites that affect a wide range of crops. - Ditylenchus dipsaci can be found in temperate regions, particularly in Europe, North America, and parts of Asia. - However, their presence has also been noted in South America and Africa. - These nematodes attack a wide range of hosts, including onions, garlic, tulips, potatoes, and other crops, leading to stunted growth, deformation, and even plant death. 13 Life Cycle: - Nematodes begin as eggs. - The eggs hatch, releasing the first-stage juveniles. - The nematodes undergo 3 molts before becoming fourth-stage larva - These juveniles attack seedlings and start causing damage. - Infected areas enlarge, seedlings become deformed, and some disintegrate or die. - Juveniles undergo 4th molting to reach adulthood - The adult nematodes develop within the plant leaves. - Hypertrophy and hyperplasia occur around the nematodes, causing the leaves to remain short and thick. - Nematodes migrate downwards into the bulb or through the plant. - Nematodes infect the scales of bulbs, causing visible damage, such as mealy or discolored rings. - Heavily infected bulbs release juveniles, and the cycle continues as juveniles cling to the bulb surfaces. Morphology: - Females are 1000-1300 µm long and 35-40 µm wide. Males are smaller than females. - They have 10-12 long and bottle-shaped esophagus with a distinct basal bulb that does not overlap the intestine. - The nerve ring is located at mid isthmus. - Amphid aperture pore-like. - The stylet is always with basal knob - Females have only one ovary and the vulva is generally 75-80% - Males have adenal bursa. Symptoms: - Leaves turn yellow, wilt, and collapse - Discoloration of bulbs - The plant may be stunted or die back - Swollen stem. prematurely - Leaves defoliate. - Garlic bulbs turn brown and become - Bloated Bulbs. lightweight. Mechanism of Damage in Different Plant: Feeding Behavior: Stem nematodes extract nutrients from the plant’s vascular tissues, particularly the stems and roots Tissue Damage: The feeding activity of stem nematodes can cause cell death and tissue necrosis. Galling and Swelling: in some cases , stem nematode induce the formation of galls or swelling on the stem or roots. Vascular Disruption: By feeding primarily on vascular tissues, stem Nematodes disrupt the plant's ability to transport water and nutrients. Reproduction impact: A high population of Stem nematodes can hinder flowering and fruit development Soil effects: As parasites, stem Nematodes can alter the soil microenvironment, impacting beneficial soil organisms and the nutrient cycle, which can further influence plant nutrients. 14 Prevention: - Clean all tools and equipment on site after working in an infested field. - Good sanitation and choice of plants. - Do not use garlic from an infested field for seed. - Nematodes survive in infested bulbs and wrappers. - Don’t bury culls in the field. Don’t move culls or crop debris to a new area. Treatment: - Hot water treatment - Can destroy the nematodes within the bulb. - by immersing the dormant bulbs in water held at 44.5°C (112°F) for three hours. - Too much heat will damage the bulbs, while too little will allow the nematodes to survive. - An insulated water tank with thermostatic controls is needed to maintain the correct temperature. SEED NEMATODE - Plant-parasitic nematodes that specifically infest and damage seeds and seedlings. - They can cause problems during the germination process or affect young plants, leading to stunted growth, poor establishment, and reduced crop yields. - These nematodes feed on plant tissues, disrupting normal physiological functions and making plants more susceptible to other diseases. - Common types include the bulb and stem nematode (Ditylenchus dipsaci) and various species of - root-lesion nematodes. EXAMPLES: Anguina tritici (Wheat Seed Gall Nematode) Host: Primarily affects wheat, but can also infest rye and other grasses Ditylenchus dipsaci (Stem and Bulb Nematode) Host: A wide range of plants, including onion, garlic, alfalfa, oats, pea, and several ornamental plants. Ditylenchus destructor (Potato Rot Nematode) Host: Potatoes, sweet potatoes, bulbs, and tubers. Life Cycle: - Have a complex life cycle that includes eggs, juvenile stages, and adults. - Their rapid reproduction can lead to significant population increases, especially in favorable conditions. 15 Host Range: - Different species of seed nematodes target specific plants or plant families. - For instance, Ditylenchus dipsaci affects a variety of crops, including legumes and bulbs, while Heterodera glycines primarily targets soybeans. Enviromental Conditions: - Moist, warm soil conditions generally favor the survival and reproduction of seed nematodes. - They are more prevalent in poorly drained soils or in areas with high humidity. Soil Health: - Healthy soil conditions support beneficial microorganisms that can suppress nematode populations. - Soil compaction, low organic matter, and nutrient deficiencies can make plants more susceptible to nematode damage. Epidemic Potential: - Seed nematodes can lead to epidemics in crops, particularly when planting infected seeds or when infested soil is used. - This can result in poor germination and reduced plant vigor. Management Practices: - Effective strategies for managing seed nematodes include crop rotation, the use of resistant varieties, soil fumigation, and good agronomic practices to enhance soil health Geographic Distribution: - The distribution of seed nematodes varies by region, influenced by climate, soil type, and agricultural practices. - Monitoring their presence is important for crop management. 16  Symptoms and Mechanism Damage in Different Plants General Damage: - Feeding on plant cells, disrupting growth. - Gall formation in seeds, reducing quality. - Toxin production, causing necrosis. Anguita tritici (Wheat) Ditylenchus angustus (Rice) Symptoms: Symptoms: - Stunted growth, - Yellowing leaves - Spikelet galls - Seed galls - Shriveled seeds. - Poor grain filling. Mechanism: Mechanism: - Forms galls that replace seeds. - Feeds on seeds, reducing yield. Ditylenchus dipsaci Aphelenchoides fragariae (Strawberry) (Onion) Symptoms: Symptoms: - Crinkled leaves - Deformed leaves - Necrotic patches. - bulb rot. Mechanism: Mechanism: - Causes leaf necrosis, reducing fruit quality. - Feeds on bulb tissues, causing decay. (Pea) Symptoms: - Stunted growth - Swollen stems - Cracked seeds. Mechanism: - Destroys cells, causing swelling and seed damage. Treatment: - Hot Water Treatment - Physical Seed Sorting - Biological Control Prevention Methods: Use of Clean Seeds Resistant Varieties: Crop Rotation - Use nematode-resistant plant varieties to Sanitation Practices reduce the likelihood of infestation. Seed Treatment Soil Fumigation: - Treat seeds with hot water (50– - Apply soil fumigants or biofumigation 55°C) or chemical nematicides methods (using plant residues with natural to kill nematodes in the seed nematicidal properties) to reduce nematode coat. populations in the soil. Controlled Irrigation: - Avoid overwatering, as excessive moisture creates favorable conditions for nematode proliferation. 17  MICROSCOPE MICROSCOPE - From the greek words: Mikron – small Scopeos - to look - Microscope is an optical instrument consisting of one or more lenses in order to magnify images of minute objects Microscopy - Science of investigating smallobjects using such instrument Variables used in Microscopy 1. Magnification 3. Working Distance - Degree of enlargement - Distance between the front surface of the - Depends on optical tube length, focal objective and the surface of the cover glass length of objective and magnifying power or specimen of eyepiece Total Magnification: - Magnification of the eyepiece x magnification of the objectives Ocular lens - 10x - 15x Scanner - 4x Low Power - 10x High Power - 40x Oil Immersion - 100x -> oil enhances the resolution power of the microscope 4. Contrast - Differences in the intensity between two 2. Resolution objects or between an object and - Ability to reveal closely adjacent structural background details as separate and distinct - Improved by staining the specimen - Extent to which details in the magnified object are maintained 18 Types of Microscopes and Its Uses 1. Light Microscope - Uses sunlight or artificial light a. Bright Field - Produces dark image against bright background Uses: to view live or stained cells b. Dark Field - Produces bright image of the object against a dark background Uses: demonstration if T. pallidum, leptospira, spirochetes c. Phase Contrast - Produces high-contrast images of transparent specimens Uses: examination of unstained living cells in natural state d. Fluorescence - Uses fluorochrome dyes that shows bright images Uses: for observation of microbes that fluoresce when stained - E.g. Acid fast Bacili and those who directly fluoresce when placed under UV lamp e.g. Cyclospora Fluorochromes >Acridine Orange - for QBC examination (malarial parasites) >Auramine Rhodamine - Examination of tubercle bacili (yellow fluorescence) >Calcofluor White - (rapid method) for examination of yeast and pathogenic fungi, bacteria, and parasites >Fluorescein Isothiocyanate (FITC) – for labeling / identification of proteins (green) e. Compound Microscope - Commonly used microscope in the laboratory f. Simple Microscope - uses mirror / sunlight as light source 19 2. Electron Microscope a. Transmission Electron Microscope - Can magnify up to >50 million times - Produced 2D images b. Scanning Electron Microscope - Up to 1-2 million times - Produces 3D images PARTS OF THE MICROSCOPE Divided into 3 groups: - Mechanical Part - Magnifying Part - Illuminating Part BASIC QUALITY PARAMETERS OF MICROSCOPIC IMAGES 1. Focus - Refers whether the image is well defined or blurry (out of focus) - Can be adjusted through course and fine adjustment knobs of the microscope which will adjust the focal length to get clear image 2. Brightness - Refers how light or dark the image is - Brightness of the image is depends on the illumination system and can be adjusted by changing the voltage of the lamp and by condenser diaphragm 20 3. Contrast - Refers how best the specimen is differentiated from the background or the adjacent area of microscopic field 4. Resolution - Refers the ability to distinguish two objects close to each other - Depends on the resolving power, which refers minimum distance between the two objects which can be distinguishable PARFOCAL AND PARCENTRAL Parfocal - Microscope’s ability to stay in focus when changing magnification Parcentral - The object in the center of view will remain in the center when the objective is rotated NICE TO KNOW - Upper left number is the magnification factor of the objective (4x, 10x, 40x, 100x) - Upper right number is the numerical aperture of the objective (0.1, 0.25, 0.65, 1.25) - Lower right number (if given) refers to the thickness of the glass cover slip (in millimeters) assumed by the lens designer for best performance of the objective (0.17) - Lower left number is the tube length in millimeters 21  CARING OF MICROSCOPE Proper Storage: Care for OIO: - Use dust cover when not in use - Wipe the oil on the objective after using - Store the microscope in a clean dry lace, - Use commercially available cleaning waterproof container, with good air solution for the oil (Cedar Wood, Mineral ventilation Oil, Silicone Oil) - Do not store the microscope in direct Care for Lamp: sunlight - Perform an annual maintenance check Handling: - Have your microscope serviced - Hold its arm securely with both hands professionally Care of Lenses: - A rule of thumb for frequency of servicing - Do not touch the optical and objective lens is every 200 hours of use or every 3 years, with bare fingers whichever comes first - Clean with suitable lens cleaning solution Rules in using Microscope: - Wipe from the center to the outside in a - Always carry with 2 hands spiral manner - Use only lens paper for cleaning - Do not force knobs - Always store covered - Be careful of the cords 22  LEAF NEMATODES - Also known as Foliar Nematodes - Microscopic roundworms primarily infest the leaves and other above-ground parts of plants. - Most common leaf nematodes belong to the genus Aphelenchoides and are known to affect a wide range of plant species, including both ornamental and food crops Aphelenchoides spp. 1. Aphelenchoides besseyi Common Name: - Rice White Tip Nematode Associated Disease: - Rice White Tip Disease Host: - Primarily Rice (Oryza sativa), but also strawberries Life Stages: - Egg, - L1-L4 Larva - Adult Feeding Mechanism: - Uses a stylet to feed on plant tissues. Survival Mechanism: - Anhydrobiosis 2.Aphelenchoides fragariae Common Name: - Strawberry Crimp Nematode Associated Disease: - Strawberry Crimp Disease Host: - Strawberries - Begonias - Ornamental plant Life Stages: - Egg - L1-L4 Larva - Adult Feeding Mechanism: - Uses a stylet to pierce plant cells. Surviving Mechanism: - Anhydrobiosis 23  3. Aphelenchoides ritzemabosi Common Name: - Chrysanteum Foliar Nematode - Black Currant Nematode Associated Disease: - Chrysanteum Foliar Disease Host: - Chrysanthemum and Black Currant Life Stages: - Egg - L1-L4 Larva - Adult Feeding Mechanism: - Uses a stylet to pierce plant cells Survival Mechanism: - Anhydrobiosis LIFE CYCLE: - The life cycle of leaf nematodes begins with females laying eggs in or on plant tissues. - These eggs hatch into juvenile nematodes, which undergo several molts as they develop. - After reaching maturity, typically within 2-4 weeks under favorable conditions, the adults are capable of reproduction, often leading to rapid population increases. - This cycle can repeat quickly, particularly in warm, moist environments, contributing to the significant impact these nematodes can have on host plants. EPIDEMIOLOGY Host Range: - Leaf nematodes have a diverse host range, affecting a variety of plants, particularly vegetables and ornamentals. - Common hosts include lettuce, carrots, and other leafy greens, as well as flowering plants like chrysanthemums and various herbs. - They can also infest some fruit crops, impacting yield and quality. - This broad host range allows leaf nematodes to thrive in various agricultural and ornamental settings, making them a significant pest for both commercial growers and home gardeners. - Their ability to affect a wide array of plants underscores the importance of effective management strategies to mitigate their impact. Environmental Conditions: - They prefer warm temperatures, typically ranging from 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit), and high humidity levels that enhance their movement and feeding activity. - Moisture-retaining soils are particularly conducive to their proliferation, as these nematodes are more prevalent in compacted soils that hold water compared to well-drained soils. 24 - These environmental factors not only support their rapid life cycle but also increase the likelihood of infestations, making it crucial for growers to monitor and manage conditions to prevent outbreaks. Soil Health: - soils with balanced pH, organic matter, and beneficial microbes can suppress their populations - Poor conditions, such as compacted, moisture-retaining soils, promote nematode proliferation and increase plant susceptibility. Well-managed soils that ensure good drainage and healthy roots can reduce infestations. - Maintaining soil health through practices like crop rotation and organic amendments is essential for mitigating the impact of leaf nematodes Epidemic Potential: - Leaf nematodes have significant epidemic potential due to their rapid reproduction and broad host range. - Favorable conditions like warmth and humidity enable quick population growth, while their ability to spread through contaminated soil and plant debris facilitates widespread outbreaks. - This can lead to substantial economic losses in agriculture, making effective management practices crucial to prevent large-scale infestations. Management Practices: - Effective management practices for leaf nematodes include a combination of cultural, biological, and chemical strategies. - Cultural practices such as crop rotation can disrupt the nematode life cycle by alternating hosts, while maintaining soil health through proper drainage and organic amendments helps create less favorable conditions for nematode proliferation. Sanitation measures, like cleaning tools and equipment, are essential to prevent the spread of nematodes. - Biological control can involve introducing natural predators or beneficial nematodes that target leaf nematodes. - Chemical control options include nematicides, but these should be used judiciously to avoid resistance and minimize environmental impact. Geographic Distribution: - Leaf nematodes are found worldwide, with their geographic distribution primarily influenced by climate and host availability. - They are particularly prevalent in regions with warm, moist conditions, which are conducive to their growth and reproduction. - This includes parts of North America, Europe, Asia, and Africa, where they can infest a variety of agricultural and ornamental crops. - The spread of these nematodes is facilitated by human activities, such as the movement of contaminated soil, plant materials, and equipment, allowing them to be established in new areas. 25 Symptoms: - Leaf Distortion - Lesion and Necrosis - Leaf Blotch - Premature leaf drop - Discolored foliage MECHANISM OF DAMAGE IN PLANTS Penetration and movement in leaves - They primarily enter plants through natural openings like stomata or through wounds. Feeding and tissue destruction - They use their stylet to enter plant cells and feed on their content. Systemic Spread - Over time, nematodes may spread from leaves to other parts of the plant, including stems and buds. This can lead to more widespread damage and even plant death in severe cases. TREATMENT Nematicides - These chemical pesticides are designed to kill nematodes. Crop Rotation - Rotating crops can disrupt the nematode life cycle, preventing them from building up in the soil. Hot Water Treatment - It involves soaking dormant plants in water at specific temperatures (120-140°F) for up to 10 minutes. Removal of Infected Plant Material - Remove and destroy infected leaves and stems. PREVENTION Maintain good sanitation - Clean tools and equipment regularly. Avoid overwatering - It could create a favorable environment for their growth and reproduction. Quarantine new plants - Isolate new plants for a period of 30-60 days before introducing them to your existing garden. 26