Plant Diseases Chapter PPA-46
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Questions and Answers

What was responsible for the near complete loss of the American chestnut?

  • A bacterial infection
  • A plant parasitic nematode
  • A viral outbreak
  • A fungal disease (correct)

    • How was chestnut blight introduced to the United States?

  • Through native tree species
  • Imported Chinese chestnut trees (correct)
  • Via contaminated soil
  • Through agricultural practices

    • What management strategies are currently used against chestnut blight?

  • Chemical pesticides exclusively
  • Genetic modification of the trees
  • Planting only native species
  • Sanitation and fungicides (correct)

    • What role did the French wine industry play in disease management?

    <p>They introduced the Bordeaux mixture fungicide</p> Signup and view all the answers

    Approximately how many acres of chestnut trees died due to the chestnut blight?

    <p>30 million acres</p> Signup and view all the answers

    Which of the following statements about Chinese chestnut trees is true?

    <p>They can tolerate the blight.</p> Signup and view all the answers

    What type of pathogen mainly caused the devastation of the American chestnut?

    <p>Fungi</p> Signup and view all the answers

    After the introduction of chestnut blight, how did the landscape of American forests change?

    <p>Many other tree species became dominant.</p> Signup and view all the answers

    What is the primary function of sexual spores produced by water molds?

    <p>To serve as a survival mechanism under adverse conditions</p> Signup and view all the answers

    How often can sporulation occur in water molds during a growing season?

    <p>Many times, provided water is available</p> Signup and view all the answers

    What is one visible example of a fungal disease mentioned?

    <p>Powdery mildew</p> Signup and view all the answers

    Which of the following pathogens cannot survive winter in Kentucky?

    <p>Cucurbit downy mildew pathogen</p> Signup and view all the answers

    How can the variation in fungal spores assist diagnosticians?

    <p>Identifying the specific pathogens</p> Signup and view all the answers

    Which type of fungal fruiting structure is produced sexually?

    <p>Ascocarps</p> Signup and view all the answers

    What is a common symptom of cucumber infection by the cucurbit downy mildew pathogen?

    <p>Yellow, angular leaf spots</p> Signup and view all the answers

    Where are spores of the cucurbit downy mildew pathogen typically produced?

    <p>On the undersides of leaves</p> Signup and view all the answers

    What is a characteristic of exposed or unprotected fungal spores?

    <p>More sensitive to environmental conditions</p> Signup and view all the answers

    What happens to a fungal spore once it makes contact with a suitable plant surface?

    <p>It germinates and hyphae emerge</p> Signup and view all the answers

    How do spores of downy mildew spread to new tissue?

    <p>Through water or rain</p> Signup and view all the answers

    What is required for plant disease to occur according to the Disease Triangle?

    <p>A combination of susceptible host, pathogen, and environment</p> Signup and view all the answers

    Which of the following diseases primarily affects solanaceous crops?

    <p>Late blight</p> Signup and view all the answers

    What is the typical overwintering site for the late blight pathogen?

    <p>In infected plant or weed tissue</p> Signup and view all the answers

    Which of the following fungi’s reproductive strategies involves both sexual and asexual processes?

    <p>Rust fungi</p> Signup and view all the answers

    Which structure is a common asexual fruiting body produced by fungi?

    <p>Pustules</p> Signup and view all the answers

    What structures do plant parasitic nematodes use to pierce plant tissues?

    <p>Needle-like mouthparts</p> Signup and view all the answers

    Which of the following symptoms is NOT commonly caused by nematode feeding?

    <p>Flower wilting</p> Signup and view all the answers

    How do plant parasitic nematodes primarily disseminate over long distances?

    <p>Movement of infested soil</p> Signup and view all the answers

    What does the presence of female nematodes at a feeding site indicate?

    <p>Longevity of feeding</p> Signup and view all the answers

    Which type of nematode feeds while remaining on the exterior of plant roots?

    <p>Stubby-root nematode</p> Signup and view all the answers

    What reproductive method can female nematodes use to produce eggs?

    <p>Both mating and asexual reproduction</p> Signup and view all the answers

    What is a common result of severe root loss due to nematode feeding?

    <p>Symptoms resembling nutrient deficiencies develop</p> Signup and view all the answers

    What differentiates the feeding behavior of dagger nematodes from that of soybean cyst nematodes?

    <p>Dagger nematodes penetrate plant tissues completely, while soybean cyst nematodes do not</p> Signup and view all the answers

    What is the primary way bacteria infect plants?

    <p>Via wounds or natural openings</p> Signup and view all the answers

    Which of the following symptoms are commonly caused by bacterial infections?

    <p>Wilting and defoliation</p> Signup and view all the answers

    What facilitates the movement of bacteria to infect plants?

    <p>Wind or splashing water</p> Signup and view all the answers

    What reproductive process do bacteria undergo for rapid multiplication?

    <p>Binary fission</p> Signup and view all the answers

    How long can some bacteria survive in soil?

    <p>Up to five years</p> Signup and view all the answers

    What happens to plant tissue once bacteria begin to reproduce inside it?

    <p>The tissue degrades and is used as food by bacteria</p> Signup and view all the answers

    Which of the following is NOT a common bacterial disease mentioned?

    <p>Powdery mildew</p> Signup and view all the answers

    What might indicate a serious bacterial infection in plants?

    <p>Water-soaked, grey-brown lesions</p> Signup and view all the answers

    Powdery mildew is known to cause a white powdery appearance on infected plants.

    <p>True</p> Signup and view all the answers

    Cedar-apple rust can complete its life cycle using only one host.

    <p>False</p> Signup and view all the answers

    Spores of the powdery mildew fungus survive winter on healthy plant tissues.

    <p>False</p> Signup and view all the answers

    Armillaria root rot is particularly aggressive towards newly transplanted and older stressed trees.

    <p>True</p> Signup and view all the answers

    Rust pathogens are only found in dry climates.

    <p>False</p> Signup and view all the answers

    Cedar-apple rust produces different spore types during different seasons.

    <p>True</p> Signup and view all the answers

    Infection by the powdery mildew pathogen occurs when rain splashes spores onto new plant growth.

    <p>True</p> Signup and view all the answers

    The unique structure known as galls is produced by cedar-apple rust on apple trees.

    <p>False</p> Signup and view all the answers

    Viruses in plants often lead to immediate death of the host plant.

    <p>False</p> Signup and view all the answers

    Insects can transmit plant viruses multiple times during a growing season.

    <p>True</p> Signup and view all the answers

    Rose rosette virus is transmitted by insects such as thrips.

    <p>False</p> Signup and view all the answers

    Plant viruses can move in and out of plant tissue as easily as fungal and bacterial pathogens.

    <p>False</p> Signup and view all the answers

    Tomato spotted wilt virus can infect a wide variety of plant species.

    <p>True</p> Signup and view all the answers

    The tobacco mosaic virus primarily infects only tobacco plants.

    <p>False</p> Signup and view all the answers

    Symptoms of rose rosette infection can appear immediately after infection.

    <p>False</p> Signup and view all the answers

    Once a plant is infected with TSWV, it does not transmit the virus to insects.

    <p>False</p> Signup and view all the answers

    Infected seeds or pollen can contribute to the spread of plant viruses.

    <p>True</p> Signup and view all the answers

    Infected plants can sometimes exhibit lesions on stems as a symptom of TSWV.

    <p>True</p> Signup and view all the answers

    Chlorosis is a symptom commonly associated with plant viral infections.

    <p>True</p> Signup and view all the answers

    The mites responsible for spreading rose rosette virus can move through wind currents.

    <p>True</p> Signup and view all the answers

    Certain viruses can remain viable in dormant plant tissue for extended periods.

    <p>True</p> Signup and view all the answers

    Once inside an insect's gut, plant viruses can only be carried for short periods.

    <p>False</p> Signup and view all the answers

    Virus-infected plants do not provide a source for vectoring mites after they are infected.

    <p>False</p> Signup and view all the answers

    Thrips acquire the tomato spotted wilt virus during their adult stage.

    <p>False</p> Signup and view all the answers

    Mosaic symptoms on plants are characterized by a uniform green color throughout.

    <p>False</p> Signup and view all the answers

    Mottle symptoms present as an irregular pattern of light and dark areas on plant leaves.

    <p>True</p> Signup and view all the answers

    Mummy refers to soft, wet tissue on fruits caused by pathogens.

    <p>False</p> Signup and view all the answers

    Necrosis is the death of plant tissue and is a symptom associated with multiple pathogen groups.

    <p>True</p> Signup and view all the answers

    Stunting symptoms indicate that a plant is growing larger than normal.

    <p>False</p> Signup and view all the answers

    Vein clearing symptoms manifest as yellowing of the entire leaf surface.

    <p>False</p> Signup and view all the answers

    Watersoaking involves wet, dark, or greasy lesions that are typically sunken.

    <p>True</p> Signup and view all the answers

    Scab lesions are characterized by a smooth surface appearance.

    <p>False</p> Signup and view all the answers

    Witches’ broom symptoms involve an abnormal brush-like shoot development.

    <p>True</p> Signup and view all the answers

    Wilt symptoms are associated with drooping leaves and reduced plant health.

    <p>True</p> Signup and view all the answers

    Exclusion techniques aim to prevent pathogen introductions to areas where they currently exist.

    <p>False</p> Signup and view all the answers

    Fungicides are usually pathogen-specific and are effective in managing only fungal pathogens.

    <p>True</p> Signup and view all the answers

    Resistance refers to selecting plants with increased tolerance to pathogens.

    <p>True</p> Signup and view all the answers

    Avoidance strategies include the practice of using diseased plants for crop rotation.

    <p>False</p> Signup and view all the answers

    Fungicides can reverse disease symptoms once applied to affected plants.

    <p>False</p> Signup and view all the answers

    Reducing plant stresses can be an effective common practice for pathogen avoidance.

    <p>True</p> Signup and view all the answers

    Quarantine is a common practice used in the avoidance strategy to manage plant pathogens.

    <p>True</p> Signup and view all the answers

    Antibiotics are primarily used to manage fungal pathogens in plants.

    <p>False</p> Signup and view all the answers

    Powdery mildew is known to infect numerous landscape and garden ______.

    <p>plants</p> Signup and view all the answers

    Spores of the powdery mildew pathogen survive winter on infected plant ______.

    <p>debris</p> Signup and view all the answers

    Organisms that cause disease are referred to as ______.

    <p>pathogens</p> Signup and view all the answers

    Cedar-apple rust is caused by a group of fungi known as ______.

    <p>rusts</p> Signup and view all the answers

    A plant disease is an abnormality caused by a living ______.

    <p>organism</p> Signup and view all the answers

    The pathogen of cedar-apple rust overwinters as galls on ______.

    <p>juniper</p> Signup and view all the answers

    One of the most notable historical impacts of plant disease was caused by the late blight of ______.

    <p>potato</p> Signup and view all the answers

    The galls produced by the cedar-apple rust release slimy 'horns' comprised of ______ during spring rains.

    <p>spores</p> Signup and view all the answers

    Plant pathogens utilize hosts for nutrients and/or reproduction at the hosts' ______.

    <p>expense</p> Signup and view all the answers

    In late summer, apple lesions produce another spore type that infects ______.

    <p>juniper</p> Signup and view all the answers

    Armillaria root rot is particularly aggressive towards ______ and older stressed trees.

    <p>newly transplanted</p> Signup and view all the answers

    Disease-causing organisms include fungi, oomycetes (water molds), bacteria, viruses, and ______.

    <p>nematodes</p> Signup and view all the answers

    Throughout the season, powdery mildew produces additional ______ causing subsequent infections.

    <p>spores</p> Signup and view all the answers

    On a global scale, plant diseases cause an estimated ______ billion in annual losses.

    <p>38</p> Signup and view all the answers

    Affected plants are referred to as ______.

    <p>hosts</p> Signup and view all the answers

    Saprophytic organisms obtain nutrients from ______ organic material.

    <p>dead</p> Signup and view all the answers

    The American chestnut was nearly wiped out by a fungal disease known as ______.

    <p>chestnut blight</p> Signup and view all the answers

    Chinese chestnuts are tolerant to the ______, while American chestnuts are not.

    <p>blight</p> Signup and view all the answers

    Disease management strategies against chestnut blight include the use of resistant ______.

    <p>varieties</p> Signup and view all the answers

    The first fungicide used in the wine industry was the ______ mixture.

    <p>Bordeaux</p> Signup and view all the answers

    Approximately ______ million acres of chestnut trees died due to chestnut blight.

    <p>30</p> Signup and view all the answers

    Fungi, bacteria, viruses, and ______ are examples of different types of pathogens that affect plants.

    <p>oomycetes</p> Signup and view all the answers

    In urban areas, American chestnut trees once provided high-quality ______ for construction.

    <p>hardwood</p> Signup and view all the answers

    In the late 1800s, chestnut blight was accidentally introduced to the United States through imported ______ trees.

    <p>Chinese chestnut</p> Signup and view all the answers

    Plant disease diagnostics begins with the observation of ______.

    <p>symptoms</p> Signup and view all the answers

    Fungi and bacteria can cause leaf spots that are similar to those caused by ______.

    <p>herbicides</p> Signup and view all the answers

    To confirm diagnoses, identification of signs such as mycelial growth and fruiting structures requires the use of a ______.

    <p>microscope</p> Signup and view all the answers

    Examination of surrounding plants can provide vital information regarding disease ______.

    <p>spread</p> Signup and view all the answers

    Patterns of injury or symptoms can give clues as to whether variety- or species- specific infections are ______.

    <p>possible</p> Signup and view all the answers

    Information regarding soil makeup, disturbances, and soil drainage patterns can assist in differentiating ______ maladies from diseases.

    <p>abiotic</p> Signup and view all the answers

    Diagnosing plant problems may require submitting samples to a ______ laboratory for further analysis.

    <p>commercial</p> Signup and view all the answers

    Several steps to disease diagnostics include examining vital site information and examining ______ tissue.

    <p>diseased</p> Signup and view all the answers

    A single plant species can have numerous cultivars or ______, which can vary in many traits.

    <p>varieties</p> Signup and view all the answers

    Symptoms may differ with plant species or ______, which is vital for diagnosis.

    <p>cultivar</p> Signup and view all the answers

    Critical information like irrigation practices and ______ date can aid in making accurate diagnoses.

    <p>planting</p> Signup and view all the answers

    In some cases, symptoms develop on plant parts that are different from the infected ______.

    <p>tissue</p> Signup and view all the answers

    A root rot pathogen may cause symptoms like dieback and ______, indicating potential troubles with the plant.

    <p>wilting</p> Signup and view all the answers

    It may be necessary to submit symptomatic plant samples to a diagnostic ______ if the cause cannot be determined.

    <p>laboratory</p> Signup and view all the answers

    Determining if a problem is present can depend on assessing normal versus abnormal plant ______.

    <p>appearance</p> Signup and view all the answers

    Collecting additional information can lead to a more complete ______ of plant health issues.

    <p>diagnosis</p> Signup and view all the answers

    Study Notes

    History and Significance

    • American chestnut trees were devastated by chestnut blight, a fungal disease introduced in the late 1800s through Chinese chestnut imports.
    • Approximately 30 million acres of American chestnuts died within 40 years due to their lack of tolerance to the blight.
    • Disease management strategies now include resistant varieties, sanitation, and fungicides.

    Pathogens

    • Fungi reproduce via spores which can be created sexually or asexually; their variation helps in pathogen identification.
    • Fungal reproductive structures can be visible (e.g., mushrooms) or microscopic (e.g., pycnidia, acervuli).
    • Downy mildew and late blight are diseases caused by water molds, which are host-specific.

    Conditions for Disease Development

    • Plant disease is influenced by a susceptible host, a viable pathogen, and a favorable environment, forming the Disease Triangle.
    • Spores germinate on contact with a plant surface under optimal conditions, leading to infection.

    Fungi

    • Fungi require suitable conditions to grow; sporulation can happen multiple times in a season when water is available.
    • Water molds can produce spores prior to dormancy and can survive harsh conditions.

    Water Molds

    • Downy mildew affects various plants; infection results in angular leaf spots and can cause defoliation.
    • Late blight primarily infects potatoes and tomatoes, characterized by water-soaked lesions that lead to defoliation.

    Bacteria

    • Around 200 bacterial types are known to cause plant diseases; they are single-celled and reproduce rapidly through binary fission.
    • Common bacterial diseases include bacterial wilt and fire blight, with symptoms such as leaf spots and wilting.
    • Bacteria spread via water, wind, and insects, often requiring wounds or natural openings to infect plants.

    Plant Parasitic Nematodes

    • Nematodes are microscopic roundworms that primarily infect plant roots, causing stunted growth and reduced yields.
    • Infestation symptoms include chlorosis, root galls, and dieback due to their feeding on plant cell contents.
    • Key examples include soybean cyst nematodes and stubby-root nematodes, which can feed externally or penetrate tissues.

    Plant Diseases Overview

    • Powdery Mildew: A fungal disease affecting many plants; spores survive winter on infected debris. Spring rains facilitate spread to new growth, leading to a white, powdery appearance.
    • Cedar-Apple Rust: A fungi-induced disease requiring multiple hosts; galls on juniper overwinter, producing spores in spring that infect apple trees, creating lesions that later infect junipers.

    Armillaria Root Rot

    • Affects recently transplanted and stressed trees, causing root decay.

    Viruses

    • Extremely small pathogens necessitating powerful magnification for observation. Viruses can persist in host plants for years, avoiding rapid mortality.
    • Common vectors include insects which acquire and transfer virus particles during feeding, enabling multiplication of viruses inside insects.

    Common Viral Diseases

    • Tobacco Mosaic Virus: Named after the first observed symptoms in tobacco, infects over 100 plant species, leading to symptoms like mottling and stunting.
    • Rose Rosette Virus: Carried by rose leaf curl mites, causing witches' broom, leaf reddening, and excessive thorn development.
    • Tomato Spotted Wilt Virus (TSWV): Infects thousands of species, transmitted by thrips. Symptoms include wilting, lesions, and mottling on fruit.

    Symptoms of Plant Pathogens

    • Mosaic and Mottling: Nonuniform coloration often seen with viral infections.
    • Necrosis: Tissue death observed in various pathogens.
    • Stunting: Reduced plant growth affecting size and vigor, ensuing from viral or nematode infections.
    • Wilt and Scorch: Common symptoms related to both fungal and viral infections.

    Plant Disease Diagnostic Techniques

    • Techniques include prevention (exclusion), pathogen management (avoidance), and selection of resistant plant varieties.
    • Exclusion: Prevent pathogen entry through quarantine and inspection, utilizing disease-free plant materials.
    • Avoidance: Use certified plants, inspect before planting, reduce stress, and rotate crops.

    Protection Against Plant Diseases

    • Implement protective measures tailored to specific pathogen threats. Fungicides mainly serve to limit fungal infections but do not cure existing diseases.
    • Resistance: Selecting disease-resistant plant varieties to mitigate the impact of common pathogens.

    Understanding these principles aids in the identification and management of plant diseases, enhancing plant health and productivity.

    Plant Diseases Overview

    • Pathogens causing plant diseases include fungi, water molds (oomycetes), bacteria, viruses, nematodes, phytoplasmas, and parasitic seed plants.
    • Major historical impact example: Late blight of potato led to the Irish potato famine in 1845, resulting in about one million deaths.
    • Losses from plant diseases globally are estimated at $38 billion annually.

    American Chestnut and Chestnut Blight

    • The American chestnut was nearly wiped out by chestnut blight, a fungal disease introduced in the late 1800s through Chinese chestnuts.
    • Approximately 30 million acres of American chestnut trees died within 40 years due to their susceptibility.
    • Management of chestnut blight now includes resistant varieties, sanitation, and fungicide applications.

    Disease Development and Symptoms

    • Symptoms of plant disease arise after a pathogen infects a host and may result from complex interactions between biotic and abiotic factors.
    • Common disease indicators include notable symptoms on specific plant parts, which can mislead diagnostics if not appropriately assessed.
    • Examples of diseases:
      • Powdery mildew: Infects various plants, characterized by white powdery growth.
      • Cedar-apple rust: Requires multiple hosts; overwinters on juniper and affects apple trees in spring.

    Plant Disease Diagnostics

    • Diagnosis begins with observing affected plants and the environment, often necessitating microscopic examination.
    • Recognizing the impact of abiotic factors (e.g., weather, soil conditions) is crucial for accurate diagnosis.
    • Key diagnostic steps:
      • Examine the site for clues about environmental conditions affecting plant health.
      • Ask questions about plant history, caretaking practices, and unusual occurrences (herbicide applications, irrigation practices).
      • Identify the specific plant parts exhibiting symptoms, as issues may not originate from the visibly affected areas.

    Management and Research

    • Disease management strategies evolved significantly since the introduction of the Bordeaux mixture fungicide to tackle issues in agricultural systems.
    • Continuous research is being conducted for better management options against persistent diseases, like chestnut blight.

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    Description

    Explore the complex world of plant diseases with insightful contributions from experts. This chapter discusses the challenges posed by pathogens, strategies for managing them, and the historical impact on species such as the American chestnut. Learn about resistant varieties and effective sanitation methods.

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