Podcast
Questions and Answers
Infectious ailments are caused by living pathogenic ______.
Infectious ailments are caused by living pathogenic ______.
organisms
Microbial control utilizes microorganisms or their by-products to manage insect ______.
Microbial control utilizes microorganisms or their by-products to manage insect ______.
pest
Inclusion viruses are obligate, intracellular, pathogenic ______.
Inclusion viruses are obligate, intracellular, pathogenic ______.
organisms
Nuclear polyhedrosis viruses (NPV) are encased in a protein crystal called ______.
Nuclear polyhedrosis viruses (NPV) are encased in a protein crystal called ______.
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Symptoms of NPV infection include darkened larval skin with yellow ______.
Symptoms of NPV infection include darkened larval skin with yellow ______.
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Bacteria that are non spore-forming can be potential ______.
Bacteria that are non spore-forming can be potential ______.
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The fat body of lepidopterous larvae is the primary site of infection for the ______ virus.
The fat body of lepidopterous larvae is the primary site of infection for the ______ virus.
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NPV infection causes the infected larva to climb to the highest point and ______.
NPV infection causes the infected larva to climb to the highest point and ______.
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Bacillus thuringiensis is pathogenic to many lepidopterous larvae and immatures of some ______.
Bacillus thuringiensis is pathogenic to many lepidopterous larvae and immatures of some ______.
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When the bacteria sporulates, it forms a toxic ______.
When the bacteria sporulates, it forms a toxic ______.
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The life cycle of Bt includes an endospore in the environment that is ingested by a susceptible ______.
The life cycle of Bt includes an endospore in the environment that is ingested by a susceptible ______.
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Type I reaction to Bt toxins results in general paralysis and death within ______ hours after ingestion.
Type I reaction to Bt toxins results in general paralysis and death within ______ hours after ingestion.
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The cessation of feeding is the first symptom observed after ingestion of ______.
The cessation of feeding is the first symptom observed after ingestion of ______.
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Some fungi cause insect disease and are transmitted from one host to another by a ______.
Some fungi cause insect disease and are transmitted from one host to another by a ______.
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The beta exotoxin produced by Bacillus thuringiensis is known as ______.
The beta exotoxin produced by Bacillus thuringiensis is known as ______.
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Infected insects may show characteristics such as weakness, disorientation, and changes in ______.
Infected insects may show characteristics such as weakness, disorientation, and changes in ______.
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Flashcards
Entomopathogenic Microorganisms
Entomopathogenic Microorganisms
Microorganisms that cause diseases in insects.
Infectious Diseases
Infectious Diseases
Diseases caused by living organisms (e.g., viruses, bacteria).
Nuclear Polyhedrosis Viruses (NPV)
Nuclear Polyhedrosis Viruses (NPV)
Insect viruses that form crystalline structures (polyhedra).
NPV Symptoms
NPV Symptoms
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Granulosis Virus (GV)
Granulosis Virus (GV)
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Cytoplasmic Polyhedrosis Virus (CPV)
Cytoplasmic Polyhedrosis Virus (CPV)
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Non-spore-forming bacteria
Non-spore-forming bacteria
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Microbial Control
Microbial Control
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Spore-forming bacteria
Spore-forming bacteria
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Bacillus thuringiensis (Bt)
Bacillus thuringiensis (Bt)
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Parasporal body
Parasporal body
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Insect damage caused by Bt
Insect damage caused by Bt
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Bt toxin activation
Bt toxin activation
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Fungal infection in insects
Fungal infection in insects
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Symptoms of fungal infection
Symptoms of fungal infection
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Insect susceptibility
Insect susceptibility
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Study Notes
Entomopathogenic Microbials
- Lecture 3-3 covers beneficial microorganisms used to control insect pests
- Microorganisms can be classified as infectious or non-infectious
- Infectious ailments result from living pathogenic organisms, like viruses, bacteria, protozoa, fungi, rickettsia, and nematodes
- Non-infectious ailments, such as those from mechanical injury, chemical agents, or nutritional deficits, are not caused by microorganisms
- Microbial control involves using microorganisms or their by-products to control insect pests
Infectious Pathogens
- Inclusion viruses are submicroscopic, obligate intracellular pathogens
- Nuclear polyhedrosis viruses (NPV) are rod-shaped and encased in an outer envelope, sometimes enclosing multiple virus rods
- Viruses are occluded (encased) in protein crystals called polyhedra
- NPVs are usually transmitted via oral ingestion of polyhedra
Virus Structure
- A typical enveloped virus has a phospholipid envelope, a protein capsid, nucleic acid (genome), and spike projections
- Baculoviruses have a multi-capsid nucleopolyhedrovirus structure with occlusion bodies (enclosed viral particles)
NPV Infection of Insect Hosts
- NPV infection begins with ingestion of polyhedra
- Polyhedra with embedded virions enter the insect's foregut
- NPVs release virions, which break down the peritrophic membrane in the midgut
- Virions multiply in the insect's hemocoel, leading to septicemia
- TIssues are destroyed, and endospores are produced before the insect dies
- Endospores are released when the cadavers disintegrate
NPV Symptoms
- Larval skin darkens, develops yellow patches or appears oily
- Skin becomes fragile, hemolymph becomes turbid
- Infected larvae often climb to the highest point and die
- Integument frequently ruptures after death, releasing polyhedra
- Other viral diseases include granulosis virus (GV) that infects the fat body of lepidopterous larvae, and cytoplasmic polyhedrosis virus (CPV) that infects the midgut epithelium of lepidopterous larvae
Bacteria
- Non-spore-forming bacteria: These bacteria are common in the digestive tracts of insects. Stress, other pathogens, parasites, or poor nutrition can cause them to enter the hemocoel.
- Spore-forming bacteria: Bacillus popillae causes milky disease in white grubs, while Bacillus thuringiensis is very pathogenic to many lepidopterous (butterfly/moth) larvae.
Bacillus thuringiensis (Bt)
- Pathogenic to many lepidopterous and some coleopteran larvae
- Transmitted orally
- When the bacteria sporulates, it forms a toxic crystal (parasporal body)
- Different lepidopteran species respond differently to various crystal and spore combinations
Toxic Products of Bt
- Bt produces alpha exotoxin, phospholipase C, beta exotoxin (thuringiensin), and delta endotoxin
- These toxins are derived from protoxins (crystal proteins)
- Proteolytic enzymes degrade protoxins into smaller toxic peptides
Types of Reactions to Bt Toxins
- Type I: insects exhibit general paralysis and die within 1-7 hours after ingestion
- Type II: insects do not develop general paralysis and die within 2-4 days after ingestion
- Type III: insects are susceptible to a combination of crystals and spores
- Type IV: some lepidopterous larvae are not susceptible to Bt toxins
Life Cycle and Action of Bt
- Bt endospores in the environment are ingested by susceptible insects
- Parasporal crystals activated by alkaline gut fluids and cause leakage into the hemocoel
- Cessation of feeding is the first symptom after ingestion
- Crystal activity depends on pH in the larval foregut and midgut
- Bt multiplies in the insect hemocoel, causing septicemia
- Endospores are produced prior to the insect's death
- Endospores are released upon cadaver disintegration
Fungi
- More than 36 fungi genera cause insect diseases
- Fungi identification can be challenging
- Most fungi transmit from one host to another via spores (often conidia)
Fungi Structure
- Sporangium houses spores
- Sporangiophore is a specialized fungal hypha that may function as a stalk
- Hyphae (long filamentous structures) form a network called mycelium
- Rhizoids anchor fungi to substrates and absorb nutrients
- Conidiophores produce conidia (spores)
- Conidia germinate into new hyphae
Fungi Infection
- Fungi invade insects by contacting the cuticle
- Conidia germinate and form appressoria
- Hyphae penetrate the cuticle
- Mycelium invades the insect
- Insect death occurs following complete invasion
Infected Insect Characteristics
- Infected insects stop feeding, exhibit weaknesses, and disorientation
- Insects may change color, showing dark spots where fungal penetration occurred
- Presence of fungal hyphae (mycelia) is observed in affected areas
How Fungi Kill Hosts
- Asphyxiation or starvation due to fungal blockage or toxins, especially common with Zygomycotina, are a mechanism
- Toxins released by the fungus disrupt insect functions
- Uptake of host nutrients and water desiccation or mummification result
Classes of Fungi
- Ascomycetes (Perfect Fungi): Basidiospores and conidiospores are asexual
- Basidiomycetes (Perfect Fungi): Typicallyseptate hyphae
- Zygomycetes (Perfect Fungi): Zygospores and conidiospores, usually coenocytic hyphae
- Deuteromycetes (Imperfect Fungi): Conidia, septate hyphae
Examples of Entomopathogenic Fungi
- Zygomycotina, Order Entomophthorales: Batkoa, Entomophthora, Entomophaga, Erynia, Neozygites, Zoophthora
- Deuteromycotina, Order Moniliales: Beauveria bassiana (white muscardine), Metarhizium anisopliae (green muscardine), Lecanicillium (Verticillium) lecanii (aphid/scale insect pathogen)
Ascomycota, Class: Sordariomycetes : Order: Hypocreales: Cordyceps
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Description
This quiz covers Lecture 3-3 on entomopathogenic microbials, focusing on beneficial microorganisms for insect pest control. It distinguishes between infectious and non-infectious ailments and explores the role of infectious pathogens, particularly viruses. Test your understanding of microbial control mechanisms and virus structures.
