PPRT 172 Lec 3-3 Virus to Fungi PDF

Lec 3-3: Entomopathogenic microbials PPRT172 Justine Bennette Millado Maria Juliet Ceniza Ruben Gapasin Beneficial Microorganisms Disease classification: Infectious: ailments resulting from the actions of living pathogenic organisms: include viruses, bacte...

Lec 3-3: Entomopathogenic microbials PPRT172 Justine Bennette Millado Maria Juliet Ceniza Ruben Gapasin Beneficial Microorganisms Disease classification: Infectious: ailments resulting from the actions of living pathogenic organisms: include viruses, bacteria, protozoa, fungi, rickettsia, and nematodes Non-infectious: ailments not caused by actions of micro-organisms, such as mechanical injury, chemical agents, nutritional deficiencies etc What is microbial control? Control which includes all aspects of the utilization of microorganisms or their by-products in the control of insect pest species Infectious Pathogens Inclusion Viruses: submicroscopic, obligate, intracellular, pathogenic organisms 1. Nuclear polyhedrosis viruses (NPV) rod-shaped viruses and are encased in an outer envelope which may enclose one or several virus rods Viruses are enclosed in the envelope are occluded (encased) in protein crystals called polyhedra Normally transmitted by oral ingestion of polyhedra  Beneficial Microorganisms VIRUS structure https://schaechter.asmblog.org/ 1. Nuclear polyhedrosis viruses (NPV): Symptoms Larval skin darkens and have yellow patches or appear oily Skin becomes fragile, Hemolymph becomes turbid Prior to death, infected larva usually climbs to highest point available and dies After death, integument frequently ruptures, releasing millions of polyhedra Other virus diseases Granulosis virus (GV) Fat body of lepidopterous larvae is the primary site of infection Cytoplasmic polyhedrosis virus (CPV) Infect the cytoplasm of the midgut epithelium of lepidopterous larvae https://live.staticflickr.com NPV Infection  Bacteria A. non spore-forming bacteria Potential pathogens Lives in digestive tract of most insects Gain entrance to hemocoel due to stress: temperature extremes, other pathogens, parasites, poor food  B. Spore-forming Most important bacterial pathogens Bacillus popillae – causes milky disease in white grubs of scarab beetles B. thuringiensis- very pathogenic to many lepidopterous larvae https://ars.els-cdn.com/ Structural difference between viruses and bacteria Bacillus thuringiensis (Bt) Pathogenic to many lepidopterous larvae and immatures of some coleopterans Transmitted orally When the bacteria sporulates, it forms a toxic crystal (parasporal body) Different lepidoptera exhibit different responses to the various combinations of crystal and Bt spores  Toxic products of B. thuringiensis Apha exotoxin and phospholipase C Beta exotoxin - thuringiensin Delta endotoxin Produced from protoxins (crystal proteins) Degraded by proteolytic enzymes to form smaller toxic peptides Types of reactions to toxins of Bt Type I: develop a general paralysis and die 1 to 7 hrs after ingestion Type II: do not develop a general paralysis and die 2-4 days after ingestion Type III: susceptible to a combination of crystals and spores; and Type IV: some lepidopterous larvae not susceptible  Life cycle and Action of Bt 1. Endospore in the environment – ingested by susceptible host 2. Parasporal crystal activated by alkaline gut & cause leakage to hemocoel After ingestion of spores, first symptom is cessation of feeding (pH 9-10.5) and the action of proteolytic enzymes within the gut Activity of crystal is dependent on pH of larval foregut and midgut  3. Multiply in hemocoel causing septicimia 4. Destroy tissues & prior to death endospores are produced 5. Endospores released when cadavers disintegrate crystal is a protoxin activated by enzymatic hydrolysis DiPEL/Bt-based insecticides FUNGI More than 36 different genera of fungi contain species which cause insect disease Identification of fungus is difficult Most fungi are transmitted from one host to another by a spore, usually a conidium How do fungi cause infection? https://media.springer nature.com/  Characteristics of infected insects Cessation of feeding, weakness and disorientation Change color, and the cuticle may show dark spots - areas of fungal penetration. Presence of mycelia in or on the affected area. How fungi kill the host Asphyxiation or starvation (e. g. Zygomycotina) Toxins released by the fungus Uptake of host’s nutrients and water results in desiccation (mummification) of the insect Classes of Fungi Ascomycota, Class: Sordariomycetes : Order: Hypocreales: Cordyceps Examples of Entomopathogenic Fungi Zygomycotina: Order Entomophthorales Batkoa Entomophthora Entomophaga Erynia Neozygites Zoophthora Zygomycotina: Order Entomophthorales : Entomopthora Deuteromycotina: Order Moniliales Beauveria bassiana – white muscardine, produce natural toxins called beauvericin Metarhizium anisopliae – green muscardine; produces the toxin destruxins Lecanicillium (Verticillium) lecanii – infects mostly aphids and scale insects