© 2009 Delmar, Cengage Learning Chapter 20 Greenhouse Diseases

© 2009 Delmar, Cengage Learning Causes Causal organisms –bacteria –fungi –viruses –phytoplasmas abiotic or noninfectious conditions

© 2009 Delmar, Cengage Learning Integrated Pest Management (IPM) Prevent problems Regular monitoring of crops and growing area Accurate diagnoses Appropriate action thresholds Effective management methods

© 2009 Delmar, Cengage Learning Disease Triangle Susceptible host Pathogenic causal organism Environment

© 2009 Delmar, Cengage Learning Beneficial Microorganisms Control pests Build soil structure Decompose organic material Eliminate toxins

© 2009 Delmar, Cengage Learning Koch’s Postulates Microorganism must be found in the organism when the disease occurs Microorganism must be isolated from the diseased organism and grown in pure culture

© 2009 Delmar, Cengage Learning Koch’s Postulates Cultured microorganism must cause disease when inoculated into a healthy organism Microorganism must be re-isolated from the inoculated, diseased experimental organism and identified as being identical to the original specific causative agent

© 2009 Delmar, Cengage Learning Fungi Characteristics –chitinous cell wall –hyphae: mycelium –reproduce by spores –heterotrophic (lack photosynthesis)

© 2009 Delmar, Cengage Learning Fungi Characteristics –categories obligate saprophytes obligate parasites facultative saprophytes facultative parasites

© 2009 Delmar, Cengage Learning Fungal Diseases Botrytis blight (gray mold) –symptoms –management

© 2009 Delmar, Cengage Learning Fungal Diseases Downy mildew –symptoms –management

© 2009 Delmar, Cengage Learning Fungal Diseases Powdery mildew –symptoms –management

© 2009 Delmar, Cengage Learning Fungal Diseases Soil-borne –species Pythium Phytophthora Rhizoctonia Thielaviopsis –symptoms –management

© 2009 Delmar, Cengage Learning Bacteria Characteristics –single-celled microorganisms –do not contain a nucleus –found in every habitat on earth

© 2009 Delmar, Cengage Learning Bacteria Management Diseases

© 2009 Delmar, Cengage Learning Viruses Characteristics –noncellular organisms –nucleic acids (RNA or DNA) surrounded by protein –reproduce in the host cell –transmitted directly through sap

© 2009 Delmar, Cengage Learning Viruses Symptoms Identification (ELISA) Management

© 2009 Delmar, Cengage Learning Phytoplasmas Characteristics –specialized bacteria (obligate plant parasites) Aster yellows –vectored by leafhoppers –management Excessive branching