8.0 Pest Management 8.02 Discuss diseases and viruses

 Definition:  Disease is a plant disorder caused by an infectious pathogen or agent

 Host plant  The plant the disease attacks  Disease causing organism or pathogen must be present  Favorable environment for disease organism to develop  Moist and warm

 Bacteria  Fungi  Viruses

 Bacteria are single celled microorganisms  Examples of common bacteria diseases:  Bacterial leaf spot are rings of different shades of brown, green or yellow spots on leaves  Bacterial blight cause plants to quickly turn brown or black as if they had been burned

 Fungi cannot make their own food  They develop hyphae, structures that grow and absorb nutrients from the host plant  Many fungi are spread by spores

 Examples of common fungi diseases:  Damping off  Rust  Powdery Mildew  Galls

 Causes young plants and seedlings to rot off at the soil level

 Causes small spots on the leaves that resemble yellow, brown, orange or red rust mainly on the underside of leaves

 Grows on the upper and lower leaf surface as white or gray powdery substance  A common disease of houseplants

 Round swellings or growths usually on tree branches or leaves

 Examples caused by bacteria or fungi are  Powdery mildew  Blights  Canker  Rots  Wilts  Smut

 Viruses are pathogens with an extremely narrow host range and are usually a threat to crops  Examples caused by viruses, bacteria, or fungi are wilts and blights

 Attacks tomatoes, pepper, poinsettias, and tobacco  Can be transferred from human hands of a smoker  Be sure to wash your hands before working with plants to control the spread of this virus  Cause leaves to have irregular mottled areas with patterns ranging from dark to light green and yellow to white

 Parasitic Plants attach to host plants  Mistletoe  Dodder  Lichens  Plant diseases must be identified before they can be treated

 Warm temperatures and moist conditions in greenhouse plant production make most plant diseases worse because of environmental conditions that support disease causing pathogens  Preventing plant diseases is better than treating the diseases.