33 DiseasesA disease is a plant disorder caused by an infectious pathogen or agent
34 Diseases There are 3 conditions necessary for diseases in plants host plantdisease causing organism or pathogen must be presentfavorable environment for disease organism to develop
35 Pathogens There are four groups of pathogens bacteria fungi viruses parasitic plants (attach to plants)mistletoedodderlichens
36 Bacteria Single celled microorganisms Examples of common bacteria diseases:Leaf spotRings of different shades of brown, green or yellow spots on leaves.Blightcause plant to quickly turn brown or black as if they had been burned
39 Fungi Cannot make their own food Examples of common fungi diseases: They develop hyphae, structures that grow and absorb nutrients from the host plantMany fungi are spread by spores.Examples of common fungi diseases:Damping off causes young plants and seedling to rot off at the soil level.Rust cause small spots on the leaves that resemble yellow, orange, brown or red rust mainly on the underside of leaves.Powdery mildew grows on the upper and lower leaf surface as white or gray powdery substance. It is a common disease of houseplantsGalls are round swellings or growths usually on tree branches or leaves.
40 Damping offA fungal disease that causes young plants and seedlings to rot off at soil level
46 Viruses Viruses are pathogens with an extremely narrow host range Examples of common viruses:Tobacco mosaic virus which attacks tomatoes, peppers, poinsettias and tobacco.Can be transfer from human hands of a smokerBe sure to wash your hands before working with plants to control the spread of this virusCause leave to have irregular mottled areas with patterns ranging from dark to light green and yellow to white
47 MosaicCaused by viruses that make the leaves have irregular mottled areas with patterns ranging from dark green to light green to yellow to white