BASIC PLANT PATHOLOGY Dr. Monica ElliottFt. Lauderdale REC
WHAT IS A HEALTHY PLANT? You can’t diagnose a plant problem without knowing how the plant looks when healthy!
PLANTS DON’T TALK! Information about a plant sample must come from person managing the plant ! Ask the right questions!
Abiotic vs. Biotic
Sooty mold is a fungus, but not a pathogen. It is feeding off insect excretions, such as honeydew.
Abiotic • Injuries • Disorders • Pathogen is not causing problem • Biotic • Pathogen is the problem
INJURY A destructive physical occurrence to the plant
INJURY NOpathogen! • Lightning strikes, Tire tracks • Car or lawn equipment exhaust • Animals - moles, armadillos, urine
DISORDER Interaction between the plant & its environment that is usually associated with imbalances of physical or chemical require- ments for plant growth.
DISORDERS NO pathogen! • Cold or heat stress • Nutritional, usually deficiencies • Air pollution • Excessive rainfall or drought • Pesticide phytotoxicity
Drought Oedema Both too much and too little water can cause disease-like symptoms.
SPOTS & PATCHES • A plant with a spot does not • automatically mean it has a • disease. • A yellow or dead patch in • the lawn does not mean there • is a disease.
DISEASE Interaction between the plant and a pathogen that disrupts the normal growth and appearance of the plant.
DISEASE Three Components: • Susceptible host • Virulent pathogen • Conducive environment Disease Triangle
Types of Pathogens • Fungi • Bacteria • Phytoplasmas(mlo) • Viruses • Viroids large small
Most bacteria can be cultured on artificial media. Phytoplasmas, viruses and viroids cannot be cultured on media.
PATHOLOGY TERMS • MYCELIA: thread-like material • that is body of fungus. • SPORES: reproductive structures • of a fungus or bacterium
Bacteria – most enter through natural • openings or wounds • Viruses – transmitted through wounds • made mechanically or by vectors • Phytoplasmas – transmitted by vectors • Fungi – enter through natural • openings, wounds; or by mechanical • pressure or enzymes they produce
FUNGUS - FUNGI • No chlorophyll, so no self energy • PATHOGEN: obtains energy • from living things • SAPROPHYTE: obtains energy • from dead things • SAME fungus can be BOTH a • pathogen and a saprophyte!
PATHOLOGY TERMS • SYMPTOMS: how plant expresses • the fact it has a disease • leaf spots, patches, tip die back, etc. • SIGNS: actual pathogen parts • associated with a diseased plant • spores, mycelia, conks, mushrooms
Plant Organs And Functions Disease Symptoms
Symptoms • spot – small, distinct lesion on leaf, fruit . . . • blight – spots that have coalesced or merged • together; more tissue being affected • rot – tissue is breaking down (fruit, roots); • usually mushy, but can be dry • wilt – plant droops due to water stress; can • be systemic (xylem) or due to root rot
Symptoms • gall – masses of undifferentiated growth; usually on stems or woody tissue • (branches) but can be on roots • - wart, clubroot, witches’-broom • canker – sunken lesions; usually on stems or • woody tissue • patches, decline – terms often used in • association with grasses (turf, grain crops)
Symptoms Caused by Bacteria • leaf spots and blights – water soaked, • greasy • soft rots of fruits • wilts (systemic – xylem) • gall (overgrowths/cell proliferation) • cankers
Symptoms Caused by Viruses • dwarfing or stunting to some degree • mosaics – light green, yellow or white • areas intermingled with green – leaves • or fruits • ring spots – chlorotic or necrotic rings – • leaves, fruits or stems • are always systemic infections