diseases interior plants. disease definition disease- abnormality in structure or function caused...
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Disease Definition
Disease- abnormality in structure or function caused by an infectious agent that injures or destroys
Often the most limiting factorConsider during plant selection
Two Disease Classifications
Infectious- damage which is caused by a pathogen or living organism
Noninfectious –physiological injury that destroys the plant’s value and are called disorders.
Terminology
Pathogen -organism causing disease: fungi bacteria viruses nematodes & mycoplasms- (not much of
a concern in the interior environment)Host - Organism the parasite lives on
Part of Nature
Normal part of natureCultivation increases diseases
cultural practices have changed uniform genetic background grown in pure stands
Suitable environment is usually wet, humid, and warm to hot
Disease Triangle
There are 3 conditions necessary for disease to occur a susceptible host a virulent pathogen a favorable environment
These make up the disease triangle. If any one is missing, disease can not occur
Disease ComplexesDisease complex- multiple pathogens
occur when plant roots are damaged before stress
Successions occur Initial colonizers of the roots Successions of fungi Invasion of diverse saprophytes Tissue then supports other organisms
Disease Process
4 steps to the disease process: infection- organism enters the plant incubation- Pathogen inhabits the host
and without producing symptoms symptom development- interaction inoculum production- pathogen
produces propagules
Disease Control Agents
Prevent pathogen establishment Plant resistanceAlter the environment SanitationPesticides
Fungi
Most common Lacks chlorophyll; microscopic Germ spores, germ tube on plant surface,
penetration Fungus grows filaments called hyphae
(coll. the mycelium) Control with fungicides and watering
Bacteria
Tiny organisms that contain cytoplasm enclosed in a cell wall; no nuclei.
They do not require a living host for replication and growth.
Most are saprophytes; some are infectious Pathogenic species are usually bacillus
(rods), the others are spirilla or cocci Control by planting resistant species
Viruses
Nucleic acid with a protein coat.Visible with an electron microscopeParasitic an multiply in living cellsPrimarily transmitted by feeding
activities or vectors Control by controlling the vector
Fungal Rots
Root Rots - brown, mushy roots due to too much water.Wilt, yellowingAbscission of leaves from the
base up Death of the roots results
Rhizoctonia
Known as: damping-off, wire stem, head rot, crown rot
Attacks: Aglaonema, Begonia, Cissus, Chamaedorea, Hedera, Hoya, Peperomia, Philodendron
Reddish-brown myceliumHyphal branches at right angles
Pythium
Water mold favored by wet conditions Known as root rot, damping-off
Wilt; progressive yellowing from the base up; exterior of root sloughs off and leaves the core giving a thread-like appearance to the roots; dark color
Aglaonema, Aloe, Chamaedorea, Dieffenbachia, Pothos, Philodendron
Damping OffPythium – Root and stem rot
Unsterile soils, more water, poor air circulation
Spread by infested soil Brown roots and blackened stem Use dust protectants, improve
drainage
Phytophthora
Phytophthora is closely related to Pythium and produces leaf spot Late blight, foliage blight, fruit rot,
crown rot, root rot Leaf damage, collapse of the plant Aglaonema, Dieffenbachia, Hedra,
Kalanchoe Peperomia, Saint Paulia
Sclerotium
Sclerotium - White fungus on the substrate surface and the plant; sclerotia (spore-like resting bodies) the size of mustard seeds Brassaia, Chamaedoria,
Dieffenbachia, Dracaena, Pothos, Peperomia.
Powdery Mildew
Ersiphaceae - Powdery Mildew Change in temperature, cold and damp White powder on the leaves; younger
leaves curl; dwarfed and deformed foliage and flowers
Use fungicides
Botrytis on Geranium
Botrytis – leaf spotleaf spot Moist atmosphere poor
cultural practice Prevention;
reduce humidity; resistance; avoid injury
Fusarium Wilt
Causes root rot Lower leaves turn yellow and
sometimes wilt; entire plant becomes chlorotic; roots blacken and mushy
Prevention is the best defense; aeration, pasteurization
Agalaonema, Asapragus, Dracaena, Spathiphyllum
Verticillium Wilt
Soil borne; enters through roots & attacks the vascular system One of the most distructive fungi Yellow leaves which die from the
base to the top; whole plant stunted; no flowers
Culture-indexed cuttings
Ascochyta Ray Blight
Fungus attacks flowers and buds Spores transported by splashing
water or air currents Completely rots the whole flower Sanitation; remove contaminated
materials
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