PLANT DISEASE DIAGNOSIS Flashcards
Identification of diseases based on symptoms and signs
Plant Disease Diagnosis
Manifestation or expression of a plant as a result of disease
Symptom
A pathogen or parts of a pathogen found on the host plant
Sign
Expressed as physiological or structural changes in a limited area of the tissues of the host
Local symptoms
Examples of Local symptoms
galls, spots, cankers
Examples of Systemic symptoms
dwarfing, wilting, yellowing, mosaic
Primary symptoms
Direct result of pathogen activity on the invaded tissues
Secondary symptoms
Physiological effects on distant and uninvaded organs
Macroscopic symptoms
Expressions of the disease in the plant or in its parts that can be studied with the unaided eye
Microscopic symptoms
Expressions of disease in cell structure or arrangement that can be studied only under the microscope
Hyperplasia
Plant overgrowth due to increased cell division
Hypertrophy
Plant overgrowth due to abnormal cell enlargement
Rosette
short, bunchy habit of plant growth
Stem-pitting
Characterized by depressions on the stem of the plant
Bunchy
leaves progressively becomes dwarfed, upright and bunched at the top of the plant
Stunt
reduction in size and vigour
Yellowing / Chlorosis
discoloration of normally green tissue due to chlorophyll destruction or failure of chlorophyll formation
Witches’ broom
broomlike growth or massed proliferation caused by the dense clustering of branches of woody plants
Enation
tissue malformation or overgrowth induced by certain virus infections
Scab
roughened, crust-like diseased area on the surface of a plant organ; a disease in which such areas form
Tumor
uncontrolled overgrowth of tissue or tissues
Gall
swelling or overgrowth produced on a plant as a result of infection by certain pathogens
Smut
characterized by masses of dark, powdery and sometimes odorous spores
Wilt
loss of rigidity and drooping of plant parts generally caused by insufficient water in the plant
Damping-off
destruction of seedlings near the soil line, resulting in the seedlings failing over on the ground
Dieback
progressive death of shoots, branches, and roots generally starting at the tip
Anthracnose
black and sunken leaf, stem or fruit lesions caused by a fungus
Blight
general and rapid killing of leaves, flowers, and stems
Shot-hole
small, diseased fragments of leaves fall off and leave holes in their space
Blotch
large, and irregular in shape, spots, or blots on leaves, flowers and stems
Canker
necrotic, often sunken lesion on a leaf, fruit stem, branch, or twig of a plant
Spot
self-limiting lesion on leaves or other parts of the plant
Mummification
drying and shrivelling of fruit
Rot
softening, discoloration and often disintegration of succulent plant tissue as a result of fungal or bacterial infection
Soft rot
rot of fleshy fruit, vegetable or ornamental in which the tissue becomes macerated by tbe enzymes of the pathogen
Ringspot
circular area of chlorosis with a green center; a symptom of many virus diseases
Mottle
irregular pattern of indistinct light and dark areas
Mosaic
intermingled patches of normal and light green or yellowish color
Signs of Fungi
spores, pustules, sclerotial bodies, mycelia, mildew (powdery / downy)
Mildew
mycelium and spores of the fungus are seen as whitish growth on the surface of leaves, stems, and fruits
Powdery mildew
Whitish growth on the upper side of the leaf surface
Downy mildew
Whitish growth on the underside of the leaf surface
Signs of Bacteria
bacterial ooze
Signs of Nematodes
egg mass, cysts/pearls (cyst nematodes), juvenile and adult nematodes
