Concepts of Plant Diseases, Diagnosis and Classification
Concepts of Plant Diseases, Diagnosis and Classification
Concepts of Plant Diseases, Diagnosis and Classification
Lower Yield
or
No Yield!
Symptoms of Plant Disease
• Refer to the expressions by the suscept or host of
pathologic condition by which a particular plant disease
may be distinguished from other diseases.
1. Primary symptoms-the immediate and direct results of
the causal agent’s activities on the invaded tissues.
2. Secondary symptoms- are the effects on the distant
and uninvaded plant parts.
3. Localized symptoms- distinct and very limited
structural changes usually in the form of lesions
(canker, leaf spot, gall) xylem, phloem
4. Systemic symptoms- more generalized pathological
conditions such as mottling, mosaic and wilting.
Symptoms of Plant Disease
5. Histological Symptoms-internal and seen only
upon the dissection of the diseased plant portion
and examination under the microscope.
• expressed as an abnormality in cell content,
structure or arrangement.
3. Hypoplastic symptoms
• inhibition or failure in the differentiation or
development of some aspect of growth.
Examples: stunting, chlorosis, mottle, mosaic, curling, and rosetting.
4. Hyperplastic symptoms
• excessive multiplication, enlargement, or overdevelopment
of plant organs including the abnormal prolonged retention
of green color.
Examples: gall formation, fasciation, scab, premature defoliation or
fruit drop and greening.
General Classification of Symptoms
4. Hyperplastic symptoms
Fruit spot
Fruit rot
Canker
Leaf spot
Wilt
Vascular wilt
Crown gall
Root rot
Disease Symptoms
Chlorosis
Leafspots
Curling
Scab
Shothole
Disease Symptoms
Etiolation Fasciation/
Die-back Fasciculation
Gumming/
Flecks Gummosis Leak
Mottling Mummification Pitting
Rosetting
Phyllody Veinclearing
Abscission Blotch
Bleeding
• SIGNS OF PLANT DISEASES
▪ Examples:
▪ fungal mycelia, spores and fruiting bodies,
bacterial ooze, nematodes and plant parts of
phanerogams (parasitic flowering plants).
Phanerogams
Bacterial ooze
Spores/Fruiting
bodies
Nematode
PLANT DISEASE DIAGNOSIS
Actual proof of
pathogenecity
require the
application of
Koch’s rules of
proof.
Robert Koch
KOCH’S POSTULATES states that:
Ralstonia solanacearum
KOCH’S POSTULATES states that:
2. according to symptom
• Leaf spots, rusts, smuts, anthracnoses, mosaics, wilts,
fruit rots
Classification of Plant Diseases
3. according to type of affected plant
▪ Vegetable diseases, diseases of field crops, diseases of
ornamentals