classification of plant disease

1. Prepared by
R MOHANAPRIYA
Assisstant Professor (Plant Pathology)
JSA College of Agriculture and Technology,
Ma. Podaiyur, Cuddalore district, Tamilnadu
Classification of Plant Diseases

2. Classification of Plant Diseases
1. Based on type of infection
a. Localized diseases
Leaf spots
b. Systemic diseases
Downy mildew & viral diseases

3. 2. Based on type of perpetuation and spread
a. Air borne disease
Paddy blast, Tikka leaf spot of groundnut.
b. Seed borne disease
int. – loose smut of wheat
ext. -
c. Soil borne disease
Damping off & root rot
d. Vector borne disease
Rice tungro virus, rice grassy stunt virus, etc.,

4. 3. Based on occurrence and geographic distribution
a. Endemic diseases
Wart disease of potato
b. Epidemic or epiphytotic diseases
Wheat stem rust & Late blight of potato
c. Sporadic disease
Wheat loose smut
d. Pandemic diseases
Late blight of potato & Wheat stem rust

5. 4. Based on multiplication of inoculums
a. Simple interest disease
Pythium sp., & Rhizoctonia sp.
b. Compound interest disease
Wheat stem rust, rice blast, powdery mildew diseases.

6. 5. Based on type of causal agents
a. Biotic agents
Fungi, bacteria, virus, phytoplasma, spiroplasma etc.,
b. Abiotic agents
Physiological disorders

7. 6. Based on host plant infected
– Diseases of cereals
– Diseases of millets
– Diseases of pulses
– Diseases of oilseeds
– Diseases of fruit crops
– Diseases of ornamentals
– Diseases of forage crops
– Diseases of fiber crops
– Diseases of vegetables
– Diseases of medicinal and aromatic plants disease

8. 7. Based on parts of the plants affected
– Root diseases
– Foliar diseases
– Fruit diseases
– Seed diseases
– Stem diseases

9. 8. Based on kinds of symptoms produced on host plants
– Leaf spot
– Leaf blight
– Anthracnose
– Wilt
– Rust
– Smut
– Bunt
– Powdery mildew
– Downy mildew
– Damping off
– Soft rot etc.,

10. PLANT DISEASE EPIDEMIOLOGY
Endemic or Enphytotic
A disease is more or less constantly occurring year after year in a
moderate to severe form in a country or locality
eg: wart disease of potato (Synchytrium endobioticum) is endemic in
Darjeeling.
Epidemic or Epiphytotic
A sudden outbreak of a disease periodically over a widespread area in a
devastatingly severe form causing severe losses or complete destruction.
eg: wheat stem rust (Puccinia graminis tritici),
powdery mildew (Erysiphe graminis vor tritici),
late blight of potato (phytophthora infestans).

11. Pandemic
When an epidemic disease spreads over continents or subcontinents and
involves mass mortality it is considered as pandemic. The outbreak of
black stem rust of wheat in India during 1947 is best example for a
pandemic disease.
Sporadic
At irregular intervals over limited areas or locations . They occur
relatively in few instances.
Eg: Fusarium wilt of cotton (Fusarium oxysporum f sp. vasiinfectum)

12. PLANT DISEASE EPIDEMIOLOGY
Disease development
Disease
Susceptible Host