Classification of plant disease

There are various types of classifications of plant disease which are explained here.

1. Classification of Plant diseases Dr Bhagyashree Khamari Assistant Professor Department of Plant Pathology Institute of Agricultural Sciences Siksha o Anusandhan (Deemed to be University) Bhubaneswar, Odisha

2. (I). Classification based on extent of infection Localized disease : If disease appear in and around the site of infection. Systemic disease : I f disease is spread throughout the system of plant.

3. (II) Based on mode of perpetuation and spread of pathogen Soil borne disease - When the pathogen perpetuates in soil. E.g. Root rot Seed borne disease   - When the pathogen perpetuates in seed (or any propagation material ). e.g. Loose smut of wheat Air borne disease   - When pathogen are disseminated by wind. e.g. rusts and powdery mildews.

4. (III) Based on the geographical distribution and extent of Occurrence Sporadic disease Endemic diseases   Epidemic or epiphytotic diseases   Pandemic diseases  

5. Disease appear at an i rregular Intervals and in small area causing l ess loss. E.g. Loose smut of wheat, Udbatta disease of rice Sporadic disease

6. Endemic disease When disease appear more or less constantly every year in moderate to severe form in a particular geographical region , i.e. country, district or location. E.g. Wart disease of potato in Darjiling

7. When disease occur in a large area, periodically, in a severe form causing huge loss. They might be occurring in the locality every year but becomes severe on arrival of favourable environmental conditions. E.g. Wheat rust Epiphytotic or epidemic Disease

8. Pandemic disease: When disease occur in a continental scale causing huge loss . E.g. Late blight disease of Potato

9. (IV) Classification base o n mo d e o f mu l t i p l i c a t i o n of pathogen Simple interest/monocyclic diseases Compound interest/polycyclic diseases

10. Simple interest or monocyclic disease Only one cycle of pathogen complete in one season . Only primary inoculum is present, no secondary inoculum. Severity is related to amount of inoculum. E .g. Soil borne diseases (Root rot, wilt), Post harvest diseases, disease which require two host (Rust) Primary inoculum

11. Several cycles of pathogen complete in one season . Severity of disease is related to amount of pathogen inoculum, their reproduction and survival of pathogen Both primary and secondary inoculum is present. Severity of disease is more. E.g. Air borne diseases like leaf spot, powdery mildew. Compound interest or polycyclic disease P rimary Secondary

12. (v) Based on Infection Process Infectious disease   - Diseases that are caused by animate causes such as fungi, bacteria, viruses and viroid. It can be transmitted to a healthy plant . Non-infectious disease – It is also referred as physiological disorders . It can not be transmitted to a healthy plant and caused by abiotic or inanimate causes like nutrient deficiency or excess or unfavorable weather conditions or soil Infectious Non-infectious

13. (VI) Based on the signs and symptoms produced by the pathogens Rusts Smuts powdery mildews downy mildews root rots Wilts Blights Cankers fruit rots leaf spots T he disease are named after the most conspicuous symptom of the disease appearing on the host surface.

14. (VII) Based on major Causes F ungal diseases B acterial diseases V iral diseases M ycoplasmal diseases

15. (VIII) BASED on parts of the plant affected Root diseases: Root rot of vegetables Stem diseases: Stem gall of coriander. Foliar disease: Leaf spot of Sorghum. Fruit diseases : Fruit rot of Brinjal

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