Classification of Diseases
- Particularly the cultivated wants usually get infected with the disease and search disease can be counted in many hundreds.
- Because of their big number the plant disease need to be grouped in various ways based on types of the pathogen that cause the disease to extend of experience and geographic distribution extent.
- which disease is associated with plants method of preparation and mode of primary infection part of the classification based on the type of pathogen indicate.
- Not only the cause of the disease but also the knowledge and information that suggest the probable development and spread of disease along with their possible control measure.
▶ On the basis of the type of pathogen that causes the disease:-
- On the basis which is most commonly used Aryan plant disease can be classified into two men group and their extension is given as under.
▶Disease caused by animate (living) pathogen:-
1.Diseases caused by microbes:-
- Fungal disease
- Bacterial disease
- Spiroplasma and fastidious vascular bacteria disease.
- Algal disease
- Protozoan disease
- Disease caused by microbes beyond cellular organisation is viral disease and disease by viroids.
2. Disease caused by organism other than microbes:-
- Parasitic higher plant disease
- A plant disease caused by fungi bacteria include phytoplasmas,spiroplasmas, fastidious vascular bacteria; viruses and viroids.
- Only of few Chlorophyceae algae have been reported causing disease in plant mainly in tropical and subtropical countries of them cephaleuros parasiticus causes red rust disease on tea, mango,citrus and guava.
- There are many parasitic higher plant which causes disease on higher plants.
- However, the definite evidence of plant disease to be costly to buy a flat unit protozoan is the phloem necrosis disease of coffee caused by phytomonas leptovaeorum.
▶On the basis of extent of hockey rance and geographic distribution:-
1.Sporadic disease:-When a disease occurs at very irregular interval and location and in relatively few instances it is referred to as sporadic disease.
2. Endemic disease:-This disease is present more or less constantly in a particular location in a moderate or severe form it is called endemic disease.
3. Epidemic or epiphytotic disease:-The term epidemic is derived from a Greek word meaning among the people and in true sense applies to those diseases of human beings which appears severely or violently among the large section of population periodically.
- The term epiphytotic has been coined to carry the same sense in case of disease of plant what the term epidemic carries in case of disease of human and animal like cattle and poultry.
- The epiphytotic which become destructive on a continental scale are represented by a specific terminology called pandemic.
▶On the basis of extent to which disease are associated with plants:-
1. Localised disease:-When the effect of infection induces disease development remaining restricted in or around the area surrounding the infection site the disease is called localised.
- The infection in these disease may remain localised throughout the growing season or they may enlarge slightly or very slowly.
- Many fungi, bacteria ,nematode, virus and parasitic higher plant cause localised disease.
2. Systemic disease:-When the effect of infection induces disease development appearing throughout the entire plant or most of its path or any of its path after an interval of time during which the pathogen spread in the host body remaining externally invisible the disease is called systemic.
- All infection caused by first vascular bacteria and protozoa and all natural infection caused by virus, viroids are systemic.