Plant diseases are caused by biotic, abiotic and mesobiotic factors.

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

2. Plant Disease
Disease is an abnormal condition that is caused due to
continuous irritation by biotic or abiotic factor which alters
physiological processes of plant resulting into loss of appearance
and reduction of yield.

3. How to identify a plant disease?
Symptoms : Visible effects of disease on plants such as changes
in color, shape, and/or functions of the plant in response to
pathogen attack. E.g. Leaf spot, blight, wilt, rot.
Signs : Presence of physical evidence of the pathogen on plant
surface. E.g. fungal fruiting bodies, bacterial ooze
Syndrome- A sum total of variety of symptoms produced by the
disease

4. SYMPTOMS
Leaf spot
Leaf spot
Seed discoloration
Wilt

5. SIGN
Powdery mildew Rust
Black Scurf of Potato

6. Causesof plantdiseases
Bioticfactors
Abiotic factors
Mesobioticfactors

7. (A) Biotic or Animate Causes
Eukaryotes
Fungi
Straminopila (Oomycetes)
Nematode
Algae
Protozoa
Parasitic Plants
Prokaryotes
Bacteria
Phytoplasma
Spiroplasma

8. (B). Mesobiotic causes
1. Virus
2. Virod
3. Virusoids
4. Prion

9. (C) Abiotic or Inanimate Causes
1. Adverse climatic conditions
(a) Light (b)Temp (c) Humidity
(d) Rain (e)Hail (f)Frost
(g) Storm (h)RH
2. Adverse soil conditions
(a) Soil moisture
(c)Structure
(e) Nutrition
(b)Texture
(d)Aeration
(f)Soil pH

10. High Temperature Excess water
Lightening injury Wind damage

11. 3. Chemical Injuries
(a) Pollution (b) Pesticides
4. Improper Cultural Practices
(a) Depth of sowing
(b) Improper irrigation
(c) Improper fertilization
(d) Improper harvesting

12. Black tip of mango (due to Sulphur
dioxide toxicity)
Khaira disease of rice (Zn deficiency)
Black heart of potato (due to lack of
oxygen in storage)
whiptail of cauliflower (Mo deficiency)

13. Pesticide injury