The document discusses how the environment affects plant disease development. It notes that three factors are required for a plant disease to develop: a susceptible host, a virulent pathogen, and a favorable environment. It then examines how several environmental factors, such as temperature, moisture, light, atmospheric pressure, rainfall, wind, soil pH, aeration, organic matter, and host nutrition can influence the development and spread of plant diseases. For example, high moisture favors late blight of potato while low moisture favors powdery mildew. The document provides examples for many of the environmental factors discussed.

1. EFFECT OF ENVIRONMENT ON PLANT
DISEASES DEVELOPMENT
DR. RAJBIR SINGH
Assistant Professor
Department of Plant Pathology
Gochar Mahavidyalaya, Rampur Maniharan, Saharanpur (UP), India
Affiliated to Ch. Charan Singh University, Meerut (UP), India
Email: rajbir25805@yahoo.com, rajbirsingh2810@gmail.com
Cell No. 91-9456613374

2. Effect of Environment on Plant Diseases
1. A susceptible host
2. A virulent pathogen
3. Favorable environment

3. 1. Effect of Temperature
Exp. Rust of wheat
2. Effect of Moisture – (i). Germination
(ii). reproduction
(iii). Penetration
(iv). spread
High moisture - Late blight of potato
Low moisture - powdery mildew

4. 3. Effect of light – stomata opening
Exp. Fusarium wilt of tomato
4. Effect of atmospheric pressure
More atmospheric pressure
decrease production of sporangia
Exp. Phytophthora infastans
Erwinia carotovora - decrease

5. 5. Effect of rainfall and dew – spread
dew is good than rain in disease development
6. Effect of wind – spread
Exp. Rust of wheat

6. 7. Effect of soil reaction or pH
Fungi- low pH
Exp. Club root of crucifers
Bacteria – high pH
Exp. Wilt of pea
8. Effect of aeration- (i). development of roots
(ii). biochemical reaction
Exp. Phytophthora parasitica
no growth on low O2

7. 9. Effect of organic matter
i). Nutrition
ii). ph
iii). Soil reaction
iv). Development of antagonism
10. Effect of host nutrition
i). N increase susceptibility
ii). P & K decrease susceptibility
Exp. (a). Cu – wilt
(b). Zn – Khaira

8. Thank You