Dispersal of plant pathogens

1. DISPERSAL OF PLANT
PATHOGENS
B. PAVAN KUMAR NAIK
Assistant Professor
Department of Horticulture

2. • second link in infection chain is the
dissemination of plant pathogens.
• Dispersal, dissemination or transmission ?

3. • Fungi
• Bacterial diseases
• Viral diseases

4. • The dispersal of infectious plant pathogens in
space occurs through two ways:
1. Autonomous or direct or active dispersal.
2. Indirect or passive dispersal.

5. I) Autonomous or direct or active
dispersal
1) Seed as the source of autonomous dispersal:
a) Contamination of the seed
b) Externally seed borne
c) Internally seed borne

6. 2) Soil as a means of autonomous dispersal
a) Dispersal in soil:
i) Contamination of soil
ii) Growth and spread of a pathogen in soil
iii) Persistence of the pathogen in soil
b) Dispersal by the soil:

7. 3) The plant and the plant organs as a means of
autonomous dispersal:
Late blight of potato was introduced in North
America and in Europe through seed tubers
brought from the native source of the in South
America.

8. II) Passive or Indirect dispersal
1) Animate agents:
a) Insects: Fungal diseases/Bacterial diseases/Viral
diseases/Mycoplasma diseases.
b) Mites
c) Fungi
d) Nematodes:Bacterial diseases/Fungal
diseases/Viral diseases/NEPO viruses/NETU viruses

9. e) Human beings:
Transportation of seeds (seed trade)
Planting diseased seed materials
During adoption of normal farming practices
By use of contaminated implements
By use of diseased grafting and budding material

10. f) Dispersal by phanerogamic parasites
g) Dispersal by birds
h) Farm and wild animals

11. 2) Inanimate agents:
a) Wind: Fungi/Nematodes/Bacteria/Viruses
and phytoplasmas.
b) Water:

12. PHENOMENON OF INFECTION/
INFECTION PROCESS
• It is the third link in the infection chain after
survival and dispersal of inoculum.
• Inoculum potential

13. The success of process of infection
depends on:
1. Host factors
• Susceptibility of host:
• Disease proneness of the host:
2. Pathogen factors
• Virulence / aggressiveness of the pathogen:
• High multiplication rate of the pathogen:
• Proper inoculum potential:

14. 3. Environmental factors
Process of infection can be grouped into three
stages, i.e., pre-penetration, penetration and
post-penetration.

16. 1. PRE-PENETRATION
1. Active invaders and
2.Passive invaders

17. PENETRATION
• Indirect Penetration:Wounds/2. Natural
openings/

18. PLANT DISEASE EPIDEMIOLOGY

20. Disease Pyramid

21. Essential components/conditions for
an Epiphytotic
1. Host factors
Distance of susceptible plants from the source
of primary inoculum
Abundance and distribution of susceptible hosts
Disease proneness in the host due to
environment
Presence of suitable alternate or collateral hosts

22. 2. Pathogen factors:
• Presence of virulent/aggressive isolate of a
pathogen
• High birth rate
• Low death rate of the pathogen
• Easy and rapid dispersal of the pathogen
• Adaptability of the pathogen

23. 3. Weather factors
• Weather conditions such as, optimum
temperature, moisture, light, etc., are very
essential for the development of an
epidemics.
• Science which deals with the relationship
between weather and epiphytotics is called
metereopathology.