农业植物病害IPM（英文）- (4).ppt

Basics of plant disease epidemiology and modeling
Introduction
The disease triangle
Effects of the environment on the pathogen
Effects of the host on the pathogen
Disease development in time and space
Concluding remarks
Epidemiology: the science that deals with the dynamic relationships between hosts and their pathogens at the population level
Disease progress curve: a plot that shows graphically how disease intensity changes over time
Time
Disease intensity
Epidemic: a change in disease intensity over time
dy
dt
How disease intensity is measured ?
Disease incidence:The proportion of infected host units, out of the total units sampled
Disease severity:The proportion of infected part (or area), in each of the sampled units
4/10*100=40%
in percent
(60+10+30+1)/10*100=%
60
10
30
1
0 0 0 0 0 0
in percent, cm2, number, index...
Plant life cycle
Seed germination
Seedling establishment
Vegetative growth
reproductive growth
Seed formation
Seed dissemination
Plant and pathogen life cycles
seed germination
seedling establishment
vegetative growth
reproductive growth
seed formation
seed dissemination
survival
epidemic
Monocyclic pathogens
Complete only one disease cycle in a growing season
The host is susceptible for a very short tine (smuts)
The infection units do not disseminate within the same growing season (soil-borne pathogens)
The environmental conditions are conducive for a short time
The growth of the pathogen is slow
Pathogens are monocyclic because:
Monocyclic pathogens
Complete only one disease cycle in a growing season
(100 - y)
QR
dy
dt
Q = amount of initial inoculum
R = infection efficacy of the inoculum
y = disease severity
Time
Disease severity (%)
Time
Disease severity (logit)
QR
Logit = ln ( )
100
100-y
Polycyclic pathogens
Complete several disease cycles in a growing season
r y
dy
dt
(100 - y)
r = apparent infection rate
y = disease severity
Time
Disease severity (logit)
r
Logit