Transcript control measure?

1.1 Introduction to integrated disease
management
•Introduction
•Effects of control measures on disease progress
•Effects of control measures within the plant tissue
•Translocation and deposition of control measures
•When to apply a control measure?
•Concluding remarks
Plant life cycle
Seed
dissemination
Seed
formation
Seed
germination
reproductive
growth
Seedling
establishment
Vegetative
growth
Pathogen life cycle
spore
dissemination
spore
formation
spore
germination
reproductive
growth
establishment
lesion
formation
Plant and pathogen life cycles
seed
dissemination
seed
formation
seed
germination
reproductive
growth
seedling
establishment
vegetative
growth
Monocyclic pathogens
Complete only one disease cycle in a growing season
Q = amount of initial inoculum
dy
R = infection efficacy of the inoculum
dt
y = disease intensity (%)
QR (100 - y)
Logit = ln (
Time
Disease intensity (logit)
Disease intensity (%)
t = time
QR
Time
100
100-y
)
For monocyclic pathogens
Disease intensity (%)
All disease plants are infected from inoculum that survived
from the previous season
Time
Pathogens are monocyclic because:
The host is susceptible for a very short tine (smuts)
The infecting structures do not disseminate within
the same growing season (soil-borne pathogens)
The environmental conditions are conducive for
infection for a short time (scab)
The growth of the pathogen is very slow
Polycyclic pathogens
Complete several disease cycles in a growing season
r = apparent infection rate
dy
y = disease intensity (%)
dt
r y (100 - y)
t = time
Disease intensity
(logit)
Disease intensity (%)
Logit = ln (
r
Time
Time
y
100-y
)
For polycyclic pathogens
Disease intensity (%)
Few plants are infected from inoculum that survived from
the previous season
Most plants are infected from inoculum that was
proliferated within the current season
Time
Control measures
Chemical
Cultural
Biological
Genetic
Induced resistance
“Strategic means”:
Means that are applied once, and their effect is apparent
for a long time (the entire growing season)
“Tactical measures”:
Means that are applied frequently, and are effective for a
relatively short time
The effects of control measures on
disease development
Depends on
the biology of the pathogen
(monocyclic or polycyclic)
and on
the characteristics of the measure
(strategic or tactical)
Monocyclic pathogens
Polycyclic pathogens
Disease intensity (%)
Disease intensity (%)
Time
Disease intensity (logit)
Time
rate
Initial disease
Time
Disease intensity (logit)
Possible effects of control measures
on disease progress
Effects on the amount
of initial disease
Time
Soil treatment
Seed treatment
Systemic fungicides
Crop rotation
Certified seeds
Sanitation
Escape (planting time)
Biocontrol agents
Disease intensity (logit)
Possible effects of control measures
on disease progress
On the rate of disease development
In monocyclic pathogens:
on the infection efficacy of
the inoculum
Time
Protectant fungicides
Systemic fungicides
Polycyclic pathogens:
Effects on the apparent
infection rate
Genotype resistance
cultural measures (e.g., heating,
ventilation)
Biocontrol measures
Disease intensity (logit)
Possible effects of control measures
on disease progress
Effects on the amount of
initial inoculum
and
Time
Systemic fungicides
On the rate of disease
development
Integration of control measures
Deposition and translocation
of control measures
Within treated leaves
Within treated plants
Deposition and translocation of control
measures within treated leaves
Deposition and translocation of control
measures within treated leaves
Protectant
measure
Mesostemic
measure
Trans-laminar
measure
Deposition and translocation of control
measures within treated leaves
Systemic measure
Measures with
re-distribution ability
Deposition and translocation of control
measures within treated plants
Application of a
systemic measure
to the root system
Deposition and translocation of control
measures within treated plants
Application of a
systemic measure
to the stem
Deposition and translocation of control
measures within treated plants
Application of a
systemic measure
to a leaf
Deposition and translocation of control
measures within treated plants
Application of a
systemic measure
to the foliage of a
growing plant
Integration of control measures
Application according to the
expected efficacy of each measure
Alternated application
Combined application
Time
Combined efficacy of control measures
Synergistic
Antagonistic
Control efficacy (%)
Additive
1
2 1+2
exp.
1+2
obs.
1+2
obs.
1+2
obs.
Control efficacy (%)
Calculation of combined efficacy of
control measures - Step 1
A = control efficacy of #1
B = control efficacy of #2
A+B(obs.)= observed control
efficacy of 1+2
1
2 1+2 1+2
obs.
exp.
A+B(exp.)= expected control
efficacy of 1+2
Abbott formula
E (exp)= A + B - (A*B)/100
Calculation of combined efficacy of
control measures - Step 2
Control efficacy (%)
SF = E (obs) / E (exp
SF = Synergy factor
E(obs.)= Observed control
efficacy of 1+2
1+2
exp.
1+2
obs.
E(exp.)= Expected control
efficacy of 1+2
Combined efficacy of control measures
SF = Synergy factor
SF > 1
synergistic
1+2 1+2
exp.
obs.
SF < 1
antagonistic
Control efficacy (%)
Control efficacy (%)
Control efficacy (%)
SF = 1
additive
1+2 1+2
exp.
obs.
1+2 1+2
exp.
obs.
Combined efficacy of control measures
Treatment Disease
severity (%)
E = 100-(t/c)*100
1
20
control efficacy of #1 = 100-(20/80)*100= 75%
2
30
control efficacy of #2 = 100-(30/80)*100= 62.5%
1+2
15
control efficacy of 1+2= 100-(15/80)*100= 85%
Control
80
Abbott formula
E (exp)= A + B - (A*B)/100
E (exp)= 75+62.5 - (75*62.5)/100=90.6%
Combined efficacy of control measures
E(obs.)= Observed control
efficacy of 1+2
E(obs.)= 85%
E(exp.)= Expected control
efficacy of 1+2
E(exp.)= 90.6%
SF = E (obs) / E (exp
SF = 85 / 90.6 = 0.93
SF < 1
antagonistic reaction
When to apply a “tactical” control measure?
Effects of the environment on
the pathogen
Effects of the control measure on
the pathogen’s life cycle
Effects of the host on the
pathogen
When to treat? Effects of the environment on the pathogen
grower
host
environment
pathogen
When to treat? Effects of the environment on the pathogen
Rain
Periods of high
relative humidity
High or low
temperatures
Hail
Sand storms
Disease intensity (%) Environmental
factor
Environmental factors
Time
When to treat? Effects of the environment on the pathogen
spore
dissemination
reproductive
growth
spore
germination
Disease severity (%)
spore
formation
establishment
Time
lesion
formation
When to apply a “tactical” control measure?
Effects of the environment on
the pathogen
Effects of the control measure on
the pathogen’s life cycle
Effects of the host on the
pathogen
When to treat? Effects of the control measure on the pathogen
control measure
host
environment
pathogen
When to treat? Effects of control measures on the
pathogen’s life cycle
spore
dissemination
spore
formation
Protectant fungicides,
biocontrol agent,
heating, ventilation
reproductive
growth
spore
germination
establishment
lesion
formation
When to treat? Effects of control measures on the
pathogen’s life cycle
spore
dissemination
spore
formation
spore
germination
Mesostemic fungicides,
biocontrol agents,
genotype resistance
reproductive
growth
establishment
lesion
formation
When to spray? Effects of fungicides in the pathogen’s life cycle
spore
dissemination
spore
formation
spore
germination
Systemic fungicides,
biocontrol agents
reproductive
growth
establishment
lesion
formation
When to treat? Effects of control measures on the
pathogen’s life cycle
spore
dissemination
spore
formation
spore
germination
Curative fungicides,
heating, ventilating,
light filters
reproductive
growth
establishment
lesion
formation
When to treat? Effects of control measures on the
pathogen’s life cycle
spore
dissemination
spore
formation
spore
germination
Eradicative fungicides,
biocontrol agents,
ventilation, heating
reproductive
growth
establishment
lesion
formation
When to apply a “tactical” control measure?
Effects of the environment on
the pathogen
Effects of the control measure on
the pathogen
Effects of the host on the
pathogen
Host resistance
When to treat? Effects of the host: age-related resistance
grower
host
Time
pathogen
Disease intensity (%)
environment
Time
Concluding remarks
Application of control measures should be based on:
The biology of the pathogen (monocyclic, polycyclic)
The possible activity of the control measure (protectant,
mesostemic, translaminar, systemic)
The relationships between the host, the pathogen and the
environment:
effects of the environment on the pathogen
effects of the control measures on the pathogen
effects of the host on the pathogen