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 germination

Seedling establishment

Vegetative growth

reproductive growth

Seed formation

Seed dissemination

survival

Pathogen life cycle

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

survival

Plant and pathogen life cycles

seed germination

seedling establishment

vegetative growth

reproductive growth

seed formation

seed dissemination

Monocyclic pathogens

Complete only one disease cycle in a growing season

(100 - y)QRdy

dt

Q = amount of initial inoculum

R = infection efficacy of the inoculum

y = disease intensity (%)

t = time

Time

Dis

ease

inte

nsi

ty (

%)

TimeDis

ease

inte

nsi

ty (

logi

t)

QR

Logit = ln ( )100

100-y

For monocyclic pathogens

All disease plants are infected from inoculum that survived from the previous season

Time

Dis

ease

inte

nsi

ty (

%)

Previous season

inoculum

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

Pathogens are monocyclic because:

Polycyclic pathogens

Complete several disease cycles in a growing season

r ydy

dt(100 - y)

r = apparent infection rate

y = disease intensity (%)

t = time

Time

Dis

ease

inte

nsi

ty

(log

it)

r

Logit = ln ( )y

100-y

Time

Dis

ease

inte

nsi

ty (

%)

For polycyclic pathogens

Time

Dis

ease

inte

nsi

ty (

%)

Few plants are infected from inoculum that survived from the previous season

Previous

season

inoculumcu

rren

t sea

son

inoc

ulum

Most plants are infected from inoculum that was proliferated within the current season

Control measures

“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

Chemical Cultural

Biological Genetic

Induced resistance

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)

TimeDis

ease

inte

nsi

ty (

logi

t)Time

Dis

ease

inte

nsi

ty (

%)

Polycyclic pathogens

Time

Dis

ease

inte

nsi

ty (

%)

Monocyclic pathogens

Initial disease

rate

Time

Dis

ease

inte

nsi

ty (

logi

t)Possible effects of control measures

on disease progress

Effects on the amount of initial disease

Soil treatmentSeed treatmentSystemic fungicides

Crop rotationCertified seedsSanitationEscape (planting time)Biocontrol agents

Time

Dis

ease

inte

nsi

ty (

logi

t)Possible effects of control measures

on disease progress

In monocyclic pathogens:on the infection efficacy of the inoculum

Polycyclic pathogens:Effects on the apparent infection rate

Protectant fungicidesSystemic fungicides

Genotype resistancecultural measures (e.g., heating, ventilation)Biocontrol measures

On the rate of disease development

Time

Dis

ease

inte

nsi

ty (

logi

t)Possible effects of control measures

on disease progress

On the rate of disease development

Effects on the amount of initial inoculum

and

Systemic fungicides 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

Mesostemic measure

Trans-laminar measure

Deposition and translocation of control measures within treated leaves

Protectant measure

Systemic measure

Measures with re-distribution ability

Deposition and translocation of control measures within treated leaves

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

Deposition and translocation of control measures within treated plants

Integration of control measures

Time

Combined application

Application according to the expected efficacy of each measure

Alternated application

Combined efficacy of control measuresC

ontr

ol e

ffic

acy

(%)

1 1+22exp.

Additive

1+2obs.

1+2

Synergistic

obs.1+2

Antagonistic

obs.

Calculation of combined efficacy of control measures - Step 1

Con

trol

eff

icac

y (%

)

1 2 1+2obs.

A = control efficacy of #1

B = control efficacy of #2

A+B(obs.)= observed control efficacy of 1+2

Abbott formula

E (exp)= A + B - (A*B)/100

1+2exp.

A+B(exp.)= expected control efficacy of 1+2

SF = E (obs) / E (exp

Con

trol

eff

icac

y (%

)

1+21+2exp. obs.

SF = Synergy factor

E(obs.)= Observed control efficacy of 1+2

E(exp.)= Expected control efficacy of 1+2

Calculation of combined efficacy of control measures - Step 2

Combined efficacy of control measuresC

ontr

ol e

ffic

acy

(%)

1+21+2exp. obs.

SF = 1additive

Con

trol

eff

icac

y (%

)

1+21+2exp. obs.

SF > 1synergistic

SF = Synergy factor

Con

trol

eff

icac

y (%

)1+21+2

exp. obs.

SF < 1antagonistic

Combined efficacy of control measures

Treatment Disease severity (%)

1

2

1+2

Control

20

30

15

80

Abbott formulaE (exp)= A + B - (A*B)/100

E (exp)= 75+62.5 - (75*62.5)/100=90.6%

control efficacy of #1 = 100-(20/80)*100= 75%

control efficacy of #2 = 100-(30/80)*100= 62.5%

control efficacy of 1+2= 100-(15/80)*100= 85%

E = 100-(t/c)*100

Combined efficacy of control measures

SF = E (obs) / E (exp

E(obs.)= Observed control efficacy of 1+2

E(exp.)= Expected control efficacy of 1+2

E(obs.)= 85%

E(exp.)= 90.6%

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

grower

pathogen

environment

host

When to treat? Effects of the environment on the pathogen

When to treat? Effects of the environment on the pathogen

En

viro

nm

enta

l fa

ctor

Time

Dis

ease

inte

nsi

ty (

%)

Rain

Periods of high relative humidity

High or low temperatures

Hail

Sand storms

Environmental factors

When to treat? Effects of the environment on the pathogen

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Time

Dis

ease

sev

erit

y (%

)

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

control measure

pathogen

environment

host

When to treat? Effects of the control measure on the pathogen

When to treat? Effects of control measures on the pathogen’s life cycle

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Protectant fungicides, biocontrol agent,

heating, ventilation

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Mesostemic fungicides, biocontrol agents,

genotype resistance

When to treat? Effects of control measures on the pathogen’s life cycle

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Systemic fungicides, biocontrol agents

When to spray? Effects of fungicides in the pathogen’s life cycle

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Curative fungicides, heating, ventilating,

light filters

When to treat? Effects of control measures on the pathogen’s life cycle

spore germination

establishment

lesion formation

reproductive growth

spore formation

spore dissemination

Eradicative fungicides, biocontrol

agents, ventilation, heating

When to treat? Effects of control measures on the pathogen’s life cycle

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

When to treat? Effects of the host: age-related resistance

Time

Hos

t re

sist

ance

Time

Dis

ease

inte

nsi

ty (

%)

grower

pathogen

environment

host

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 pathogeneffects of the control measures on the pathogeneffects of the host on the pathogen