Uptake & Systemicity of Fungicides - LandbrugsInfo · Uptake & Systemicity of fungicides ... spray...

Dr. Andreas GoertzCrop Protection ResearchDisease Control Monheim

Uptake & Systemicity ofFungicidesDanish Advisor Course - Aarhus – September 2012

Uptake & Systemicity of fungicides

• Background

• Benzophenones

• SDHIs

• Strobilurins

• Triazoles

• Q&A session

Agenda

• Danish Advisor Course – September 2012


What is Uptake?

Definition:

Uptake is the process by which a substance crosses an absorption barrier and is absorbed into the body.

Agrochemicals are taken up and distributed in the p lant generally in a passive way along concentration gradients and according to their phys ico-chemical properties

The absorption barrier in plants is the cuticle

(similar to polymer membrane)


What is Systemicity?

Definition:

Systemicity is the uptake of a compound into the plant (root or leaf) leading to a

translocation (in xylem -or- phloem -or- both) and activity away from the site of application.

ApplicationActivity

Application

UPTAKE

TRANSLOCATION

� ACTIVITY

Uptake into the plant is a requirement for systemic ity.A limited number of compounds is distributed in the canopy via the vapour phase.

Activity

Activity

Vapour pressure (mPa): the pressure at which a liquid is in equilibrium with its vapour at 25°C. It is a measure of the tendency of a material to vapourise. The higher the vapour pressure the greater the potential.

Physico-chemical parameters of commercial fungicides

TFS

TFS

TFS

TFS

UTC

UTCUTC

UTC

low

high

Distribution of 14C-labelled Trifloxystrobin in

soybeans 7 days after spray application


Factors determining the vapour phase distribution o f a fungicide are its physico-chemical characteristics, the environmental conditions and t he canopy strutcure

There are four basic types ofsystemicity …

Local systemicityAbsorption to the leaf surface and limited uptake with some diffusion around the site of application (no long distance transport)

Trans-laminar systemicityA compound applied to one surface of the plant leaf and acts on the other side of the leaf after penetration (not necessarily connected with long distance transport)

Xylem systemicityA compound which is translocated over long distance only in direction of the xylem stream; movement is upwards the growing point of the plant (acropetal, apoplastic)

Phloem systemicityA compound which is translocated over long distance also in direction of the phloem stream; movement is downwards from the shoots to the roots (basipetal, symplastic)

Incr

easi

ngde

gree

ofsy

stem

icity


Spray application ofcompound on upper

leaf surface

spray droplet on upper leaf surface xylem

phloem

compoundtaken up




Xylem systemicityA compound which is translocated over long distance only in direction of the xylem stream; movement is upwards the growing point of the plant (acropetal, apoplastic)

Phloem systemicityA compound which is translocated over long distance also in direction of the phloem stream; movement is downwards from the shoots to the roots (basipetal, symplastic)

Incr

easi

ngde

gree

ofsy

stem

icity



Xylem SystemicityA compound which is translocated over long distance only in direction of the

xylem stream (acropetal)

activityactivity

root stem leafapplicationapplication




Xylem systemicityA compound which is translocated over long distance only in direction of the xylem stream; movement is upwards the growing point of the plant (acropetal)

Phloem systemicityA compound which is translocated over long distance also in direction of the phloem stream; movement is downwards from the shoots to the roots (basipetal)

Incr

easi

ngde

gree

ofsy

stem

icity


Additonal systemicity terms exist….


Episystemicity

Leaf surface distribution in waxy layers via vapour phase. If the vapour pressure of theactive substance is sufficiently high, migration can begin from its deposition on the leafsurface, via vaporization and gas-phase transportation

Mesostemie

Episystemicity + translaminar systemicity; the active substance is absorbed by waxy layers; superficial chemical vapour movement and re-deposition on plant surfaces; the active substance also penetrates into plant tissue, ensuring protection to both leaf surfaces. There is little or no transport within the vascular system of plants.

step 1

Spraydropletformation

Tank

step 3Spray deposit properties

The fungicide transfer to the target consist of sev eral steps arranged in series:step 2Retention

Leaf

PCF F F

F : step affected by formulation PC : step affected by physico-chemical properties of the fungicide

Important factors affecting fungicide activity

step 4Penetration

step 5Redistribution/translocation- long distance translocation

(in xylem or in both , xylemand phloem)

step 6Binding at target site

PC

PC

PCF Quelle: Pontzen, Baur

Physico-chemical properties affect fungicides activ ity at several steps; physico-chemical properties of a compound and formulation can have a strong impact on fungicide activity


WettingSpreading

Apple = > 90 % Oilseed rape = 20-40 % Barley = < 5 %

Typical water retention


The surface characteristics influence the retention /wettability of the spray solution on the leaf surface

Barley is extremelycovered with epicuticular

waxes

Smooth surface consistingof a layer of amorphous

waxes


step 2Retention

LeafF

WettingSpreading



step 2Retention

LeafF

WettingSpreading

• When a spray droplet lands on a leaf or other plant surfaces it may be retained on the plant surface or bounce off the surface and ultimately land on some other plant parts or the soil.

• Droplets with a high dynamic surface tension like aqueous fungicide spray dropsfrequently bounce off or run off leaf and stem surfaces.

• In contrast, droplets with a low dynamic surface tension are more likely to beretained on plant surfaces.

Source: W.B. McCloskey



step 2Retention

LeafF

WettingSpreading

• The addition of surfactants or wetting agents reduces the dynamic surface tensionof water droplets.

• Reducing dynamic surface tension allows spray droplets to spread out upon impact and increase the area of contact with the plant surface.

• Reduced dynamic surface tension and increased area of contact reduces thepropensity for spray droplets to bounce or roll off plant surfaces.


100

80

60

40

20

0

Ret

entio

n (%

)

Optimized formulation

Smooth leaf surface Rough leaf surfacedue to crystalline waxes

Water or SC-formulation

OptimizedSpray Retention


step 2Retention

Leaf

F

WettingSpreading



step 2Retention

LeafF

Horizontally positioned barley leaves were sprayed with an Air

Injection nozzle at 200 l/ha

Prosaro

Standard

An optimization of the product formulation can clea rly improve the retention and spreading of spray droplets on plant surfaces

WettingSpreading




PCF

Spray deposit properties most important for fungici de performance. Deposit properties are decisive for the next step – release of the active f or penetration into the leaf

• Leaf surface characteristics

• Formulation type (spreading, solvents, humectants, etc.)

• Physical state of the active in the deposit (amorphous or cristallin)

• Physico-chemical properties of the active substance (solubility, melting point)



PCF


• Surfactants or wetting agents can improve the absorption by reducing the rate ofspray droplet drying and crystallization of active ingredient

Greater fungicide absorption occurs from amorphous spray deposits compared to crystalline deposits.


Melting point (°C) is the temperature at which the given active substance changes its physical state from solid to liquid.



uptake

50 100 150 200

mp [°C]

Importance of formulation

The higher the melting point the lower is the bioavailability out of deposit (very roughly correlation!). The higher the melting point the higher is the importance of formulation - for cuticle uptake..

Propiconazole = -23 °C

Source: PPNB – Pesticide Properties Data Base

• Lipophilicity

• Solubility

• Molecular Volume

� Well understood

� Well describable

� Prediction possible

Physico-chemical propertiesPhysico-chemical properties

• Temperature

• Humidity

• Wind

• Plant species

� Some understood and describable

� Prediction difficult due to influence of formulation

Environment & PlantEnvironment & Plant

• Retention

• Solubility

• Permeability

• Spreading

� In principle understood

� Describable

� Not predictable

FormulationFormulation

The penetration of a fungicide through the cuticule is a very complex interplay of different factors – clear predictions are difficult

Penetration of a compound through the cuticule


step 4Penetration

F PC


leaf: cross-section

Spray deposit

cuticle

cell wall

epidermal cell

Cuticular waxes

1-2

µm

Source: Braune, W. et. al. (1983), Pflanzenanatomisches Praktikum

Barrier for leaf uptake of fungicides: the cuticule

lipophil / solid

hydrophil / liquid

Jeffree, C.E. (1996), Structure and ontogeny of pla nt cuticles

The cuticle is the intial contact point between an a grochemical and the plant and, where uptake into plant tissues is required for biological activ ity, it is the main absorption barrier to penetrati on


step 4Penetration

PCF


Surface wax

Cutin + wax

Polysaccharides+ cutin

Pectin(negatively charged)

Lipophilic/solid

Hydrophilic / liquid

100 -300 nm

• Structural features of the cuticule

CW: cell wallP: pectin lamellaCL: cuticular layerCP: cuticle proper


step 4Penetration

PCF

Leaf uptake and subsequent redistribution strongly dependent on the partition behaviour of the fungicide between lipophilic compartments and hydro philic compartments

Cell wall ishydrophilic and is

hydrated

Lipophilicity of a compound is usually expressed as logP OW , which is the log of the partition coefficient (KOW) of a compound between octanol and water .

KOW = CO / CW (= distribution between the two phases)

W

O CO = 1000 mg / l

CW = 1 mg / lKOW = 1000 / 1

= 1000log POW = +3

Example with a lipophilic compound:

.

………….………….………….………….………….………….………….………….………….………….………….………….………….………….………….………….

………….………….………….………….………….………….………….………….………….………….………….………….………….………….

.

…………. …………. …………. …………. …………. …………. …………. …………. …………. …………. …………. …………. …………. …………. …………. ………….

More lipophilic(“organic” loving)and hydrophobic(“water” hating)

More hydrophilic(“water” loving)and lipophobic

(“organic” hating)log Pow = - 3

A contrastingexample



Lipophilicity of a compound is usually expressed as logP OW , which is the log of the partition coefficient (KOW) of a compound between octanol and water .


0

20

40

60

80

Num

ber

ofco

mpo

unds

logP (pH 7)

< 0 0-1 1-2 2-3 3-4 4-5 > 5

Large range of variation in lipophilicity; clear pr eferred range: logP 2.5-4.5



Cuticule penetration of fungicides with molar volume > ca. 400 very limited. However, adjuvants can compensate limited mobility up to 100 -fold


step 4Penetration

F PC

Molecular weight The relative molecular mass (molecular weight) of a chemical is the mass of a molecule

of the chemical relative to the mass of a carbon atom taken as exactly 12.

The mean molecular weight of fungicides shows a ste ady increase over time. This leads A) to increasing limitations by reduced bioavailablity and B) the need for adjuvanted formulations




0

20

40

60

80

0 6 12 18 24 30

EW 250 SC 430 & adjuvant, 1g/L SC 430

Pen

etra

tion

(%)

Time (h)

Cuticle penetration of tebuconazole

Droplet application to isolated aple leaf cuticles


step 4Penetration

F PC



step 4Penetration

F PC

�� Improved availability of active out of the deposit by- better solubility of a.i. in deposit- avoidance of a.i. precipitation- precipitation of a.i. in the amorphous state- long lasting resolubilisation by high humidity/dew (humectants)- better coverage/spreading

� Improved/reduced cuticle uptake

�� Improved penetration of active by changing the barrier of the cuticle(swelling agents)

Formulation type and adjuvants (in-can or tankmixed ) can be of major importance for the penetration of agrochemicals and can in parts compe nsate unfavourable phys-chem properties of the active

Penetration: Effects of Adjuvants and Solvents


Long distance translocation of fungicides is always passive and solely dependent on physico-chemical properties



PC


Log P < 2.5 3.2 ± 0.5 > 4.0

step 5Redistribution/translocation-- long distance translocation


PC



Fast movementto leaf margins

Retention plus movement Strong

retention

Larger logP = stronger retention in leaf = less move ment

Xylem movementafter penetration


Long distance translocation of fungicides is always passive and solely dependent on physico-chemical properties



PC


Mobility in plant tissue

2.5 3.0 3.5 4.0

Lipophilicity [logP]

0

20

40

60

80

A: Lipophilie

Anz

ahl d

er

Ver

bind

unge

n

logP (pH 7)

< 0 0-1 1-2 2-3 3-4 4-5 > 5




• Bayer-Fachsymposium 2011 – Dr. Andreas Goertz

• protective dropletapplication of fungicide tothe leaf base

Unbehandelt SDHI + SBI



PC


SDHI + SBI

The systemic translocation enables the control of f ungal growth not directly covered by fungicide application

Water solubility (mg/L) the mass of an active substance that can dissolve in a given volume of water. Value reported is at 20°C.


0

20

40

60

80

< -1 -1-0 0-1 1-2 2-3 3-4 > 4

log 10 (solubility mg/L)

All protective fungicides: < 10 ppmMost prot. Fungicides: < 2 ppm

Large range of variation in water solubility; clear preferred range: 1-100 pm; low water solubility common property of protective fungicides


fast transport to leaf margin good distribution

Compound remains in application area

application

good water solubility

> 3000 mg/l

medium water solubility

1 – 3000 mg/l

minor water solubility < 1 mg/l

e.g. Metalaxyle.g.

Prothioconazolee.g.

Trifloxystrobin


Its just a momentum. The “stages” are fluent depend ing on solubility and water availability, etc.




Bioavailability

Water solubility[g/L]

1000 100 10 1

Importance of formulation

The higher the solubility the higher the potential for bioavailability from the aequous phase. Water solubility is of lower importance within the plant and xylem mobility is stronger influenced by lipophilicityparameters.


step 1

Spraydropletformation

Tank


The fungicide transfer to the target consist of sev eral steps arranged in series:step 2Retention

Leaf

PCF F F

F : step affected by formulation PC : step affected by physico-chemical properties of the fungicide


step 4Penetration

step 5Redistribution/translocation- long distance translocation(in xylem or in both , xylemand phloem)

step 6Binding at target site

PC

PC

PCF Quelle: Pontzen, Baur

Physico-chemical properties affect fungicides activ ity at several steps; physico-chemical properties of a compound and formulation can have a strong impact on fungicide activity


WettingSpreading


• Uptake and systemicity of fungicides is a complex interplay of various factors (incl. physico-chemical properties, formulation, environmental conditions, etc.)

• The optimum physical-chemical property requirements for compounds differ widelydepending on their applications.

• Formulation can (partly) compensate unfavourable physico-chemical properties

• An optimization of the product formulation can clearly improve the retention and spreading of spray droplets on plant surfaces

• Formulation type and adjuvants can be of major importance for spray deposit formationand cuticular penentration of fungicides

• The penetration of a fungicide through the cuticule is a very complex interplay of different factors – clear predictions are difficult

• Leaf uptake and subsequent redistribution strongly dependent on partition behaviour ofthe fungicides between lipophilic and hydrophilic compartments

• Systemic translocation of fungicides in the xylem solely dependent on the physico-chemical properties and is always passive

Summary of the theoretical background


• Background

• Triazoles

• Strobilurins

• Benzophenones

• SDHIs

• Q&A session

Agenda



Uptake & Systemicity of Fungicides

DISCLAIMER

The following theorectical conclusion in regard to the mode of transport of listedfungicides solely base on the physico-chemical properties of each active ingredientpublished on http://sitem.herts.ac.uk/aeru/footprint/index2.htm. Influences of formulation type and adjuvants potentially added to the spray solution, and environmental factors are NOT considered.

Therefore one has to be very cautious in generalizing conclusions. Any use of this information for further external purpose should only be done with additional involvement of experts.


Uptake & Systemicity of Triazoles

• translaminar activity• acropetal translocation• no episystemicity

Theoretical conclusion

• reasonable water solubility= favourable for long distance translocation

• medium logP = favourable for acropetal translocation

• low vapour pressure = no vapour phase activity

Epoxiconazole

Physico-chemicalproperties of Triazoles

Molecularweight

Water solubility at 20 °C (mg/L)

MeltingPoint (°C)

LogPVapour

pressure at25 °C (mPa)

Epoxiconazole 329,8 7,1 136,7 3,3 0,01

Metconazole 319,8 30,4 104,2 3,85 0,000021

Prothioconazole 344,3 300 141,8 3,82 0,0004

Tebuconazole 307,8 36 105 3,7 0,0013






• reasonable water solubility= favourable for long distance translocation

• Medium/high logP = favourable for acropetal translocation


Metconazole


Molecularweight


MeltingPoint (°C)

LogPVapour


Epoxiconazole 329,8 7,1 136,7 3,3 0,01

Metconazole 319,8 30,4 104,2 3,85 0,000021


Tebuconazole 307,8 36 105 3,7 0,0013





Molecularweight


MeltingPoint (°C)

LogPVapour


Epoxiconazole 329,8 7,1 136,7 3,3 0,01

Metconazole 319,8 30,4 104,2 3,85 0,000021


Tebuconazole 307,8 36 105 3,7 0,0013



• good water solubility = favourable for long distance translocation

• medium/high logP = favourable for acropetal translocation


Prothioconazole





Molecularweight


MeltingPoint (°C)

LogPVapour


Epoxiconazole 329,8 7,1 136,7 3,3 0,01

Metconazole 319,8 30,4 104,2 3,85 0,000021


Tebuconazole 307,8 36 105 3,7 0,0013



• reasonable water solubility = favourable for long distance translocation

• medium/high logP = favourable for acropetal translocation


Tebuconazole



• Background

• Triazoles

• Strobilurins

• Benzophenones

• SDHIs

• Q&A session

Agenda


Uptake & Systemicity of Strobilurins



Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026

Trifloxystrobin 408,4 0,61 72,9 4,5 0,0034

Physico-chemicalproperties ofStrobilurins

• Medium water solubility = favourable for long distance translocation

• relative low logP = favourable for acropetal translocation


Azoxystrobin




Azoxystrobin

Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026



• Systemic xylem mobility• Translaminar activity



• relative low logP = favourable for acropetal translocation





Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026




• Medium logP = favourable for acropetal translocation

• Low melting point = rapid foliar uptake

• high vapour pressure = vapour phase activity

Picoxystrobin




Picoxystrobin

Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026



• Systemic xylem mobility• Translaminar activity• Episystemic distribution



• Medium logP = favourable for acropetal translocation


• high vapour pressure = vapour phase activity




Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026



• Relatively low water solubility = unfavourable for long distance translocation

• high logP = unfavourable for acropetal translocation



Pyraclostrobin




Molecularweight


Melting Point (°C)

LogPVapour


Azoxystrobin 403,4 6,7 116 2,5 0,00000011

Picoxystrobin 367,3 3,1 75 3,6 0,0055

Pyraclostrobin 387,8 1,9 64,5 3,99 0,000026



• Local-systemic• translaminar activity• limited acropetal translocation


• Relatively low water solubility = unfavourable for long distance translocation

• high logP = unfavourable for acropetal translocation



Pyraclostrobin


The various strobilurin fungicides have very differe nt physio-chemical properties which consequently confer a wide range of biokinetic behav iours

Source: Bartlett et al. 2002



Trifloxystrobin(Mesostemic)

vapour phase activity and deposit

effect

Active on the surface of the plant

Absorbed through the cuticle

Penetration into plant tissue

Translaminar movement

Transport in the vascular system

low

high

Point of application


Distribution of 14C-labelled Trifloxystrobin in soybeans 7 days

after droplet application

The various strobilurin fungicides have very differe nt physio-chemical properties which consequently confer a wide range of biokinetic behav iours



The various strobilurin fungicides have very differe nt physiocchemical properties which consequently confer a wide range of biokinetic behav iours

Source: Bartlett et al. 2002


• Background

• Triazoles

• Strobilurins

• Benzophenones

• SDHIs

• Q&A session

Agenda


Uptake & Systemicity of Benzophenones


Molecularweight


Melting Point (°C)

LogPVapour


Metrafenone 409,3 0,492 100 4,3 0,153

Physico-chemical properties of Benzophenones


• High molecular weight = low mobility in cuticule

Metrafenone





• Low water solubility = unfavourable for translocation

Metrafenone

0

20

40

60

80

< -1 -1-0 0-1 1-2 2-3 3-4 > 4log 10 (solubility mg/L)

Molecularweight


Melting Point (°C)

LogPVapour


Metrafenone 409,3 0,492 100 4,3 0,153







• High logP = limited xylem systemicity, but translaminar movement

Metrafenone

Molecularweight


Melting Point (°C)

LogPVapour


Metrafenone 409,3 0,492 100 4,3 0,153







• High logP = limited xylem systemicity, but translaminar movement

• High vapour pressure = vapour phase distribution

Metrafenone

• absorbed in waxy cuticle• penetrates into the leaf• translaminar activity• local redistribution in the

canopy (episystemicity)• limited xylem translocation• local systemicity


Molecularweight


Melting Point (°C)

LogPVapour


Metrafenone 409,3 0,492 100 4,3 0,153



• Background

• Triazoles

• Strobilurins

• Benzophenones

• SDHIs

• Q&A session

Agenda


Uptake & Systemicity of SDHIs



• Low logP = favourable for acropetal translocation

• Low vapour pressure = no vapour phase activity

BoscalidSource: PPNB – Pesticide Properties Data Base

Molecularweight


Melting Point (°C)

LogPVapour


Boscalid 343,2 4,6 143,3 2,96 0,00072

Fluopyram 396,8 15 117,5 3,3 0,0012

Physico-chemical properties of SDHIs






Boscalid

• penetrates into the leaf• translaminar activity• translocation in the xylem



Molecularweight


Melting Point (°C)

LogPVapour


Boscalid 343,2 4,6 143,3 2,96 0,00072

Fluopyram 396,8 15 117,5 3,3 0,0012








Fluopyram

Molecularweight


Melting Point (°C)

LogPVapour


Boscalid 343,2 4,6 143,3 2,96 0,00072

Fluopyram 396,8 15 117,5 3,3 0,0012







Fluopyram

• penetrates into the leaf• translaminar activity• translocation in the xylem



Molecularweight


Melting Point (°C)

LogPVapour


Boscalid 343,2 4,6 143,3 2,96 0,00072

Fluopyram 396,8 15 117,5 3,3 0,0012



• Background

• Benzophenones

• SDHIs

• Strobilurins

• Triazoles

• Q&A session

Agenda




Answers to the questions raised in advance to the today‘s course

?


Uptake & Systemicity of FungicidesQuestion: Is there a transport to new leaves emerged after treatment or only to the leaf tipson already developed leaves or is there a transport through the leaf sheaths?

Answer: Theoretically, fungicides with episystemic properties can redistribute around existingleaves and to newly emerging leaves in the vapour phase

Influencing factors:

• phys-chem properties,• environmental conditions• (humdity, temperature, wind), • formulation, • Crop & canopy structure

TFS

TFS

TFS

TFS

UTC

UTCUTC

UTC

low

high

The establishment of a vapour phase activity in far mers field is not predictable, clearly



Answer: Theoretically, xylem-systemic fungicides are capable of moving to newly expaningand newly emerging growth as the wheat or barley crop develops

• This movement occurs via translaminar mobility to consecutive leaf layers and subsequent xylem systemicity within them and/or by direct physical ‚pick-up‘ from the leaf axils by thenewly emerging foliar tissue as it passes through the axil ‚reservoir‘.

• Influencing factors: phys-chem. properties, environmental conditions (rainfall, dew), formulation, crop

The transport of xylem-systemic fungicides to new l eaf levels is theoretically possible, depends however on certain influencing factors

Question: Is there a transport to new leaves emerged after treatment or only to the leaf tipson already developed leaves or is there a transport through the leaf sheaths?


low

highDistribution of 14C-labeled

Prothioconazole in soybeans

Dry plants Moistened plants

Uptake & Systemicity of FungicidesQuestion: Is there a transport to new leaves emerged after treatment or only to the leaf tipson already developed leaves or is there a transport through the leaf sheaths?

Moisture stimulates a redistribution of Prothiocona zole over the leaf as well as along the petiole and the stem. Consequently, the active can enter th e stem and is translocated to the apex.



Answer : NO, because of the complex interplay of various influencing factors


• Amount of a.i. bioavailable• disease pressure• occurring disease spectrum• epidemiology of fungal pathogens• environmental conditions (temparture, rainfall, dew, humidity)• variety (different canopy structure)• canopy size (area to be protected)• metabolic stability of compounds in plants• Distribution of compound in plant tissue

Biological tests under practical conditions are nee ded to have at least a basis for such a “guess”

Question: Can we use these information information to „guess“ how long time the effect of a spraying is lasting when we spray at different growth stages in cereals, grass seed andoilseed rape with different fungicides?



Answer :

Question: Why do we sometimes get scorch (phytotox) on leaves in cereals by use of triazoles

0

20

40

60

80

100

0 5 10 15 20 25

time (h)

pene

trat

ion

(%)


• environmental conditions• (heat, sunshine)• formulation (solvents, adjuvants)• application time• mixed application with other products

(liquid fertilizer, adjuvants, etc.) • variety

Penetration of the fungicide Tebuconazolethrough an isolated apple cuticle

10 °C

20 °C

30 °C

Thank you!Dr. Andreas Goertz

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