USE OF FOLIAR APPLICATIONS OF

PHOSPHONATE FUNGICIDE TO CONTROL

PHYTOPHTHORA ROOT ROT IN AVOCADOS

USE OF FOLIAR USE OF FOLIAR APPLICATIONS OF APPLICATIONS OF

PHOSPHONATE FUNGICIDE PHOSPHONATE FUNGICIDE TO CONTROL TO CONTROL

PHYTOPHTHORA ROOT ROT PHYTOPHTHORA ROOT ROT IN AVOCADOSIN AVOCADOS

Tony Whiley, John Leonardi, Ken Pegg and Peter Langdon, Queensland Horticulture

Institute

TonyTony WhileyWhiley, John, John LeonardiLeonardi, Ken, Ken PeggPegg and and Peter Langdon, Queensland Horticulture Peter Langdon, Queensland Horticulture

InstituteInstitute

• Infection causes a decline in tree health with an associated loss in yield and fruit quality

•• Infection causes a decline in Infection causes a decline in tree health with an associated tree health with an associated loss in yield and fruit qualityloss in yield and fruit quality

• Phytophthora root rot is a significant root disease of avocados growing in all states of Australia and throughout New Zealand

•• Phytophthora root rot is a Phytophthora root rot is a significant root disease of significant root disease of avocados growing in all states of avocados growing in all states of Australia and throughout New Australia and throughout New ZealandZealand

• In 1987 a 20% formulation of mono-dipotassium phosphonate (Fosject ) was registered for trunk injection or

as a 0.1% foliar spray to control Phytophthora root rot

•• In 1987 a 20% formulation of monoIn 1987 a 20% formulation of mono--dipotassium phosphonatedipotassium phosphonate ((FosjectFosject ) ) was registered for trunk injection or was registered for trunk injection or

as a 0.1% foliar as a 0.1% foliar spray to control spray to control Phytophthora Phytophthora root rotroot rot

• Good commercial control has been achieved with 1-2 trunk-injection treatments/year

•• Good commercial control has been Good commercial control has been achieved with 1achieved with 1--2 trunk2 trunk--injection injection treatments/yeartreatments/year

• The 0.1% foliar spray has not given good control of root rot in mature, fruiting trees

•• The 0.1% foliar spray has not The 0.1% foliar spray has not given good control of root rot in given good control of root rot in mature, fruiting treesmature, fruiting trees

• Increased labour costs have made trunk-injection an expensive management procedure

•• Increased labour costs have made Increased labour costs have made trunktrunk--injection an expensive injection an expensive management proceduremanagement procedure

• The development of new technology for phosphonate application was commission by the Australian avocado industry in 1997

•• The development of new technology The development of new technology forfor phosphonatephosphonate application was application was commission by the Australian commission by the Australian avocado industry in 1997avocado industry in 1997

• Soil application through fertigation•• Soil application throughSoil application through fertigationfertigation

• Foliar application with formulations of increased concentrations

•• Foliar application with formulations Foliar application with formulations of increased concentrationsof increased concentrations

• Soil application was discarded due to:

•• Soil application was discarded Soil application was discarded due to:due to:

• Leaching•• LeachingLeaching

•• Potential increasedPotential increasedphosphonatephosphonate tolerancetolerance

•• Rapid oxidation (PORapid oxidation (PO33 POPO44))

Tolerance of P. cinnamomi toPhosphonic Acid

Tolerance of Tolerance of P.P. cinnamomicinnamomi totoPhosphonicPhosphonic AcidAcid

0

10

20

30

40

50

60

70

80

50 100 500 1000 >1000

UntreatedTreated

0

10

20

30

40

50

60

70

80

50 100 500 1000 >1000

UntreatedTreated

Source: Duvenhage (1994); Weinert et al. (1997) Source: Duvenhage (1994);Source: Duvenhage (1994); WeinertWeinert et alet al. (1997) . (1997) In vitro phosphonic acid conc. (µµµµg/mL)In vitroIn vitro phosphonicphosphonic acid conc. (acid conc. (µµµµµµµµg/g/mLmL))

%ag

e of

P.c

inna

mom

iiso

late

s%

age

of

%ag

e of

P.P.

cinn

amom

ici

nnam

omi i

sola

tes

isola

tes

In this paper we describe results from research into foliar application of new formulations ofPhosphonate fungicide

In this paper we describe In this paper we describe results from research into results from research into foliar application of new foliar application of new formulations offormulations ofPhosphonatePhosphonate fungicidefungicide

The research into foliar-appliedphosphonate has examined:

The research into foliarThe research into foliar--appliedappliedphosphonatephosphonate has examined:has examined:

• Efficacy•• EfficacyEfficacy• Phytotoxicity•• PhytotoxicityPhytotoxicity

• Fruit residues•• Fruit residuesFruit residues

• Withholding periods•• Withholding periodsWithholding periods• Application methodology•• Application methodologyApplication methodology

• Phosphonate storage•• PhosphonatePhosphonate storagestorage

Experimental SitesExperimental SitesExperimental Sites

• Childers•• ChildersChilders• Duranbah•• DuranbahDuranbah• Pemberton•• PembertonPemberton

• Commercial orchards• Hass•• Commercial orchardsCommercial orchards•• HassHass

Experimental TreatmentsExperimental TreatmentsExperimental Treatments

• Foliar 0.1% phosphonate•• Foliar 0.1%Foliar 0.1% phosphonatephosphonate

• Foliar 0.5% phosphonatewith pH adjusted

•• Foliar 0.5%Foliar 0.5% phosphonatephosphonatewith pH adjustedwith pH adjusted

• Foliar 1.0% phosphonatewith pH adjusted

•• Foliar 1.0%Foliar 1.0% phosphonatephosphonatewith pH adjustedwith pH adjusted

• Trunk-injectedphosphonate (20 & 40%)

•• TrunkTrunk--injectedinjectedphosphonatephosphonate (20 & 40%)(20 & 40%)

PhytotoxicityPhytotoxicityPhytotoxicity

• Previous problems with foliar-applied Aliette

•• Previous problems with Previous problems with foliarfoliar--appliedapplied AlietteAliette

• Higher concentrations of product being evaluated

•• Higher concentrations of Higher concentrations of product being evaluatedproduct being evaluated

• Suitability for use as a tank-mix with other pesticides

•• Suitability for use as a tankSuitability for use as a tank--mix with other pesticidesmix with other pesticides

• Tank mix at pH 7.2•• Tank mix at pH 7.2Tank mix at pH 7.2• No surfactant or stickers•• No surfactant or stickersNo surfactant or stickers

• No copper hydroxide•• No copper hydroxideNo copper hydroxide• Do not apply as a tank mix

with other pesticides•• Do not apply as a tank mix Do not apply as a tank mix

with other pesticideswith other pesticides

• 0.5% safer than 1.0%•• 0.5% safer than 1.0%0.5% safer than 1.0%

PhytotoxicityPhytotoxicityPhytotoxicity

EfficacyEfficacyEfficacy

• Phosphonic acid root concentration (20-50 mg/kgfw)

•• PhosphonicPhosphonic acid root acid root concentration (20concentration (20--50 mg/50 mg/kgkgfwfw))

• Improvement in tree health (0 -10 scale)

•• Improvement in tree health Improvement in tree health (0 (0 --10 scale)10 scale)

Treatments Root mass % healthy roots Tree health(1-3) (0-10)

Untreated 1.7 50.0 2.8Worm casts 1.3 74.5 3.8PO3 at 0.1% 2.3 73.0 2.0PO3 at 0.5% 2.5 91.0 1.6PO3 at 1.0% 2.3 90.0 1.6Injected PO3 2.5 85.0 1.0

Treatments Root mass % healthy roots Tree health(1-3) (0-10)

Untreated 1.7 50.0 2.8Worm casts 1.3 74.5 3.8PO3 at 0.1% 2.3 73.0 2.0PO3 at 0.5% 2.5 91.0 1.6PO3 at 1.0% 2.3 90.0 1.6Injected PO3 2.5 85.0 1.0

Tree & Root Health after PO3 Sprays (1999)

Tree & Root Health after PO3 Sprays (1999)

Duranbah (1999)Duranbah (1999)Duranbah (1999)

Improvement in Tree Health Following Foliar PhosphonateImprovement in Tree Health Improvement in Tree Health

Following FoliarFollowing Foliar PhosphonatePhosphonate

Childers (1999/00)Childers (1999/00)Childers (1999/00)

Treatments Health Improvement(0-10)

Control -2.8 aPO3 @ 0.1% -0.4 bPO3 @ 0.25% + Bion 1.6 cPO3 @ 0.5% 1.6 cPO3 @ 0.5% + Bion 1.0 cPO3 @ 1.0% 1.6 cTrunk-injected PO3 @ 20% 1.2 c

TreatmentsTreatments Health ImprovementHealth Improvement(0(0--10)10)

ControlControl --2.8 2.8 aaPOPO33 @ 0.1%@ 0.1% --0.4 0.4 bbPOPO33 @ 0.25% +@ 0.25% + BionBion 1.6 1.6 ccPOPO33 @ 0.5%@ 0.5% 1.6 1.6 ccPOPO33 @ 0.5% +@ 0.5% + BionBion 1.0 1.0 ccPOPO33 @ 1.0%@ 1.0% 1.6 1.6 ccTrunkTrunk--injected POinjected PO3 3 @ 20%@ 20% 1.2 1.2 cc

Root PO3 Conc. 2 & 4 Weeks after Spraying

Root PORoot PO33 Conc. 2 & 4 Weeks Conc. 2 & 4 Weeks after Sprayingafter Spraying

Treatments PO3 conc. (mg/kg)2 weeks 4 weeks

Untreated 0.6 b 0.7 cPO3 at 0.1% 5.3 b 9.0 cPO3 at 0.5% 26.8 a 38.3 ab

PO3 at 1.0% 37.7 a 50.9 aInjected PO3 not treated 31.6 b

Treatments PO3 conc. (mg/kg)2 weeks 4 weeks

Untreated 0.6 b 0.7 cPO3 at 0.1% 5.3 b 9.0 cPO3 at 0.5% 26.8 a 38.3 ab

PO3 at 1.0% 37.7 a 50.9 aInjected PO3 not treated 31.6 b

Maleny (1999)Maleny (1999)

Trunk injection is 138% more efficient

than spray application

Trunk injection is Trunk injection is 138% more efficient 138% more efficient

than spray applicationthan spray application

20

40

60

80

100

120

T-i 20%

PO3T-i 4

0% PO3

Foliar

0.5-1

% PO3

P-Foliar

0.5-1%

PO3

20

40

60

80

100

120

T-i 20%

PO3T-i 4

0% PO3

Foliar

0.5-1

% PO3

P-Foliar

0.5-1%

PO3

Yie

ld (k

g/tr

eeY

ield

(kg/

tree

Yie

ld (k

g/tr

ee

Pemberton (1999/00)Pemberton (1999/00)Pemberton (1999/00)

Effect of Phosphonate on Hass Yield

Effect ofEffect of PhosphonatePhosphonate on on Hass YieldHass Yield1.61.6 1.81.8 2.72.7

0.70.7

Fruit ResiduesFruit Residues

• Maximum Residue Level (MRL) for avocados in Australia is 100 mg/kg - it varies between countries

•• Maximum Residue Level (MRL) Maximum Residue Level (MRL) for avocados in Australia is 100 for avocados in Australia is 100 mg/kg mg/kg -- it varies between countriesit varies between countries

• Fruit residues are influenced by:•• Fruit residues are influenced by:Fruit residues are influenced by:• Time of application •• Time of application Time of application

0

25

50

75

100

125

150

175

3rd Nov 30th Jan 16th July0

25

50

75

100

125

150

175

3rd Nov 30th Jan 16th July

Foliar applicationFoliar application

Fruit ResiduesTime of Application

Fruit ResiduesFruit ResiduesTime of ApplicationTime of Application

Phos

phon

icPh

osph

onic

acid

con

c. (m

g/kg

)ac

id c

onc.

(mg/

kg) 3-5 mm33--5 mm5 mm

1/3 grown1/3 grown1/3 grownMatureMatureMature

Fruit ResiduesFruit Residues

• Maximum Residue Level (MRL) for avocados in Australia is 100 mg/kg

•• Maximum Residue Level (MRL) Maximum Residue Level (MRL) for avocados in Australia is 100 for avocados in Australia is 100 mg/kg mg/kg

• Fruit residues are influenced by:•• Fruit residues are influenced by:Fruit residues are influenced by:• Time of application •• Time of application Time of application

• Crop load •• Crop load Crop load

30

40

50

60

70

80

0 50 100 150 20030

40

50

60

70

80

0 50 100 150 200

r2 = 0.96rr22 = 0.96= 0.96

Yield (kg/tree)Yield (kg/tree)Yield (kg/tree)

Roo

tpho

spho

nic

acid

con

c. (m

g/kg

)R

oot

Roo

t pho

spho

nic

phos

phon

icac

id c

onc.

(mg/

kg)

acid

con

c. (m

g/kg

)

Sprayed with 0.5%phosphonateSprayed with 0.5%Sprayed with 0.5%phosphonatephosphonate

Fruit ResiduesCrop Load

Fruit ResiduesFruit ResiduesCrop LoadCrop Load

MeanMean PhosphonicPhosphonicAcid Residue in Fruit Acid Residue in Fruit

52.8 mg/kg52.8 mg/kg

Withholding PeriodWithholding Period

• Requirement of NRA•• Requirement of NRARequirement of NRA

• Establishes minimum time between treatment and harvest

•• Establishes minimum time Establishes minimum time between treatment and harvestbetween treatment and harvest

Mature Fruit PO3 Concentrationafter Spraying Phosphonate

Mature Fruit PO3 Concentrationafter Spraying Phosphonate

0

1

2

3

4

0 0.5 10

1

2

3

4

0 0.5 1Concentration of foliar spray (%)Concentration of foliar spray (%)

Phos

phon

icPh

osph

onic

acid

con

c. (m

g/kg

)ac

id c

onc.

(mg/

kg)

Mature Fruit PO3 Concentrationafter Spraying Phosphonate

Mature Fruit PO3 Concentrationafter Spraying Phosphonate

0

1

2

3

0.08 1 3 7 140

1

2

3

0.08 1 3 7 14Phos

phon

icPh

osph

onic

acid

con

c. (m

g/kg

)ac

id c

onc.

(mg/

kg)

Days after applicationDays after application

Application Application MethodologyMethodology

High volume (1500 L/ha)High volume (1500 L/ha)

Low volume (600 L/ha)Low volume (600 L/ha)

HighHigh vsvs Low Volume Low Volume ApplicationApplication

0

5

10

15

20

25

High Low Low x 20

5

10

15

20

25

High Low Low x 2

High = 60 g/treeLow = 25 g/treeHigh = 60 g/treeHigh = 60 g/treeLow = 25 g/treeLow = 25 g/tree

Application rateApplication rateApplication rate

Roo

tR

oot p

hosp

honi

cph

osph

onic

acid

con

c.ac

id c

onc.

(mg/

kg)

(mg/

kg)

Application MethodologyTreatment Timing

Application MethodologyApplication MethodologyTreatmentTreatment TimingTiming

Gro

wth

Gro

wth

Gro

wth

Spring Summer Autumn WinterSpringSpring SummerSummer AutumnAutumn WinterWinter

Application MethodologyTreatment Timing

Application MethodologyApplication MethodologyTreatmentTreatment TimingTiming

Gro

wth

Gro

wth

Gro

wth

Spring Summer Autumn WinterSpringSpring SummerSummer AutumnAutumn WinterWinter

Application MethodologyTreatment Timing

Application MethodologyApplication MethodologyTreatmentTreatment TimingTiming

• Phosphonic acid is phytotoxic to pollen germination and growth

•• PhosphonicPhosphonic acid isacid is phytotoxicphytotoxic to to pollen germination and growthpollen germination and growth

• > 400 mg/kg PA in flowers reduces the number of pollen tubes reaching the ovaries

•• > 400 mg/kg PA in flowers reduces > 400 mg/kg PA in flowers reduces the number of pollen tubes reaching the number of pollen tubes reaching the ovariesthe ovaries

• Yield reduction may occur•• Yield reduction may occurYield reduction may occur

Crop Load Affects RootPhosphonic Acid Concentration

Crop Load Affects RootCrop Load Affects RootPhosphonicPhosphonic Acid ConcentrationAcid Concentration

10

20

30

40

50

60

70

100 120 140 160 180 20010

20

30

40

50

60

70

100 120 140 160 180 200

rr22 = 0.98= 0.98

Yield (kg/tree)Yield (kg/tree)Yield (kg/tree)

Roo

tR

oot p

hosp

honi

cph

osph

onic

acid

con

c. (m

g/kg

)ac

id c

onc.

(mg/

kg)

Maleny (1999)Maleny (1999)

Phosphonate StoragePhosphonate Phosphonate StorageStorage• Claims made that phosphonate

deteriorated in storage after 90 days

•• Claims made thatClaims made that phosphonatephosphonatedeteriorated in storage after 90 deteriorated in storage after 90 daysdays

• Investigated stability ofphosphonate in sealed containers that were filled or half-filled and stored for 6 months

•• Investigated stability ofInvestigated stability ofphosphonatephosphonate in sealed containers in sealed containers that were filled or halfthat were filled or half--filled and filled and stored for 6 monthsstored for 6 months

• Phosphonate oxidises from PO3to PO4

•• PhosphonatePhosphonate oxidises from POoxidises from PO33to POto PO44

DaysDaysDays

250

300

350

400

0 191

Full sealHalf seal

250

300

350

400

0 191

Full sealHalf seal

PO3

Con

c. (m

g/kg

)POPO

33C

onc.

(mg/

kg)

Con

c. (m

g/kg

)Phosphonate StoragePhosphonatePhosphonate StorageStorage

ConclusionsConclusions• Foliar applied phosphonate at 0.5%

a.i. will give commercial control of Phytophthora root rot in mature trees

•• Foliar appliedFoliar applied phosphonatephosphonate at 0.5% at 0.5% a.i. will give commercial control of a.i. will give commercial control of Phytophthora root rot in mature treesPhytophthora root rot in mature trees

• Application frequency will vary depending on numerous factors and may be managed through monitoringphosphonic acid in roots

•• Application frequency will vary Application frequency will vary depending on numerous factors and depending on numerous factors and may be managed through monitoringmay be managed through monitoringphosphonicphosphonic acid in rootsacid in roots

ConclusionsConclusions• To reduce the risk of phytotoxicity•• To reduce the risk ofTo reduce the risk of phytotoxicityphytotoxicity

• Don’t add wetting agent or spreader•• Don’t add wetting agent or spreaderDon’t add wetting agent or spreader

• Use copper oxychloride for anthracnose control

•• Use copper oxychloride for Use copper oxychloride for anthracnose controlanthracnose control

• The tank solution should be adjusted to pH 7.2

•• The tank solution should be adjusted to The tank solution should be adjusted to pH 7.2pH 7.2

• Don’t mix with other pesticides•• Don’t mix with other pesticidesDon’t mix with other pesticides

ConclusionsConclusions• Spring and summer flush maturity

are the two most effective treatment times

•• Spring and summer flush maturity Spring and summer flush maturity are the two most effective treatment are the two most effective treatment timestimes

• It is the number of grams of product applied per tree that is critical in providing protection

•• It is the number of grams of product It is the number of grams of product applied per tree that is critical in applied per tree that is critical in providing protectionproviding protection

• Phosphonate fungicide is a stable product provided it is stored in a sealed container

•• PhosphonatePhosphonate fungicide is a stable fungicide is a stable product provided it is stored in a product provided it is stored in a sealed containersealed container

AcknowledgmentsAcknowledgmentsAcknowledgmentsWe wish to thank the following for financial support to carry out the research presented in this paper:Australian Avocado Growers FederationHorticulture AustraliaQueensland Horticulture Institute

We wish to thank the following for financial We wish to thank the following for financial support to carry out the research presented in support to carry out the research presented in this paper:this paper:Australian Avocado Growers FederationAustralian Avocado Growers FederationHorticulture AustraliaHorticulture AustraliaQueensland Horticulture InstituteQueensland Horticulture Institute

We also thank John Dorrian, Spencer Gray, Graham Anderson, Graeme Thomas and Wayne Franceschi for their contribution to the research program. Dr CliveKaiser provided concepts that assisted with the research program and Phil Hargreaves of DNR carried out thephosphonic acid analyses

We also thank JohnWe also thank John DorrianDorrian, Spencer, Spencer GrayGray, Graham , Graham Anderson, Graeme Thomas and WayneAnderson, Graeme Thomas and Wayne FranceschiFranceschi for for their contribution to the research program. Dr their contribution to the research program. Dr CliveCliveKaiser provided concepts that assisted with the research Kaiser provided concepts that assisted with the research program and Philprogram and Phil HargreavesHargreaves of DNR carried out theof DNR carried out thephosphonicphosphonic acid analysesacid analyses