Update on Managing Citrus Black Spot, Citrus Canker, andPostbloom Fruit Drop

Megan M. DewdneyAssociate Professor of Plant Pathology and Extension Specialist University of Florida, IFASCitrus Research and Education Center

CITRUS CANKER

What is new in the Production guide?o Actigardo Not a traditional pesticide

– Plant activator that triggers natural defense mechanism called systemic acquired resistance (SAR)

– No direct effect against pathogenso Activates plant defense system prior to diseaseo Active ingredient: Acibenzolar‐S‐methyl

– Group 21 fungicide mode of action• Not a reference to efficacy against bacteria

Actigard trialso Conducted by Jim Grahamo Recently registered for use on

citrus in Floridao Intended to supplement copper

applications for fruit protection– Some foliar activity on non-

bearing trees

Chemical versus natural induction of SARo Can be naturally or chemically induced

– Natural induction is caused by a low level of plant pathogen attack

– Systemic throughout the planto Disease can develop before natural induction

becomes effectiveo High inoculum levels can overcome activationo Chemical induction has the advantage of being

able to occur before disease onset– Apply in anticipation of disease

Application dates for non-bearing trials (2 year-old ‘Vernia’)

Treatment Rate per tree

# of apps 2011

Untreated control ‐‐‐ ‐‐‐ ‐‐‐Actigard drench (0.007 oz) 4 4/1, 6/1, 7/29, 9/20Actigard micro‐sprinkler

(0.007 oz) 4 4/1, 6/1, 7/29, 9/20

PlatinumActigard drenchAdmire Pro

(0.035 fl oz)(0.007 oz)(0.046 fl oz)

232

4/1, 8/34/28, 6/1, 7/136/1, 7/29

Actigard drenchKocide 3000 spray

(0.007 oz)(0.0667 oz)

410

4/1, 6/1, 7/29, 9/20Every 21 days from 4/1 to 10/5

Kocide 3000 spray (0.0667 oz) 10 Every 21 days from 4/1 to 10/5

Graham and Myers, 2013 Crop Protection

Non-bearing trial 2011 ‘Vernia’

0

10

20

30

40

50

60

70

UTC Actigarddrench

Actigardsprinkler

Platinum,Actigard,Admire

Actigarddrench,

Kocide spray

Kocide spray

% le

aves

a

c

b

c cc

Graham and Myers, 2013 Crop Protection

Trees rated in October

Application dates for bearing trial on 7 year-old ‘Ruby red’ grapefruit Treatment # of

appsPer tree rate

Application dates (2015)

Untreated control ‐‐‐ ‐‐‐ ‐‐‐Actigard drench 4 0.031 3/16, 5/15, 7/15, 9/15Actigard drenchKocide 3000 spray

410

0.0310.459

3/16, 5/15, 7/15, 9/15Every 21 days from 3/16 to 9/21

Kocide 3000 spray 10 0.459 Every 21 days from 3/16 to 9/21

Bearing trial on 7 year-old ‘Ruby red’ grapefruit in 2015 (>8 ft. tall)

0

10

20

30

40

50

60

70

UTC Actigard Actigard, Kocide Kocide

% fr

uit w

ith le

sion

s

totaloldyoung

Fruit evaluated October 13a

a

ab

b

bc c

bc

b

b

b

Jim Graham

Actigard use recommendations

o New plantings (0‐3 year‐old trees)– Start as first growth beginning and continue non‐

bearing cycle– Soil applied neonicotinoid insecticides can induce

SAR and can be alternated with Actigard– Use other canker management methods as well– Maintain SAR throughout season

o Objective to limit the establishment of canker during juvenile phase

Actigard use recommendationso Young and mature bearing plantings

– Initiate post‐bloom, prior to conditions favorable to canker

– Use other canker management methods as well– 4‐5 year‐old trees

• Continue throughout spring, summer, and fall on 30‐60 day intervals depending on tree size and planting density

– 6+ year‐old trees • Continue throughout summer on 30‐45 day intervals

depending on tree size and planting density

o Can limit foliar lesion development and reduces inoculum potential

POSTBLOOM FRUIT DROP

Buttons in 0.25m2/tree sideJanuary 12-17, 2017

Valencia Old Buttons Fort Meade 2017

Fungicide treatment

Rhyme + Ferbam + Cohere

Luna Experience + Activator 90Topsin M

Topguard + Ferbam + Cohere

Luna Sensation + Activator 90 UTCPristine

Priaxor 9 + Cohere

Topguard 5 + Cohere

Rhyme + Cohere

Luna Sensation + Ferbam + Activator 90

Priaxor 11 + Cohere

Topguard 8 + Cohere

Luna SensationEndura

Quadris Top

Num

ber o

f old

but

tons

per

tree

sid

e (0

.25

m2 )

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45

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Trial detailso Valencia oranges in Fort Meade area

– Infected with HLB but relatively healthy– Off‐season bloom on most trees– Trees in block were slow to bloom compared to

others in area– Trees selected for uniform disease pressure

• HLB and PFD

o Applications made on recommendation of PFD model

o Applications on March 24

PFD trials 2017 – ValenciaProduct Active Ingredient Rate/acreRhyme 2.08 SC Cohere

Flutriafol 5 oz.16 fl oz.

Rhyme 2.08 SCFerbam GranufloCohere

FlutriafolFerbam

7 oz.5 lb16 fl oz.

Topguard EQ 4.3SC Cohere

Flutriafol + azoxystrobin 5 oz.16 fl oz.

Topguard EQ 4.3SCCohere

Flutriafol + azoxystrobin 8 oz.16 fl oz.

Topguard EQ 4.3SCFerbamCohere

Flutriafol + azoxystrobinFerbam

5 oz.5 lb16 fl oz.

Pristine Pyraclostrobin + boscalid 18.5 oz.Endura boscalid 6.5 oz.PriaxorCohere

Pyraclostrobin + fluxapyroxad 9 fl oz.16 fl oz.

PFD trials 2017 – Valencia cont.Product Active Ingredient Rate/acrePriaxorCohere

Pyraclostrobin + fluxapyroxad 11 fl oz.16 fl oz.

Topsin M Thiophanate‐methyl 2.0 lbLuna Sensation Trifloxystrobin + fluopyram 6.5 fl oz.Luna SensationActivator 90

Trifloxystrobin + fluopyram 6.5 fl oz.0.25% v/v

Luna SensationFerbamActivator 90

Trifloxystrobin + fluopyramFerbam

6.5 fl oz.5 lb0.25% v/v

Luna ExperienceActivator 90

Tebuconazole + fluopyram 8 fl oz.0.25% v/v

Quadris Top Azoxystrobin + difenoconazole 15.4 fl oz.Untreated control ‐‐ ‐‐

Buttons in 0.25m2/tree sideJune 5-6, 2017

Valencia New Buttons Fort Meade 2017

Fungicide treatment

Topgd. + Ferb. + Coh.

Luna Sen.+ Ferb. + Act.Topsin M

Rhyme + Ferbam + Cohere UTC

Luna SensationPristine

Topguard 5 + Cohere

Priaxor 11 + Cohere

Luna Experience + Activator 90

Rhyme + Cohere

Priaxor 9 + Cohere

Topguard 8 + CohereEndura

Luna Sensation + Activator 90

Quadris Top

Num

ber o

f new

but

tons

per

tree

sid

e (0

.25

m2 )

0

2

4

6

8

10

12

14

16

18

20

22

No Signficant Differences

Number of fruit/tree sideJuly 20-27, 2017

Valencia Fruit Fort Meade 2017

Fungicide treatment

Endura

Topguard 5 + Cohere

Luna Sensation

Rhyme + Ferbam + Cohere

Rhyme + Cohere

Quadris Top

Luna Experience + Activator 90Topsin M

Topguard + Ferbam + Cohere UTCPristine

Priaxor 9 + Cohere

Priaxor 11 + Cohere

Topguard 8 + Cohere

Luna Sensation + Ferbam + Activator 90

Luna Sensation + Activator 90

Num

ber o

f fru

it pe

r tre

e si

de

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Conclusionso Weather was very dry for major bloomo Significant differences in the number of

buttons prior to trial initiation despite random selection

o The number of buttons for 2017 did not have significant differences

o Most treatments did not have significantly more fruit than UTC– Likely because of low disease pressure

Buttons in 0.25m2/tree sideJanuary 26-27, 2017

Navel Old Buttons Polk City 2017

Fungicide treatment

Headline + Ferbam 6Abound

Headline + Ferbam 4 UTC

Quadris Top + Abound + activator 90

Abound + activator 90Headline

Quadris Top + Abound

Headline + Ferbam 5Ferbam 5

Ferbam 6

Num

ber o

f old

but

tons

per

tree

sid

e (0

.25

m2 )

0

5

10

15

20

25

A ABABC ABC ABC A-D A-D

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Trial detailso Navel oranges in Polk City area

– Heavily infected with HLB– Off‐season bloom on most trees– Trees hedged on one side in January

• Consequence bloom not consistent on trees but majority at end of March

• Bloom very long on trees– Trees selected for uniform disease pressure

• HLB and PFD but more trees collapsed this year

o Applications made on recommendation of PFD model

o Applications on March 14 and 26

PFD trials 2017 – Navels Product Active Ingredient Rate/acreAbound Azoxystrobin 15.5 fl oz.

AboundActivator 90

Azoxystrobin 15.5 fl oz.0.25% v/v

Quadris TopAbound

Azoxystrobin + difenoconazoleAzoxystrobin

15.4 fl oz.3.2 fl oz.

Quadris TopAboundActivator 90

Azoxystrobin + difenoconazoleAzoxystrobin

15.4 fl oz.3.2 fl oz.0.25% v/v

Headline Pyraclostrobin 15 fl oz.

HeadlineFerbam

PyraclostrobinFerbam

15 fl oz.4 lb

HeadlineFerbam

PyraclostrobinFerbam

15 fl oz.5 lb

HeadlineFerbam

PyraclostrobinFerbam

15 fl oz.6 lb

Ferbam Granuflo Ferbam 5 lb

Ferbam Granuflo Ferbam 6 lb

Untreated control ‐‐ ‐‐

Buttons in 0.25m2/tree sideMay 19-22, 2017

Navel New Buttons Polk City 2017

Fungicide treatment

Headline + Ferbam 4Abound

HeadlineFerbam 5 UTC

Abound + activator 90

Headline + Ferbam 5

Headline + Ferbam 6Ferbam 6

Quadris Top + Abound

Quadris Top + Abound + activator 90

Num

ber o

f new

but

tons

per

tree

sid

e (0

.25

m2 )

0

2

4

6

8

10

12

14

16

18

20

22

24

26

No Signficant Differences

Number of fruit/tree sideJuly 19-20, 2017

Navel Fruit Polk City 2017

Fungicide treatment

Headline + Ferbam 6

Headline + Ferbam 4Headline

Headline + Ferbam 5 UTC

Quadris Top + Abound + activator 90

Abound + activator 90

Quadris Top + AboundFerbam 5

AboundFerbam 6

Num

ber o

f fru

it pe

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Conclusionso Significant differences in the number of

buttons prior to trial initiation despite random selection

o The number of buttons from 2017 infectionhad no significant differences

o Some treatments significantly better than UTC

o Ferbam is still best when mixed with other fungicides– See poster to for details on economic benefit

Any Questions?