Major postharvest diseases of citrus in Californiacitrus in California

and their management

James E AdaskavegJames E. AdaskavegProfessor

Department of Plant Pathology and MicrobiologyUniversity of CaliforniaUniversity of California

Riverside, CA, USA

California citrus production- Over 100 000 ha: 70% of acreage is- Over 100,000 ha: 70% of acreage is

oranges, 17% is lemons- Ranking: g

- Oranges: 80% of US fresh market production

f d i- Lemons: 90% of US production- Tangerines, mandarins, clementines:

increasing acreageg g

- Major export markets: Canada, Asia, Japan Korea, Mexico

California citrus production

Navel oranges 135,000 A $452

Crop Acreage Value (x106)

- 94 million cartons ($7/carton)Valencia oranges 46,000 A $180

- 28 million cartons ($8/carton)Lemons 44,000 A $375

- 44 million cartons ($12/carton)Tangerines 14,000 A $59

- 7.4 million cartons ($11/carton)Grapefruit 11,500 A $79

- 12 million cartons ($7/carton)

Total Value $1.1 Billion

Important pre- and postharvest fungal diseases and disorders of citrus in Californiaand disorders of citrus in California

Disease CauseBrown rot Phytophthora spp.

Septoria spot Septoria citri

Anthracnose Colletotrichum gloeosporioides

Clear rot Green/Blue mold Penicillium sppClear rot, Green/Blue mold Penicillium spp.

Sour rot Galactomyces citri-aurantii

S /Bl d Al B hStem- /Blossom-end rot Alternaria, Botryosphaeria spp., etc.

MRD Environmental conditions

All are high-rainfall diseases – disease incidence in most years is relatively low.

Fruit decays initiated preharvest

B t d bAlternaria decay caused by Alternaria sp.

Brown rot caused by Phytophthora spp. Infection through intact tissue.

Tear stain and anthracnose caused by Colletotrichum gloeosporioides

Stem end rot caused by Botryodiplodia theobromae

Symptoms and signs of Septoria spot on orange fruit

Pycnidia are formed within the dark lesions.dark lesions. Conidia are exuded in spore tendrils.

Fruit decays initiated at or after harvest

Penicillium decays –decays wound pathogens

Green mold caused by Blue mold caused by

p g

Green mold caused by Penicillium digitatum(most important on citrus)

Penicillium italicum

citrus)

Penicillium soilage

Sour rot caused by Geotrichum citri-aurantiiPostharvest decays of citrus:

y

• Second most important postharvest disease ofpostharvest disease of citrus

• Pathogenic on ‘weak’, wounded, bruised, and split fruit

• Infects all citrus speciesInfects all citrus species but due to long-term storage is especially prevalent in lemons andprevalent in lemons and grapefruit.

• Chilling stimulates infection

Integrated Postharvest Disease Management

Posthar est deca control tili ing a ariet ofPostharvest decay control utilizing a variety of complementary disease management strategies.

May include but not limited to:• Handling procedures• Spore exclusion and sanitation• Use of sanitizers and fungicides• Temperature management • Monitoring inoculum levels and fungicide resistance

Postharvest fungicide treatments as a component of postharvest handling

Example: Lemons in California

Fruit arrival Sorting

Chlorine washChlorine wash, soda ash treatment, water rinse

Application of ppfungicide and fruit coating

Usage of borax, sodium carbonate (soda ash), and sodium bicarbonate in postharvest treatments of lemonsbicarbonate in postharvest treatments of lemons

Wash with chlorine d d

soda ash tankand detergent

Direction of fruit movement

Usage of borax, sodium b t ( d h)carbonate (soda ash),

and sodium bicarbonate in postharvest p

treatments of lemons

Treatment with heated soda ash

W t iWater rinse after soda ash treatment

Storage wax applicationPack wax application

Bulk Boxing, shipping, marketingpacking in

bins

marketing

Storage for up to 3

thmonths

S tiChlorine wash after storage Sorting

Fungicide and pack wax applicationBoxing and marketing

Current and future postharvest fungicides for decay control of citrus in the USy f

DMI-imidazolesBenzimidazolesPhenolsSodium Imazalil

(Deccocil, Freshgard, Fungaflor)

Thiabendazole (TBZ)

Sodium ortho-phenyl

phenate(SOPP)

Phenylpyrroles QoIsAnilino-

pyrimidines

(SOPP)

DMI-triazolesy py

Azoxystrobin*(Diploma)

Pyrimethanil*(P b t )

pyrimidines

Fludioxonil*(Graduate)

Propiconazole

* R d d i k f i id i EPA l ifi ti f ti id ith

(Diploma)(Penbotec) (Graduate)

2012-13 ?* Reduced risk fungicides is an EPA classification of a pesticide with:1) Low environmental impact 3) Compatible with IPM programs 2) Greater human and animal safety 4) Used at lower rates

Efficacy of old and new 'reduced-risk' fungicides against postharvest decays of citrusg p y

Fungicide Common Name

Green Mold*

Blue Mold Sour RotSporulation

Control

Imazalil Imazalil +++S/+R +++ -+++

Thiabendazole TBZ +++ -++++S/+R

SOPP SOPP ++ +-

Graduate/Pyrimethanil Penbotec +++ +++ -++

++S/+R

FludioxonilGraduate/Scholar +++ +++ -+++

Azoxystrobin Diploma +++ -+-Propiconazole ?

*- No multiple-resistance: Azoxystrobin, fludioxonil, and i h il ff i i d d b

Propiconazole(In development)

---- +++ +++++++?

pyrimethanil are effective against decay caused by TBZ- or imazalil-resistant Penicillium populations.

Current Challenges in Managing Postharvest Decays of Citrus in CaliforniaDecays of Citrus in California

Penicillium decays –Imazalil and TBZ: wide-spread resistance

Imazalil • Old EC formulations must be phased out new• Old EC formulations must be phased out, new

formulations must be phased into usage

New fungicidesNew fungicides • Codex MRLs and Japanese food usage tolerances

pending for azoxystrobin, fludioxonil, & pyrimethanilPropiconazole is being developed• Propiconazole is being developed

• Best usage strategies are being developed• Understanding resistance potential• Resistance management strategies need to be

implemented

Current Challenges in Managing Postharvest D f CitDecays of Citrus

Sour rot (Geotrichum citri-aurantii)–I d d t di f th bi lImproved understanding of the biology

• Biological and molecular species identification• Population dynamics• Understanding resistance potential

Propiconazole development • Efficacy and usage strategiesEfficacy and usage strategies

Septoria spot –Preharvest treatments for postharvest control pPostharvest treatments

Brown rot (Phytophthora spp.) –N t i lNew materials

Efficacy of new fungicides against Penicillium decaysagainst Penicillium decays

Understanding Performance: Contact vs. Systemicy

Timing of postTiming of post--inoculation treatments with Scholarinoculation treatments with Scholar

Control 9 h after inoculation

15 h after inoculation12 h after inoculation

Treatments with aqueous solutions of 1,000 ppm Scholar

15 h after inoculation12 h after inoculation

Time effect in controlling citrus green moldTime effect in controlling citrus green mold-- Treatments selected times after inoculation Treatments selected times after inoculation --

SInoculated fruit studies -• P. digitatum sensitive (top) or

resistant (bottom) to imazalil Fluand TBZ

• Spray treatments selected times after inoculationR

• Fungicides: each at 1,000 ppmFlu

Incidence of decay in the controls was >90%

Treatment time after inoculation (h)

Fungicides with systemic activity (azoxystrobin, imazalil, TBZ, pyrimethanil) have a longer post-infection activity than Scholar.

Sporulation Control and Optimizing treatment efficacy

Compatibility with fruit coatings

F ngicide application methodsFungicide application methods

Aqueous applicationa

d

ControlAzoxystrobin

Effect of fruit coatings Effect of fruit coatings on the efficacy of on the efficacy of

db

c

a

AzoxystrobinFludioxonil

Pyrimethanil

Imazalil

postharvest fungicides postharvest fungicides for sporulation controlfor sporulation controlInoculated fruit studies -• P. digitatum resistant to imazalil

and TBZ

Storage fruit coatinga

cControl

Azoxystrobin

• 30 sec dip treatment• Fungicides: each at 500 ppm• Storage coating: 1:15 dilution

0 1 2 3 4

cb

a

FludioxonilPyrimethanil

Imazalil

Sporulation Rating 0 1 2 3 4

Efficacy of Scholar and Diploma for sporulation

l i i dcontrol is increasedwhen applied in storage fruit coating.

Control Fludioxonil in storage coating

gPyrimethanil does not control sporulation.

Addition of sodium bicarbonate improves fungicide Addition of sodium bicarbonate improves fungicide efficacy and extends postefficacy and extends post--infection activityinfection activity

Control

Fludioxonil

SBC

a

c

b

Inoculated fruit studies -• Dip-treatments 14 or 24 h

after inoculationSBC

Fludioxonil + SBC

C t l

b

d 14 h

after inoculation• Fludioxonil at 500 ppm,

SBC at 3% (w/v)Control

Fludioxonil

SBC

a

b

b24 h

Fludioxonil + SBC0 20 40 60 80 100

Decay incidence (%)

c

Efficacy of Scholar is increased whenis increased when applied in mixture with sodium bi b t

Control Fludioxonil + SBC

bicarbonate

Application methods for postharvest fungicidepostharvest fungicide

treatmentsFlooderFlooder

CDA

Comparative efficacy of postharvestComparative efficacy of postharvestapplication methodsapplication methodspppp

Azoxystrobin

a

b

Drench

CDA/BrushesAzoxystrobin

a

b CDA/Rollers In-line drench (flooder) applicationsFludioxonil

a

b

b

applications provide the highest efficac

Pyrimethanil

0 2015105 25 30

b

b

efficacy.

Efficacies for each fungicide were compared to the least efficient application method

Standardized improved efficacy (%)

application method.Statistical comparisons of application methods were done for each fungicide.

Summary

1. Fungicide properties: contact vs. systemic –determines treatment timing

2. Anti-sporulation activity: important characteristic for stored fruit.

3. Mixtures of fungicides, or of fungicides with sanitizers or other treatments (e.g., SBC)

4. Application methods: Treatments are best done as staged postharvest applications - Aqueous

li ti f ll d b li ti i f itapplication followed by an application in fruit coating.

FUNGICIDE RESISTANCEFUNGICIDE RESISTANCE MANAGEMENT IN CITRUS

A Coordinated Effort for the Prevention of Fungicide Resistance with the WidespreadFungicide Resistance with the Widespread

Use of New Pre- and Postharvest Fungicides in CitrusFungicides in Citrus

All new fungicides including Scholar should beAll new fungicides, including Scholar, should be considered high risk for developing resistance.

Avoid what happened with TBZ and imazalil

Fungicide resistance management for postharvest decays of citrus fruitfor postharvest decays of citrus fruit

A high risk for resistance development in postharvest pathogens of citrus fruit:pathogens of citrus fruit:

• Treated fruit are sometimes stored for long periods and the pathogen is exposed to the fungicides.p g p g

• Sometimes repeated treatments of the same fruit lot

• The pathogens produceThe pathogens produce abundant spores.

• All postharvest fungicides are single-site mode of action materials.Many parallels to postharvest• Many parallels to postharvest aspects of pome fruit.

Resistance development in pathogen populationsRecipe for resistance development:

Resistance development

Recipe for resistance development:Large

amount of Low fungicide Repeated exposure + + development

is optimalpathogen propagules

gconcentration

pto the

fungicide+ + =

Populations of Penicillium spp. in packinghouse can

Sub-optimal application

method

Long-term exposure in storage.

Fruit re-packing andp gbe high.

Sporulation often not inhibited by

method. Equipment not

calibrated.Cost-saving.

Fruit re packing and second fungicide

application.

posth. fungicides.

Resistance management strategies target these factors by usingoptimal application methods fungicide mixtures and sanitation

g

optimal application methods, fungicide mixtures, and sanitation procedures that minimize the pathogen population that is being

exposed and the number of survivors after treatment.

Method for detecting rare resistant variants within a populationMethod for detecting rare resistant variants within a populationSelection plates amended with a fungicide Selection plates amended with a fungicide p gp g

concentration gradient used for airconcentration gradient used for air--samplingsampling

……

EC95 for mycelial growth Pds

P di it t Ai liP. digitatumradially streaked on a plate with afungicide conc

Air sampling plate with P.

digitatum (EC95concentrationfungicide conc.

gradient (e.g. imazalil)

concentration indicated)

Method for detecting rare resistant variants within a populationMethod for detecting rare resistant variants within a populationExposure of selection plates in a packinghouseExposure of selection plates in a packinghouseExposure of selection plates in a packinghouseExposure of selection plates in a packinghouse

Summary: Resistance potential and characterization of resistant isolates of P.

EC95

Fludioxonil PyrimethanilAzoxystrobin*

digitatum

Fludioxonil Pyrimethanil

Lab selection No Yes Yes

Azoxystrobin

Field selection

P th i it

No

/

Yes Yes

Resistance factor

Pathogenicity

-

-

HR ≥ 1,577 ppmMR = 3 – 26 ppm

++/+++

> 255

+++

Res. frequency -

MR 3 26 ppm

10-410-6 - 10-7

Codes: - : not applicable; +++: Highly pathogenic; ++: Moderately pathogenic.

* Isolates of P. italicum resistant to azoxystrobin were commonly found

Trends in postharvest fungicide registrations in the US:P i tPre-mixtures

Imidazole Anilinopyrimidine+ PhilabusterImidazoleImazalil

Anilinopyrimidinepyrimethanil

+ = Philabustercitrus - registered

PhenylpyrroleFludioxonil

QoIAzoxystrobin+ =

Graduate A+citrus - registered

Azoxy SBI CitrusFludioxonil Azoxy-strobin+ =+ Propicon-

azole

Citrus –in development

Use of fungicide mixtures: The resistance potential of fungicide mixtures is lower than for single active g g

ingredients

Single applications Mixture applications(i.e., Graduate A+)

• Resistance frequency of

Rfmix = 10-10- 10-11

• Resistance frequency ofpyrimethanil (Rfpyr): 10-4

Rfmix 10 10• Resistance frequency of

fludioxonil (Rffld): 10-6 - 10-7

Each application is still a selection event, but the

ud o o ( fld): 0 0

pp ,probability for changes to occur concurrently at independent loci is lower than for a single locus.

Septoria spot of citrus caused by Septoria citriA di f l f it d t i• A disease of leaves, fruit, and twigs of oranges, lemons, and grapefruit.

• Occurs in many citrus growing• Occurs in many citrus-growing countries

Early symptoms:Early symptoms:Small, irregular, pitted,

shallow lesions

Advanced symptoms:Dark lesions that extend into the albedo.

• Negotiations between USDAEconomic • Negotiations between USDA-APHIS/UC researchers and Korean officials in the fall of 2004.

importance of Septoria spot

• Further detection of diseased fruit in Korea could result in closure of

Septoria spot

this important export market.• Disease levels in export fruit have

t k t t b l t i ito kept to an absolute minimum.• Citrus industry representatives

thought the Septoria quarantinethought the Septoria quarantine was in retaliation against the US quarantine against Korean citrus because of citrus canker

NAVEK Program - Integrated approach to minimize the occurrence of Septoria spot on oranges for exportp p g p

Field applications with copper/zinc/lime1st application calendar-based

2nd and 3rd appl based on environmental conditions

Guidelines2 and 3 appl. based on environmental conditions

(using the Septoria Risk Assessment Model)

Survey of orchards for symptomatic f it b fi ld lColor Guides fruit by field personnel

Fruit sample evaluation for disease detection

Sampling Frequency, Sample Size, and HarvestGuidelinesFruit sample evaluation for disease detection

- Pre-screening, Incubation and Molecular assays -

Communication of res lts to CCQC

Detection procedures

results to CCQC, packinghouses, APHIS

Postharvest fungicide Guidelines

p

applications

Shipment requirements

Guidelines

Table 1. Summary of Septoria spot‐positive fruit lots detected in the CCIP or NAVEK programs and by the Korean National Plant Quarantine Service during the 2004/2005 to 2009/2010 seasonsto 2009/2010 seasons

KoreaIncidence of  Incidence of 

CCIP/NAVEK program

Season VarietyTotal samples processed

samples positive for Septoria spot (%)

samples positive for Septoria spot (%)

2004‐2005 Navel 2521 1.35 1.86Valencia 648 0 00 0 00Valencia 648 0.00 0.00

2005‐2006 Navel 4879 0.55 0.02Valencia 531 0.56 0.00

2006‐2007 Navel 3121 0.80 0.06Valencia 113 0.88 0.00

2007‐2008 Navel 4996 3.20 0.40Valencia 525 5.70 0.00

2008‐2009 Navel 3380 2.75 0.44/0.95*2008 2009 Navel 3380 2.75 0.44/0.95Valencia 182 0.85 1.10

2009‐2010 Navel 4286 1.31 0.07Valencia 135 0.00 0.00

*‐ The higher value includes 17 fruit lots declared positive by NPQS but that were disputed by NAVEK.

In vitro toxicity of fungicides against S. citri

Spiral gradient dilution assayFungicide EC50 mycelial

gro th

Mycelial strip

g growth

Azoxystrobin 0.01 ppmDifenoconazole 0.02 ppm

Conidial streak

TBZ 0 25Chlorothalonil 0.16 ppm

Imazalil 0.10 ppmMancozeb 0.06 ppm

TBZ Azoxystrobin

TBZ 0.25 ppmFludioxonil 0.45 ppm

Pyrimethanil >10 ppm

Among the fungicides evaluated, azoxystrobin, was the most effective material. (Azoxystrobin will be soon be registered for postharvest use on citrus in CA)on citrus in CA).

Evaluation of copper alternatives for management of Septoria spot of oranges

Control a

Septoria spot of oranges

Control

Kocide 2000 6 lb

Bravo 720 4 pints

a

ab

b Orange fruit were d d t t d

Bravo 720 6 pints

Ziram 76W 8 lb bb

wounded, treated, inoculated, and incubated for 7 weeks

20CDithane M45 8 lb0 5 10 15 20

b

Disease incidence (%)

at 20C.

Possible copper alternatives were identified.

Residue trials for chlorothalonil (Bravo Echo) were approvedResidue trials for chlorothalonil (Bravo, Echo) were approved for a possible registration on citrus.

The collision between regulatory agencies and the California citrus industryy

USDA-APHISAllow export of US commoditiesp

UCR

Citrus growers andNPQS – KoreaPrevent importation of

Citrus growers and associations, CCQC (California Citrus

a quarantine disease(Quality Council)Market citrus fruit

The collision between US and international regulatory agencies and US citrus industries

USDA-EPA New fungicide registrations (IR-4, New requirements for tolerances)

USDA-APHIS Allow export of US commoditiesFDC (Florida Dept.

of Citrus)CDFA (CA Dept. Food & Ag ) Allow

)Prevent importation of a quarantine disease

NPQS – Korea

Ag.) Allow export of CA commodities

diseaseUCR

NPQS KoreaPrevent importation of a quarantine disease

Citrus growers and associations, CCQC

Korean Dept. Food & Ag Revision ofquarantine disease , Q

(California Citrus Quality Council) Market citrus fruit

& Ag. Revision of standards & specs for food (MRLs)

National and international tolerances of postharvest fungicides on citrus

Fungicide Active

Trade Name Ingredient Codex US Japan KoreaHong Kong Taiwan

Tolerance/MRL (ppm) – Lemon, Orange, Grapefruit

Tradi-TBZ Thiabendazole 7,7,7 10,10,10 10,10,10 10,10,10 Codex 10,10,10

Deccocil, Fungaflor, Freshgard

Imazalil 5,5,5 10,10,10 5,5,5 5,5,5 Codex 2,2,2

Traditional

Freshgard

SOPP Sodium o-phenylphenol 10,10,10 10,10,10 10,10,10 10,10,10 Codex 10,10,10

SBC Sodium bicarbonatebicarbonate

Diploma Azoxystrobin 15,15,15 10,10,10 No FA 0.5,0.5,0.5 Codex 1,1,1

Graduate Fludioxonil 10 10 10 10 1 10 No FA 0 5 0 5 0 5 Codex 1 1 1

NewGraduate Fludioxonil 10,10,10 10,1,10 No FA 0.5,0.5,0.5 Codex 1,1,1

Graduate A+ Azoxystrobin/ Fludioxonil

15,15,15/ 10,10,10 see above No FA 0.5,0.5,0.5 /

0.5,0.5,0.5 Codex 1,1,1 / 1,1,1

P b t P i th il 7 7 7 11 10 10 N FA 0 5 0 5 0 5 C dPenbotec Pyrimethanil 7,7,7 11,10,10 No FA 0.5,0.5,0.5 Codex -,-,-

Philabuster Pyrimethanil/ Imazalil 7,7,7/ 5,5,5 11,10,10/

10,10,10 No FA 0.5,0.5,0.5 / 5,5,5 Codex -,-,- /

2,2,2

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