Fungal Diseases of Citrus Fruit and Foliage

Megan Dewdney PMA 5205 Foliar Fungal Diseases to be Covered

oAlternaria Brown Spot (and leaf spot of rough lemon) oGreasy spot oMelanose oScab Diseases oBlack Spot oPostbloom Fruit Drop oPseudocercospera Fruit and Leaf Spot What Is a Fungus?

oEukaryotic microorganisms and members of Kingdom Fungi oAbsorb dissolved molecules as food sources Generally secrete enzymes into environment Do not photosynthesize oMost fungi grow as tubular, elongated cells Typified by filamentous growth Individual filamentous threads are called hyphae A group of hyphae is the mycelium Oomycetes and Fungi are Not Closely Related

Fungi

Stramenopila/ Oomycota (“Oomycetes”) Differences Between Oomycota & Eumycota

Feature Oomycete True Fungi Neighboring taxonomic groups Diatoms and golden brown algae Animals Hyphal architecture Aseptate tubular hyphae Either single cell or septated hyphae One or more nuclei per compartment Vegetative hyphae ploidy Diploid except in cells leading to Typically haploid or dikaryotic; often gametes (haploid) with stable or semi-stable diploid stage post-mating Typical genome size (Mb) 50-250 10-40 Major components of cell walls Cellulose and glucose polymers Chitin and/or chitosan and glucans Asexual spore types Undesiccated, unicellular sporangia Desiccated single or multicellular (multinucleated cells) conidia (one nucleous/cell) Motile asexual spores Nearly universal biflagellated Rare, only chytrids, and monoflagellated Sexual spores Oospores on the end of specialized Varied types, often occur in large hyphae with one zygotic nucleous numbers within complex structures

Modified from Howard S. Judelson & Flavio A. Blanco Nature Reviews Microbiology 3:47-58 Note on Terminology o Many Ascomycete fungi have historically had what is know as an anamorph and teleomorph  Anamorph: asexual or imperfect stage  Teleomorph: sexual or perfect stage  Have separate names but now names are being consolidated (synonyms) o Fungi where no sexual stage has been identified are grouped into the ‘Fungi Imperfecti’ Synonym: Deuteromycte Some Basidiomycetes have also lost sexual stage  Ex. Rhizoctonia spp. o Glossary of plant pathology terms: o www.apsnet.org/edcenter/resources/illglossary/Pages/default.aspx Alternaria Brown Spot oCausal agent: Alternaria alternata Synonyms: Alternaria citri and A. alternata pv. citri No known sexual stage oImportant disease on tangerines and tangelos o1903 First described in Australia on Emperor mandarin Alternaria Brown Spot cont. o1974 First identified in Florida oAlso found in South Africa, Turkey, Israel, Spain, Colombia and other countries oHost specific toxin Isolates from tangerines and tangelos do not infect rough lemon except in rare circumstances Disease on rough lemon same organism with different toxin Considered separate pathotypes of A. alternata

Alternaria alternata oNo sexual stage known oNecrotrophic oConidia are small, thick walled, pigmented and multicellular oThe conidiophores are determinate and pigmented oConidia are borne in chains oHyphae penetrate host tissue directly; No appressorium *appressorium = specialized structure at the end of a hyphae that anchors to the plant and forms further structures to infect the plant Tissue Susceptibility oHighly susceptible cultivars  Dancy, Minneola, Orlando, Sunburst, Murcott, Nova, and Lee oLeaves susceptible from formation to when fully expanded and hardened oFruit are susceptible from petal fall to 5 cm (2 inch) in diameter Symptoms Alternaria Brown Spot Disease Cycle Caused by Alternaria alternata When are the Conidia Released? oConidia released by rain events or sudden changes in relative humidity oIn field trapping, number of conidia in the air related to leaf wetness duration oNumber of airborne conidia not related to infection severity Timmer et al., 1988 Infection Conditions oOptimum temperatures 23-27°C Can get infection between 17-32°C oInfection can occur with as little as 4-6 hours of leaf wetness but disease severity increases with leaf wetness What factor allows for the 4 hour infection period? Canihos et al., 1999 Alternaria Brown Spot Disease Cycle Caused by Alternaria alternata Cultural Controls oDisease-free nursery trees oCareful choice of planting site Air drainage important Wider spacing oNo vigorous rootstocks oNo over-fertilization or over-watering oHedge in late March oNo overhead irrigation Fungicides oCopper – Works well for fruit but not leaves oFerbam – Only moderately effective oStrobilurins – Most effective but specific MOA Azoxystrobin Trifloxystrobin Pyraclostrobin oFirst spray when spring flush ¼-1/2 full expansion; high inoculum another before full expansion or at petal fall oRest of the year maintain protective coating ALTER-RATER: A Forecasting System oWeather-based point system to better time fungicide applications oPoints assigned based on: Rainfall and leaf wetness Average daily temperature oThresholds vary by cultivar susceptibility The ALTER-RATER Suggested Threshold Scores Score Situation Heavily infested Minneola, Dancy, 50 Orlando, Sunburst; Many flatwood groves, East coast, and SW Florida. Moderately infested Minneola or Dancy, 100 many Murcotts; Ridge and north Florida groves.

Light infestations, any variety, mostly 150 Ridge and north Florida groves. ALTER- RATER Daily Points Rain > 0.1 inch LW > 10 hr Avg daily Temp (°F) Assigned score + + 68-83 11 + + > 83 8 + + < 68 6 + _ 68-83 6 + _ > 83 4 + _ < 68 3 _ + 68-83 6 _ + > 83 6 _ + < 68 4 _ _ 68-83 3 _ _ > 83 0 _ _ < 68 0 Greasy Spot oCausal agent: Zasmidium citri-griseum Synonyms: Mycosphaerella citri Anomorph only: Stenella citri-grisea; Cercospora citri-grisea oOther similar diseases described around world but caused by other fungi in the Mycosphaerellaceae oImportant disease on most types of citrus o1915 First described in Florida and Cuba Greasy Spot cont. oAlso occurs in Texas, the Caribbean, Central and South America, and parts of Asia oPrimary effect is to cause defoliation which can lead to decreases of yield and fruit size Up to 25% on sweet orange in Florida  Up to 45% on grapefruit Zasmidium citri-griseum oLoculoascomycete Pseudothecia up to 90 µm Found in leaf litter Ascospores fusiform and hyaline with one septum (2-3 x 6-12 µm) Asexual form

oConidia are pale olive brown, cylindrical with indistinct septae that can be in chains oTwo types of conidiophores  Most common simple, smooth, dark and erect  Rare, in clusters (fasciculate) found in necrotic areas on leaves Mycelium oEpiphytic hyphae Highly branched Rough walls Olive brown color when young but darken with age and the walls become smooth oAppressoria formed in stomatal chambers oMycelia within leaf grow intercellularly and are not very branched Tissue Susceptibility oHighly susceptible cultivars Grapefruit, Pineapple, Hamlin, and Tangelos oLess susceptible cultivars Valencia, Temple, Murcott, and most tangerines oYoung and mature leaves susceptible to infection oImmature fruit susceptible Symptoms Greasy Spot Disease Cycle Caused by Zasmidium citri-griseum Pseudothecia Maturation Moisture

Mondal and Timmer, 2002 Pseudothecia Maturation Temperature

Mondal and Timmer, 2002 Optimal Temperatures for Ascospore Production o20 °C = 68.0 °F o24 °C = 75.2 °F o28 °C = 82.4 °F o32 °C = 89.6 °F

Mondal and Timmer, 2002 Peak Ascospore Ejection

The peak ascospore ejection 35 o 2000-01 30 2001-02 period has shifted to earlier in 1969 season 25 20

Why? 15

10

Is this beneficial? Percent ascospores of total 5

0

A M J J A S O N D J F M

Months Epiphytic Growth oOccurs during the wet summer months oAscospore dose does not determine level of epiphytic growth oSimilar patterns on fruit and leaves

Mondal and Timmer, 2005 Epiphytic Growth and Infection oTissue penetrated only through stomata oHigh density of penetration required for symptoms oRequires high humidity oSymptoms caused by swelling stimulated by hyphae Greasy Spot Disease Cycle Caused by Zasmidium citri-griseum Cultural Controls oReduce leaf litter in winter and early spring Disking Frequent irrigation to promote decomposition Mulch leaf litter Put urea or lime on the leaf litter oProblem with this approach Not enough of the leaf litter is decomposed Fungicides oPetroleum oil – gives adequate control on less susceptible cultivars oCopper – more consistent control than oil oStrobilurins – same concerns about MOA Azoxystrobin Trifloxystrobin Pyraclostrobin oFenbuconazole – moderate risk for resistance DMI fungicide or sterol biosynthesis inhibitors Spray Timing oLess susceptible cultivars One spray between May and June often sufficient especially in Northern production regions oIn South Florida, more susceptible cultivars and in groves with severe defoliation Two sprays; one mid-May – June, the second once flush has expanded A third and final spray may be needed for fresh grapefruit in a grove that was heavily infested the previous year Spray Timing Effects

5 Unsprayed control May spray 4 July spray August spray 3 May+June spray

2

1 Epiphytic mycelial growth growth mycelial Epiphytic

0 May Jun Jul Aug Sep Oct Nov Dec Jan Melanose oCausal agent: Diaporthe citri Synonym: Phomopsis citri (Anomorphic stage) oDisease is present in most citrus producing countries oImportant only where fresh fruit is produced in humid areas oCauses lesions on fruit and leaves oAll citrus susceptible but grapefruit and lemons are the most susceptible Diaporthe citri oAscospores formed in perithecia  Spherical with flattened base (125-160 µm)  Long tapered beaks (200-800 µm) oAscospores are hyaline  2 cells each with 2 oil droplets (guttulae)  3.2-4.5 x 11.5-14.2 µm Asexual Stage oPycnidia are dark, ovoid and erumpent with thick walls  Found scattered on dead twigs  200-450 µm  Spores are extruded in a tendril (cirrhus) Asexual Stage cont. oTwo forms of hyaline conidia o α-conidia are unicellular 2 oil droplets (biguttulate) 2.5-4 x 5-9 µm o β-conidia Filiform and hooked Don’t germinate and are predominant form in older pycnidia Likely a spermatial spore for mating 0.7-1.5 x 20-30 µm Tissue Susceptibility oSpring flush usually not severely infected oOn summer flush, infection can lead to defoliation especially after dieback oLeaves become resistant once fully expanded oFruit resistant 12 weeks after petal fall and when infection occurs later during the 12 weeks, lesions are smaller Grapefruit are susceptible until 7-10 cm in diameter Symptoms Melanose Disease Cycle Caused by Diaporthe citri Pycnidia Production

Mondal et al., 2004 Pycnidia Production oWetting period, twig diameter, temperature and disease severity on the twig all had significant effects on pycnidia formation oFormation takes between 3-5 months in field and can occur on dead twigs

Mondal et al., 2004 Conidia Production oMost of the inoculum is produced on twigs that die between January and April oConidia produced at low %RH are viable for several weeks to months

Mondal et al., 2007 Infection oConidia germinate 6 hrs at 16°C 4 hrs 20 to 28°C oLiterature has varying times and temperatures needed for infection oOptimum temp determined to be 24-28°C

Agostini et al., 2003 Melanose Disease Cycle Caused by Diaporthe citri Cultural Controls oSelect younger groves for fresh fruit Less dead wood for inoculum production oRemove dead wood from canopy oClear out brush piles Fungicides oCopper –Most economical but can cause blemishes in hot dry weather oStrobilurins – Low residual activity compared to copper but useful in hot weather Azoxystrobin Trifloxystrobin Pyraclostrobin Spray Timing oOranges and Tangerines First spray mid to late April One to two applications sufficient oGrapefruit (fresh market) First application when fruit ¼ to ½ inch Copper to be applied every 3 weeks until fruit resistant in late June to early July There is a model to determine whether copper residues are sufficient to control disease based on weathering of copper and the growth rate of fruit Citrus Scab oCausal agent: Elsinoë fawcettii Synonym: Sphaceloma fawcettii oFound in most humid citrus production regions oImportant for fresh fruit production oSweet orange scab: E. australis (syn. S. australis) Found in southern South America and South Korea Newly discovered in Texas and Louisiana Elsinoë fawcettii and E. australis oOnly been found in Brazil oDistinguished by ascospore size E. fawcettii 5-6 x 10-12 µm E. australis 12-20 x 15-30 µm oFunction in the disease cycle is unknown but clearly not essential Asexual Stage oConidia are hyaline, single celled and elliptical Indistinguishable between species Can reproduce by budding oAlso fusiform conidia (E. fawcettii) Pigmented Germinate to form hyaline conidia oConidia borne in acervuli Host Range and Tissue Susceptibility oYoung leaves and fruit are susceptible Leaves immune to infection in a few days Fruit remain susceptible up to two months oSummer flush can be especially badly affected oThe host range of E. fawcettii is complicated oMatter of considerable ongoing phylogenic research Host Range Disease Pathogen Pathotype Hosts Citrus scab Elsinoë FBHR Lemon, grapefruit, Temples, fawcettii sour orange, sweet orange, Satsuma, many tangerines FNHR Lemon, grapefruit, Satsuma Tyron’s Lemon, Cleopatra Lemon Lemon SRCG Satsuma, Rough lemon, Clementine, grapefruit Sweet orange scab E. australis Sweet orange Sweet oranges, tangerines Natsudaidai Natsudaidai

FBHR – FL broad host range; FNHR – FL narrow host range; SRCG – satsuma, rough lemon, clementine, grapefruit Symptoms Citrus Scab/Sweet Orange Scab Disease Cycles Caused by Elsinoë fawcetti and E. australis

F Infection

oContradictory information in the literature about leaf wetness and temperature oOptimal temperature range 23.5 to 27 °C oOptimal leaf wetness Between 12 and 24 hrs

Agostini et al., 2003 Conidia Production oConidia can be produced in 1-2 hours with sufficient wetness oOptimum temperature 24-28°C oSpores are splash dispersed oThe greater the number of spores, the greater the number of lesions oTend to see more disease with low lying areas where there more dew and longer dew periods Citrus Scab/Sweet Orange Scab Disease Cycles Caused by Elsinoë fawcetti and E. australis

F Cultural Controls oDisease-free nursery trees Start clean and problems are unlikely oHedge and top badly-affected plantings Does not move far even within trees oNo vigorous rootstocks oNo overhead irrigation Fungicides oCopper oFerbam oStrobulurins – Most effective but specific MOA Azoxystrobin Trifloxystrobin Pyraclostrobin oFenbuconazole Spray Timing oSprays are mainly for groves with a recent history of Scab oFirst spray – spring flush 2-3 inches  can be omitted if severity was light oPetal fall oThree week after petal fall Black Spot oCausal agent: Phyllosticta citricarpa Synonyms: Guignardia citricarpa; Phoma citricarpa oHosts : Citrus species and hybrids oSweet oranges, mandarins and tangerines, lemons, grapefruit o‘Tahiti’ lime - non-symptomatic infection Black Spot cont. oRind spots cause the most economic damage Internal quality unaffected oReduces fruit value for the fresh market oRestricts export of fresh fruits Mostly to European countries and formerly the U.S oCauses premature fruit drop reducing yield Particularly with late harvest cultivars World Distribution as of 2019 o Occurs mostly in summer rainfall areas or areas with prolonged dew or fog in warm weather

https://gd.eppo.int/ Current Quarantine Areas oFive Counties with Disease Collier Hendry Polk Lee Charlotte oNewest finds in Lee and Charlotte Phyllosticta citricarpa (sexual stage) oNever found in fruit – in leaf litter oForm aggregated ascomata - peritheciod pseudothecium 100-175 µm diameter oAscopores are aseptate, hyaline, multiguttulate and cylindrical with swollen middles 4.5-6.5 x 12.5-16 µm

Tran et al., 2017 Baayen et al. 2002 Asexual Stage oForms pycnidia Dark brown or black Form on fruit, leaves, twigs and fruit pedicles 115-190 µm oConidia are obovate, hyaline, aseptate, and multiguttalate 5.5-7 x 8-10.5 µm oSpermatia are dumbbell shaped 5 -8 x 0.5-1

Glienke et al. 2011 Tissue Susceptibility oHosts include Citrus species and hybrids oSymptomatic hosts: Sweet oranges, mandarins and tangerines, lemons, grapefruit oNon-symptomatic host: ‘Tahiti’ lime Produces ascospores from leaves oFruit are susceptible for 5-6 months post-petal fall Leaf susceptibility period still uncertain Symptoms Black Spot Disease Cycle Caused by Phyllosticta citricarpa Inoculum Basics oMajor source of inoculum: decomposing infected leaves on orchard floor (ascospores) oAdditional source of inoculum: lesions on infected fruits, leaves and branches (conidia) oMeans of spread: Wind (ascospores); Water splash (ascospores and conidia) Infection Conditions oOptimal conditions for infection: Temp 21 – 32 °C Wetting period 24 - 48h oSymptom expression: 1 – 12 months Very long latent period oSurvival of the fungus: leaves, twigs, fruits, peduncles, and leaf litter What is Needed for Ascospores oRequirement for two opposite mating types to be present to get ascospores oOnly one mating type found in Florida MAT1-2

Wang et al. 2016 The Lonely Peninsula oWanted to know the proportion of mating types in Florida compared to Queensland, Au Number of isolates State, Total Location Hetero Country number Alpha HMG -karyon Collier 50 0 50 0 Florida, Hendry 62 0 62 0 US Polk 1 0 1 0 Total 113 0 113 0 Beerwah 2 0 2 0 Queens Emerald 1 1 0 0 -land Gayndah 4 1 3 0 Australia Mundubbera 16 8 5 3 Tiaro 3 2 1 0 Total 26 12 11 3 Wang et al. 2016 Still Only One Mating Type oGlobal population study found 2 mating types in all locations except Florida oGreatest genetic diversity from Australia and China oSouth Africa and Brazil had low genetic diversity Likely founder effect oFlorida population was clonal even with expanded marker set oCarstens et al. 2017 Role of P. citricarpa Spermatia oSpermatia are commonly found in culture and leaf litter samples Role in life cycle hypothesized to be male gametes oFirst ascospores produced in culture Demonstrated meiosis via multilocus genotyping of ascospores Needed direct contact of isolates carrying opposite idomorphs or spermatia suspension oTran et al. 2017 Black Spot Disease Cycle Caused by Phyllosticta citricarpa Cultural Controls oIncrease air flow in trees to reduce leaf wetness where possible oAvoid cultivars with significant off-season bloom Older fruit can supply inoculum to infect new fruit oReduce leaf litter to reduce inoculum oMinimize trash when picking to avoid inadvertent movement of the fungus from one location to another oClean equipment between groves with disinfestants Quaternary ammonium (2000 ppm) or bleach (200 ppm) Fungicides oCopper - all formulations; use maximum label rate oStrobilurins azoxystrobin pyraclostrobin trifloxystrobin ofenbuconazole oPremixed Fungicides pyraclostrobin and boscalid azoxystrobin and difenoconazole Black Spot Application Timing o Fruit is susceptible for 5-6 months post-petal fall Copper and/or strobilurins Copper and/or strobilurins Copper Copper Copper

Late Spring Continue applications at 1 month intervals (April/May)

Use strobilurins when concerned about copper phytotoxicity Postbloom Fruit Drop oCausal agent: Colletotrichum acutatum Synonym: Glomerella acutata Formerly thought to be Colletotrichum gloeosporioides Approximately 5% of blossoms can be infected by C. gloeosporiodies in Brazil oWidespread throughout humid subtropics and tropics of the Americas oProblematic in years with high rainfall around bloom oFirst reported in Belize in 1979 Colletotrichum acutatum oConidia are fusiform rather than round Pigmented to give spore mass a salmon color Slower growing than C. gloeosporioides oBorne in an acervulus  Few setae on host tissue or in culture oAppressoria are the survival structures Host Range oAffects most citrus cultivars oMost severe on sweet oranges, lemons, and limes oLess severe on grapefruit and tangerines oIs a limiting factor for citrus production in high rainfall areas of Belize, Mexico, Costa Rica, and the Caribbean islands Susceptible Tissue oOpen flowers are the most susceptible oUnopened or pin-head bloom much less severe infection oDoes not appear to affect the foliage except that around the calyxes which is distorted with large veins oFruitlets abscise at base of ovary to form persistent calyxes or ‘buttons’ Pinhead Popcorn Open Symptoms Post Bloom Fruit Drop Disease Cycle Caused by Colletotrichum acutatum oFlowering solid line  Open and nearly open flowers up to 100 oFlower disease incidence dashed line  On newly open flowers at time of assessment

Timmer and Zitko, 1993 Disease Progress oInoculum levels most important oRainfall and leaf wetness are important oNeed infection of early bloom to get inoculum build up Amplifies inoculum levels for subsequent waves of bloom oOptimum temperature for conidia germination is 23°C but over 50% of conidia can germinate between 10-30°C Post Bloom Fruit Drop Disease Cycle Caused by Colletotrichum acutatum Cultural Controls oNo overhead irrigation If necessary only at night Get an expected wetness period overnight so not changing disease outcome considerably oIf there are trees in decline from other diseases such as tristeza, blight, or HLB that promote off season bloom, remove them from your PFD prone block Fungicides oFerbam oStrobulurins – Most effective but specific MOA Azoxystrobin Trifloxystrobin Pyraclostrobin oPremixed fungicides Azoxystrobin and difenoconazole Pyraclostrobin and boscalid Pyraclostrobin and fluxapyroxad Application Timing oTiming specific to grove situation oHighly weather dependent oDisease will not wait for the next time sprayer available ohttp://pfd.ifas. ufl.edu/ Needed Information oShould be scouting bloom several times a week during bloom Including off-season bloom Bloom intensity Bloom stage Pin-head Popcorn bloom Open flowers Needed Information cont. oDisease history for last 5 years Persistent calyxes Declining trees? Was there PFD on early bloom? Is there PFD now and is it scattered? oRainfall 5 previous days In millimeters; from inches multiply by 25.4 Approximate leaf wetness How many separate rain events oWhen was the last fungicide application? New PFD Infection Forecasting Program oHosted on Agroclimate.org Under tools/crop diseases Similar to Strawberry Advisory System (SAS) Each circle represents a FAWN weather station Criteria to select oPalmdale station selected Map zooms in automatically Sufficient oNeed to indicate bloom bloom intensity Will I recoup costs if application made? Many open flowers, Flowering stage some pinhead or button o bloom remaining Last fungicide application o None If there is an infection event oConditions could allow for infection event Still need sufficient o Link to current FPG bloom oFungicide applications minimum 7 days apart Recommendations Fungicide o recommendations change based on risk level Disease simulation tab oGraphical representation of infection risk Can select time frame oForecasted risk (from NOAA weather data) for three days from actual date Help plan if infection will be favored by weather in near term Infection risk levels oHigh risk (red area) Index above 0.51; Spray as soon as possible oModerate risk (yellow area) Index between 0.21 -0.5; Spray recommended oLow risk (green area) Index between 0-0.2; No spray recommended Daily summary of data oGives leaf wetness, temperature, PFD index and risk level Weather variables daily average PFD index max. daily value Weather data oCan look at the weather data for every 15 min. Temperature, relative humidity, rainfall, leaf wetness oFind out when drying periods occur After 4 hours of drying, PFD index resets to zero Pseudocercospora Fruit and Leaf Spot oPseudocercospora angolensis oSyn.: Phaeoramularia angolensis No know teleomorph oSerious disease of fruit and foliage in much of Sub-Saharan Africa except South Africa oFirst described in Angola and Mozambique in 1952 oQuarantine disease Host Range oAll citrus species oMost susceptible Grapefruit, oranges, pummelo and mandarin oLess susceptible Lemon oLeast susceptible Lime oYield losses between 50-100% not uncommon Pseudocercospora angolensis oForms dense tufts (synnemata) of light chestnut multi- septate conidiophores oEmerge from the stromata through stomata on lower leaf surfaces oConidia are single or catenulate (2-4) Hyaline, cylindrical and slightly flexuous One to six septate (mostly 3-4) 3-7 x 240 µm Pseudocercospora angolensis Susceptible Tissue oYoung leaves are highly susceptible to infection from lesions older tissues oYoung fruit up to golf ball size are highly susceptible oNot certain whether the fruit have a reduced susceptibility or become immune Symptoms Disease Spread oSo far restricted to humid tropics of Africa between 80-1500 m oFavoured by prolonged wet weather followed by dry periods with temps between 22-26°C oLong distance spread by windborne conidia Infected planting material may also contribute to long distance spread oWithin orchard spread by splash dispersed conidia Environmental Conditions

Pretorius, 2005 Controls o Inoculum control via collecting and destroying all fallen fruit and leaves in affected orchards  Burying or burning o Plant windbreaks around the citrus orchards  Wind is the primary dispersal agent spores o Discouraging inter-planting in affected orchards with mature producing trees  Prevents creation of a microclimate of relatively cool temperatures and high RH  Potential inoculum source for young trees o Judicious pruning of shoots to allow light penetration into aeration within the tree canopy  shorten leaf wetness period, lower RH and moderate temperatures Seif and Hillocks, 1993 Fungicides oAlternate benylate and copper sprays every 2 weeks from a week following the onset of rains oWhen fruit are golf ball sized an addition 3 copper sprays should be applied followed by another benylate

Seif and Hillocks, 1993 and 1997