Boxwood blight Factsheet Final Blight Factsheet.pdf · pseudonaviculata is known to be present in the United States (Gehesquière et al. 2016), where it was first identified on boxwood

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Dr.FulyaBaysal-GurelandPrabhaLiyanapathiranage

OtisL.FloydNurseryResearchCenterCollegeofAgriculture,HumanandNaturalSciencesTennesseeStateUniversityfbaysalg@tnstate.edu

Boxwood blight is caused by two fungal species, Calonectria pseudonaviculata (syn.

Cylindrocladium pseudonaviculatum, C. buxicola) and C. henricotiae. As of yet, only C.

pseudonaviculata is known to be present in the United States (Gehesquière et al. 2016),

where it was first identified on boxwood in nurseries and landscape plantings in North

CarolinaandConnecticut in2011(Ivorsetal.2012).Since that timeboxwoodblighthas

been confirmed in 22 additional states (Alabama, Delaware, Florida, Georgia, Illinois,

Kansas, Kentucky, Massachusetts, Maryland, Maine, New Hampshire, New Jersey, New

York, Ohio, Oregon, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia,

WashingtonandWestVirginia)andtheDistrictofColumbiaintheUnitedStates.Buxusspp.

(boxwood),Sarcococcaspp.(sweetbox)(Henricotetal.2008,Malapi-Wightetal.2016)as

well asPachysandra terminalis (Japanese spurge) (LaMondia et al. 2012), P. procumbens

(Alleghenyspurge)(LaMondiaandLi2013)andP.axillaris(WindcliffFragrant)(LaMondia

2017), have been reported as hosts to this pathogen (P. procumbens and P. axillaris by

inoculation).VariationsinboxwoodblightdiseasesusceptibilityoccurwithinBuxus(Table

1)andPachysandraspeciesandcultivars(Table2).

Thepathogencan infectallgrowthstagesofboxwoodplantsandmakeplantproduction

economicallyunacceptable.Thisfungusspreadsrapidlyovershortdistancesanddefoliates

ANR-PATH-7-2017

BoxwoodBlight

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mostoftheplantsintheBuxaceaefamily.Warm,humid,andshadyconditionsfavordisease

development.Infectionisfavoredat64-77˚F.

Thepathogencanspreadashortdistanceviarainor irrigationwater,wind,plantdebris,

contaminatedtoolsandequipment(suchaspruningtools),workers(contaminatedboots

and clothing), and animals (pets, insects, birds etc.). But, Themainmechanism for long

distancespread,however,isthoughttobemovementofcontaminatedplantsandcuttings,

including boxwood greenery used for holiday decorations (confirmed on boxwood

greenery inWarrenCo.,TN in2016).Thepathogenmaypersist asmycelium in infected

leavesleftonthesoilsurfaceoronthoseburiedinthesoilforatleast5years(Henricotet

al. 2008). While conidia of C. pseudonaviculata can remain viable in soil for 3 weeks,

microsclerotiawereshowntosurviveforatleast40weeksatoptimalconditions(Dartet

al.2015).Extremesofheatandcoldmaykillthepathogeninplantdebrisbut,atmoderate

temperatures,itmayremaininsoilforlongperiods(ShishkoffandCamp2016).Whenthe

environmental conditions are favorable,microsclerotia produce newmycelium and new

lesionscanbeobservedwithinoneweek.

Initially,reddish-browntobrownconcentriccircularspotswithtantolightbrowncenters

arevisibleoninfectedleaves(Figure1),andangulardiamond-shapeddarkbrowntoblack

lesions(Figure2)canbefoundonstemsfromthebasetotheshoottip.Later,wholeleaves

willturnbrownanddefoliationwillbeginfromthelowerbranchesandspreadtotheupper

canopy(Figure3and4).Duringfavorableconditions,thefungussporulatesandproduces

whitesporemassesontheundersideoftheleavesandstemthatarevisibletothenaked

eye(Figure6and7).Thepathogendoesnot initiallyattacktheroots;so largeplantscan

survivebyproducingnew leaves evenwhile theplant is attackedby thepathogen.With

repeated cyclesofdefoliations anddiebackunderdisease-conducive conditions, though,

largeplantsandrootedcuttingsinthenurseriesmaygetdestroyed.

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Figure1and2.Leafspotsofboxwoodblight.

Figure3and4.LeafspotsanddefoliationcausedbyCalonectriapseudonaviculataon

boxwood.

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Figure5.BlackstemcankercausedbyCalonectriapseudonaviculataonboxwood.

Figure6and7.Undersideofinfectedboxwoodleafshowingwhite-coloredsporemasses.

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Theblackcankersorstreaksdeveloponthegreenstemsoftheboxwoodblightdisease

infectedplants(Figure5).Thisisthemajorsymptomthatcanbeusedtodifferentiatethis

diseasefromotherboxwooddiseasessuchasVolutellablight(Figure8)andMacrophoma

leafspot(Figure9);boxwoodpestssuchasboxwoodleafminer(Figure10and11);or

boxwoodabioticdisorderssuchaswinterinjuryorsunscald(Figure12).

Figure8.Volutellablightonboxwood. Figure9.Macrophomaleafspotonboxwood.

Figure10and11.Boxwoodleafminerdamage.

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Figure12.Abioticdisorderonboxwood.

ManagementStrategies

Scouting and early diagnosis of infected plants is critical for the avoidance of boxwood

blightdiseasespreadandtheimplementationofeffectivediseasecontrolstrategies.Ifyou

would like to confirm that boxwood blight has infected your plants, you can submit a

sampletoyourlocaluniversity’splantdiagnosticlaboratory.

Since boxwood blight can be introduced via contaminated plants and cuttings, careful

inspections need to be done prior to and also after the purchase of host plantmaterial.

Newly purchased plants should be isolated from existing boxwood, sweet box or spurge

plantings or production areas in nurseries for at least one month. During this isolation

period fungicide applications are not recommended since the fungicide treatments can

suppress symptom development and mask proper diagnosis. In particular, moderately

tolerantor tolerantcultivarsneed tobe inspectedcarefullyduring thisperiodsince they

maycarrythepathogenwithoutobvioussymptoms.Usingboxwoodgreenery forholiday

decorations is not recommended in close proximity to landscape boxwood plantings or

boxwood production areas. Homeowners who had holiday decorations using boxwood

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should,disposetheminsealeddoublebagsinalandfill;boxwoodgreeneryshouldnotbe

placed in a compost pile. Once infected plants are detected, they should be destroyed

immediately to reduce thepotential for spreadof thedisease.Alongwith theplants, leaf

andstemdebrisshouldberemovedfromthelandscapeornurserybecausethepathogen

cansurvive fora long time(up to fiveyears) inplantdebris.Before leafdebrishasbeen

blownbywind,buriedbyerosionorbeguntodecompose,flamingthesoilsurfaceswitha

propanepushflamercansignificantlyreducelevelsofinoculaofC.pseudonaviculatainthe

upperlayerofsoil.

Sanitation of tools, equipment, and hard surfaces is critical for boxwood blight

management. Different types of disinfectants containing sodium hypoclorite, hydrogen

dioxide, hydrogen peroxide + peroxyacetic acid + octanic acid, phenolic compounds (O-

benzyl-p-chlorophenol), and alcohol as active ingredients are helpful. To improve the

effectivenessofdisinfectants,surfacesneedtobecleanedandfreeofsoilandotherorganic

matterbeforeusingdisinfectants (Baysal-Gurel2016).At least5minutesof contact time

with the disinfectant is suggested for tools; 10 minutes is suggested for pots or other

surfaces.Ifthereisafieldorlandscapeareawhereboxwoodaresuspectedtobeaffected

byboxwoodblight,donotwork in thoseareaswhen theplants arewet, andwear clean

disposablebootiesandcoverallsanddisposeof thebootiesandcoverallsbeforeentering

otherboxwoodareas.Donotgofromareasofknowninfectionstoareaswhereinfections

havenotbeenseen.

Properirrigationcanreducediseasespreadaswell.Dripirrigationisbetterthanoverhead

irrigation, as it supplies water to the root system of the plant without the potential of

spreadingthediseasethroughsplashing.

Fungicides can be used to prevent this disease in conjunction with other management

strategies previously mentioned. When there is a risk of boxwood blight occurring,

repeatedapplications(at7-or14-day intervals)of fungicidesmaybenecessary.Aspray

program that includes fungicides with different modes of action is ideal for fungicide

resistancemanagement(Table3).

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Table 1. Susceptibility of boxwood species and cultivars (as container grown plants orunrootedcuttings)toboxwoodbightdisease.

Buxusspecies Cultivar HighlySusceptible

Susceptible ModeratelySusceptible

ModeratelyTolerant

Tolerant

B.sempervirens ‘Aurea-pendula’ ¢ B.sempervirens ‘Pendula’ ★ B.sempervirens ‘JustinBrouwers’ ✚ B.sempervirens ‘Suffruticosa’ ✚★ n¢ B.sempervirens ‘VardarValley’ n ★ B.sempervirens ‘Scupi’ ★ n B.sempervirens ‘Rotundifolia’ ★ ¢ B.sempervirens ‘Northland’ ★ nB.sempervirens ★ nB.sempervirens ‘Denmark’ ★ ¢ n B.sempervirens ‘Handsworthiensis’ ★ ¢ nB.sempervirens ‘Elegantissima’ ✚ B.sempervirens ‘American’ ✚ B.sempervirens ‘Jensen’ ✚ B.sempervirens ‘Asheville’ ¢ B.sempervirens ‘Rochester’ ¢ B.sempervirens ‘AureaMaculata’ ¢ B.sempervirens ‘LatifoliaMaculata’ ¢ B.sempervirens ‘LatifoliaAurea

Maculata’ ¢

B.sempervirens ‘Route50’ ¢ B.sempervirens ‘NewportBlue’ ★ B.sempervirens ‘Gordo’ ✚ B.sempervirens ‘Myosotifolia’ ¢ B.sempervirens ‘PierCove’ ¢ B.sempervirens ‘HenryShaw’ ¢ B.sempervirens ‘Liberty’ ¢ B.sempervirens ‘Ohio’ ★ B.sempervirens ‘Decussata’ ★ B.sempervirens ‘Marginata’ ✚★ n B.sempervirens ‘GrahamBlandy’ ★ n B.sempervirens ‘Fastigiata’ ✚ B.sempervirens ‘DeeRunk’ ★ ✚ B.sempervirens ‘Angustifolia” ¢ B.sempervirens ‘Longwood’ ¢ B.sempervirens ‘NorthernNew

York’ ¢★ n

B.sempervirens ‘Arborescens’31793

★ n

B.sempervirens ‘Arborescens’57953

★ n

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ModeratelyTolerant

Tolerant

B.sempervirens ‘EdgarAnderson’ ★ nB.sempervirens ‘Myrtifolia’ ★ nB.sempervirens ‘NorthStar’ ¢B.microphylla ‘GreenPillow’ ✚ B.microphylla ‘GraceHendricks

Phillips’ ★ ✚

B.microphylla ‘Sprinter’ ¢ B.microphylla ‘Hohman’sDwarf’ ¢ B.microphylla ‘GoldenDream’ ✚B.microphylla ‘JohnBaldwin’ ★ ✚ nB.microphylla ‘BabyGem’ nB.microphylla ‘WeddingRing’ ¢B.microphyllavar.japonica

'MorrisMidget' ✚

B.microphyllavar.japonica

‘MorrisDwarf’ ✚


‘National’ ★ n


‘JimStauffer’ ✚★


‘Gregem’ ★


‘GreenBeauty’ ✚¢


‘WinterGem’ ✚ n★

B.sinicavar.insularis

‘Wintergreen’ ¢★


‘Nana’

✚¢


‘Pincushion’ n★


‘WinterBeauty’ ★

B.sinicavar.insularisxB.sempervirenshybrids

‘ChicagolandGreen’‘Glencoe’

✚ ★


‘GreenVelvet’ ★ ¢


‘GreenMountain’ ✚★

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ModeratelyTolerant

Tolerant


‘GreenGem’ ★ ✚


‘GreenMound’ ✚ n★

B.koreanaxB.sempervirenshybrids

‘GreenIce’ ★

B.harlandii ★ ✚nB.harlandii ‘Richard’ ¢ B.bodineiri ★ nB.wallichiana ★ Buxussp. ‘Franklin’sGem’ ¢ Buxussp. ★ nBuxussp. ‘NorthernEmerald’ ¢✚ Gancietal.2012.SusceptibilityofcommercialboxwoodvarietiestoCylindrocladiumbuxicola.

http://americanhort.theknowledgecenter.com/library/Americanhort/docs/government%20relations/boxwood%20blight/NCSU_boxblight_tolerance.pdf

¢ Gancietal.2013.Susceptibilityofcommercialboxwoodcultivarstoboxwoodblight.https://plantpathology.ces.ncsu.edu/wp-content/uploads/2013/05/final-Cult-trials-summary-2013.pdf?fwd=no

n Milleretal.2016.Evaluationofboxwoodcultivarsforresistancetoboxwoodblight,2015.★ Shishkoffetal.2015.Evaluatingboxwood(Buxusspp.)susceptibilitytoCalonectriapseudonaviculata

byinoculatingcuttingsfromthenationalboxwoodcollectionattheUSNationalArboretum.PlantHealthProgress16:11-15.PlantHealthProgressdoi:10.1094/PHP-RS-14-0033.

Table 2. Susceptibility of Pachysandra species and cultivars to boxwood blight disease(LaMondia2017).

Pachysandraspecies

Cultivar HighlySusceptible


ModeratelyTolerant

Tolerant

P.terminalis ‘Common’ X P.terminalis ‘Crinkled’ X P.terminalis ‘GreenCarpet’ XP.terminalis ‘GreenSheen’ X P.terminalis ‘Variegated’ X P.axillaris ‘Windcliff’ X

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Table3.ActiveingredientswitheffectivenessagainstboxwoodblightinUStrials.

Activeingredient FRACCode ReferenceAzoxystrobin 11 Ivorsetal.2013Benzovindiflupyr+azoxystrobin 7+11 LaMondia2016

Baudoinetal.2015Boscalid+pyraclostrobin 7+11 Baudoinetal.2015

LaMondia2015Chlorothalonil M5 Baudoinetal.2015

Ivorsetal.2013LaMondia2015

Cyprodinil+fludioxonil 9+12 Ivorsetal.2013LaMondia2015

Fludioxonil 12 Ivorsetal.2013Fluoxastrobin+chlorothalonil 11+M5 Ivorsetal.2013Fluxapyroxad+pyraclostrobin 7+11 MaurerandLaMondia2016

LaMondiaandMaurer2017Mancozeb M3 LaMondia2014Metconazole 3 Ivorsetal.2013Myclobutanil 3 LaMondia2015PolyoxinDzincsalt 19 Ivorsetal.2013Propiconazole 3 LaMondia2015Propiconazole+chlorothalonil 3+M5 Ivorsetal.2013Pyraclostrobin 11 Ivorsetal.2013Tebuconazole 3 Ivorsetal.2013Thiophanate-methyl 1 LaMondia2016

Ivorsetal.2013Thiophanate-methyl+chlorothalonil 1+M5 Ivorsetal.2013Trifloxystrobin 11 Ivorsetal.2013Trifloxystrobin+triadimefon 11+3 PalmerandShishkoff2014NOTE:BeforeapplyingANYdiseasemanagementproduct,besureto:1)readthelabeltobesurethattheproductisallowedforthecropandthediseaseyouintendtocontrol;2)readandunderstandthesafetyprecautionsandapplicationrestriction.

References

Baudoin,A.,Avenot,H.F.,Edwards.T.P.,Diallo,Y.,Lucerconi,C.B.2015.Evaluationoffungicidesforcontrolofboxwoodblight,2014.PlantDiseaseManagementReportsNo.9:OT006.

Baysal-Gurel,F.2016.Selectionandusageofdisinfectantsfornurseryproduction.TSU-16-0235(A)-15-61065.http://www.tnstate.edu/extension/documents/Disinfectant%20factsheet.pdf

Dart,N.,Hong,C.,CraigC.A.,Hu,X.2015.Soil inoculumproduction,survival,andinfectivityoftheboxwood blight pathogen,Calonectria pseudonaviculata. Plant disease December 2015, Vol.99,Number12Pages1689-1694

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Ganci, M., Benson, D.M., Ivors, K.L. 2012. Susceptibility of commercial boxwood varieties toCylindrocladiumbuxicola.http://americanhort.theknowledgecenter.com/library/Americanhort/docs/government%20relations/boxwood%20blight/NCSU_boxblight_tolerance.pdf

Ganci, M., Ivors, K.L., Benson, D.M. 2013. Susceptibility of commercial boxwood cultivars toboxwood blight. https://plantpathology.ces.ncsu.edu/wp-content/uploads/2013/05/final-Cult-trials-summary-2013.pdf?fwd=no

Gehesquière, B., Crouch, J.A., Marra, R.E., Van Poucke, K., Rys, F., Maes, M., Gobin, B., Hofte, M.,Heungens,K.2016.CharacterizationandtaxonomicreassessmentoftheboxblightpathogenCalonectria pseudonaviculata, introducing Calonectria henricotiae sp. nov. Plant Pathol. 65,37–52.

Henricot,B.,Gorton,C.,Denton,G.,andDenton, J.2008.Studieson thecontrolofCylindrocladiumbuxicolausingfungicidesandhostresistance.PlantDisease92:1273–1279.

Ivors,K.L.,Lacey,L.W.,Milks,D.C.,Douglas,S.M.,Inman,M.K.,Marra,R.E.,andLaMondia,J.A.2012.First report of boxwood blight caused byCylindrocladium pseudonaviculatum in theUnitedStates.PlantDis.96:1070.

Ivors, K.L., Lacey, L.W., Ganci, M., 2013. Evaluation of fungicides for the prevention of boxwoodblight,2012.PlantDiseaseManagementReports7:OT014

LaMondia, J. A., Li, D. W., Marra, R. E., and Douglas, S. M. 2012. First report of CylindrocladiumpseudonaviculatumcausingleafspotofPachysandraterminalis.PlantDis.96:1069.

LaMondia,J.A.,andLi,D.W.2013.FirstreportofCylindrocladiumpseudonaviculatumcausingleafspot and stem blight ofPachysandra procumbens. Plant Health Progress. doi:10.1094/PHP-2013-0226-01-BR.

LaMondia, J. A. 2014. Fungicide efficacy against Calonectria pseudonaviculata, causal agent ofboxwoodblight.PlantDis.98:99-102.

LaMondia,J.A.2015.ManagementofCalonectriapseudonaviculatainboxwoodwithfungicidesandlesssusceptiblehostspeciesandvarieties.PlantDis.99:363-369.LaMondia, J. A. 2016. Evaluation of fungicides for management of boxwood blight, 2014. Plant

DiseaseManagementReports10:OT010.LaMondia,J.A. andMaurer,K.2017.Evaluationoffungicidesformanagementofboxwoodblight,

2016.PlantDiseaseManagementReports11:OT016.LaMondia, J. A. 2017. Pachysandra Species and cultivar susceptibility to the boxwood blight

pathogen, Calonectria pseudonaviculata. Plant Health Progress. doi:10.1094/PHP-01-17-0005-RS.

Malapi-Wight,M.,etal.2016.PlantDis.100:1093.https://doi.org/10.1094/PDIS-10-15-1159Maurer,K.andLaMondia,J.A.2016. Evaluationoffungicidesformanagementofboxwoodblight,

2015.PlantDiseaseManagementReports10:OT011.Miller,M.E.,Norris,R.S. andCubeta,M.A.2016. Evaluationofboxwoodcultivars for resistance to

boxwoodblight,2015.PlantDiseaseManagementReports10:OT009.Palmer,C.andShishkoff,N.2014.Boxwoodblight:anewscourge,anewparadigmforcollaborative

research.OutlooksonPestManagement25(3)DOI:10.1564/v25_jun_10Shishkoff et al. 2015. Evaluating boxwood (Buxus spp.) susceptibility to Calonectria

pseudonaviculata by inoculating cuttings from the National Boxwood Collection at the USNational Arboretum. Plant Health Progress 16:11-15. Plant Health Progressdoi:10.1094/PHP-RS-14-0033.

Shishkoff, N. and Camp, M.J. 2016. The effect of different temperatures and moisture levels onsurvivalofCalonectriapseudonaviculata inboxwood leavesand twigsandasmicrosclerotiaproducedinculture.PlantDiseaseOct2016,Volume100,Number10,2018-2024.

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Foradditionalinformation,contactyourlocalnurseryspecialistofficeat:

TennesseeStateUniversityCollegeofAgriculture,HumanandNaturalSciences

3500JohnA.MerrittBlvd.,Box9635Nashville,TN3720-1561http://www.tnstate.edu/extension

TennesseeStateUniversity,OtisL.FloydNurseryResearchCenter

472CadillacLaneMcMinnville,TN37110http://www.tnstate.edu/agriculture/nrc/

PrecautionaryStatement

Toprotectpeople and theenvironment,pesticides shouldbeused safely.This is everyone’s responsibility,especiallytheuser.Readandfollowlabeldirectionscarefullybeforeyoubuy,mix,apply,storeordisposeofapesticide.Accordingtolawsregulatingpesticides,theymustbeusedonlyasdirectedbythelabel.

Disclaimer

This publication contains pesticide recommendations that are subject to change at any time. Therecommendations in this publication are provided only as a guide. It is always the pesticide applicator’sresponsibility,bylaw,toreadandfollowallcurrentlabeldirectionsforthespecificpesticidebeingused.Thelabelalways takesprecedenceover the recommendations found in thispublication.Useof trade,brand,oractive ingredientnames in thispublication is forclarityand information; itdoesnot implyapprovalof theproducttotheexclusionofothersthatmaybeofsimilarandsuitablecomposition,nordoesitguaranteeorwarrant the standard of the product. The author(s) and Tennessee State University assume no liabilityresultingfromtheuseoftheserecommendations.

Dr.ChandraReddy,Dean,TennesseeStateUniversity,CollegeofAgriculture,HumanandNaturalSciencesDr. Latif Lighari, AssociateDeanExtension, Tennessee StateUniversity, College of Agriculture,Human andNaturalSciencesDr.NickGawel,Superintendent,OtisL.FloydNurseryResearchCenter,TennesseeStateUniversity,CollegeofAgriculture,HumanandNaturalSciences

TSU-17-0036(A)-15i-61065-TennesseeStateUniversitydoesnotdiscriminateagainststudents,employees,orapplicantsfor admission or employment on the basis of race, color, religion, creed, national origin, sex, sexual orientation, genderidentity/expression,disability,age,statusasa protected veteran,genetic information, or anyother legally protected classwithrespecttoallemployment,programsandactivitiessponsoredbyTennesseeStateUniversity.Thefollowingpersonhasbeendesignatedtohandleinquiriesregardingnon-discriminationpolicies:RitaWilliamsSeay,OfficeofEquityandInclusion,[email protected],3500JohnMerrittBlvd.,McWherterAdministrationBuilding,Suite260,Nashville,TN37209, 615-963-7438.TheTennesseeStateUniversitypolicyonnondiscriminationcanbefoundatwww.tnstate.edu/nondiscrimination.

Documents

Boxwood blight Factsheet Final Blight Factsheet.pdf · pseudonaviculata is known to be present in the United States (Gehesquière et al. 2016), where it was first identified on boxwood