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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Buxusspecies Cultivar HighlySusceptible
Susceptible ModeratelySusceptible
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’ ✚
B.microphyllavar.japonica
‘National’ ★ n
B.microphyllavar.japonica
‘JimStauffer’ ✚★
B.microphyllavar.japonica
‘Gregem’ ★
B.microphyllavar.japonica
‘GreenBeauty’ ✚¢
B.microphyllavar.japonica
‘WinterGem’ ✚ n★
B.sinicavar.insularis
‘Wintergreen’ ¢★
B.sinicavar.insularis
‘Nana’
✚¢
B.sinicavar.insularis
‘Pincushion’ n★
B.sinicavar.insularis
‘WinterBeauty’ ★
B.sinicavar.insularisxB.sempervirenshybrids
‘ChicagolandGreen’‘Glencoe’
✚ ★
B.sinicavar.insularisxB.sempervirenshybrids
‘GreenVelvet’ ★ ¢
B.sinicavar.insularisxB.sempervirenshybrids
‘GreenMountain’ ✚★
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Buxusspecies Cultivar HighlySusceptible
Susceptible ModeratelySusceptible
ModeratelyTolerant
Tolerant
B.sinicavar.insularisxB.sempervirenshybrids
‘GreenGem’ ★ ✚
B.sinicavar.insularisxB.sempervirenshybrids
‘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
Susceptible ModeratelySusceptible
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
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