quarantine evaluation of eucryptorrhynchus brandti (harold

292

1 VirginiaPolytechnicInstituteandStateUniversity,Blacksburg,Depart-mentofEntomology,VA24061-0319,USA.

Correspondingauthor:L.T.Kok<[email protected]>.©CABInternational2008

Quarantine evaluation of Eucryptorrhynchus brandti (Harold)

(Coleoptera: Curculionidae), a potential biological control agent of tree of

heaven, Ailanthus altissima, in Virginia, USA

L.T. Kok, S.M. Salom, S. Yan, N.J. Herrick and T.J. McAvoy1

Summary

Treeofheaven,Ailanthus altissima(Mill.)Swingle,isanimportedinvasiveweedtreefromChinathathasbecomeestablishedthroughoutmuchofthecontinentalUSA.Itcolonizesdisturbedforestsites and often out-competes native vegetation. Short-term cultural and chemical controls of thisweed are expensive and have limited efficacy. Eucryptorrhynchus brandti(Harold)andEucryptor-rhynchus chinensis(Olivier),twocurculionidspecies,arepestsofA. altissimainChinaandhavenootherknownhosts.Theobjectivesofourprojectareto(1)assessthepeststatusofA. altissimainVirginiaand(2)evaluateE. brandtiforitspotentialasabiologicalcontrolagent.Astatewidesurveyshowed significant presence of tree of heaven but no native herbivores with potential of controlling it,suggestingbiologicalcontroltobeanattractivemethodofmanagement.AsE. brandtirequireslivetreesfordevelopment,quarantinestudieshavefocusedondevelopingarearingtechniqueandtesting the host specificity on native plants approved by the Technical Advisory Group for Biological ControlAgentsofWeeds.PreliminaryresultsindicatethatE. brandtifeedsonlyontreeofheaven,withgreatlyreducedfeedingobservedoncorkwood,Leitneria floridanaChapman,andparadisetree,Simarouba glaucaDC.

Keywords: rearing,Eucryptorrhynchus brandti, host specificity testing, natural enemy.

IntroductionAilanthus altissima, tree of heaven, is an introducedspeciesinEurope(Balleroet al.,2003;Lenzinet al.,2004),Africa,SouthAmericaandNorthAmerica(Dinget al.,2006).SeedswereintroducedfromChinatoParisbetween1740and1750(Hu,1979;Tellman,2002)andinNorthAmericaasanornamentalshadetreeduringthe late 18th century from Europe into Philadelphia,Pennsylvania (Feret, 1985; Tellman, 1997). MultipleintroductionsintoNewYorkoccurredduringtheearly19thcentury(Davies,1942;DameandBrooks,1972;Hu,1979).

Currently,treeofheavenisfoundin41ofthelower48continentalUSAfromWashingtontoNewEnglandand south to Florida, Texas and Southern California(USDA-NRCSPlantsDatabase,2007).Itisoftenusedasanornamentaladjacenttosidewalks,streetsandinparkinglots.InVirginia,treeofheavenisadominantspeciesalongroadsidesandoccupieshundredsofacresintheShenandoahNationalPark(Marler,2000).

Tree of heaven has many beneficial attributes and often is regarded as an important ornamental speciesinthecountriesoforiginbecauseofitsaestheticvalueandability towithstandenvironmentalpollutantsandwaterstressinanenvironmentcausedbyhumanactivi-ties(Dinget al.,2006).TraditionalChineseculturehasusedtreeofheavenforitsanti-tumourproperties(Am-miranteet al.,2006).Initsnativerange,treeofheavenisfeduponbymorethan40phytophagousarthropodspeciesandissusceptibletonearly20pathogens(Ding

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QuarantineevaluationofEucryptorrhynchus brandti

et al., 2006). Few pathogens occur in the USA, andonlyonehascaused isolated fatalityofan individualtreeofheavenplant (Dinget al.,2006).Noneof thepathogens occurring in the USA appears to be specific to treeofheaven (Dinget al.,2006).Treeofheavenproducesallelopathiccompoundscapableofinhibitingthe growth of nearly 90 tree species (Mergen, 1959;Heisey, 1990a,b; Lawrence et al., 1991; Heisey andHeisey,2003).Thelackofnaturalenemiesof treeofheavenanditsabilitytosuppressplantgrowthoverawiderangeofhabitatsallowit toout-competenativeflora in North America.

Chemicalcontroloftreeofheavenisthemostcom-moncontrolmethod.Herbicidesregisteredfortreeofheaven control are dicamba, glyphosate, imazapyr,metasulfuron methyl and triclopyr. They are appliedasfoliarsprays,basal-barktreatments,injectionorap-plied to cut stumps. However, chemicals often causetreatedsitestobebarrenofanyplantliferesultinginthere-intrusionofinvasivespeciesliketreeofheaven.Thereisaconcernthatcontinuedlarge-scaleherbicideapplications may become detrimental to the environ-mentinadditiontobeinglaborintensiveandcostly.Forexample,ataheavilyinfested4-hasiteonthemedianofinterstate81inVirginia,theVirginiaDepartmentofTransportationestimatedthatthecosttocontroltreeofheavenwas$8750perhaandproducedonly‘reason-able’control.

ThelackofnaturalenemiesoftreeofheavenintheUSAandthepotentialforbiologicalcontrolledtofor-eignexplorationtoidentifypotentialbiocontrolagentsinChina.AsurveyoftheChineseliteraturesuggestedthatEucryptorrhynchus brandtiHaroldandEucryptor-rhynchus chinensis (Olivier) (Coleoptera:Curculioni-dae)wouldbepotentialagentstoinvestigate(Dinget al.,2006).E. brandtiisaunivoltinebeetlespeciesna-tive to China where it is considered a pest. In someareasofChina,80%to100%of treeofheaven treessurveyedwereattackedbyE. brandti andE. chinen-sis causing 12% to 37% mortality (Ge, 2000; Ding et al., 2006). Chinese people make considerable effortstocontrolE. brandtiwithchemicalsandhavefoundanematode(Steinernema feltiae)thatcanproduce70%mortality in the field (Dong et al.,1993;Jianguanget al.,2004).ThegeneralbiologyofE. brandtiisnotwellknown.However,itsdevelopmentisprobablysimilartothatofothercurculionidspeciesassociatedwithwoodytrees(Barrett,1967).Adultsfeedonleaves,budsandpetioles(Dinget al.,2006).Larvaedevelopunderthebark and emerge as adults, leaving round emergenceholesapproximately4mmindiameter.

Ourgoalwastoidentifyinsectherbivoresthatcanreduce the spread of tree of heaven. Specific objectives wereto(1)surveyfornativeinsectherbivoryonA. al-tissimaindifferentregionsofVirginiatoidentifyanyspecieswithpotentialtoimpacttreeofheavenand(2)importselectedherbivoresfromthenativehabitatofA. altissima for host-specificity evaluation under quaran-

tinetodeterminetheirpotentialforsurvivalanddevel-opmentinVirginia.

Materials and methodsTree of heaven in Virginia

Locations distributed throughout three differentregions of Virginia were identified to determine the extentofA. altissima colonization.The regionswereRidgeandValley(AppalachianMountains),PiedmontandCoastalPlain(Fig.1).Withineachregion,atleasttwositeseachalonghighways,rights-of-wayornatu-ralforestdisturbanceareaswereselected.Ateachsite,alltreespeciesandtheirpercentcoverwithinthetreeofheaven infestationwere recorded.Observationsofherbivoresfeedingontree-of-heavenweredonebyvi-sually examining at least 200 leaflets for herbivores. Herbivoreswerealsocollectedbybeatingleavesover1m2beatsheets.Anyherbivoresfoundwerecollectedand identified. Insect sampling also consisted of whole treeobservationforactivityanddamagefrominsects.Wholetreeobservationincludeddetailedexaminationof foliage, stems, buds and seeds (when available).Where obvious insect damage was detected, insectswere collected if located. Our objective was not tocarry out a biodiversity study or complete census ofinsectsfoundontreeofheavenbuttofocusoninsectscolonizingorfeedingontreetissuecausingobservabledamage.Thesurveybeganinthesummerof2004andcontinuedin2005.Eachsitewasvisitedmonthlydur-ingthegrowingseason(MaytoOctober).

Concurrent with the survey effort was the assess-ment of impact of identified herbivores on the growth, reproductionandsurvivaloftreeofheaven.Whendam-ageassociatedwithinsectfeedingorcolonizationwasfound,itwasfollowedbymoreintensivesamplingofthecausalagents.Theintentionwastodetermine,foreach identified herbivore, the level and timing of activ-ityacrossallregionsandsitetypes.Werecognizethatnativeherbivores arenot likely to effectively controltreeofheaven,astheweedhasbeenhighlysuccessfulthusfar.However,thisinformationwillbehelpful,asweevaluateexoticbiologicalcontrolagentsandtheirpotentialinteractionwithourexistingfauna.

Quarantine testing of an exotic weevil imported from China

As part of a collaborative project with Dr. DingJianqing, Biological Control Institute, ChineseAcad-emyofAgriculturalSciences, twoweevil species,E. brandti and E. chinensis, identified as important pests ofA. altissima,werestudiedinChina.E. brandti wasimported into the US Department of Agriculture’s(USDA)Animal andPlantHealth InspectionService(APHIS)approvedQuarantinefacilityatVirginiaTechbeginningin2004.

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Survival and development:AdultE. brandtiisrearedontreeofheavenfoliageandstemsincontainersatsev-eral constant temperatures (20°C to30°C)within therangethatthespecieswillencounterintheUSreleaseareas.Biologicaldata recorded includedsurvivalanddevelopmenttimesoftheegg,larvalandadultstages,aswellasfecundityofthefemalesandegghatchrates.Twocolonieswereestablished;onecolonywasmain-tainedforproductionandthesecondusedforbiologi-cal and host specificity studies.Production colony:Thiscolonyhasbeenmaintainedandcagedinscreenedplasticboxes(30´15´165cm)at22°C. Groups of five males and five females were placedinthecages.Ineachcage,treeofheavenbillets,with the upper ends sealed with heated paraffin to re-ducedesiccation,wereprovidedforovipositionandfo-liageaddedforadultfeeding.Vermiculitewasaddedtothebottomofthecageandkeptmoist.Weekly,billetswereremovedandplacedinseparatecagesforlarvaldevelopment.Newlyemergedadultswere transferredtonewovipositioncages.Fecundity:Singlepairsofmaleandfemalewerecagedinscreenedplasticboxes,asintheproductioncolonycages,andreplicated.Treeofheavenbilletswereaddedand checked for oviposition daily by removing thebarkandexamining thecambiumforeggs.After ini-

tiationofoviposition, thebarkwascheckeddailyforeggs.Egg and larval development:Eggsrecoveredfromthebillets were placed in Petri dishes with moistened filter paperandrearedatseveralconstanttemperaturesandcheckeddailyforhatching.Newlyhatchedlarvaewereinoculatedintreeofheavenbilletsbydrillinga7-mmdiameterholeintothecambiumandinsertingonelarvainto the hole. Billets were checked at an appropriatetimeafterinoculationtodeterminewhendevelopmentto thesecondinstaroccurred.Thisprocedurewasre-peatedatleastthreetimesforsubsequentinstarsuntilpupation.Physiological host specificity testing: Host-rangestudiesincludedaseriesofno-choiceandchoicefeed-ingandovipositiontests.Testplantspecieswerefromthreegroups,withatotalof30species:18taxonomi-cally related species (Simaroubaceae, Meliaceae andRutaceae),sixecologicallyrelatedspecies,andsixeco-nomically related species. The taxonomically relatedspecieswere chosenbasedonWapshere’smethodofcentrifugalphylogentictesting(Wapshere,1974).Thismethodinvolvesexposingthebiologicalcontrolagenttoasequenceofplantsfromthosemostcloselyrelatedtothetargetspeciesprogressingtosuccessivelymoreandmoredistantly relatedplantsuntil thehost range

98

99

N

20 0 20 40 Kilometers

Tidewater

Piedmont

Mountains

Radford

Blacksburg

Dayton

Rocky Bar

New Post

Milton

Vera

York River State Park

Nassawadox

= Survey site

Figure 1. Ailanthus altissima (Mill.)SwinglesurveysitesinVirginia,USA:(1)Mountain,includingRadford(forest),Blacksburg(forest),Dayton(forest)andRockbar(roadside);(2)Piedmont,includingVera(forest),Milton(roadside)andNewPost(roadside);(3)Coastalplain,includingYorkRiverStatePark(roadside)andNas-sawadox(forest).

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isthoroughlydetermined.TheecologicallyassociatedspecieswerechosenbasedonourobservationsinVir-ginia.ThisspecieslistiscurrentlyunderreviewbytheTechnical Advisory Group (TAG) USDA/APHIS. A suitable host is defined as a plant species that will sup-portfeeding,ovipositionandlarvaldevelopmentoftheinsecttotheadultstage,andthelatteriscapableofpro-ducingviableprogeny.Ifanyofthesefourconditions

isnotmet,theinsectwillnotbeabletosurviveandisthereforenotabletosustainapopulationsolelyontheplantspeciesinquestion.Feeding tests:FoliageandbilletsofthespecieslistedinTables1and2wereused inchoiceandno-choiceteststodate.Testswereconductedfor7daysat20°C.

No-choice.Leafclustersofeachtestplantspecieswerecagedwith threeadults.Theamountof feedingwas determined by placing a transparent millimetersquaregridoverthefeduponportionoftheleaves.Thecontrolcagemaintainedatthesametimewithtreeofheavenwaswithoutweevils.

Choice.Twoseriesoftestswereconducted,onewithtree of heaven in the cage and one without. In the first testseries,oneclusteroftreeofheavenleavestogetherwithleafclustersofoneormorenon-targetspecieswasplacedincageswithadultbeetles.Inthesecondseries,twoormorenon-targettestspeciesbasedonavailabil-itywereplacedinthecagewithnotreeofheaven.Theavailabletargetspecieswereselectedrandomly.Feed-ingwasrecordedasdescribedabove.Oviposition tests:No-choice.Billetsofonetestplantspecieswereplaced in cageswithonegravid femaleand compared with control billets of tree of heavenwithoutweevils.Thecambiumwasexaminedforeggsafter1week.Foliageofthesamespeciesasthebilletwasplacedinthecagewiththeadultsforfood.

Choice.Twoormorespeciesofbilletswereplacedin cages with one gravid female.Two series of testswerecarriedout,withtreeofheavenplusoneormoreotherspeciesinthecageandonewithonlyanon-target

Table 1. Plant species to be tested for their suitability as hosts of Eucryptor-rhynchus brandti (Harold). Species are listed with the most closely related listed first and the most distant last.

Family Species CommonnameSimaroubaceae ChineseAilanthus altissima(Mill.)

SwingleTreeofheaven

Simarouba glaucaDC ParadisetreeSimarouba tulaeUrban AceitillofalsoLeitneria floridanaChapman CorkwoodCastela emoryi (Gray) Moran &Felger

Crucifixion thorn

Castela erectaTurp. Cockspur,goat-bush,retama,rupagüita

Holacantha stewartiiC.H.Muell. Stewart crucifixion thornPicramniaceae Alvaradoa amorphoidesLiebm. Mexicanalvaradoa

Picramnia pentandraSw. FloridabitterbushMeliaceae Swietenia mahagoni(L.)Jacq. WestIndianmahogany

Citrus aurantifolia(Christm.)Swingle LimeCitrus aurantiumL. SourorangeCitrus limon (L.)Burm.F. LemonCitrus paradisi Macfad. GrapefruitCitrus reticulateBlanco TangerineCitrus sinensisOsbeck SweetorangePtelea trifoliate L. CommonhoptreeZanthoxylum americanum Mill.

Northernprickly-ash

Table 2. Economically important and ecologically asso-ciated plant species to be tested.

Family Species CommonnameEconomically importantAceraceae Acer rubrumL. RedmapleFagaceae Quercus albaL. Whiteoak

Quercus rubraL. RedoakJuglandaceae Carya glabra

(Mill.)SweetPignuthickory

Juglans nigraL. BlackwalnutMagnoliaceae Liriodendron

tulipiferaL.Tulippoplar

Ecologically associatedAnacardiaceae Rhus typhinaL. StaghornsumacCuppressaceae Juniperus

virginianaL.Easternredcedar

Leguminosae Robinia pseudoacaciaL.

Blacklocust

Pinaceae Pinus virginianaMill. VirginiapineRosaceae Crataegusspp. Hawthorne

Prunus serotinaEhrh. Blackcherry

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Tabl

e 3.

T

ree

spec

ies

com

posi

tion

and

thei

r pe

rcen

t cov

erag

e (%

) at

nin

e su

rvey

site

s in

Vir

gini

a, U

SA.

Spec

ies

Mou

ntai

nPi

edm

ont

Coa

stal

pla

inM

ean

Day

ton

Roc

kBar

Bla

cksb

urg

Rad

ford

New

Pos

tM

ilton

Vera

Nas

saw

adox

York

Riv

er

Stat

ePa

rkAi

lant

husa

ltiss

ima

(P

.Mill

.)Sw

ingl

e15

8580

3035

7015

2015

32

Que

rcus

pal

ustr

isM

uenc

hh25

515

6010

1514

Pinu

svirg

inia

naP

.Mill

.95

11Ju

nipe

rusv

irgin

iana

L.

1015

1015

6Pi

nust

aeda

L.

404

Robi

nia

pseu

doac

acia

L.

1510

1520

5Li

quid

amba

r sty

raci

flua

L.10

1540

7Pi

nus s

trobi

L.

1050

7Rh

us g

labr

aL.

2015

4Pr

unus

virg

inia

naL

.15

1025

205

6Li

riod

endr

on tu

lipife

raL

.20

204

Acer

neg

undo

L.

1015

3Ile

x op

aca

Ait.

303

Jugl

ans n

igra

L.

520

3Ac

er ru

brum

L.

1010

2U

lmus

am

eric

ana

L.5

1Ac

er sa

ccha

rinu

mL

.10

1

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testplantspecies.Foliagewasaddedforfood.After1week,thebilletswerecheckedforeggs.

ResultsSurvey of VA and impact assessment of native herbivores

Seventeentreespecieswerefoundtoco-existwithtree of heaven in Virginia, with coverage of tree ofheavenrangingfrom15%to85%(Table3).Thecom-monassociatesfoundwithtreeofheavenwereQuer-cusspp.,observedinsixoftheninesurveysites,withcoveragerangingfrom5%to60%.Twentyinsecther-bivore species were collected from tree of heaven in2004and2005(Table4).The12beetles(Coleoptera)inTable4hadlittleimpactontreeofheaven.Theirpo-tentialasbiologicalcontrolagentsisminimalbecauseoftheirlowabundanceandbroadhostrange.Theonly

abundantColeopteraherbivorethatmaybecausingse-riousdamagetotreeofheavenaretheambrosiabeetlesEuwallacea validus (Eichoff) and Xyleborus atratusEichoff. These emerged from dying tree of heaven.We suspect that these species only attacked the dy-ingordead treesandhad littleeffectonhealthy treeofheaven.BasedonourobservationsofherbivoresinVirginiain2004and2005,theseherbivoreshadaneg-ligibleimpactontreeofheaven.

Ailanthus webworm, Atteva punctella Cramer,wastheonlyherbivoreconsistentlypresentinallsiteswithatotalofover30(eggs,larvae,pupaeandadults)pervisit.A. punctellacaused>50%defoliationfor1-year-oldseedlings.However,itseffectonlargertrees(>3cmdiameter)wasminimal,causinglessthan5%defoliationwithnovisible impact.Thepopulationofthis speciespeakedaroundAugust (Table5)withnosignificant difference among the three geographic re-gions[F(22,11)=0.63,p=0.83)Twootherinsectspecieshavebeenreportedtofeedontreeofheavenfoliage:Cynthiamoth,Samia cynthia(Drury),andtheAsiaticgardenweevil,Maladera castanea(Arrow)ineasternUSA(Drooz,1985).However,theirpresencewasnotidentified in this survey, and it is unlikely that these twoinsectspecieswillhaveanyimpactonthetreeofheaveninVirginia.

Quarantine testing of E. brandti imported from China: Development and rearing of E. brandti in the laboratory

Atotalof500and1200E. brandtiadultswerere-ceivedfromourcooperatorinChinain2005and2006,respectively.In2005,weinitiatedastudytoevaluatetheoptimumconditions for rearingE. brandti.Eigh-teen adults (nine females, seven males and two un-sexed)emerged from treeofheavenbillets inSpring

Table 4. Insect herbivores found on Ailanthus altissima (Mill.) Swingle in 2004 and 2005 from nine sur-vey sites in Virginia, USA.

Herbivores CommonName Numberindividuals/

siteColeopteraOdontota dorsalis

(Thunberg)Locustleafminer

0.7

Chrysomelidaespp. Leafbeetle 2.5Bruchid spp. Seedbeetle 1.3Popillia japonica

NewmanJapanesebeetle 3.4

Neotrichophorus spp. Clickbeetle 5.2Chrysolina

quadrigemina SuffrianFleabeetle 0.3

Apion spp. Weevil <0.1Merhynchites spp. Leafrolling

weevil<0.1

Sphenophorus spp. Snoutbeetle 0.3Orchestes spp. Weevil <0.1Scolytinae spp. Ambrosiabeetle <0.1Lepidoptera <0.1Ectropis crepuscularia

D.andS.Thesmallengrailed

<0.1

Thyridopteryx ephemeraeformis(Haworth)

Bagworm <0.1

Atteva punctella(Cram.) Ailanthuswebwormmoth

>30

Saturniidaespp. Silkwormmoths <0.1HemipteraEmpoasca sp. Leafhopper 0.7Anormenis sp. Planthopper 2.3Acanalonia sp. Planthopper 1.2OrthopteraScudderia furcata

BrunnerKatydid 0.5

Table 5. Mean (±SD) number of webworm, Atteva punc-tella Cramer, including eggs, larvae, pupae and adults, in 2004 and 2005, at three survey re-gions: Piedmont, Mountain and Coastal Plain.

Month Region

Mountain Piedmont CoastalPlain2004 June 4.0±1.4 37 28July 11.5±8.9 54.3±17.9 37.5±26.2Aug. 46.5±17.0 91.3±15.0 58.0±2.8Sept. 36.3±30.4 21.7±13.0 5.0±5.72005May 2.0±2.8 0.3±0.6 0June 6.5±7.5 17.0±23.6 21.0±5.7July 12.0±5.7 111.0±163.7 75.0±19.8Aug. 12.5±10.6 46.3±55.6 84.5±50.2Sept. 102.5±88.4 106.0±112.2 52.5±31.8

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2006,indicatingthattheweevilcouldcompleteitslifecycleinacuttreeofheavenlog.

Atapproximately20°C,mostE. brandtidevelopedfrom egg to adult in 3 months. However, some indi-vidualsdidnotcompletewithin9monthsandwerestilllarvaeafter9months.

E. brandtididnotexpelfrassfromthebillet.Frassremainedinthebilletwithinthefeedinggalleries.Thismade it difficult to know where the weevils were lo-catedandtheirlifestagewithoutdissectingthebillet.Only 15% (18/119) of the weevils completed their life cycleandemerged.Afewweevilsthatcompletedde-velopmentfailedtoemerge,possiblyduetopoorfoodqualityandquantity.Threeyounglarvaewereremovedfromonebilletandtransferredtoanotherbyinserting

themintoa7-mmdiameterhole.Frasswasobserved3,6,9and11daysafterthetransfer,andtwolarvaecom-pleteddevelopmenttotheadultstage.Theydevelopedintoadultsbutdiedinsidethetunnel.Thissuggeststhattransfer of larvae into an artificially drilled hole has the potentialtobeusedasabioassaytotestlarvaldevelop-mentonnon-targetspecies.

Basedon the aboveobservations,wedeveloped arearing procedure in 2006. Live tree of heaven treeswereperiodicallycut into1-mlengths,withdiameterrangingfrom10 to22cm.Oneendwas treatedwithparaffin and the other end was placed in a 5-cm water bathtohelpmaintainviablephloemtissueaslongaspossible. Groups of four billets were placed in a cage togetherwithupto150weevils(maleandfemale)for

Table 6. No choice foliage feeding tests of Eucryptorrhynchus brandti (Harold) adults on target and test species.

Family Species Commonname N X−±SD

(mm2peradultperday)

Simaroubaceae Ailanthus altissima(Mill.) Swingle

Treeofheaven 9 56.4±21.0aa

Simarouba glaucaDC Paradisetree 9 8.5±0.4.8bLeitneria floridanaChapman Corkwood 9 21.0±9.2b

Rutaceae Citrus aurantifolia (Christm.)Swingle

Lime 3 0c

Citrus aurantiumL. Sourorange 3 0cAceraceae Acer rubrumL. Redmaple 4 0cAnacardiaceae Rhus typhinaL. Staghornsumac 4 0cCupressaceae Juniperus virginianaL. Easternredcedar 4 0cFagaceae Quercus alba L. Whiteoak 2 0c

Quercus ruba L Redoak 2 0cJuglandaceae Carya glabra(Mill.)Sweet Pignuthickory 4 0c

Juglans nigraL. Blackwalnut 2 0cLeguminosae Robinia pseudoacaciaL. Blacklocust 4 0cMagnoliaceae Liriodendron tulipiferaL. Tulippoplar 4 0cPinaceae Pinus virginianaMill. Virginiapine 2 0cRosaceae Crataegusspp. Hawthorne 4 0c

Prunus serotinaEhrh. Blackcherry 2 0ca Means within a column followed by different letters are significantly different at P<0.05,Tukey–Kramermultiplecomparisontest.

Table 7. Two choice foliage feeding tests of Eucryptorrhynchus brandti (Harold) adults on target and test plant species.

Family Species Commonname n Testspecies A. altissima

X̄±SD(mm2peradultperday)

X̄±SD(mm2peradultperday)

Simaroubaceae Simarouba glaucaDC Paradisetree 9 0.9±1.7a 40.4±15.0a

Leitneria floridana Chapman Corkwood 9 2.7±1.9a 41.6±18.5a

Aceraceae Acer rubrumL. Redmaple 4 0a 26.6±1.6a

Magnoliaceae Liriodendron tulipiferaL. Tulippoplar 4 0a 28.7±16.8a

Anacardiaceae Rhus typhinaL. Staghornsumac 4 0a 22.3±16.8a

Leguminosae Robinia pseudoacaciaL. Blacklocust 4 0a 27.0±5.0a

Rosaceae Prunus serotinaEhrh. Blackcherry 2 0a 26.0±8.4a

a Denotes significant differences (P£ 0.05)betweenAilanthus altissimaandthetestspecies(Student’sttest).

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2to3weeks.Thebilletsanddeveloping larvaeweremaintained at 22°C.After 2 months, the billets werechecked daily to capture emerging adults. Through2006, 523 F1 generation adults emerged. Generally, theirsizewassmallerthanweevilsshippedfromChina.As we refine this rearing method, we will focus on us-ing fewer weevils in the oviposition cages to reducecompetitionamongdevelopinglarvaeinthebillets.

Adult feeding testOfthespecies tested, feedingbyE. brandtiadults

occurred only on species in Simaroubaceae. Tree ofheavenwashighly favored for feedingover thenon-targetspeciestested(Table6).Inno-choicetests,adultsconsumed nearly seven and three times more of treeofheavenfoliagethanS. glaucaandL. floridana,re-spectively.Nofeedingoccurredon15othernon-targetspecies. In two-choice tests, an even less non-targetspeciesfoliagewasconsumed.WhengivenachoiceoftreeofheavenandS. glaucaorL. floridana,E. brandtiadultsconsumed48and15timesmoretreeofheavenfoliage than the two non-target species, respectively.No feeding occurred on five species outside of Sima-roubaceae(Table7).

Billet inoculation assaySevenE. brandtilarvaewereinoculatedinto7.5-cm

diameter´76-cmlongbilletsoftreeofheaven,Rob-inia pseudoacacia, Prunus serotina and Citrus au-rantifoliatodetermineifyounglarvae(<30daysold,approximately second instar) can survive on plantsother than tree of heaven. These preliminary assayswerereplicatedtwice,andlarvaeremainedinbilletsfor30 days. Our results indicate a high level of specificity fortreeofheaven.Nofeedingoccurredinspeciesotherthan treeofheaven, resulting in100% larvalmortal-ity(Fig.2).Thisiscomparedwith36%larvalsurvivalin A. altissima past the instar when the larvae wereinoculated.

ConclusionsThe surveywork inVirginiahelped characterize treespecies associatedwith treeofheaven,withQuercusspp.beingthepredominantassociateregardlessofre-gion.Theinsectsfoundfeedingontreeofheavenwereofinconsequentialvalueintermsofdamagingtheweedtree and contributing to its overall control. Rearingstudies have improved to the point that a continuous

Figure 2. ExampleofEucryptorrhynchus brandti (Harold) larvalgalleriesineachof4speciestested.NotethatgallerieswerecreatedonlyinAilanthus altissima (Mill.)Swingle(photocredit,N.Herrick).

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colonyofE. brandtiispossible.Theuseofbilletswithone end sealed with paraffin and the other sitting in watermaybeanadequatebioassayforlarvalsurvivaltests. Preliminary results from the quarantine studiesshowedthattheriskofthisbeetleattackingnon-targettreesisminimal.Continuedtestingisongoing.

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