REVISTA
BRASILEIRA
DE
Entomologia
AJournalonInsectDiversityandEvolution w w w . r b e n t o m o l o g i a . c o mBiology,
Ecology
and
Diversity
Biology
of
Blepyrus
clavicornis
(Compere)
(Hymenoptera:
Encyrtidae),
a
parasitoid
of
Pseudococcus
viburni
(Signoret)
(Hemiptera:
Pseudococcidae)
Vitor
Pacheco
da
Silva
a,b,∗,
Mauro
Garcia
a,
Marcos
Botton
baUniversidadeFederaldePelotas,Pós-Graduac¸ãoemFitossanidade,DepartamentodeFitossanidade,Pelotas,RS,Brazil bEmbrapaUvaeVinho,BentoGonc¸alves,RS,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:Received28November2016 Accepted24May2017 Availableonline7June2017
AssociateEditor:AdeneydeFreitasBueno Keywords: Biologicalcontrol Chalcidoidea Obscuremealybug Parasitism
a
b
s
t
r
a
c
t
Encyrtids(Hymenoptera:Encyrtidae)arethemostimportantanddiversegroupofnaturalenemiesof
mealybugs(Hemiptera:Pseudococcidae).Blepyrusclavicornis(Compere)isthemostcommonparasitoid
associatedwithPseudococcusviburni(Signoret)intheSerraGaúcharegion,Brazil.Weconducted
labora-torystudiestoassessthedevelopmenttime,sexratio,adultlongevity,hoststageselectionforparasitism,
andeffectoffoodonthelongevityofadultfemalesofB.clavicornis.Theexperimentswereconductedina
climatechamberat25±1◦C,70±10%RHand12:12L:Dphotoperiod.ThesolitaryparasitoidB.
clavicor-nisparasitizedthird-instarandadultfemalestagesofP.viburni.Thedevelopmenttimewasmorethan
30days(31.75±0.38forfemalesand30.02±0.34formales)whenB.clavicornislaideggsinadult
mealy-bugfemales,and35days(36.50±0.50forfemalesand34.24±0.43formales)onthird-instarmealybug
nymphs.Thewaspsdidnotsurvivelongerthanfourdayswhentheywerefedonlywater,whilefemales
survivedforabout30dayswhenfedwithhoney.Thelifespanoffemalesisabout20dayslongerthanthe
lifespanofmales.AlthoughB.clavicorniscanprovidesignificantnaturalcontrol,reducingthenumberof
individualsinthenextgenerationbyparasitizingadvancedmealybuginstars,weconsideritunpromising
foruseinappliedbiological-controlprograms.Furthermore,thepredominanceofmalesintheprogeny
observedheresuggeststhatP.viburnimaynotbethemostsuitableorpreferredhostforB.clavicornis.
©2017SociedadeBrasileiradeEntomologia.PublishedbyElsevierEditoraLtda.Thisisanopen
accessarticleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction
Mealybugs(Hemiptera:Pseudococcidae)arecommonpestsin fruitproduction(Francoetal.,2009;Daaneetal.,2012).Theobscure mealybugPseudococcus viburni(Signoret)is acosmopolitanand polyphagousspeciesfoundin56countries.Itfeedsonmembers ofnearly90plantfamiliesand240genera(Garcíaetal.,2016),and isoneofthemainpestspeciesofvineyards(Vitisspp.,Vitaceae) inBrazilaswellasothercountriesoftheAmericas(Correaetal., 2012;Daaneetal.,2012;PachecodaSilvaetal.,2014).P.viburni alsoattacksotherplantsofeconomicimportance,suchasapples (Rosaceae)andpears(Rosaceae)(Ciampolinietal.,2002;Dapoto etal.,2011).Itfeedsontheleaves,trunks,cordons,canes,fruitsand rootsofhostplants.Similarlytoothermealybugspecies,P.viburni causesdamagetoleavesandgrapeclustersduetoitscopious secre-tionofhoneydew,whichprovidesasubstrateforthedevelopment
∗ Correspondingauthor.
E-mail:vitorcezar@gmail.com(V.PachecodaSilva).
ofsootymold,responsibleforlossesinproductivity,marketability andqualityofgrapes(Daaneetal.,2012).Moreover,thespecies hasbeenrelatedtothetransmissionofGrapevineleafrollassociated virusandGrapevineTrichovirusAandB,virusesthatcausevineyard degeneration,andlossesintheproductivityandqualityofclusters (Garauetal.,1995;Golinoetal.,2002).
Theobscuremealybugispresumedtohaveoriginatedinthe NeotropicalRegion(Charles,2011),whereawidediversityofits natural enemies,mainlyparasitoids(Hymenoptera:Encyrtidae), are present (Pacheco da Silva et al., in preparation). Biological andchemicalcontrolhavebeenusedagainstmealybugs,however, chemicalcontrolisoftennotsuccessfulduetotheircryptichabit andthepresenceofhydrophobicwaxesonthebodysurface(Franco etal.,2009).Hence,biologicalcontrolisagoodalternativemethod forsuppressingmealybugpestpopulations.
TheparasitoidwaspgenusBlepyrusHowardisalittle-studied groupthatprobablyoriginatedintheNewWorld(Noyes,2000). Mostofthe18describedspeciesarerestrictedtotheAmericas(4 speciesinSouthAmerica, 14inCentralAmerica and8inNorth America); exceptfor Blepyrusinsularis(Cameron),whichoccurs http://dx.doi.org/10.1016/j.rbe.2017.05.003
0085-5626/©2017SociedadeBrasileiradeEntomologia.PublishedbyElsevierEditoraLtda.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http:// creativecommons.org/licenses/by-nc-nd/4.0/).
Fig.1. (A)Blepyrusclavicornisfemaleand(B)male.Scale:1mm.
worldwide.In southern Brazil,Blepyrusclavicornis(Compere), a solitarykoinobiontendoparasitoid,isthecommonestparasitoid developinginP.viburni(PachecodaSilvaetal.,inpreparation). AdultfemalesofB.clavicornisaredarkmetallicblue,withpartof antennaandlegsyellowishandblack.Thebodyisabout2.0–3.5mm inlength(Fig.1A)(Noyes,2000).Malesaresmaller(2.0mmlong) andmorehairythanfemales,withblackbodies(Fig.1B). Mem-bersofthegenusareassociatedmainlywiththemealybuggenera PseudococcusWestwoodandDysmicoccusFerris(Noyes,2016).No informationaboutthedevelopment,reproductionandhost selec-tionofB.clavicornsisavailable.
Knowledgeofthebiologicalcharacteristicsofnaturalenemies isessentialinordertoselectpotentialspeciesforusein biological-controlprograms.Inthisstudyweinvestigatedcertainbiological characteristicsofB.clavicornis,asaprimaryparasitoidofP.viburni.
Materialandmethods
Mealybugculture
A colony of P. viburni was established using field-collected insects from a commercialstrawberry field in Farroupilha, Rio Grande do Sul (RS), Brazil (29◦08.705S, 051◦24.773W). Adult femaleswereidentifiedasP.viburniusingthekeyofWilliamsand GranaradeWillink(1992).Thecolonywaskeptinthelaboratory ofentomologyatEmbrapaGrapeandWine,BentoGonc¸alves,RS. MealybugsweremaintainedinsproutedpotatoesSolanum tubero-sumL.(Solanaceae),rearedinplasticcontainerswithavolumeof 1L(14cmdiameter×9cmdeep),closedwithacoverwitha10 cm-diameteraperturecoveredwithmuslintoallowventilationand preventthecrawlersfromescaping.Colonieswerekeptinaclimate chamberat25±1◦C,70±10%RHandintotaldarkness.
Parasitoidculture
The rearing colony of B. clavicornis was established in the laboratoryfromadultsemergedfrommummifiedP.viburni individ-ualscollectedinthesamecommercialareawherethemealybugs werecollected during 2014 and 2015.The species was identi-fiedby Dr. Daniel Alejandro Aquino (National University of La Plata,LaPlata,Argentina).Parasitoidswererearedinacryliccages (15cm×20cm×24cm)withfour5cm-diameter apertures cov-eredwithmuslintoallowventilation,andone15-cmaperturewith asleeveconsistingofamuslintube,onP.viburnirearedonsprouted potatoes.Parasitoidadultswerefedweekly,withastreakofhoney dilutedincornsyrup(50:50)onaluminumfoil.Thecolonywas maintainedunderthesameconditionsasthemealybugcolonies,
exceptforthephotoperiodfortheparasitoids,whichwas12:12L:D (preliminaryobservationsshowedthatthereisnoparasitismofB. clavicornisintotaldarkness).Colonieswerekeptinseparate facil-itiestoavoidparasitoidcontamination.Inordertoobtainnewly emergedadultsforexperiments,mummiesweretransferredwith afinepaintbrushintoindividualgelcapsulesandkeptinclimate chambersinthesameconditionsdescribedabove.
Choiceandno-choicetestforhostselection
Todeterminethehost-stagepreferenceoftheparasitoid,the experimentswereconductedinarenasconsistingofaplastic con-tainerof500mL(11cmdiameter×7.5cmdeep)withacoverwith an8cm-diameterapertureclosedwithamuslin.Eachcage con-tainedadiskoffilterpapertoabsorbtheexcesshoneydew,apiece ofaluminumfoil(2×4cm)withastreakofhoneydilutedinwater (50:50),andamealybug-infestedsproutedpotato.
Choiceandno-choicetestswereperformed.Inthechoicetest, 60mealybugs,15fromeachinstar(crawlers,secondinstar,third instar,and youngadultfemales)wereprovidedinthecages.To allowthemealybugstoattachtothesproutedpotatoes,theywere introducedintothecages24hbeforetheywereprovidedtothe par-asitoids.Themealybuginstarwasestimatedaccordingtothebody length: first nymphal instar (<0.5mm); second nymphal instar (0.8–1.0mm);thirdnymphalinstar(1.5–1.8mm)andyoungadult females(2.8–3.2mm)(themeasurementsarethemeanlengthofat least15insectsforeachstage).Newlyemergedadultcoupleswere kepttogetheraftertheiremergence,andafterthreedaystheywere introducedintoanarenafor24h,afterwhichtheywereremoved fromthecage.
Intheno-choicetest,20mealybugs,allfromthesameinstar, wereprovided in each cage, usingthe samemethod described above.After24hkeptwiththeparasitoids,mealybugswere sepa-ratedaccordingtotheirstageandplacedonnewsproutedpotatoes. Mealybugswereobserveddailyandanychangeswererecorded. When a mummy was observed, it was removed and placed in a gel capsule until emergence. The sex ratio (number of females/(number of females+number of males), measured at emergence,andthepercentageofparasitismwereevaluated.At least10replicationswerecarriedoutforboththechoicetestand theno-choicetest.Experiments werecarried outintheclimate room(25±1◦C,70±10%RHand12:12L:Dphotoperiod). Determinationofdevelopmenttimeandlongevityofadultwasps
Forthisexperiment20youngadultfemalesand20third-instar nymphsfixedonsproutedpotatoeswereexposedtoeachcouple
oftheparasitoidsfor24h.Thecontainerusedintheexperiment hadthesameconditionsasdescribedabove.Newlyemergedadult coupleswereformed,andwhenthefemaleswere3daysoldthe coupleswereintroducedineach cagewithmealybugsfor24h. Tenreplicates(cages)werecarriedout foreachhoststage.The developmenttime andsexratiooftheprogenywereevaluated. Afteremergence,waspswereplacedinindividualglasstubes(2cm diameter×8cm deep) closedwith Parafilm® and fedon honey dilutedwithwater(50:50).Theparasitoidswerecheckeddailyuntil allindividualsweredead.Thedevelopmenttimeandlongevityof B.clavicorniswasdeterminedat25±1◦C,70±10%RHand12:12 L:Dphotoperiod.
Influenceoffoodonadultfemalelongevity
NewlyemergedadultfemalesofB.clavicorniswereintroduced intoglasstubes(2cmdiameter×8cmdeep),closedwithParafilm®. Foodwasofferedonaluminumfoil(2×4cm).Thefollowing treat-mentswere evaluated: (i)water, (ii)honey diluted withwater (50:50),or(iii)purehoney.Treatments(i)and(ii),beingliquid, wereofferedassmalldropletsappliedwithaninsulinsyringe.Pure honeywasofferedasastreakwitha20-mLsyringe.Waterwas sup-pliedtwiceaweek,andtheothertreatmentswerechangedweekly. Parasitoidswerecheckeddailyuntilallhaddied.Accidentaldeath (e.g.insectsgluedonhoney)wereexcludedfromtheresults.At least30replicateswerecarriedoutpertreatment,keptat25±1◦C, 70±10%RHand12:12L:Dphotoperiod.
Statisticalanalysis
ThedatawereanalyzedstatisticallywiththesoftwareSPSS.The numberofparasitizedmealybugsinthechoiceandno-choicetests, aswellasthelongevityofadultfemalesfedondifferentfoodswere analyzedwithaone-wayANOVA,followedbyTukey’stestata sig-nificancelevelofp<0.05formeanseparation.Whennecessarythe dataweretransformedbeforeanalysis.Thedataforthe propor-tionofparasitismbetweenthechoiceandno-choicetestsandthe developmenttimewereevaluatedusingapairedt-test.
Results
Choiceandno-choicetestforhostselection
TheproportionofmealybugsparasitizedbyB.clavicornis dif-feredsignificantlyamonghoststages(choicetest:F=43.75;df=3; p<0.001;no-choicetest:F=24.30;df=3;p<0.001)(Fig.2).There wasnomummificationofthefirst-andsecond-instarindividuals. Inthechoicetest,thenumberofparasitizedmealybugswas sig-nificantly higherfor adults (53.30±7.99%)than for third-instar females(0.66±0.66%).Intheno-choicetest,40.00±4.94%ofadults wereparasitized,while23.30±6.19%ofthird-instarfemaleswere parasitized.
Immaturedevelopmenttimeandlongevity
ThedevelopmenttimeofB.clavicornislarvaewasaffectedby thehoststage of P.viburni(female:t=−3.590; df=20;p=0.02. male:t=−7.901;df=138;p<0.001),rangingfrom13.75±0.43to 19.00±2.00daysforfemales,andfrom13.17±0.08to16.43±0.80 daysformales,dependingonthedevelopmentstageofthehost (Table1).
Atthebeginningof themummification,thetegumentofthe hostmealybugsbecame a hardstructure (mummy),considered astheparasitoidpupalstage.Therewasnodifferencein pupal developmenttimebetweenhoststages,withameanof17days ofdevelopment.However,thesexoftheparasitoidaffectedthe
100 80 60 40 20 N1 N2 N3 Adult A a A a A b c B Host stage % of par asitism
Choice test No-choice test
Fig.2.PercentageofparasitismofB.clavicornisonP.viburniinchoiceandno-choice testsforhost-instarselection.N1,firstnymphalinstar;N2,2ndnymphalinstar; N3,3rdnymphalinstar.Graybars(±standarddeviation)followedbythesame letter(uppercase)andwithbars(±standarderror)followedbythesameletters (lowercase)donotdifferbyTukeytest(p<0.05).
durationofthepupalstage,whentheparasitismoccurredonadult femalemealybugs:theparasitoidpupaldurationwasshorterfor malesandlongerforfemales(t=2.238;df=21;p=0.03)(Table1).
Asingleparasitoidadultemerged fromeachmummyof the host;evidently,B.clavicornisisacceptedasasolitaryparasitoid. Survivaloftheparasitoidoffspring(meanproportionofoffspring emergedfromthetotalnumberofmummies)was58%for para-sitoidsthatdevelopedinadulthosts,and66%forparasitoidsthat developedinthird-instarhosts.Forbothsexes,thedevelopment timedecreasedwithincreasedhostage(female:t=−3.819;df=20; p=0.001,and male:t=−7.118; df=65;p<0.001) (Table1).The developmenttimeoffemaleswashigherthanmalesinbothhost stages(adult:t=3.339;df=64;p=0.02,andthirdinstar:t=3.428; df=21;p=0.04).
Thesexratio oftheparasitoidoffspringwasaffectedby the mealybughoststage(t=5.658;df=8;p<0.001).Althoughthe pro-portionofmaleswashigherthanfemalesinbothhostinstars,more femaleparasitoidsemergedfromtheadulthoststage(meansex ratio=0.307±0.20),whereasthethird instarproduced ahigher proportionofmales(meansexratio=0.02±0.08).
Thelifespanoftheadultparasitoidswasnotaffectedbyhost instar.However,itwassignificantlydifferentbetweenthesexes (adult:t=2.945;df=19;p=0.008,andthirdinstar:t=2.238;df=18; p=0.01).Femalewaspslivedlongerthanmalewasps(Table1). Influenceoffoodonadultfemalelongevity
Diet significantly influenced the longevity of B. clavicornis (F=17.587; df=2; p<0.001) (Fig. 3). When fed on water, the longevitywasstronglyaffected,andneithersexsurvivedformore than4days(3.90±0.69d).Thelongevityoftheparasitoidswere longerwhentheyfedon50%honey(33.28±4.74d),longerthan thosefed100%honey(20.00±2.20d).
Discussion
TheresultsshowedthatB.clavicornisprefersadvancedstages (adultandthird-instarfemales)ofP.viburniforparasitism,more than younger stages (no-choice test). Nonetheless, when given achoiceamongdifferenthoststages,thenumberofparasitized mealybugs was higher on adult females. No emergence of B.
Table1
Mean(±SE)developmenttime(days)ofeggtolarva,pupa,andtotalimmaturestages,longevityandsexratioofB.clavicornisondifferenthoststagesofP.viburni.
Hoststage Eggtolarva Pupa Immaturedevelopmenttime
(eggtoadult)
Longevity Sexratio
♀ ♂ ♀ ♂ ♀ ♂ ♀ ♂
3rdInstar 19.00±2.00Aaa16.43±0.80Aa 17.50±2.50Aa 17.81±0.49Aa 36.50±0.50Aa 34.24±0.43Ba 30.52±3.17Aa 11.07±2.57Ba 0.02±0.08a
Adult 13.75±0.43Ab 13.17±0.08Ab 18.00±0.38Aa 16.87±0.32Ba 31.75±0.38Ab 30.02±0.34Bb 33.28±4.74Aa 12.89±0.84Ba 0.30±0.20b
aWithinthecolumns(uppercaseletters),pairsofmeansfollowedbythesamelettersarenotsignificantlydifferent(p<0.05),withinthelines(lowercaseletters),pairsof
meansfollowedbythesamelettersarenotsignificantlydifferent(p<0.05).
1,0 0,8 0,6 0,4 0,2 0,0 0 20 40 60 Days Sur viv or r ate
Water Honey 50% Honey 100%
Fig.3. SurvivorshipcurvesforB.clavicornis.Influenceoffoodonlongevity,forthree treatments:100%honey,honeydiluted50:50inwater,andwateralone(control) (ANOVA:F=17.58;df=2;p<0.001).
clavicorniswasobserved fromfirst- and second-instar nymphs. TheseresultscorroboratetheobservationonAnagyruspseudococci (Girault),anothersolitarymealybugparasitoid,similarinbodysize, whenparasitizingPlanococcusficus(Signoret)(Daaneetal.,2004; Gülec¸ etal.,2006).IslamandCopland(1997)suggestedsome pos-siblereasonsfor A. pseudococcipreference for larger stages:(i) smallerhoststagescanbelessfrequentlyencounteredbythe par-asitoids;(ii)thesmallbodysizeoffirstandsecondnymphalstages candifficulttheoviposition;or(iii)smallerhoststageswere iden-tifiedbywaspsasbeinginsufficientasfoodresourcesforparasitoid development.
Anotherhypothesisfortheunsuccessfulparasitismofsmaller stagescouldbethedefensesstrategiesusedbyP.viburniagainst parasitoids.Thebehavioraland immunesystem(encapsulation) defenseshaveastrongimpactontheparasitismrateofmealybugs (BlumbergandVanDriesche,2001);however,eventhoughthese twostrategieswerenotevaluatedhere,theywereprobablynotthe causefortheabsenceofparasitismintheearlyimmatureinstars. TheencapsulationdefenseofP.viburniagainstparasitoideggsoften occursin larger-bodied hosts thanin theinitial, smallerstages (Karamaounaand Copland, 2009).Similarly, behavioral defense (abdominalflipping,escaping;andreflexbleeding)isatechnique usedbyadultfemalesagainstparasitoids(Bugilaetal.,2014). Prob-ablysmallermealybugsalsousethistechnique,butnotwiththe sameefficiencyaslargerfemales.Thisbehaviorandthe encapsu-lationofeggsandlarvaecouldhaveinfluencedtheparasitismrate ofB.clavicornismoreinlargerhoststhaninthefirstandsecond nymphalstages.
ThecompletedevelopmenttimeofB.clavicornisfromthe par-asitismtoemergenceofadultwaspsrangesfrom30to36days, depending on the parasitoid sex and host stage. Mummifica-tion occurs aftertwo weeks of parasitism, and only one wasp emergesfromeachmummy.Thedevelopmenttimeforparasitoids
decreasedwithincreasedhostage.Asimilarrelationshipbetween parasitoid development time and host stage was observed for other,closely related, solitary ercyrtid parasitoids,e.g. Aenasius bambawaleiHayat(Abdinet al.,2013)and Aenasiusvexans Ker-rich(Bertschyetal.,2007).B.clavicornisisakoinobiontparasitoid, andafterparasitizationP.viburnicontinuestogrowandtolayeggs untilmummification.ThesamewasobservedforLeptomastixepona (Walker)parasitizingP.viburni(KaramaounaandCopland,2000) andforothermealybugspecieswhenparasitizedbyencyrtid par-asitoids(CadéeandVanAlphen,1997;ChongandOetting,2006). Thepreferenceforlargerhosts,andthefactthatthefemale mealy-bugcontinuestolayeggsafterparasitism,canbelimitingfactors forthepracticaluseofB.clavicornisinappliedbiologicalcontrolof P.viburni.
Parasitizedadultmealybugsproducedmorefemalewaspsthan thethird-instarstage.Probably,B.clavicornislaytheirfemaleeggs onmoresuitablehosts[sexallocation,astrategywherethefemales choosetolayfemaleeggsonlargerhosts(King,1993)].Sex alloca-tionhasanimportanteffectonbiologicalcontrol,sincewaspsthat developedonlargerhoststendtohavelargerbodysizes,whichcan affecttheperformanceofthewaspsasabiological-controlagent (Sagarraetal.,2001).P.viburnifemales usedinthis studywere about3mmlong;however,inthefieldandintherearingcolony weobservedlargerpre-reproductivefemales,almost4mmlong (personalobservation).Apparently,undernaturalconditionsthe parasitoidshavemoresuitablehostsavailableforoviposition.
Theprogenyobservedherewasmale-biasedinthechoiceand nochoice-tests,wherethirdinstarsproducedmalesalmost exclu-sively,aspredictedbyKing(1993).AhigherproportionofL.epona maleswasobservedonparasitoidsemergedfromsmallerthanfrom largerhosts(KaramaounaandCopland,2000).Gülec¸etal.(2006) alsoobservedamale-biasedA.pseudococcipopulationwhenthese waspswereparasitizingyoungermealybugs.Daaneetal.(2004) observedthatmostA.pseudococcifemalescamefromlargerhosts. InstrawberryfieldsintheSerraGaúcharegion,B.clavicornisisthe mostcommonparasitoidofP.viburni,anditspopulationsare male-biased(70%oftheinsects collectedparasitizing P.viburniwere males)(unpublisheddata). Someaspectsmayhave affectedthe sexpopulationinthefield,suchascompetitionwithother encyr-tidmealybugsandthepresenceofothermealybugsinthevicinity ofthestrawberryfield.Severalparasitoidspecieshavebeen col-lectedinthesameareawhereB.clavicorniswascollected(Pacheco daSilvaetal.,inpreparation).Amongthesewaspsarespeciesof Anagyrus,whichstudiessuggesthavethesamehostpreferenceas B.clavicornis(Daaneetal.,2004;Gülec¸etal.,2006).Other mealy-bugswerecollectedonstrawberryplantsinthesamearea,such asFerrisiameridionalisWilliams,butprobablyitwasnottheonly speciespresentonotherplantssurroundingthecommercialarea. BlepyrusspeciessuchasB.insularis(Cameron)andBlepyrus sac-charicolaGahanhavebeenreportedtoparasitizeFerrisia(Noyes, 2016).Therefore,inthefield,femalesmayhaveawiderchoiceof bodysizesofP.viburniandothermealybugspeciestolayfemale eggs.
Thelifespanofadultwaspsdifferedbetweenthesexes.Gülec¸ etal.(2006)alsoobservedthatfemalewaspslivelongerthanmales.
Supplementarysweetfoodaffectedthelifespanof adultfemale wasps(Beltràet al.,2012).Flowerscanbeanimportant source of carbohydratesfor mealybug parasitoids, asobserved for the encyrtidparasitoidC.perminutus(Daviesetal.,2004).Honeydew isanothersourceofcarbohydratesusedbywasps;Sandanayaka etal.(2009)observedthatAcerophagusmaculipennis(Mercet)had asimilarlifespanwhenitfedonhoneyandonhoneydewfromP. viburni.
Theresultspresentedhereshowthatadultfemalesandthird instarsarethemostsuitableandpreferredhoststagesforB. clav-icornisparasitism;andwhensuppliedwithcarbohydrates,female waspscanliveforalmost30days.However,thepreferenceofB. clavicornisforthirdnymphalinstarsandadultfemales,andthefact thatthemealybugscontinuetolayeggsafterbeingparasitized,are factorslimitingtheuseofthisparasitoidinbiological-control pro-gramsforP.viburni,becausereleasesofwaspsintothefieldmust betimedaccordingtotheavailabilityofthepreferredmealybug hostinstar.Furthermore,themalebiasofpopulationsobserved inthefield,andhereconfirmedinthelaboratory,suggeststhatP. viburnimaynotbethemostsuitableorpreferredhostspeciesfor B.clavicornis.
Conflictsofinterest
Theauthorsdeclarenoconflictsofinterest.
Acknowledgments
WethankElisângelaCarolinaWeberGalzerandJoelPasinato for their assistancewith the laboratoryand field experiments; DanielAlejandroAquinofromtheNationalUniversityofLaPlata, Argentinafortheparasitoididentification;andBoraKaydanforhis importantsuggestions,whichimprovedthemanuscript.Research fundingwasprovidedbyEmbrapaGrapeandWineandthe Pro-gramadeApoioàPós-Graduac¸ão(PROAP-CAPES),Brazil.Voucher specimens are deposited at the laboratory of entomology of EmbrapaGrapeandWine,Brazil.
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