Table Of Content45
Effects ofInsecticide Use on Abundance and Diversity of
Tomato Pests and Associated Natural Enemies in Hawai'i
MARY F. PURCELL', MARSHALLW. JOHNSON
& BRUCE E. TABASHNIK
DepartmentofEntomology,UniversityofHawaiiatManoa,Honolulu,Hawai'i96822,USA
ABSTRACT.AsurveyofinsectswasconductedinFall 19S9plantingsof7commercial
fresh market tomato farms in Maui, Moloka'i and Hawai'i islands. The primary pests
whichattackedUiefruitwereHelicoverpazea,Keiferialycopersicella.Bactroceracucur-
bilae(Coquillett).andSpodopteraexigua.Thekey foliarpestswereagromyzidleafmin-
crs and whiteflies. Uriomyzasalivaeand L trifolii were the 2 leafminerspecies found
attacking the foliage on all farms. Liriomyza salivae was the dominant species, and
accountedfor68%oftheleafminersrearedfromtomatoleaflets.Ninespeciesofleafmin
erparasitoids wereobserved in the7 farms. Diversity ofparasitoid specieswas 2to 3
timeslowerinfarmswhichusedinsecticidesonacalendarbasisthanfarmswhichapplied
insecticides only when pests reached nominal thresholdsorused selective insecticides.
Diglyphusbegini wasthedominantleafminerparasiloid,representing85%ofthepara
sitesreared fromtomatoleaflets.Themeanparasitismralesofleafminersovertheplant
ingperiodranged50-60%infarmsusinginsecticidesonanominalorselectivebasis,and
8-17% inthecalendaruse farms.Thepredominantwhiteflyspecieswasthegreenhouse
whitefly, Trialeurodesvaporariorum,whichexceededeconomicinjurylevelsin2ofthe
"calendar" farms forupto 33% ofthesampling periods. Irregularripening disorderof
tomatoes,inducedbyBemisiatabaciBiotypeBwasobservedforthefirsttimeinthestate
ofHawai'iin I siteonHawai'iisland.Potentialmanagementalternativesforkeypestsof
tomatoesin Hawai'iarediscussed.
INTRODUCTION
FreshmarkettomatoesareaprincipalvegetablecropinthestateofHawai'i.In 1989,
they were valued at 3 million dollars, acreage was 101 ha, and thetotal production was
about 130metric tons (Anonymous 1990). Several pests inflictyieldreductionsindirect
ly by foliar feeding. These include the agromyzid leafminers, Liriomyza salivae Blan-
chard and L trifolii Burgess, greenhouse whilefly, Trialeurodes vaporariorum (West-
wood),andtheswcelpoiatowhilefly,Bemisiatabaci(Gennadius).BemisiatabaciBiotype
B isanimportant vectorofseveral plantvirusesandhasbeenassociatedwithotherplant
disordersofunknownetiology(Brown&Costa, 1992,Costa& Brown 1991,Hoelmeret.
al. 1991, Bharathanetal. 1990,Schusteretal. 1990). Irregularripeningisarelativelynew
disorderoftomato,andwasfirstrecordedinFloridain 1987(Maynard&Cantliffe 1989).
The disorder is characterized by incomplete ripening of longitudinal sections of fruit.
Symptoms arc associated with feeding ofB. tabaciand symptoms are more severe with
increasingdensityofwhiteflyfeeding(Schusteret al. 1990).
About 17 parasitoid species were introduced by the Hawai'i Department ofAgri
cultureinthe 1970stocontrolLiriomyzaleafminersandwhiteflies(Funasakietal. 1988).
Asacomplex,severalparasitoidspeciesappeartoprovideeffectivecontrolinwatermelon
(Johnson 1987). Ofthese,Chrysonotomyiapunctiventris(Crawford),Halticopteracircu-
lus(Walker) werethe predominant parasitoidsin watermelon. However,extensiveuseof
insecticides has been reported to adversely affect them (Johnsonet al. 1980). In tomato,
theeulophids, Diglyplmsbegini(Ashmcad) and D. intennedius(Girault) werecommon
lyobserved intomato fieldsinO'ahu (M.W. Johnson, unpubl. data).
Parasites such as EncarsiaformosaGahan and E. transvenaTimberlake have been
introduced forthe control ofgreenhouse whitefly, but appeartobe rare in tomatoes and
1.Presentaddress:Tropicall-'ruitandVegetableResearchLaboratory.USDA-ARS.P.O.Box4459.Hilo.Hawai'i
96720.USA.
46 Proceedings ofthe Hawaiian Entomological Society Vol. 32
othervegetablecrops(Gcrling 1983).Preliminaryobservationsinthegreenhouseindicate
thatthehemipteranomnivore, Cyrtopeltismodesius Distant, maybeanimportantpreda
tor of the greenhouse whitefly. It is predaceous on a variety ofother insects including
Helicoverpa (= Heliothis) zea (Boddie) eggs and larvae, and Uriomyza larvae (Illing-
worth 1937, Parella& Bethke 1982). However, C. modesius feedsboth on thestemsand
blossomsoftomato plants anddecreases fruitset(Illingworth 1937).
Theprimarydirectpestsoftomatofruitincludethetomatofruitworm,H. zea,toma
to pinwonn, Keiferia lycopersicella (Walsingham), beet army worm,Spodoptera exigua
HUbner,thesoutherngreenstinkbug,Nezaraviridula(Linnaeus),andthemelonflyBac-
trocera cucurbitae (Coquillclt). In general, natural enemies do not reduce levels offruit
infestationbelow3%,andinsecticidesareusedtocontrolthesepests.Applicationofpes
ticidesoften result insignificantoutbreaksofpests suchasthe whitefliesand leafminers
viadevelopmentofpesticideresistanceand/orsuppressionofnatural enemies.
Theobjectivesofourstudy wereto: I)classify therelativeimportanceofthe major
pestsofcommercial tomatoesin Hawai'i; 2)determinethespeciesdiversityofimportant
natural enemy species; and 3) evaluate the impact ofgrower management practices on
pestand natural enemy populations.
MATERIALS ANDMETHODS
Studies wereconducted in 7 commercial tomato plantings: Kula, Maui (450 m and
900melev.); Ho'olehua,Moloka'i;Glenwood,Volcano,CaptainCook,and Kealakekua,
on Hawai'i Island, beginning 22 September 1989 and ending 23 January 1990. Surveys
wereinitiatedfromthesecondtofourthweekaftertomatoesweretransplantedintheHeld
andcontinueduntilthefourth-sixthtomatoharvest.Thesizeoftomatoplantingssurveyed
rangedfromca.0.4-4ha. Blackplasticmulchanddripirrigationlineswerelaidalongthe
rowsandtomatotransplantswereplantedinholesmadeintheplastic.Alltomatoesexcept
plantings from the2 farms inMauiwerestakedandtrcllised.Tomatoeswereprunedto2
mainbranchesatleastonceduringtheplantingcycle.TomatoesinGlenwoodandVolcano
weregrown incommercial shadehouses.
InSeptember 1989,growersfromeachof7 farmswereinterviewedtodetermineihe
typeand frequencyofchemicalandbiologicalcontrol used.Thefarmswereclassifiedby
3 main types ofmanagement tactics, and included: I) Calendar, insecticides toxic to a
wide range ofinsects (e.g., mcthomyl, oxamyl, dimethoate, endosulfan, fenvaleratc and
esfenvalerate)wereappliedonaregularbasis. Decisionstoapplyinsecticidesweremade
without regard to insect pest infestation levels; 2) Nominal thresholds: broad-spectrum
insecticides wereonly applied when insect populations approachedorsurpasseddamag
ing levels. Thresholds were based on growers' experience, not scientific determination.
Timingofcontrol tacticswasbasedonperiodicsamplingandassessmentsofinsectnum
bers by the grower; and 3) Selective: the microbial insecticide, Bacillus thuringiensis
kurstaki (Bt) which is specific to a few lepidoptcran pests (e.g., H. zea ) was applied.
Naturallevelsofparasitesandpredatorswererelieduponforleafminerandwhiteflycon
trol.
Each farm was divided into 4 randomly selected sections, forweekly sampling for
insects. Within each ofthe 4 sections, 15 tomato leaflets were collected at random and
takentothelaboratoryforcountingandidentification. Usingalightmicroscopewithback
lighting,activeleafminerlarvaeandparasitizedlarvaewerecounted.Immaturewhiteflies
werealsocounted by placing aclearacetategrid with 1 cm2 squaresoverthe leafunder-
surface(Johnsonet al. 1991),andcountingthenumberofwhitefly nymphsandpupaeat
random on four I cm2 sectors. Whitefly pupae were examined forthepresence ofpara-
sitoids. Aftercounting, leaves wereheld in papercartons (Johnsonetal. 1980) to allow
Purcell et al.: Effects of Insecticides on Tomato Insects 47
foremergence of adult leafminers and parasitoids. After S weeks, adult leafminers and
parasitoidspecies were identified.
Cynopellismodesius, wassampled byshaking5 flowerbearingbranchesatrandom
withineachofthe4sectionsofeachfarm,andcountingthenumberofnymphsandadults
fallingontoabeating tray (3S.S cm.diam.).
Wing-style phcromone traps, each with a specific lure (Ecogen Inc., Goodyear,
Arizona) wereused to monitorthe lepidoptcransK. iycopersicella, H. tea, andS. exigua.
Asingle trap was hung froma stakeortrellis wire within thecenterofeach farm.Traps
werehungatthecenterofthetomatocanopyandraisedastheplantsgrewinheight.Trap
bottomswerereplacedweekly,andmothswerecounted. Lureswerereplacedineachtrap
every4weeks. When tomatoesreached the maturegreen stage,30fruit fromeachofthe
4sectorsofallfarmsexceptKula900mwererandomlyselectedandthefruitwereexam
inedforevidenceoffeedingdamagecausedbyIhclepidoptcransandsoutherngreenstink
bug. In addition,a numberoffruit withoviposition scars ("stings") from melonfly were
counted. Fruit samples werecollected weekly for4-8 weeks, dependingon theduration
ofharvesting in each farm. Numbersoffruit damaged by each species was converted to
percentages.
Statistics
Themeannumberofunparasitizedand parasitized Icafminerlarvaeperleafletandwhite-
flics percm1on each leaflet foreach sampledate were calculated, and alsocombined to
calculate the mean numberofinsects recordedduring theentire planting cycle. Species
diversityofIcafminerparasitoidsinthedifferent farms wascalculatedusingtheShannon
index ofdiversity (Magurran 1988):
H'="IPi\nPi (1)
where H' = index of diversity, andpj is the proportion of individuals found in the «th
species.Tocalculatedifferencesindiversity indicesamongthedifferentfarms,wecalcu
lated the varianceofH' and thetstatistic(P£0.05; Magurran 1988):
VarH'= { [IPi(l/ip^2-(Ip Inp()*]/V" } + [(S- I)(2fiPy'] (2)
t=(H', - H'2)(VarH', +VarH'2)" ' (3)
Differences in percent parasitizationofleafminers wereanalyzedusingtheGeneral
Linear Models Procedure and Sheffe's Ftest (SAS 1988) for pairwise comparisons be
tweenthe3 managementcategories.
RESULTSANDDISCUSSION
Insecticide Use
Ofthe 7 farms, insecticides wereappliedon acalendarbasis in 3 farms: Glenwood,
Volcano and Kula 900 m (Table I). In these farms, primarily organophosphate and py-
rcthroidinsecticideswereusedweeklyorbiweekly.Morethan20treatmentswereapplied
duringtheplantingcycleinthesefarms.Threefarmsin Ho'olehua,Kealakekua,andKula
450mused"nominalthresholds."In2ofthe"nominal"farms,alternativetreatmentssuch
asinsecticidalsoap,Btandthematingdisruptant,lycopersilurefortomatopinworm,were
applied.The Kula(450m)farmer'ssprayequipmentdidnotadequatelycoverthefoliage
48 Proceedings of the Hawaiian Entomological Society Vol. 32
Table1. InsecticideuseatseventomatofarmsinHawai'i.
Pesticide No.or
Use FarmSite Chemicalsused Targestpcst(s) applications
Calendar Clenwood esfenvalerate lepidoptera1 8
methomyl leafminer 5
oxamyl whiteflies,leafminer 7
endosulfan whitefly 2
Total:22
Volcano dimethoate leafminer 6
oxamyl whitefly 5
methomyl lepidoptera,leafminer 1
fenvalerate leafminer,whitefly, 5
lepidoptera
insecticidalsoap whitefly 6
Total:23
Kula900m mevinphos lepidoptera ■ 9
methomyl leafminer 9
fenvalerate lepidoptera 4
Total:22
Nominal Kcalakekua esfenvalerate lepidoptera 2
endosulfan whitefly 4
methomyl leafminer 2
oxamyl whitefly.leafminer 2
B. l.k2 tomatofruitworm 6
insecticidalsoap whilefly 5
Total:21
Ho'olehua lycopersilure3 tomatopinworm 2
malalhion+bait• melonfly 2
methomyl leafminer,lepidoptera 2
esfenvalerate lepidoptera 1
B. i.k. tomatofruitworm 4
Total: 11
Kula450m disyston leafminer 1
azinphosmethyl leafminer 1
methomyl whitefly,leafminer 2
mevinphos lepidoptera 2
oxamyl whilefly,leafminer 1
Total:7
Selective CaptainCook B. t.k. tomatofruitworm 2
1. Lcpidoptcranpests:tomatopinworm,tomatofruitworm,andbeetarmyworm.
2. Bacillusthuritigiensisvar.kurslaki
3.NoMale®(Ecogen.Goodyear.AZ)
4.Proleinbail(Nulure®)addedtoinsecticideandappliedtowindbreakvegetation(Sudangrass)
Purcell et al.: Effects of Insecticides on Tomato Insects 49
300
Selective
Calendar Nominal
Fig.1.RelativenumberofUriomyzasativaeandL irifolii adultsemerged fromleavesthroughout
entireplantingcycleineachofseventomatofarmsinHawai'i.
orfruit; and spray records were notavailable afterthefirstmonth ofplanting(Table 1).
In Ho'olehua, Sudan grass windbreaks were treated with maiathion and protein bait to
control melon flies, which commonly roost in weeds andothernon-host plants(Nishida
& Bess 1950). In theCaptain Cook farm, Bl was applied early in the season forH. zea
control andthereforeclassifiedin the"selective" managementcategory.
Leafminers
Twoagromyzids,LsativaeandL trifolii,wereobservedinthe7tomatofarms(Fig.
I). Liriomyza sativae was the dominant species in 6 ofthe sites, accounting for 68% of
theleafminerspeciescollected. Incontrast,L. trifoliipopulationswereabout50%higher
than L. sativae in the Volcano, which was a "calendar" farm. L trifolii has developed
resistancetoinsecticidesmorerapidly than L sativae(Masonetal. 1987), andmayhave
reachedhighlevelsbecauseofahistoryofintensiveinsecticideuseatthisfarm(Table I).
Leafminerlevels in Kula 900mand Ho'olehua werebelow 0.2perleafletthrough
outthe sampling period, and werenot included in Fig. 2. In general, leafminernumbers
were below 1 perleafletin 2 ofthe3calendarfarms, indicating susceptibilitytoinsecti
cides. However, in the Volcano farm, levels exceeded 4 per leaflet for 3 weeks, despite
morethan6applicationsofinsecticidesfor leafminers.Thissuggeststhatresistantpopu-
A) 'CALENDAR'
(II
o
Gtenwood,HI
Volcano,HI
2 5 5 57 i t fi-3 i
IW ++ [
ft first harvest
V..:
o
o
I
■
263 277 291 30S 319 333 347 361 010 024 256 270 284 298 312 326 340 354 003 017 031
Julian Julian
B)'NOMINAL' 0
X
Kealakekua,HI Kula, Maui (450m)
,12 4 9 9 9 9 9 3 1 4
0.6 ' 4 3 2 4 2 7 S.
7 7 7 &r
0.S f 4 H
m
0.4 I *
J first>harvect o
0.3
o
5"
0.2
A I
0.1 V -
s
CO
0.0256 270 284 296 3t2 326 340 354
Julian
Fig.1.Densityofunparasitized(opencircles)andparasitized(closedcircles)larvaeinCalendarandNominalfields.Arrowsindicatetimesofinsecticideapplication. 1
=esfenvaleraie,2=methomyl,3=oxamyl,4=endosulfan,5=dimethoate,6=fenvalerate,7=insecticidalsoap,8=mevinphos,9-B. thuringiensiskurstaki(Btk),
10=disyston, 11=mevinphos, 12=azinphosmethyi.
Purcell et al.: Effects of Insecticides on Tomato Insects 51
Table 2. Leafminer parasitoids collected in fresh market lomato farms in Maui, Moloka'i and
Hawai'i.
Calendar NominalThreshold Selective
Glen- Volcano Kula Molokai Kcalakekua Kula Capt.
Parasiloidspecies: wood 900m 450m Cook
Larvalparasitoids:
Chrysonotmayia 0 0 0 0 0 46 1
puncliventris
(Crawford)
C.formosa 0 0 0 0 I 0 0
(Westwood)
Closiemcerus 0 0 0 0 0 0 2
utahensisCrawford
Diglyphus 0 9 1 1 15 39 48
intermedius(Girault)
D.begini(Ashmead) 22 21 17 3 21 374 87
Hemiptarsenus 0 0 0 0 2 0 0
semialbiclavus
(Girault)
Larval-pupal
parasitoids:
Ganaspidium 0 0 0 3 0 16 2
utitis(Beardslcy)
Chrysocharis 1 0 0 1 10 14 4
oscinidis(Crawford)
Haliicoprera 0 0 0 0 3 1 4
cinulusWalker
Grandtotal 23 30 18 8 52 490 148
No.species 2 2 2 4 6 6 7
H'(diversityindex)/' 0.18a 0.56b 0.43b 1.00c l.41d 0.80c 0.87c
I. Meanswiihinarowfollowedbydifferentlettersaresigniilcantlydifferent (Pi0.05,Itest,Maguiran1988).
Table3. TotalparasitismratesofUriomyzaleafminers.
PesticideUse/Farm Mean % parasitism!SEM Peak % parasitism
Calendar
Glenwood 17.8±6.1 b 66.7
Volcano 8.2+4.1 b 61.1
Nominalthreshold
Kealakekua 52.0± 11.4a 100.0
Kula450 62.2±8.4a 100.0
Selective
CaptainCook 57.8±8.1 a 92.6
Means withinacolumnfollowedbythesameletterarenotsignificantlydifferent(P<
0.05:Scheffe'sFicst:SASInstitute1988).
52 Proceedings of the Hawaiian Entomological Society Vol. 32
lations ofL trifolii were present. Populations were also below economically damaging
levels in 2 of the nominal farms, which suggests that less frequent applications (i.e.,
Ho'olehua)werejustaseffectiveascalendarapplications. Preliminarydataindicatesthat
tomato yields are reduced only when peak seasonal density exceeds 6 live larvae per
leaflet, (M.W. Johnson, unpubl. data). Based on these levels, treatments for leafminer
were probably unjustified in the calendar and nominal farms, and that leafmincrs may
have been developing resistance to some ofthe materials used inVolcano and Kula 450
(i.e.,methomyl,oxamyl;Fig. 2). Indeed,in theselectivefarm,whichdidnotapplyinsec
ticides for leafminer, levelsdid notexceed0.8 miners per leaflet (Fig. 2), which indicat
edthatnatural controlswereeffective.
Nineparasitichymenopterousspeciesassociatedwiththelcafminerswereidentified
whichincluded6larvaland3larval-pupalparasitoids(Table2).Larvalparasitoidsinclud
ed Diglyphus begini (Ashmead), D. intermedius (Girault), Chrysonotomyia fonnosa
(Westwood),C.punctiventris(Crawford),Closterocenisutahensis(Crawford),andHemi-
ptarsenus semialbiclavus (Girault). Larval-pupal parasitoids were Ganaspidium utilis
Beardsley, Chrysocltarisoscinidis(Crawford),andHallicopteracirculus(Walker).The2
mostcommonparasitoidswereD.beginiandD. intermedius,whichaccountedfor84.8%
and 14.6% respectively ofthe parasitoids collected from tomato leaflets overthe entire
plantingcycle(Table2).Diglyphusbeginiisalsoreportedlythemostcommonparasitoid
associatedwithtomatoesinCalifornia,whileC.fonnosaandD. intermediusarethedom
inantspeciesin Floridatomatoes (Johnson & Hara 1987). High levelsofresistanceinD.
begini to pyrcthroids and 2 organophosphate insecticides have been documented (Rath-
manetal. 1990).ThepresenceofD. intermediusin2ofthe3 calendarsitessuggeststhat
itmayalsobedevelopingresistancetotheseinsecticides.
Significantlyfewerparasitoidspecieswereobservedinthecalendarfarmsthaninthe
nominal threshold orselective farms (t = -5.04; df= 5, P=0.004;Table2).Absenceof
many species such as C.punctiventrisand C. oscinidisfromthecalendarfarmssuggests
that these species were adversely affected by frequent insecticide applications. In addi
tion, thediversity index ofspecies in eachofthecalendarfarms wassignificantly lower
thanin thenominalthreshold ortheselective farms(Table2).
PercentageparasitisminGlenwood(calendar)climbedtoamaximumof38%or0.5
parasitoidsperleafletbytheendoftheplantingcycle(Fig.2). Insecticidetreatmentswere
haltedfor2weeksatthissite,whichcouldhaveaccountedforthisincrease. But,D. begi
niatthissitewas alsoshowntoberesistanttoconcentrationsbelow field ratesofoxam
ylandmethomyl (Rathmanetal. 1990). Diglyphusbeginiappearedtobesuppressedini
tiallybyintensiveapplicationsofoxamyl,methomylandesfenvalerate(Fig.2). However,
the 2 week break in applications may have allowed these populations to increase.
Parasitism levels continued to risedespite 2applications ofesfenvalerateand methomyl
inthefinalweeks,suggestingthatresistantpopulationsmighthavebeenpresent,although
furtherwork is neededtoverifythisresult.
Interestingly, the farm with the highestdiversity levels was Kealakekua, a nominal
thresholdsite(Table2), whichrestricteditsuseofbroadlytoxicinsecticidesto3applica
tions in the first 3 weeks after planting (esfenvalerate, oxamyl and endosulfan), and 3
applications during harvest when whitcflics exceeded perceived economic levels.
Leafminerparasitoids mayhavebeenableto survivethisregimeofapplications,perhaps
because residues of insecticides on the leaf surface had decreased to sublethal levels.
Overall parasitism rates were fourfold higherin the nominal and selectivefarms than in
thecalendarfarms (F= 11.95;df=4,54; P-0.0001;Table3). However, nodifferences
inparasitismoccurredbetweenthenominal thresholdandselectivefarms(Table3).
In addition to the relatively high rates of leafminer parasitism observed in the
Purcell et al.: Effects of Insecticides on Tomato Insects S3
Captain Cook, HI
1.0
9 9 unparaslized
I I
0.8 first harvest
g 0.6
I 0.4
J2 0.2
0.0
256 270 284 298 312 326 340 354
Julian date
Fig. 3. Density ofunparasitized (opencircles) and parasitized(closed circles) leafminerlarvae in
SelectiveHeld.Arrowsindicatetimesofinsecticideapplication.9=0. ihuringiensiskurstaki(Btk).
Captain Cook (selective) farm, large numbers of Cyrtopeltis modestus Distant were
observed at this farm (Fig. 3). Cyrtopeltis modestus was sporadically observed in the
Kealakekua farm, but was absent from thesamplesofthe remaining5 farms suggesting
high susceptibility to insecticide applications. In the Captain Cook farm. C. modestus
increasedasthe leafminerpopulationsinitiallydeclined.ThesedatasuggestthatC.mod
estus also contributed to mortality of the leafminer larvae. As a gcneralist predator, it
probably does not discriminate between internally parasitized and unparasitized larvae;
this could also account for mortality ofparasitoids as well. In the Captain Cook farm,
theredidnotappeartobeanumericalresponsebetweenparasitoidsand larval Ieafminers.
Perhaps C. modestus was reducing the impact ofthese parasitoids.There are no studies
thatdocumenttheimpactofC.modestusonleafminerpopulations,butithasbeenreport
edasa facultativepredatorofIeafminers inCalifornia(Parrclla& Bcthke 1982).
Whiteflies
Thegreenhousewhitefly,Trialeurodesvaporariorum (Westwood) waspresentin all
farms(Fig.4). IntheGlenwood,Volcano,and Kealakekuafarms,despiteintensiveinsec
ticide use(up to 23 applications), whitefly populations exceeded economic injury levels
fora 10 and 20% yield loss as defined by Johnson et al. (1992) for2-8 weeks (Fig; 4).
Otherstudiesshowthatthegreenhouse whitefly is resistant toseveral classesofinsecti
cides and it is increasingly difficult to control whiteflies with chemicals (Omer et al.
1993). Whiteflies werepractically absentinthe Ho'olehuaand Kula(900 m) farms, and
thusare notincluded inFig.4.
54 Proceedings ofthe Hawaiian Entomological Society Vol. 32
Captain Cook ('selective')
Total miner
Whitefly nymphs
6 " per 4 cm2
-M- Cyrtopeltis per bran
4 "
w
2 "
270 284 298 312 326 340 354
Julian day
Fig.4.Densityofwhiteflynymphsvs.densityofCynopellismodestus(CaptainCook).
Table4.Meaninfestationoftomatoesbyfruitpestsatharvest.
MeanPercentInfestedFruit1
Pesticide No. TPW TFVV BAW Total FruitFly SGSB Total
use/Farm Harvests Ltps stings punctures damage
Calendar:
Glenwood 4 0.2 0.0 0.4 0.6 0.4 0.0 1.0
Volcano 4 0.0 0.4 0.2 0.6 0.0 0.0 0.6
Nominal:
Kealakekua 7 0.2 0.8 0.0 I.I 0.1 3.3 4.5
Moloka'i 6 0.6 0.6 1.2 2.3 1.0 0.0 3.3
Kula450m 4 3.1 8.9 1.7 13.8 0.6 0.0 14.4
Selective:
Capt.Cook 8 0.0 2.4 0.2 2.6 0.0 7.8 7.8
Totals 33 4.1 13.1 3.7 21.0 2.1 11.1
I.TPW=Tomatopinworm.TFW=Tomatofruitworm,BAW=Beetarmyworm,SGSB=southerngreenstinkbug.
Whitefly densities in theselectivefarm inCaptainCookonlyslightlyexceeded the
5% economic injury level for 2 weeks. Large populations ofthe predator, C. modestus
may havehelpedregulate populationsofthewhitefliesinthis farm(Fig. 4). Greenhouse
whiteflynumbersinthenominalthresholdfarminthe2Kulasitesdidnotexceedtheeco
nomic injury level, although C. modestus was absent from the samples, which suggests
