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Home , Methoprene, Pyriproxyfen

Journalof theAmerican Association, ll(l):72-76, 1995 Copyright@ 1995by the AmericanMosquito Control Association, Inc.

COMPARATIVE TOXICITY OF SELECTEDLARVICIDES AND INSECT GROWTH REGULATORSTO A FLORIDA LABORATORY POPULATION OF AEDES ALBOPICTUS

ARSHAD ALI, JAI K. NAYAR' ANDRUI-DE XUE

University of Florida, IFAS, Cental Florida Research and Education Center, 2700 East CeleryAvenue, Sanford, FL 32771-9608

ABSTRACT. Five (OPs) (, chlorpyrifos methyl, , , and temephos), 3 (, , and ), and 2 microbial (Bacillus thuringiensis serovar. israelensls [.8.l. i. ] and Bacillus sphaericus) were tested as larvicides against aFlorida Aedesalbopictus population colonized in the laboratory. In addition, 3 insect growth regulators (IGRS) (, ,and ) were evaluated. All OPs, except for malathion, were highly effective as indicated by low LC"os rangrng from 0.0069 ppm (chlorpyrifos) to 0.026 ppm (fenthion);the larvae wereconsidered tolerant to malathion (LCoo: 1.043ppm). LCrovalues of pyrethroids were: 0.0175 ppm (bifenthrin), 0.0079 ppm (cypermethrin),and 0.0031 ppm (permethrin). Commercial products of.B.t.i.,Vectobaco and Bactimos@were consideredeconomically effective againstAe. albopictus larvae but products of B. sphaericw were ineffective (LCoos> 28 ppm). The IGRs showed exceptional activity. Pyriproxyfen (LCro:0.000376 ppm), was 2.23 and,21.5 times more toxic than diflubenzuron and methoprene,respectively. In general,toxicity ranking of chemicalsand microbials testedwas: IGRs > pyrethroids > OPs > rnicrobials.

INTRODUCTION urban, rural, and sylvan situations enhancesits chancesto be a true vector species(O'Meara et Since the initial establishmentof Aedesalbo- al.1993). pictrzs(Skuse) populations in Harris County, TX, Consideringthe rapid spread,escalating biting in August 1985 (Sprengerand Wuithiranyagool nuisance, and the vector potential of Ae. albo- 1986), this mosquito species has rapidly ex- pictus in the USA, it is essentialto monitor sus- panded its distribution in the continental USA. ceptibility of this mosquito speciesto available At present,established populations of Ae. albo- .Khoo et al. (1988)and Robert and pictus occurin the mid-Atlantic and southeastern Olson (1989) reported the susceptibility of adult United States(C. G. Moore, personal commu- Ae. albopictusto various adulticides in the USA. nication). In Florida, Ae. albopictus was found Larval susceptibility ofa Kentucky strain to se- for the first time in Duval Jacksonville, County, lected insecticides was studied by Cilek et al. in I 986 et al. I 988),and hassince spread @eacock ( 1989).Recently, in fieldtrials, Nasci et al. (1994) to all of the state's 67 counties (G. F. O'Meara, reported control of Ae. albopictuslawae in Lou- personal communication). This mosquito is most isiana usingtime-release larvicidal formulations. common throughout northern Florida, but is less We evaluated severallarvicides and insect growth abundant in the central part ofthe is state, and regulators(IGRs) againsta laboratory colonized currently relatively rare in south Florida (O'Meara population of Ae. albopicluscollected from Vero et al. 1993). Beach,FL. Such dataonAe. albopictusareneed- Presently,Ae. albopictusprimarily posesonly ed from around the USA to establish localized a biting nuisance in the USA. However, public baseline information and to formulate control health officials and agenciesare concernedabout criteria for this recently introduced mosquito. the rapid spreadofthis species.North American strains of Ae. albopictus have experimentally shown a high degree of vector competence to MATERIALS AND METHODS several arboviruses that causediseases, such as dengue hemorrhagic fever, Rift Valley fever, A laboratory colony from field-collected Ae. eastern equine encephalitis, , and albopictus was establishedat the University of others(Mitchell l99l). The ability of this exotic Florida Medical Entomology Laboratory mosquito to occupy a wide variety of habitats in (FMEL), Vero Beach. About 200 host-seeking females were collected near tires and artificial containers maintained on the grounds of FMEL on May 21, 1993.Females were bloodfed on a I Florida Medical Entomology l-aboratory, IFAS, chicken and F, eggswere collected the following University of Florida, 200 9th Street SE, Vero Beach, 4 wk. Eggswere periodically hatched as needed FL 32962. for larval bioassaypurpose and larvae were reared 的 199 5 Toxrcrrv or Lmvlcrpns,c'ND IGRs to Az. ,u'norrcrus

to late 3rd , an d early late 4th in stars fo llow in g larval mortality. In IGR tests, cups were exam- stan d ard m o sq u ito rearin g tech n iq u es. ined daily for any larval, pupal, or adult mor- F iv e o rgan op h o sp h ates (O P S) (Ch 10rp y五fo s, tality, and cumulative mortality was recorded at ch lo rp y rifo s m eth y l,fen th io n ,m alath io n ,an d te― the termination of the test when adult emergence m ep h o s), 3 p y reth ro id s o ifen th i n , cyp eII leth ― was completed in control cups and no living lar- ー H n ,an d p erm eth i n ),2 1n icro b ials (」αc〃′冴S ″乃タ vae or pupaeremained. A I 4-h photoperiod and ガ″」夕″Sな Sero v ar. な/α2姥″sお [β.″.'.] an d 』. 26 ! 2oCweremaintained in the evaluationroom ッ カααた″5), an d 3 1G R s, (d in u b en zu rO n , m eth ― during the tests.Mortality in treatmentswas cor- o p ren e,an d ttm p rO X y fen )w ere tested again stИa rected for control mortality and the data were α′う。p テごと″s larvae . subjectedto a log-dose-probitregression analysis T ech n ical grad e m atcrials o f ch lorp yrifo s (U.S. Environmental Protection Agency 1994)to ° 0 (9 9 /0), Ch 10 rp y五fo s m eth y l (9 9 .8 /o), fen th io n estimatelarval dosageresponse to the larvicides 0 0 0 (9 6 .5 /o),m alath io n (9 5 /o9,tCm ep h o s (9 6 .5 /o),b i― and IGRs. 0 0 fen th i n (9 3 .7 /o), Cy p erm eth 五n (9 2 .3 /o), p er_ 0 ° m eth i n (9 4 .6 /o), d in u b en zu ro n (9 0 /0), m eth O _ 0 0 RESULTS p ren e (9 5 .6 /o), an d p y i p ro xy fen (9 7 /o) w ere u tilized in th is stu d y .T h e O P s,p yreth ro id s,an d Susceptibility of Ae. albopictas larvae to the 0 IG R s w ere d issolv ed in aceto n e to p rep are 1 /o various OPs varied considerably(Table l). Lar- stock solut on (w /Vland 6-9 sei al dほlution s.T w o vae were most susceptibleto chlorpyrifos (LCno forln u lation s of 』.″.サ, a techn ical p ow der (T P ) : 0.0069 ppm) and least susceptibleto mala- ヽ電CtOb ac ①,con tain ing 5,00 0 1n ternation al T o対c thion (LCro : 1.043 ppm). Chlorpyrifos and U n its [IT U ]/m D an d a n Ow ab le co n cen tratc (F C ) chlorpyrifos methyl were almost equally toxic as (B aCtim Os⑤, containing l,200 1T U /m 9 , and 2 indicated by LCnosof 0.0069 ppm (chlorpyrifos) form ulations of』.w んα夕rた″s,a T P いB G ‐6 184, and 0.0087 ppm (chlorpyrifos methyl). Similar- containing 2,478 1T U /m D and an F C (SphCri_ ly, fenthion and temephos were almost equally ③ m O S ), CO n tain in g 3 0 0 1T U /m g w ere also cv al― toxic with LCnosof 0.026 ppm (fenthion) and u ated o A ll β,ど.テ, an d 』. w 力αで/た冴s fo rm u latio n s 0.021 ppm (temephos).Chlorpyrifos was 3 times 0 w ere m ix ed in w ell w ater (p H 6 .8) to p rep are 1 /o more toxic than temephosand l5l times more KW /V ) StO Ck so lu tio n s an d 4 - 7 serial d ilu tio n s. toxic than malathion. The high LCno of 1.043 M o sq u ito b io a ssay m eth o d s fo r O P s an d p y ― ppm (malathion) as compared to other OPs sug- reth ro id s w ere siin llar to th o se o f いツ【u lla et al. gestedthat the exposedlarval population of Ae. (19 8 2).』.″.J.an d 』.】β力αタメ'C″S b io assay rn eth o d s albopictuswas tolerant to malathion. u sed th e tcst p ro ced u res o f A li et al. (19 8 1) an d Among the pyrethroids, permethrin was 2-3 A li and N ayar (1986).T he IG R s w ere evaluated times more toxic than cypermethrin and 5-6 in th e m an n er d esci b ed b y W 【u lla et al. (19 7 4 ). times more toxic than bifenthrin (Table l). Per- F o r O P s an d p y reth ro id s, late 4 th ‐in star Z 夕. αか methrin was 2-3 times more toxic than chlor- う?pたサ″s w ere utilized. T he IG R s w ere tested pyrifos or chlorpyrifos methyl whereasthe LCno again st late 3rd an d early 4 th in stars, an d early of cypermethrin was similar to that of chlorpyr- 4th in star И2. αわOp た,″s w ere expo sed to 』 ″.′. ifos and chlorpyrifos methyl. an d 』. ずp んα2/】c体 . In all ev alu atio n s, 2 0 m o s‐ Both formulations of B.t.i. werc effective q u ito larv ae w ere p laced in 12 0 -m l d isp o sab le against Ae. albopictu.swith LCnosof 0.38 ppm p ap cr cu p s co n ta in in g 10 0 m i tap w ater.F o u r to (Vectobaco)and 1.913ppm (Bactimos@)(Table 9 d ifFeren t co n cen tratio n s o f each iarv icid e o r 2). A comparison ofthe larvicidal activity, keep- IG R w ere tested o n at lea st 3 d irFeren t o cca sio n s. ing in consideration the potency (ITU/mg) dif- E ach co n cen tratio n w a s rep licated 3 tiin es an d 3 ferenceofthe 2,B.r.i.formulations, indicated that u n treated co n tro ls Tc ceiv in g o n ly l m l o faceto n e Vectobac@was slightly superior in activity than w ere m ain tain ed d u i n g th e O P ,p y reth ro id ,an d [email protected]|.ae were tolerant to both for- IG R tests. C on trols in β ″.′. an d 』. ずp ttα夕rたをな mulations of B. sphaericzs(Table 2). tests d id n o t req u ire ad d itio n o f aceto n e b ecau se The IGRs showed exceptionally superior ac- th eir sto ck so lu tio n s an d sei al d ilu tio n s w ere tivity againstAe. albopictusas indicated by low p rep ared in w ell w ater. O n e m l o f 10/O b eef liv er LCnosin the ppb range (Table 3). The juvenoid, 十 y ea st (1:1) W as ad d cd to each cu p o n ly o n cc pyriproxyfen (LCno: 0.000376ppm) was 2.23 fo r cu p s recciv in g O P s, p yreth ro id s, コ.″.テ,, an d times and 2 I .5 times more active than difluben- 」. w んαで″,ご″品 an d th etr resp ectiv e co n tro ls; in zuron and methoprene, respectively. Difluben- IG R tests ia sting fo r 7- 10 d ay s, larv al fb o d w as zuron was 9.6 times more active than metho- ad d ed to each cu p at 2 ‐d ay in terv also L arval m o r‐ prene. However, methoprene in general had a tality in th e tests o f O P s, p y reth ro id s, an d β.″`,. similar level of activity against Ae. albopictus w as sco red aftcr 2 4 h o F ex p o su re. B a c,′′クs when compared with the most toxic OP, chlor- sp れαでr,ご″s tests w ere exten d ed to 4 8 h to assess pyrifos and the , permethrin. ４ Jounxer on rnp AMBnrc,cNMoseurro Covrnor Assocrerrox V O L. 1 1, N o 。1

Table l. Comparative laboratory toxicity of various organophosphateand pyrethroid larvicides to laboratory-rearedrlate 4th-instar Aedesalbopictus.

0 L a M cid es L C 50 9 5 /o C L L C ,。 9 5% C L Slope O rgan oph osph ates Chlorpyrifos 0 .0 0 3 3 O .0 0 14- 0 .0 0 5 2 0 .0 0 6 9 0 .0044-0 .0 19 3 4 .00 Chlorpyrifos methyl 0 .0 0 4 3 0 .0 0 0 6 9-0 .0 0 6 9 0 .0 0 8 7 0 .00 59-0 .106 4 .22 Fenthion 0 .0 12 0 .0 1 1- 0 .0 14 0 .0 2 6 0 .022-0 .0 32 4 .0 9 Malathion 0 .3 7 9 0 .3 3 8-0 ,4 2 1 1.0 4 3 0 。9 17- 1.20 9 2 .92 Temephos 0 .0 10 0 .0 0 9-0 .0 1 1 0 .0 2 1 0 .0 17-0 .0 27 4 .0 8 P yreth ro id s Bifenthrin 0 .0 0 5 2 O .0 0 4 5-0 .0 0 6 0 0 .0 17 5 0 .0 14 3-0 .0 224 2 .4 5 Cypermethrin 0 .0 0 2 6 0 .0 0 16- 0 .0 0 4 0 0 ,0 0 7 9 0 .004 9-0 .0 189 2.6 3 Permethrin 0 .0 0 0 9 5 0 .0 0 0 8 2-0 .0 0 1 1 0 .0 0 3 1 0 .00 2 5-0 .0040 2.4 8 l C olony m aintainod frOm neld _caught adults collected in M ay 1993,V ero Bcach ,F L .

DISCUSSION Ae. albopiaus to chlorpyrifos and chlorpyrifos methyl. Among pyrethroids, only permethrin has Limited laboratory data exist for comparing been previously evaluated againstAe. albopictus susceptibility of various populations of Ae. al- in with ppm bopictus in the USA to larvicides and IGRs. larvae the USA, an LCro of 0.0028 (Cilek However, somele. albopictuslarvalstudies from et al. 1989),a value very closeto the LCro Asia showing temephosLCros of <0.017 ppm of 0.0031 ppm permethrin in our study. How- (Toma etal. 1992,Wu et al. 1992), and fenthion ever, a wide range (0.003-0.663 ppm) of larval LCros of 0.0055-0.006ppm (Herbert and Per- LCros was reported for permethrin against var- kins I 973, Toma et al. I 992) are compatible with ious geographicalstrains of Ae. albopictusin Chi- the Vero Beach,FL, population (temephosLCrs na (wu et al. 1992\. : 0.01 ppm; fenthion LCro : 0.012 ppm). Our The Vero Beach strain of Ae. albopictus,wil}r study and severalprevious laboratory bioassays a larval LCro of 0.38 ppm B.t.i. in the present with malathion against Ae. albopictus lamae study, was 9 times more tolerant to this micro- (Herbert and Perkins 1973, Cilek et al. 1989, bial larvicide than the Kentucky strain (LCno : Toma et al. 1992) have indicated the possibility 0.0449ppm) (Cilek et al. 1989)when compared ofresistanceto this .No data are avail- on equal potency basis of International Toxic able in the literature on larval susceptibility of Units (ITLD/mg. Our study on B. sphaericus

T ab le 2 . C o m p arative lab oratory to xicity of 』αctiL船 ″カタ/i4g,c 裕なserov ar. な惚タル俗なan d l , αciti凋 ずpttαerjctt in v tt ou s fo m ulation s of d ifFeren t p oten cies to lab o ratory―reared early 4th‐h star Иttas αわり,cr潜. kthal concentration (ppm) Formulation 0 0 (potency)' L C 50 9 5 /o C L L C 9。 9 5 /o C L S lo p e B. thuringiensis israelensis(24-h exposure) V ectobacO ,T P (5,0 00 1T U /m 9 0 .18 1 0 .14 9-0 .2 19 0 .3 8 0 0 .3 0 2_ 0 .5 3 6 3 .9 8 Bactim osO ,FC (1,200 1T U /m 9 0 .84 9 0 .7 89-0 .9 14 1.9 13 1.7 17-2.176 3.63 , .spttαer↓c″ざ(4 8‐h cxp osu re) A B G -6 184 , T P - (2,4 7 8 1T U /m D 5.90 2.34- 14.8 1 28.09 14 .20 26 1.34 1.89 O Sph erim o s ,F C - (30 0 1T U /m 9 36.96 32.78-4 1.62 176.5 1 14 5.11 224 .13 1.89 l C olony m aintainod IIom flcld‐caught ad ults collected in M ay 1993,V ero B ca●h,F L = 2 T P = techni(泊l pOw der;F C = aow ablc conccntratc,IT U /m g Intem ational T oxic U 由ts/m 3・ 的 199 5 Toxrcrrv or l,envrcrprs er.rp IGRs ro Aa. Ar.Boptcrvs

Table 3. Comparative toxicity of 2 juvenile hormone (methoprene and pyriproxyfen) and one chitin synthesis inhibitor (diflubenzuron) insect growth regulators (IGRs) to laboratory-reared' t* ra- ""a ""rtt

Lethal concentration (PPm) 0 0/ IG R s L C 50 9 5 /o C L L C 9。 9 5 /o C L S lo p e Diflubenzuron 0 .0004 5 0 .000 39-0 .0004 9 0 .00 0 84 0 ,000 76-0 .0009 7 4 .72 Methoprene 0 .00 22 0 .00 14-0 .002 9 0 .00 8 1 0 .00 68-0 .0 1 2.29 Pyriproxyfen 0 ,000 11 0 .0000 74-0 .000 14 3 0 .000 376 0 .000 2 57-0 .000 692 2 .3 1 i C olony m aintaincd from lleld ,caught ad ults collectcd in M ay 1993,V cro B cach ,F L

showing Lros of 28.09 ppm (ABG-6184) and any, CT (diflubenzuron) for providing technical 176.51ppm (Spherimos@)confirmed the reports and/or formulated materials used in this study. ofDagnogoand Coz (1982)and Ren et al. (1987) This is Florida Agricultural Experiment Stations that Ae. albopictus larvae were tolerant to this Journal Series No. R-03812. microbial larvicide. Our laboratory data on IGRs are in general agreementwith those of Kawada (1993) who re- REFERENCES CITED ported 50o/oemergence inhibition of Ae. albopic- Ali, A. and J. K. Nayar. 1986. Efrcacy of Bacillus /zs causedby methoprene at l.l ppb, difluben- sphaericus Neide againstlarval mosquitoes(Diptera: zuron at 0.3 ppb, and pyriproxyfen at 0.024 ppb. Culicidae) and midges (Diptera: Chironomidae) in In our study the same level of emergenceinhi- the laboratory. Fla. Entomol. 69:685-690. bition was caused by methoprene at 2.2 ppb, Ali, A., R. D. Baggsand J. P. Stewart. 1981. Suscep- and mosquitoes diflubenzuron at0.45 ppb, and pyriproxyfen at tibility of someFlorida chironomids to various formulations of Bacillus thuringiensisset- 0.ll ppb. '14:672-677. ovar. israelensls.J. Econ. Entomol. We observed that the OPs (except for mala- Cilek. J. E., G. D. Moorer, L. A. Delph and F. W. thion), pyrethroids, and IGRs were highly effec- Knapp. 1989. The Asian tiger mosquito Aedesal- tive againstthe larval Ae. albopictuspopulation. bopictus,in Kentucky. J. Am. Mosq. Control Assoc. Products of B.t.i. appeared to be economically 5:267-268. effectiveagainst this population. Theselarvicides Dagrrogo,M. and J. Coz. 1982. Un insecticidebiol- and IGRs could be safely used in Ae. albopictus ogique: Bacillus sphaericus. l. Activite larvicide de control programs becauseadverse effects on as- B. sphaericus sur quelques especes et souches de Ser.Entomol. Med. sociatedaquatic nontarget organismsin the var- moustiques.Cah. O.R.S.T.O.M. Parasitol.20: I 33-138. ious habitats of Ae. albopictus,such as small con- Herbert, E. W. and P. V. Perkins. 1973. Comparative tainers, tires, etc. would be of minimal concern. tests of five insecticides agaitst Aedes albopictwlat- Insect growth regulators, particularly difluben- vae from south Vietnam. Mosq. News 33:76-78. zuron and pyriproxyfen, offer an excellent po- Kawada, H. 1993. Can mosquitoesbe carriersof lar- tential for the control of Ae. albopictus andwar- vicides? Potential new strategy for mosquito control rant further laboratory and field studies on gsing , pp. 14-17. In: Proc. formulation researchto elucidate long-term ef- Int. Conf. Insect Pests in Urban Environ., Cam- fectivenessand residual activitv. bridge, England. Khoo, B. K., D. J. Sutherland,D. Sprenger,D. Dick- erson and H. Nguyen. 1988. Susceptibility status ACKI\OWLEDGMENTS of Aedes albopiaus to three topically applied adul- ticides.J. Am. Mosq. Control Assoc.4:31G313. We thank Miles, Inc., Kansas City, MO (fen- Mitchell,C. J. 1991. Vectorcompetenceofnorthand thion), DowElanco, Indianapolis, IN (chlorpyr- south American strains of Aedes albopictus for cer- ifos and chlorpyrifos methyl), American Cyan- tain arboviruses: a review J. Am. Mosq. Control amid Co., Princeton, NJ (malathion and Assoc.7:446-45 l. temephos),FMC, Philadelphia, PA (bifenthrin, Mulla.M. S..H. A. DarwazehandL.Ede. 1982. Eval- cypermethrin, and permethrin), Novo Nordisk uation of new pyrethroids against immature mos- Entotech, Inc., Davis, CA (Bactimos@ and quitoes and their eflects on nontarget organisms. Mosq. News 42:583-59O. Spherimos@), Abbott Iaboratories, North Chi- Mulla, M. S., H. A. Darwazeh and R. L. Norland. IL (Vectobaco cago, and ABG-6184), Mc- 1974. Insect growh regulators evaluation proce- Laughlin Gormley King Co., Minneapolis, MN dures and activity againstmosquitoes. J. Econ. En- (pyriproxyfen), Zoecon, Dallas, TX (metho- tomol. 67:329-332. prene), and Uniroyal Chemical Co., Inc., Beth- Nasci, R. S., G. B. Wright and F. S. Willis. 1994. JounNer or rnp AvrrrceN Mosqurro CoNrnol AsstrcrerroN Vor,. ll, No. I

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