[~pn.J. Sanit. 2001. Vo1. 44 No. 4 p. 349-353 19931 Laboratory evaluation of insect growth regulators against several species of anopheline mosquitoes Hitoshi KAWADA,*Yoshinori SHONO,*Takaaki ITO* and Yasuo ABE* Agricultural Science Research Center, Takarazuka Research Center, Sumitomo Chemical Co., Ltd., Takarazuka 665, Japan (Received: May 27, 1993) Key words: insecticide, insect growth regulator, pyriproxyfen, methoprene, diflubenzuron, Anopheles, vector. -- - Abstract : Larvicide efficacy of insect growth regulators (pyriproxyfen, metho- prene and diflubenzuron), in comparison with the larvicidal and adulticidal efficacy of conventional insecticides, against several species of Anopheline mosquitoes includ- ing several insecticide resistant; strains were evaluated in laboratory conditions. In all species, no cross resistance between IGRs and the other kinds of insecticides, such as organophosphate, organochlorine, carbamate and pyrethroid, was observed. Relative effectiveness of pyriproxyfen to methoprene ranged from several to 40 times and that to diflubenzuron ranged from 19.5 times to more than 400 times. In this respect, IGRs (insect growth regu- lators) seem to be useful insecticides. Pyri- proxyfen, a juvenile hormone mimic, had Anopheline mosquito is one of the most high activities to mosquitoes in the field important vectors of tropical diseases. Re- (Kawada et al., 1988; Suzuki et al., 1989; sidual spray on the wall surface and treat- Okazawa et al., 1991). In this study, we ment of breeding areas with chemicals, such evaluated the larvicide efficacy of pyriproxy- as organochlorine, organophosphate and car- fen against several species of Anopheline bamate insecticides, have been employed as mosquitoes in laboratory conditions, compar- the best and appropriate ways of controlling ing with other insecticides, and discuss the these mosquitoes. However, as a result of possibility of its use as a new vector control over-use or inappropriate treatment of in- agent. secticides, many cases of insecticide resistance development have been reported (Heming- way and Georghiou, 1983; Scott and Georg- hiou, 1986; Hemingway et al., 1986). The I. Test chemicals. Pyriproxyfen : 4-phe- adoption of insecticides with different modes noxyphenyl (RS)-2- (2-pyridyloxy) propyl of action from conventional ones and the ether (576 emulsifiable concentrate). Metho- combination use of them could provide a prene : isopropyl- (2E, 4E) - 11-methoxy-3, 7, solution to overcome this problem. 11-trimethyl-2, 4-dodecadienoate (570 emul- * , , , , , : sifiable concentrate). Diflubenzuron: 1- (4- 4L%r% (%)5~%i&&@%%~f%F@E% chlorophenyl) -3- (2, 6-difluorobenzoyl). urea (7665 ZgfiSd 4-2-1) (25% wettable powder formulation in com- 350 Jpn. J. Sanit. 2001. Table 1 Anopheline mosquitoes used in the study. Species Strain Site of collection Institution introduced A. stephensi SUS - St. Marianna Univ. MLT-R Pakistan London Univ. A. gambiae SUS Tanzania London Univ. DLD-R Burkina fuso London Univ. DDT-R Africa London Univ. A. albimanus SUS - London Univ. OPC-R El-Salvador London Univ. A. fa~auti Solomon Islands Ministry of Health, Solomon Islands SUS, strain which shows normal susceptibility to insecticides; MLT-R, malathion resistant DLD-R; dieldrin resistant; DDT-R, DDT resistant; OPC-R, organophosphate and carbamate resistant. mercial (Dimilinm, Sankyo Co., Ltd.) was ally applied to the dorsal mesothorax of a used) . Temephos : 0, Or-(thiodi-4, l-pheny- 2- to 3-days-old female adult. Insects treated lene) bis (0, 0'-dimethyl phosphorothioate) were kept under the conditions noted above (5% emulsifiable concentrate) . Fenitro- and fed with 3% sugar solution. Mortality thion: 0, 0-dimethyl 0-4-nitro-rn-tolyl phos- was observed 24 hr after treatment. The data phorothioate (59% emulsifiable concentrate). obtained were corrected by the mortality of Malathion : diethyl mercaptosuccinate S-ester untreated adults and LDj0 was calculated with 0, 0-dimethyl phosphorodithioate (55% by Bliss' probit method (Bliss, 1934). emulsifiable concentrate) . Propoxur : 2- (1- (2) Larval susceptibility : An emulsifi- methylethoxy ) phenol methylcarbamate (5% able concentrate of each chemical and wet- emulsifiable concentrate) . DDT : dichloro table powder of diflubenzuron were used. diphenyl trichloroethane. Dieldrin : ( 1R, 4S, The test formulation was diluted with de- 4aS, 5R, 6R, 7S, 8S, 8aR)-I, 2, 3, 4, 10, 10- ionized water at appropriate concentrations. hexachloro-1, 4, 4a, 5, 6, 7, 8, 8a-octahydro- Thirty 4th instar larvae were released into 6, 7-epoxy l, 4 :5, 8-dimethanaphthalene. Per- 150 ml of each test solution in an aluminum methrin : 3-phenoxybenzyl ( 1RS, 3RS : 1RS, cup. After 24 hr, mortality was observed and 3SR) -3- (2, 2-dichlorovinyl) -2, Z-dimethyl- LD5, was caIculated in the same manner cyclopropane carboxylate (5% emulsifiable noted above. In the case of IGRs, larvae concentrate). were reared in the solution until adult emer- 2. Test insects. Adults and larvae of gence. The percentage of emergence was Anopheline mosquitoes, A. stephensi, A. garn- corrected by that of control to calculate ICio biae, A. albimanus, A. farauti, were used. in the same manner noted above. Table 1 shows their collection sites and the institutes which provided colonies to us. In- sects were reared at 25°C and 60% RH, under 16L-8D photoperiodic regime. Resist- 1. Adult and larval susceptibility to insecti- ant strains were selected periodically with cides insecticides at the larval stage in OPC-R Adult and larval susceptibility to insecti- strain of A. albimanus and adult stage in the cides is shown in Figs. 1 and 2. Adult MLT- other strains. R strain of A. steplzensi showed higher resist- 3. Bioassays. All experiments were con- ance to malathion (R/S ratio= 71 ) than lar- ducted under the same conditions described vae (R/S ratio=2.6). The degree of cross above. resistance between malathion and fenitrothion (1) Adult susceptibility: A 0.3 ace- was small in this strain. This is due to the tone solution of the test chemical was topic- resistance factor of malathion carboxyleste- Vo1. 44 No. 4 1993 LDjO for SUS stram Pemethrin Dieldrin DDT Propoxur Malathion Fenitrothion 1 10 100 Relative resistance ratlo Fig. 1 Efficacy of insecticides to adult Anopheline mosquitoes by topical application. Figures in abscissa indicate resistance ratio to SUS strain (strain which shows normal susceptibility to insecticides). Figures in ordinate indicate LDzo (pg/female) for SUS strain: upper, A. stephensi; middle, A. gambiae; bottom, A. albimanus. LC50 far SUS stman .................... ............................... ........................ Malathion (I 19 .............................. Fenitrothion ooii 10 100 Re1atiL.e res~sta~lceratio Fig. 2 Efficacy of insecticides to larval Anopheline mosquitoes. Figures in abscissa indicate resistance ratio to SUS strain (strain which shows normal susceptibility to insecticides). Figures in ordinate indicate LC, (ppm) for sus strain: upper, A. stephensi; middle, A. gambiae; bottom, A. albinanu5. 352 Jpn. J. Sanit. 2001. Table 2 IC,, values of IGRs against the last instar larvae of Anopheline mosquitoes ICso (ppb) Species Strain Pyriproxyfen Methoprene DiAubenzuron A. stephensi SUS 0.043 0.54 0.84 (0. 01 1-0.16) (0.39-0.77) (0.71-0.99) MLT-R 0.025 0.75 1.6 (0.019-0.034) (0.099-5.6) (1.4-1. 7) A. gambiae SUS DLD-R 0.0098 0.039 0.87 (0.0025-0.038) (0.011-0. 14) (0.76-0.99) DDT-R 0.0040 0.072 1.9 (0.0028-0.0057) (0.0023-2.3) (0.53-7.1) A. albimanus SUS OPC-R 0.00042 0.016 0.20 (0.000035-0.005) (0.012-0.021) - A. farauti 0.0017 - - (0.011-0. 16) - - Numbers in parentheses are 95% fiducial limits. Blank area indicates that no test was done. rase (Scott and Georghiou, 1986). Differ- was 41 for adult and 100 for larva). ences in adult and larval susceptibility of three strains of A. gambiae to organophos- 2. Larval susceptibility to insect growth phate and propoxur were not observed. Re- regulators sistance ratio of DDT-R strain to DDT was Larval susceptibility to insect growth regu- significant but moderate (R/S ratio was 4.8 lators is shown in Table 2. IC,, of pyriproxy- for adult and 8.8 for larva). Cross resistance fen ranged widely from 0.00042 ppb (A. between DDT and dieldrin or permethrin was albimanus OPC-R) to 0.043 ppb (A. ste- not observed. Resistance ratio of OPC-R phensi SUS). In A. stephensi there was no strain of A. albimanus to organophosphate difference in susceptibility to pyriproxyfen of was smaIler than that to propoxur. Larvae SUS strains and that of malathion-resistant of this strain showed higher resistance to strain. In contrast, in A. albimanus and A. temephos than the other strains. gambiae, susceptibility to pyriproxyfen was Larval resistance ratio of each strain was rather higher in resistant strains than in SUS relatively smaller than that of adult except strains. These results indicate that there is for A. albimanus OPC-R. This seems to be no cross resistance between pyriproxyfen and explained by the fact that A. albimanus OPC- the other insecticides, such as organophos- R strain was selected at larval stages with phate, carbamate and pyrethroids. Schaefer severe contamination of various insecticides et al. (1988) also reported that IC,,s of for agricultural use (Bruce-Chwatt, 1985). pyriproxyfen for SUS and organophosphate A. gambiae DLD-R strain showed high resist- resistant strain for Culex quinquefasciatus ance to dieldrin in both stages (R/S ratio were 0.018 and 0.022 ppb, and those for C. Vol. 44 No. 4 1993 tarsalis were 0.021 and 0.052 ppb, respective- Hemingway, J. and G. P. Georghiou (1983): ly. There also seemed to be no cross resist- Studies on the acetylcholin esterase of Anopheles ance between methoprene or diflubenzuron albimanus resistant and susceptible to organo- phosphate and carbamate insecticides. Pestic. and the other insecticides. Relative effective- Biochem. Physiol., 19: 167-1 71. ness of pyriproxyfen to methoprene was less Hemingway, J., K. G. Jayawardena and P.