Recherche et rapports

Field Evaluation of an Insect Growth Regulator Pyriproxyfen Against Anopheles punctulatus on North Guadalcanal, Solomon Islands.

Okazawa, T. et al.,

Journal of The American Mosquito Control Association 7, (4) : 604 -607. 1991

A small scale trial was conducted using natural pools. They were treated with pyriproxyfen 0.5% granules (Sumilarv) at dose rates from 0.01 ppm – 0.1 ppm. The pools were muddy, had vegetation and were subject to heavy rainfall which would dilute any larvicide applied. To determine the activity of pyriproxyfen 4th instar larvae and pupae were removed from the pools on a regular basis and taken to the lab to check for emergence inhibition. Adult emergence was completely inhibited for 2 months at 0.1 ppm even after several floodings by heavy rain. Lower doses of 0.01 and 0.05 ppm lasted for 1 month. The recommendation was that this long lasting efficacy at low dosages indicates that this compound could make larviciding feasible in terms of costs and operations.

Field Evaluation of a New Insect Growth Regulator, Pyriproxyfen, Against Anopheles farauti, the Main Vector of Malaria in the Solomon Islands

Suzuki, H. et al.

Japanese Journal of Sanitary Zoology, 40 (4) 253-257. 1989.

A field study to control Anopheles farauti with pyriproxyfen (S-31183) was carried out in northern Guadalcanal, Solomon Islands. Pyriproxyfen was applied to 2 breeding sites: one with fresh water and another with brackish water. Pyriproxyfen at a dosage of 0.1 ppm. inhibited emergence of An. farauti completely, at both test sites, for at least 5 weeks after treatment. The efficacy (more than 70% inhibition) lasted for c 2 months. The body colour of the larvae and pupae in the test sites whitened noticeably after the application of the compound.

Laboratory and Field Comparison of Pyriproxyfen, Polystyrene Beads and Other Larvicidal Methods against Malaria Vectors in Sri Lanka.

Yapabandra, A.M.G.M. et al.

Acta Trop., 82(3), 211-223. 2002

The gem miners in central Sri Lanka had dug many shallow pits which later filled with water and became breeding places for mosquitoes. In a small scale field trial on Anophelines, pyriproxyfen (Sumilarv 0.5G) was evaluated at dose rates of 0.01 and 0.1 mg a.i/l (0.01 ppm and 0.1 ppm). They found it was more effective than temephos and required re-application only twice a year to control malaria vectors which was very cost effective while temephos had to be applied 12 times a year.

Control of Malaria Vectors with the Insect Growth Regulator Pyriproxyfen in Gem Mining Area in Sri Lanka.

Yapabandra, A.M.G.M. et al.

Acta Trop., 80(3), 265-276. 2001 (Abstract Only)

Trials were conducted in a project aimed to control of malaria vectors, Anopheles culicifacies and Anopheles subpictus using a granular formulation of pyriproxyfen (Sumilarv 0.5G) in Sri Lanka. The gem pits and river bed pools were treated with pyriproxyfen at a rate of 0.01 mg a.i/l (0.01 ppm) and it was found that this reduced adult population density of both species. It also reduced malaria incidence to about 24% of that in the controls. In addition prevalence of parasitemia was reduced.

Control of Vectors and incidence of Malaria in an Irrigated Settlement Scheme in Sri Lanka by using the Insect Growth regulator Pyriproxyfen.

Yapabandara, A.M.G.M. & Curtis, C.F.

Journal of the American Mosquito Control Association, 20(4):395-400. 2004

An evaluation of pyriproxyfen (Sumilarv 0.5G) was made to determine its impact in reducing malaria vector populations and the incidence of malaria in 12 villages with an area of 9,800 ha in an irrigated settlement scheme. From these villages 6 were selected for application of pyriproxyfen and 6 were left untreated as controls. The pools in river beds and irrigation ditches are the breeding places of the major malaria vectors Anopheles culicifacies and Anopheles subpictus. All villages in the trials were also receiving Indoor residual spray (IRS) using lambdacyhalothrin. Since all 12 villages had their houses sprayed, the results show the difference between villages with IRS alone and those with IRS plus pyriproxyfen larviciding. Malaria incidence was monitored by passive case detection using the data collected from 2 field clinics and 2 clinics at out- patient departments at a hospital and one dispensary. Patients reporting with malaria were checked to identify if they came from one of the trial villages. Treatment rate with pyriproxyfen (Sumilarv) was 0.01 mg a.i.per litre. (0.01 ppm). Field bioassays indicated that a single treatment of pyriproxyfen inhibited the emergence of adult populations for 190 days. The treatment caused significant reduction in adult populations of Anopheles culicifacies (78%) and Anopheles subpictus (72%). In addition, the incidence of malaria was reduced in the treatment villages by about 70% compared with controls. The conclusion is made that pyriproxyfen can be a very effective means of malaria control if all possible vector breeding places in the area can be located. Note: malaria monitoring was only passive case detection so the impact may have been greater than shown in the paper if active case detection had been conducted.

Laboratory evaluation of insect growth regulators against several species of Anopheline mosquitoes

Kawada, H. et al.

Japanese Journal of Sanitary Zoology 44 (4). 349-353. 1993. (Abstract Only)

Larvicide efficacy of insect growth regulators (pyriproxyfen, methoprene and diflubenzuron), in comparison with the larvicidal and adulticidal efficacy of conventional insecticides, against several species of Anopheline mosquitoes, including 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.

Potential Use of Pyriproxyfen for Control of Aedes aegypti (Diptera: Culicidae) in Iquitos, Peru.

Sihuincha, M. et al.

Journal of Medical Entomology 42(4) 620-630. 2005.

The effects of pyriproxyfen (Sumilarv 0.5G) were evaluated against local populations of Aedes aegypti, the vector of Dengue. Bioassays showed that it prevented adult emergence from pupae at extremely low concentrations (LC50 = 0.012 ppb). There was no adult emergence from water sampled from storage water tanks that had been treated with 50-83 ppb a.i. pyriproxyfen. Five months after treatment despite constant dilution of the water in these tanks it was found that the water was still lethal to larvae and pupae. Additional studies conducted in the laboratory showed that groups of female blood-fed mosquitoes exposed to residues of c 0.003 g a.i. pyriproxyfen/m² could transfer enough chemical to new oviposition sites to prevent c80% emergence from larvae developing in that previously uncontaminated water. Although the fecundity of the adult females used as transfer vehicles was unaffected, the subsequent eclosion (hatching) of the eggs that these females laid decreased by 70-90%. It was also shown that if water sources were treated with very high concentrations of pyriproxyfen (>30,000 ppb) they were as likely to be used as oviposition sites as untreated sites.

Laboratory and Field Evaluation of the Insect Growth Regulator Pyriproxyfen (Sumilarv 0.05G) Against Dengue Vectors.

Vythilingam, I. at al.

Journal of the American Mosquito Control Association, 21(3):296-300. 2005.

Dengue fever is considered to be the most important arboviral disease to humans today. The vectors Aedes aegypti and Aedes albopictus need to be controlled to control the disease. Larviciding is an important component of Dengue control but resistance of the vectors to temephos (Abate) is increasing. Insect Growth regulators are selective and at practical application rates have no apparent ill effect on prevailing non-target organisms. Pyriproxyfen (Sumilarv 0.5G) was tested against Aedes aegypti at 0.01 and 0.02 mg a.i. /L water (0.01 and 0.02 ppm) in 60 litre earthenware jars. Efficacy was measured as inhibition of adult mosquito emergence of introduced Aedes aegypti larvae. Both concentrations provided 100% control for 4 months. In additional experiments where 10 litres of water was replaced fortnightly (to simulate actual usage as domestic water container), 100% control was still obtained over 4 months with 0.02 mg a.i./L and greater than 93-100% control was obtained over 4 months with 0.01 mg a.i. mg/L. In field trial conditions pyriproxyfen at a dosage 0.02 mg a.i./L provided 100% control for 10 weeks against Aedes albopictus even though water was replaced daily or weekly. Although the activity of pyriproxyfen declines after 10 weeks those tests in plastic tubs showed much higher levels of sustained residual activity compared with those in earthenware jars. Pyriproxyfen did not have an impact on non-target organisms.

Histopathological Effects of an Insect Growth Regulator 4-phenooxyphenyl (RS) -2-(2-pyridylox) propyl ether (Pyriproxyfen) on the Larvae of Aedes aegypti.

Syafruddin et al.Japanese

Journal of Sanitary Zoology 41 (1). 15-22. 1990.

The mode of action of pyriproxyfen was examined using histopathological methodology. In larvae treated with pyriproxyfen several disrupted mitochondria and vacuoles were frequently seen. In addition those treated with a dose of 10 ppb for 48 hours failed to produce a well structured fourth instar cuticle and its epidermal cells were severely vacuolated. The cuticle of the fourth instar larvae the cuticle seemed so badly damaged that the epicuticle partially detached and the endocuticle was partially digested. Its epidermal cells were so severely vacuolated that no cytoplasmic organelles could be identified. These results suggest that pyriproxyfen may act to maintain the larval form of the cuticle and to prevent epidermal cells from producing newly well-structured cuticle which normally occurs during larval development.

Field Evaluation of an Insect Growth Regulator, Pyriproxyfen, against Aedes togoi larvae in brackish water in South Korea.

Lee, D.K.

Journal of Vector Ecology, 26(1):39 -42. 2001

Aedes togoi is the dominate vector of malayi filariasis in South Korea. The larvicide granular formulation of 0.5% pyriproxyfen (Sumilarv) was evaluated for inhibition of emergence of Aedes togoi in brackish water of rock pools in Korea. Complete adult emergence inhibition in 4th stage larvae and pupae was effected days at a dose rate of 0.05 mg/l (0.05 ppm) after treatment. Inhibition/mortality rates were 100% throughout except for one test at 41-51 days and then it was still 100% at 62-70 day test, so could well have gone on longer. In conclusion, the authors say that 0.5% pyriproxyfen granules provided the greatest initial and residual activities against Aedes togoi larvae in rock pools with brackish water and it effectively inhibited adult emergence of Aedes togoi for more than 2 months at a concentration of 0.05 mg/l. (0.05 ppm) It is suggested that the dose rate for control of Aedes togoi for the long term might be 0.05-0.01 mg/l (0.05 – 0.01 ppm) of 0.5% pyriproxyfen granules.

Larvicidal Effect of the Juvenile Hormone Mimic Pyriproxyfen on Culex Pipiens.

El-Shazly, M.M. & Refaie, B.M.,

Journal of American Mosquito Control Association, 18(4):321-328, 2002

The larvicidal activity of pyriproxyfen was evaluated against 4th instar Culex Pipiens under 5 constant temperatures in the laboratory. Toxicity of pyriproxyfen (Sumilarv) increased with temperature. The 50% lethal concentrations ranged between 0.00111 ppm at 20°C and 0.00013 ppm at 32°C. A similar trend was observed for the 90% lethal concentrations which varied from 0.00379 ppm to 0.00024 at the 2 temperatures. Electron microscopy revealed the effects of pyriproxyfen on larvae were the destruction of pro-cuticle lamellae, formation of cuticular vacuoles, deformed mitochondria and destruction of nuclear envelopes and the epidermal layer, in addition to an increase in electron-dense lysosome like bodies.The authors conclude that pyriproxyfen can be used as a larvicidal agent over a wide range of temperatures.

Comparative Toxicity of Selected Larvicides and Insect Growth Regulators to a Florida Laboratory Population of Aedes albopictus.

Ali A. et al.

Journal of The American Mosquito Control Association 11 (1). 72-76. 1995. (Abstract Only)

Five organophosphates (OPs), 3 pyrethroids, and 2 microbial pesticides were tested as larvicides against a Florida Aedes albopictus population colonized in the laboratory. In addition, 3 insect growth regulators ( IGRS) (diflubenzuron, methoprene, and pyriproxyfen) were evaluated. The IGRs showed exceptional activity. Pyriproxyfen (LC90 = 0.000376 ppm), was 2.23 and 21.5 times more toxic than diflubenzuron and methoprene, respectively. In general, toxicity ranking of chemicals and microbials tested was: IGRs > pyrethroids > OPs > microbials.

Field Evaluation of an Insect Growth Regulator, Pyriproxyfen, Against Culex pipiens pallens and Culex tritaeniorhynchus.

Kamimura, K, & Arakawa, R.Jpn. J.

Sanit. Zool.; 42 (3). 249-254. 1991

A synthetic chemical, 0.5% granules of pyriproxyfen, which acts as a juvenile hormone, was tested against Culex pipiens pallens and Cx. tritaeniorhynchus under field conditions. This compound was extremely effective against larvae of both species which showed high resistance to organophosphorus insecticides. Complete inhibition of adult emergence continued for 3 weeks or more in open polyethylene containers and irrigation ditches at a dosage of 0.01 ppm, in cesspools at 0.05 ppm and in sewers with inflow of house wastewater at 0.1 ppm (AI). Activity of the compound was retained after a drying of the test site for several days.

Laboratory Evaluation of the Lethal Efficacy of an Insect Growth Regulator, Pyriproxyfen, Against Anopheles sinensis (Diptera, Culicidae) Larvae

Lee WonJa, Lee DongKyu; Lee, W. J.; Lee, D. K.

Entomological Research, Vol. 35, No. 1, 39-43. 28 2005. Entomological Society of Korea. Seoul. (Abstract Only)

The granular formulation of 0.5% pyriproxyfen is a mosquito insect growth regulator larvicide. It was evaluated for residual activity for killing and/or emergence inhibition against 3rd stage larvae of Anopheles sinensis in the laboratory. Mortality rates ranged from 60.9% to 79.7% at 0.01, 0.05 and 0.1 mg/litre of water during the first seven days. Except for the lowest concentration (0.01 mg/litre) mortality rates were greater than 80% from day 8 through 28. Mortality rates for 0.01 mg/litre concentrations were 70.4% from days 8-14, and thereafter exceeded 80% through day 28. The residual activity gradually increased post-treatment since the granular formulation of pyriproxyfen has a gradual solubility and increases concentration of active ingredient over time. The mortality rates of An. sinensis larvae and pupae eventually reached 100% for the three (0.01, 0.05, 0.1 mg/litre) concentrations.

Mosquito Control Evaluations of an Insect Growth Regulator, Pyriproxyfen, Against Culex pipiens pallens (Diptera, Culicidae) Larvae in Marsh Area, Korea

Lee DongKyu.

Korean Journal of Entomology, 32,(1), 37-41. 15, (2002). (Abstract Only)

During July-September 2001, a study evaluating the efficacy of the granular formulation of 0.5% pyriproxyfen (Sumilarv) against C. pipiens pallens was conducted in marshes and ponds in Busan, Korea Republic. In marshes where the mosquitoes predominantly breed, pyriproxyfen treatment at 0.05 mg/litre (0.05 ppm) produced a 95% mean mosquito larval reduction for the first 4 weeks, in spite of heavy precipitation (total, 274.4 mm) during the period. Reduction rates of 72.6% and 32.3% were observed during the 5th and 7th week post-treatment, respectively, probably due to heavy input of sewage and flood. However, the reduction rate increased to 94.5% during the 8th week post-treatment, probably due to the insecticide's slow release granular formulation. A second pyriproxyfen treatment resulted in complete mortality of C. pipiens pallens from the first week through the 3rd week. A satisfactory larval control level of 96.6% was still obtained during the 4th week post-treatment. In the ponds, pyriproxyfen treatment at 0.05 mg/litre resulted in complete eradication of C. pipiens pallens from the first week through the 4th week post-treatment. During the second treatment, complete eradication was observed only during the first and 2nd week post-treatment. Still, an 84.4% and 97.9% reduction in the mosquito population was observed during the 3rd and 4th week post-treatment, respectively.

Mosquito Control in Dar es Salaam. II. Impact of Expanded Polystyrene Beads and Pyriproxyfen Treatment of Breeding Sites on Culex quinquefasciatus densities.

Chavasse DC. Et al.

Medical and Veterinary Entomology; 9 (2), 147-54, 1995. (Abstract Only)

Open breeding sites such as areas of flooded land and blocked drains were treated with pyriproxyfen (an insect growth regulator) at a concentration of 0.1 ppm. Emergence of Cx quinquefasciatus adults from these sites was inhibited for 4 weeks during the rainy season and for up to 11 weeks during the dry season.

Residual Efficacy of Insect Growth Regulators Pyriproxyfen, Triflumuron and S-methoprene Against Aedes aegypti (L.) in Plastic Containers in the Field

Sallehudin Sulaiman; Siti Hajar, A. S.; Hidayatulfathi Othman

Tropical Biomedicine, 21, (1), 97-100. 2004.

The efficacy of three insect growth regulators, pyriproxyfen (Sumilarv 0.5G), triflumuron (Starycide SC480) and s-methoprene (Altosid liquid larvicide), was evaluated for residual activity against the dengue vector, A. aegypti, in plastic containers placed outdoors. At 1.0 and 5.0 mg/litre concentrations, when exposed for four months under natural condition, pyriproxyfen showed complete inhibition of adult emergence during 22-28 and 36-42 days, respectively, which declined to 90% emergence inhibition during 43-49 and 64-70 days post-treatment, respectively. At similar concentrations, triflumuron caused complete inhibition of adult emergence during 29-35 and 50-56 days, respectively, which declined to 90% emergence inhibition during 64-70 and 99-105 days post-treatment, respectively. At 1.0 and 5.0 mg/litre concentrations, S-methoprene caused complete inhibition of adult emergence during 22-28 and 29-35 days, respectively. At 5.0 mg/litre concentration, S-methoprene caused 84% emergence inhibition during 57-63 days post-treatment. In controls, the range of adult emergence varied between 79-100% during the study period.

Laboratory Evaluation of 2-[1-methyl-2-(4- phenoxyphenoxy)ethoxy] pyridine against Larvae of Mosquitoes and Housefly

Hatakoshi, Makoto et al.

Japanese Journal of Sanitary Zoology, 38(4), 271-4, 1987.

A newly synthesized juvenile hormone active compd., S-31183 (2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy] pyridine) (Sumilarv) was evaluated for its inhibition of emergence of adult Culex pipiens pallens, Anopheles stephensi, Aedes aegypti and Musca domestica in the laboratory. It was more active than methoprene, diflubenzuron, or temephos against last instar larvae of C. p. pallens, A. stephensi and A. aegypti.

Effectiveness and Residual Activity Comparison of Granular Formulations of Insect Growth Regulators Pyriproxyfen and s-Methoprene against Florida Mosquitoes in Laboratory and Outdoor Conditions.

Naya, J.K, Ali, M., & Zaim, M.

Journal of the American Mosquito Control Association, 18(3):196-201. 2002.

The efficacy and residual activity of granular formulations of two insect growth regulators s-methoprene and pyriproxyfen (Sumilarv 0.05G) against laboratory reared larvae of Aedes aegypti, Aedes albopictus, Aedes taeniorhynchus, Anopheles quadrimaculatus and Culex nigripalpus were conducted in the laboratory and outdoors in plastic tubs. Culex quinquefasciatus was exposed to these two IGRs in the laboratory only. Each IGR was applied at 0.02 and 0.05 ppm active ingredient (a.i.) against five of the mosquito species while Culex quinquefasciatus was exposed to 0.02 and 0.04 ppm. of s-methoprene and 0.01 and 0.02 ppm of pyriproxyfen. S-Methoprene gave variable results at 0.02 and 0.05 ppm of inhibition of adult emergence. Culex quinquefasciatus and Aedes albopictus were the most tolerant to s-methoprene. Pyriproxyfen at comparable treatment rates to s-methoprene caused very high levels (>80-100%) of initial and residual emergence inhibitions of the tested species in the laboratory as well as outdoors. In several species, pyriproxyfen induced complete inhibition of adult emergence for several weeks after treatment, even at the lower rate of 0.02 ppm. The World Health Organization has recommended the use of pyriproxyfen for the control of some mosquito species at specified rates in certain habitats. In concluding, the authors say that this study clearly demonstrated the superior activity of pyriproxyfen over s-methoprene on the basis of equal concentrations of the active ingredient, against a wide variety of mosquitoes in the laboratory and in experimental tubs placed outdoors. These results suggest that complete inhibition of adult emergence of these mosquitoes may be achieved with rates even lower than 0.02 ppm a.i. of pyriproxyfen.

Laboratory Evaluation of Selected Larvicides and Insect Growth Regulators Against Field Collected Culex quinquefasciatus Larvae from Urban Dhaka, Bangladesh.

Arshad, Ali et al.

Journal of the American Mosquito Control Association, 15(1), 43-46, 1999

Five organophosphate insecticides, three pyrethroids, one phenyl pyrazole, two microbials and three insect growth regulators were evaluated against field collected Culex quinquefasciatus from urban Dhaka. The toxicity ratings of all chemicals, microbials and IGRs was phenyl pyrazole > IGRs > pyrethroids > microbials > OPs. The comparison between the IGRs showed pyriproxfen being the most active (LC90 = 0.0011 ppm) which was three times more active than diflubenzuron (LC90 = 0.0034 ppm) and 47 times more active than methoprene (LC90 = 0.052 ppm).

Potential for Resistance to Pyriproxyfen: A promising new Mosquito Larvicide.

Schaefer, C.H. & Mulligan, F.S.

Journal of American Mosquito Control Association, 7(3):409-411, 1991.

An organophosphate resistant strain of Culex quinquefasciatus was pressured with pyriproxyfen (Sumilarv) for 17 generations to see if resistance to this IGR developed rapidly. Egg viability began declining in the F7 generation and became lower as the selection process continued; by the F17 generation egg viability was too low to proceed further. Susceptibility tests on the larvae of the F5, F10, F15 and F17 generations showed no indication of increased tolerance to pyriproxyfen.

Possible Selective Advantage of Anopheles spp. (Diptera: Culicidae) with the Oxidase- and Acetylcholinesterase-based Insecticide Resistance Genes after Exposure to Organophosphates or an Insect Growth Regulator in Sri Lankan Rice Fields

Hemingway, J.et al.

Bulletin of Entomological Research, 78(3), 1988

Treatment of rice fields in Sri Lanka with monocrotophos at 0.1 mg/L or pirimiphos-Me at 0.1 mg/L gave a selective advantage to larvae of Anopheles subpictus and A. nigerrimus carrying the oxidase- and acetylcholinesterase-based resistance genes. However, this selective advantage was apparent for <10 days after spraying. There was no mortality of any larval instar with monocrotophos 12 days after spraying, and no fourth-instar larval mortality with pirimiphos-Me 17 days after spraying. The chemical degradation curves for these compounds indicated that this short duration of efficacy was due to the instability of the compounds in water under field conditions. In contrast, the new growth regulator S-31183 (2-[1-methyl-2- (4-phenoxyphenoxy)ethoxy]pyridine) (Sumilarv) sprayed at 0.1 mg/L conferred no selective advantage to larvae with either resistance mechanism and had a total efficacy period of at least 71 days. This difference can be attributed to the greater toxicity of the growth regulator and its slower chemical degradation under field conditions when compared to the organophosphates.

Changes in Susceptibility to Pyriproxyfen, a JH Mimic, During Late Larval and Early Pupal Stages of Culex Pipiens molestus.

Yoahiaki Kono et al.

Med. Entomol. Zool.48 (2) 85-89, 1997

Five strains of Culex pipiens molestus were used to evaluate pyriproxyfem. The five strains included three different susceptible strains, as well as one resistant to organophosphates and another which showed resistance to pyrethroids and methoprene. Tests were conducted in the laboratory using a range of concentrations. The EC-50 values were calculated for pyriproxyfen and ranged from 0.15 – 0.67 ppb, while methoprene showed very wide range of dosages 0.23 -5.32 ppb. Therefore, pyriproxyfen showed potent activity against all strains and even against the methoprene resistant strain, demonstrating a lack of cross resistance. Results also showed that the mosquito larvae showed maximum susceptibility at the late fourth instar and to just after pupation.

Horizontal Transfer of the Insect Growth Regulator Pyriproxyfen to Larval Microcosms by Gravid Aedes albopictus and Ochlerotatus triseriatus mosquitoes in the Laboratory

Dell Chism, B, & Apperson, C.S.

Medical & Veterinary Entomology 17, 211-220, 2003.

The insect growth regulator pyriproxyfen is highly active against mosquitoes. By continuous immersion of 3rd and 4th instar larvae the concentration found to cause 50% inhibition of adult emergence was determined as 0.200 ppb (0.0002 ppm). For Aedes albopictus and 3.5 to 7 times less for Ochlerotatus triseriatus 0.0288 ppb (0.0000288 ppm). To test the theory that mosquitoes could transfer pyriproxyfen to larval breeding sites the following tests were conducted. Gravid adult mosquitoes were forced to walk on surfaces treated with pyriproxyfen and the allowed to oviposit. A significant response was found with Oc. Triseriatus yielding up to 70% inhibition rate. Ae. Albopictus yielded up to 73% emergence inhibition.The use of IGR treated oviposition containers to achieve the horizontal transfer of pyriproxyfen to mosquito oviposition sites could be a field management technique. Forcibly exposing gravid female mosquitoes to pyriproxyfen treated paper surface did not affect their fecundity but from 1st to 2nd gonotrophic cycles the egg hatch declined by 30%.

Utilization of Bloodfed Females of Aedes aegypti as a Vehicle for the Transfer of the Insect Growth Regulator Pyriproxyfen to Larval Habitats.

Itoh, T. et al.,

Journal of the American Mosquito Control Association, 10(3):344-347. 1994.

Bloodfed female Aedes aegypti were exposed to a surface treated with pyriproxyfen at 1.0 g/m² for 30 minutes and then allowed to lay eggs in cups of water containing 4th instar larvae. Adult emergence from the immatures was highly inhibited and transmission of pyriproxyfen from females to the water was revealed. The transfer of the chemical to the water decreased with time before the blood meal. Pyriproxyfen obviously affected egg maturation of females treated before blood meals as the number of eggs deposited decreased concurrently with the number of days before blood meals. These laboratory experiments support the possibility of utilizing blood-fed female mosquitoes of Aedes aegypti as a vehicle for pyriproxyfen for the control of mosquitoes in small and inconspicuous larval habitats.

Sensitivity of Larvivorous Copepod Species Mesocyclops pehpeiensis and Megacyclops viridis to the Insect Growth Regulator, Pyriproxyfen.

Wang, S., et al.

Journal of American Mosquito Control Association, 21(4):483-488, 2005.

Copepods are used as a biological control method in some countries; however combination of their use with insecticides would usually result in the death of the copepods. The effects of the insect growth regulator pyriproxyfen were evaluated on the mortality, fecundity, longevity and predation capability of 2 species of copepods, Mesocyclops pehpeiensis and Megacyclops viridis under laboratory conditions. Pyriproxyfen showed no significant effects on either the development or reproduction of Mesocyclops pehpeiensis at 0.1 ppm, which is a 10 fold greater concentration than the reported effective dosage for controlling mosquito larvae (0.01 ppm), but Megacyclops viridis development was impaired by Pyriproxyfen at 0.1 ppm. However, with Megacyclops viridis survivors developed faster, killed more mosquito larvae (they are predators), yielded more eggs and survived longer than the control group. Therefore these results show that although pyriproxyfen caused early mortality in sensitive species the survivors were those selected for faster development, better predation ability and greater longevity during their reproductive stage. Therefore, under natural conditions pyriproxyfen would cause modifications to the copepod population rather than a complete loss. The results show that a combined application of copepods and pyriproxyfen to control Aedes populations is feasible.

Chemical Persistence and Effects of S-31183, 2-(1-methyl-2-(4-phenoxyphenoxy)ethoxy)pyridine, on Aquatic Organisms in Field Tests

Schaefer, C. H., Miura T.

Journal of Economic Entomology 83 (5) 1768-1776 1990.

A candidate mosquito larvicide, S-31183, 2-(1-methyl-2-(4-phenoxyphenoxy)ethoxy)pyridine (Sumilarv), was highly compatible with other organisms in mosquito-breeding habitats. When S-31183 was applied at a rate of 0.11 kg (AI)/ha (0.1 lb/acre) (20 times greater than required for controlling Aedes nigromaculis larvae to rice plots, no detectable residues (<0.00005 ppm) were found after 2 d in treated water. S-31183 did not accumulate in soil, there were no residues (<0.005 ppm) after 3 d in fish (Lepomis macrochirus Rafinesque), and the residue on rice plants declined to<0.005 ppm after 7 d. Despite slight induction of morphogenetic aberrations in Odonata at adult emergence and minor suppression of reproductive capacity of Daphnoid cladocerans and ostracods, S-31183 was safe to aquatic, non-target organisms, including mosquito predators.

Efficacy, Non-Target Effects, and Chemical Persistence of S-31183, a Promising Mosquito (Diptera:Culicidae) Control Agent.

Schaefer, C.H., et al

Journal of Economic Entomology, 81(6), 1648-55, 1988. S-31183, 2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine (Sumilarv), was highly effective in inhibiting normal development of mosquito larvae into adults in laboratory and field trials. Late fourth instars were the most sensitive stage. Mortality occurred in the pupal stage and, at lower doses, resulted in formation of abnormal adults. No long-term bioaccumulation problem was apparent following dynamic or static exposures to fish. Non-target aquatic organisms that coexist in mosquito breeding habitats were not affected adversely by treatments which were effective against mosquitoes. Thus, S-31183 shows efficacy against mosquito larvae, a high degree of safety to associated non-target organisms, and chemical persistence that appear to be compatible with the environment.

Report of the Fourth WHOPES (World Health Organization Pesticide Evaluation Scheme) Working Group

WHO/CDS/WHOPES/2001.2

  • Effects of pyriproxyfen on aquatic nontarget organisms

    The document reviews many papers on the effect in the environment of pyriproxyfen and concludes as follows: The laboratory and field data clearly indicates that pyriproxyfen will not adversely affect a vast majority of aquatic invertebrates and fish when applied at rates usually <50 ppb in mosquito control programs. In the case of some adverse effects on certain organisms, the populations of affected organism will recover in relatively short time periods.

  • Laboratory efficacy trials

    Many studies are reviewed; results show studies with 13 species of mosquitoes. Since Sumitomo-recommended label rates are 10-50 ppb a.i., then the results for LC50 and LC95 fall well below this show the extreme activity of the product.

  • Field trials

    To pass WHOPES many field trials must be conducted. Firstly, existing published data is reviewed. They concluded that it was obvious from field data that a single low application rate of pyriproxyfen generally resulted in good control of a variety of mosquito species in the field. This result is due to the high activity and stability of pyriproxyfen under field conditions. The granular formulation of pyriproxyfen showed the most stable activity in the field among tested formulations.

  • WHOPES supervised trials

    Pyriproxyfen was compared alongside (S)-methoprene. There were 5 species of mosquitoes used in laboratory and semi-field efficacy studies. In all cases pyriproxyfen outperformed (S)-methoprene at similar dose rates of 0.02 and 0.05 ppm. It gave better % inhibition of adult emergence and persisted much longer. Indian TrialsPyriproxyfen was tested in the field in cesspits, stagnant and slow moving drains, and disused wells. Dose rates were equivalent to 0.01 – 0.05 g of 0.5% pyriproxyfen per m². Adult emergence inhibition in cesspits was very effective from 6 – 12 weeks depending in dose rate. In stagnant drains protection varied from 2 -10 weeks again depending on dose rate. In a disused well where the water was cleaner, a minimum of 18 weeks was obtained and up to 26 weeks.

  • WHOPES Conclusions and Recommendations

    Pyriproxyfen applied at mosquito control application rates has been shown to be safe to humans. This IGR is recommended at rates of 5 to 10 g a.i./ha, however higher rates of up to 100 g a.i./ha may be required for control of mosquitoes in heavily polluted waters. Manufacturers note: This product is normally recommended for application rates of 0.01-0.05 ppm of active ingredient. Dose rates per hectare can be inaccurate as the depth of the water will affect final concentration of the active ingredient.

Chronomid Midges (Diptera, Chironomidae) as Pests and Their Management.

ALI, A.
Cent Med Agric Vet Entomol, USDA-ARS, Gainesville, FL. USA

Source information: ZOOLOGICHESKII ZHURNAL; 75 (11). 1653-1667, 1997. (Abstract Only)

Many man-made aquatic ecosystems resulting from natural and anthropogenic factors in recent years has led to increasing the numbers of aquatic chronomid midges in many regions of the world. Adult midges cause nuisance problems, human allergies and have a severe economic impact. Nearly 100 of the 4000 known Chronomid species are documented as pests. Organochlorine, organophosphates (OPs), pyrethroids and insect growth regulators (IGRs) are being tested to reduce the numbers of midges. The best results for chemical control have come from OP insecticides (chlorpyrifos and temephos) and IGRs (diflubenzuron, methoprene, pyriproxyfen). The OP insecticides provided the larval field control for 2-5 weeks at less than 0.56 kg AI/ ha and less than 1-5 ppm. In some cases midge larvae were tolerant to these materials. IGRs (especially pyriproxyfen) provided more than 90% suppression of midge emergence for several weeks at less than 0.25 kg AI/ ha.

Evaluation of the Juvenile Hormone Mimic Pyriproxyfen (S-31183) Against Nuisance Chironomids (Diptera: Chironomidae), with Particular Emphasis on Polypedilum nubifer (Skuse)

Trayler. K.M. et al.

Journal of the Australian Entomological Society; 33 (2). 127-130. 1994. (Abstract Only)

Laboratory bioassays of the juvenile hormone mimic pyriproxyfen against late instar larvae of the nuisance chironomid Polypedilum nubifer revealed that 0.01 ppm pyriproxyfen caused a 90% inhibition of emergence of this species. A field trial of pyriproxyfen at 0.01 ppm was conducted using in situ enclosures. Pyriproxyfen significantly reduced the emergence of P. nubifer and another chronomid, Kiefferulus intertinctus (Skuse), for 24 days. Pyriproxyfen may provide a satisfactory alternative pesticide to organophosphate control agents currently in use.