Field evaluation of a lethal ovitrap against dengue vectors in Brazil.

Field evaluation of a "lethal ovitrap" (LO) to control dengue vector Aedes mosquitoes (Diptera: Culicidae), was undertaken in two Brazilian municipalities, Areia Branca and Nilopolis, in the State of Rio de Janeiro. The LO is designed to kill Aedes via an insecticide-treated ovistrip (impregnated with deltamethrin). In each municipality, the intervention was applied to a group of 30 houses (10 LOs/house) and compared to 30 houses without LOs in the same neighbourhood. Five LOs were put outside and five LOs inside each treated house. Three methods of monitoring Aedes density were employed: (i) percentage of containers positive for larvae and/or pupae; (ii) total pupae/house; (iii) total adult females/house collected by aspirator indoors. Weekly mosquito surveys began during the month before LO placement, by sampling from different groups of 10 houses/week for 3 weeks pre-intervention (i.e. 30 houses/month) and for 3 months post-intervention in both treated and untreated areas. Prior to LO placement at the end of February 2001, Aedes aegypti (L) densities were similar among houses scheduled for LO treatment and comparison (untreated control) at each municipality. Very few Ae. albopictus (Skuse) were found and this species was excluded from the assessment. Post-intervention densities of Ae. aegypti were significantly reduced for most comparators (P < 0.01), as shown by fewer positive containers (4-5 vs. 10-18) and pupae/house (0.3-0.7 vs. 8-10) at LO-treated vs. untreated houses, 3 months post-treatment at both municipalities. Numbers of adult Ae. aegypti females indoors were consistently reduced in LO-treated houses at Areia Branca (3.6 vs. 6.8/house 3 months post-intervention) but not at Niloplis (approximately 3/house, attributed to immigration). These results demonstrate sustained impact of LOs on dengue vector population densities in housing conditions of Brazilian municipalities.

Evaluation of the efficacy of lambda-cyhalothrin applied by three spray application methods for emergency control of Aedes aegypti in Costa Rica.

An extended duration formulation of lambda-cyhalothrin (Icon CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new hand-held sprayer (Twin-Fog) or as a low-volume spray (LV) from a backpack mist blower against Aedes aegypti was evaluated in Costa Rica. Spray applications were made at the front door for 1 min or to each room for 15 sec for the ULV and LV, and thermal fog applications were made to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and mosquito collections from within houses using hand-held, battery-powered aspirators. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for the ULV and thermal fog spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 3 wk of significant control (P < 0.05) based on adult Ae. aegypti house collections.

Attraction of Anopheles (Diptera: culicidae) to volatile chemicals in Western Kenya.

Anopheles gambiae s.l. and Anopheles funestus Giles are the primary vectors of malaria in East Africa. Identification of host-location olfactory cues may increase trap sensitivity for vector control and surveillance programs. Solid-state army miniature light traps were operated near sleeping humans in huts at night without lights and augmented with the potential attractants: L-lactic acid, Limburger cheese volatiles, hexanoic acid, and carbon dioxide. Mosquito response varied between species and gender. Female An. funestus exhibited a greater response to traps baited with L-lactic acid in combination with carbon dioxide than carbon dioxide alone in two different experiments.

Evaluation of the efficacy of lambda-cyhalothrin applied as ultra-low volume and thermal fog for emergency control of Aedes aegypti in Honduras.

An extended-duration formulation of lambda-cyhalothrin (Demand CS) applied as either an ultra-low volume (ULV) or thermal fog spray from a new handheld sprayer (Terrier) against Aedes aegypti was evaluated in Honduras. Spray applications were made at the front door for 1 min or to each room for 15 sec, both for the ULV and thermal fog applications to houses in separate blocks for each treatment. The efficacy and duration of effectiveness of the spray was determined from sentinel caged mosquito mortality and collection of mosquitoes within houses with a backpack power aspirator. Sentinel caged mosquito mortality in both open and sequestered locations was 97-100% for all spray treatments, with control mortality less than 2%. Both ULV applications (front door and each room) provided 4 wk of significant control (P < 0.01) based on adult Ae. aegypti house collections.

Behavior of resting Aedes aegypti (Culicidae: Diptera) and its relation to ultra-low volume adulticide efficacy in Panama City, Panama.

The resting behavior of Aedes aegypti (L.) adults was investigated in 14 districts of Panama City, Panama, in relation to ground ultra-low volume (ULV) applications of malathion. Adults primarily rested inside the premises (75.1%) at a distance > 6 m from the street (86.4%). Both sexes rested mainly in bedrooms, living rooms, and bathrooms. The small ULV aerosol droplets (2-4 microns) penetrated all indoor resting sites of Ae. aegypti, but in low amounts. Because of the low amount of insecticide reaching the primary resting sites within the premises, limited control of the Ae. aegypti was obtained. This limited the potential effectiveness of ground vehicle ULV applied insecticide as a dengue epidemic control method.

Laboratory testing of a lethal ovitrap for Aedes aegypti.

Laboratory tests were conducted to determine the feasibility of making the mosquito ovitrap lethal to Aedes aegypti (L.) when they attempt to oviposit in the trap. Heavy-weight velour paper strips (2.54 x 11 cm) were used as an alternative to the wooden paddle normally provided as a substrate for mosquito oviposition. The paper strips were pretreated with insecticide solutions and allowed to dry before being used in oviposition cups of 473 ml capacity, filled with water initially to within 2.5 cm of the brim. Insecticides chosen for their quick knock-down efficacy were bendiocarb 76% WP (1.06 mg a.i./strip) and four pyrethroids: permethrin 25% WP (0.16 mg a.i./strip), deltamethin 4.75% SC (0.87 mg a.i./strip), cypermethrin 40% WP (2.81 mg a.i./strip), and cyfluthrin 20% WP (0.57 mg a.i./ strip). For experimental evaluation, two oviposition cups (one with an insecticide-treated strip and one with an untreated strip) were placed in cages (cubic 30 cm) with gravid female Ae. aegypti mosquitoes (aged 6-8 days) from a susceptible laboratory strain. Mortality-rates of female mosquitoes were 45% for bendiocarb, 47% for permethrin, 98% for deltamethrin, 100% for cypermethrin, and 100% for cyfluthrin. Young instar larvae added to the treated cups died within 2h. After water evaporation from the cups for 38 days, fresh mosquito females had access to previously submerged portions of the velour paper paddle, and mortality rates of 59% or more occurred. Cups that had water (360 ml) dripped into them, to simulate rain, produced female mosquito mortality rates of > 50% and all larvae died within 3 h of being added. These tests demonstrate that the ovitrap can be made lethal to both adults and larvae by insecticidal treatment of the ovistrip. Field efficacy trials are underway in Brazil to access the impact of this simple, low-cost, environmentally benign approach on populations of the dengue vector Ae. aegypti.

Bacillus sphaericus inhibits hatching of phlebotomine sand fly eggs.

The effect of Bacillus sphaericus, at various concentrations, on hatching of phlebotomine sand fly eggs was examined using laboratory bioassays. Aqueous suspensions of B. sphaericus, strain 2362, inhibited hatching of eggs of Phlebotomus duboscqi and Sergentomyia schwetzi by 95% at concentrations as low as 0.05 and 0.11 mg/cm2, respectively. In contrast, B. sphaericus did not affect the ability of pupae to emerge as adults.

Phlebotomine sand fly control using bait-fed adults to carry the larvicide Bacillus sphaericus to the larval habitat.

Sugar meals of plant origin are an important component of the sand fly diet. We show that sugar solution baits have potential as vehicles for phlebotomine sand fly control. In the laboratory, adult Phlebotomus duboscqi Neveu-Lemaire and Sergentomyia schwetzi (Adler, Theodor, and Parrot) that have consumed an aqueous sucrose solution containing Bacillus sphaericus Neide toxins and are subsequently eaten by larvae produce significant larval death (P < 0.01). In the field, when vegetation near animal burrows and eroded termite mounds was sprayed with sucrose solution with or without incorporation of the larval toxicant B. sphaericus, 40% of female sand flies fed in situ. Dispersing B. sphaericus-carrier sand flies caused significant larval mortality (P < 0.01) in resting and breeding sites in animal burrows 10-30 m from the sprayed vegetation for 2-12 wk posttreatment. Also, adult sand fly populations breeding and resting inside animal burrows were significantly reduced (P < 0.01) following direct application of the sucrose/B. sphaericus solution to the burrow entrances. This control effect lasted 4-10 wk post-treatment. The effect was not seen for sand fly populations breeding and resting inside eroded termite mounds. This approach may be useful for the application of biological control agents against phlebotomine sand flies in biotypes where larvae and adults use the same habitats.

Isolation of the insecticidal components of Tagetes minuta (Compositae) against mosquito larvae and adults.

Application of Tagetes minuta floral extract to silica gel column chromatography produced 2 fractions with the hydrogenate part 20-30 times more toxic to larvae and 12-13 times more toxic to adults of Aedes aegypti and Anopheles stephensi, respectively, than the oxygenate part. Further fractionation by column chromatography of the hydrogenate fraction produced 4 thiophenes, 5-(but-3-ene-1-ynyl)-2,2'-bithiophene, 5-(but-3-ene-1-ynyl)-5'-methyl-2,2'-bithiophene, 2,2',5',2"-terthiophene, and 5-methyl-2,2',5',2"-terthiophene. These compounds in Tagetes minuta are largely responsible for the toxicity exhibited against the tested mosquitoes.

Phlebotomine sand fly (Diptera: Psychodidae) control using a residual pyrethroid insecticide.

Cyfluthrin was evaluated in the field as a residual insecticide to develop a new strategy for control of Old World phlebotomine sand fly vectors of leishmaniasis, which live and rest inside termite mounds and animal burrows. This insecticide was evaluated as a residual spray in Baringo District, Kenya, during 1993. Termite mounds and animal burrows were treated with a cyfluthrin/corn oil mixture (1.5% AI) using an 8-liter hand-pumped sprayer. Treatment of animal burrows and termite mounds with cyfluthrin provided control of sand flies inside these structures for 12 wk. Numbers of sand fly adults collected in light traps were reduced by up to 90% for 2 wk following treatment. This indicates that cyfluthrin provides short-term area control of adult sand flies when applied to termite mounds and animal burrows.

Insecticide barrier spraying for the control of sand fly vectors of cutaneous leishmaniasis in rural Guatemala.

An initial evaluation of insecticide barrier spraying directed against sand fly vectors of cutaneous leishmaniasis was done in a nonclimax forested area with heavy undergrowth in Peten, Guatemala. A 100 m-wide swath of vegetation was sprayed once with a 1:3 mixture of cyfluthrin insecticide and a palm oil carrier using back-pack sprayers to simulate a central cantonment area in one site while another site remained as an untreated control. Prior to spraying and throughout 87 days post-treatment, sand fly populations were monitored at both sites with light traps set at ground and canopy levels at 50-m intervals radiating out from the centers of the cantonments, 150-m in the four cardinal directions. A total of 2,876 female sand flies were captured, representing 16 species. Three species, Brumptomyia galindoi, Lutzomyia panamensis, and Lu, ovallesi, comprised 70% of the total collection. The single insecticide barrier significantly reduced sand flies from reaching the cantonment area for more than 80 days, while sand fly populations outside the treated cantonment and in the untreated (control) cantonment remained high (52 sand flies in the treated cantonment versus 235 sand flies in the untreated cantonment).

Field evaluation of four repellents against Leptoconops americanus (Diptera: Ceratopogonidae) biting midges.

Four repellents, deet, AI3-37220, AI3-35765, and CIC-4, prepared as 12.5% ethanol solutions, were evaluated against biting midges on Stansbury Islands, UT. Leptoconops americanus Carter was the only species that was biting human volunteers during the study. This species bit primarily on the ears at rates up to 840 bites per hour. All four repellents significantly reduced the number of bites on treated volunteers. AI3-37220 consistently provided the longest period of protection, giving 97 and 74% protection at 4 and 8 h, respectively. In a direct statistical comparison, AI3-37220 significantly outperformed deet. CIC-4 and AI3-35765 were the least effective repellents, providing 45-47% protection 8 h after application.

Toxicity of extracts from three Tagetes against adults and larvae of yellow fever mosquito and Anopheles stephensi (Diptera: Culicidae).

Whole-plant Soxhlet extractions for the three Tagetes species showed that T. minuta had the greatest biocidal effect on the larvae and adults of Aedes aegypti (L.) and Anopheles stephensi Liston. Bioassays of simultaneous steam distillation extractions of the various parts of T. minuta found extracts from the flowers provided LD90s of 4 and 8 ppm against the larvae and 0.4 and 0.45% against the adults of A. aegypti and A. stephensi, respectively. Further research on T. minuta floral extracts as new biorational insecticides are discussed.

Barrier spraying to control the malaria vector Anopheles albimanus: laboratory and field evaluation in the Dominican Republic.

To develop a new strategy for control of exophilic/exophagic malaria vectors which rest on peridomestic foliage, Anopheles albimanus was used for laboratory bioassays of mosquito adulticides applied to various vegetation types. Of the three classes of insecticide tested, the pyrethroid (permethrin at 112 g/ha) showed greater foliar persistence than either the carbamate (bendiocarb at 340 g/ha) or the organophosphorus compound (malathion at 277 g/ha). Field evaluation of barrier spraying against An.albimanus was evaluated in rural villages of southwest Dominican Republic during 1989. The pyrethroid deltamethrin was sprayed aerially for ultra-low volume application at treatment rates of 17-19 g a.i./ha in a radius of 500 m around two villages. An.albimanus were monitored by light-traps and human bait collections at both treated villages, compared with two similar untreated villages, up to 9 nights posttreatment. Densities of female An.albimanus were significantly reduced in the sprayed villages for at least 8 or 9 nights. Further evaluation of barrier spraying is recommended to determine optimal pyrethroid formulations and applications rates, their impact on non-target fauna and efficacy against malaria transmission.

Penetration of ultra-low volume applied insecticide into dwellings for dengue vector control.

Determinations on the penetration of ultra-low volume applied insecticide into dwellings was accomplished with a model house in Frederick, MD, USA, and native houses in Santo Domingo, Dominican Republic. Results from the model house tests show that aerosol droplets, with a volume median diameter of 4 microns, penetrated and remained suspended in low recesses of the building during the first 2 min after spraying. Similar results were found with tests in Santo Domingo, where man-made or natural obstructions were determined to be critical factors in aerosol penetration.

Botanical derivatives in mosquito control: a review.

A review on the reported uses of chemicals derived from botanical sources is presented, along with the part of the plant used for extraction, the mosquito species studied and the bioactivity observed for 344 plant species. Examples of phytochemicals evaluated against mosquitoes as general toxicants, growth and reproduction inhibitors, repellents and ovipositional deterrents are given. The effects of mosquito species and life stage specificity, solvents used for extraction, phototoxic activity and the geographical source from where the plant compounds are derived are discussed.

Integrated use of planaria (Dugesia dorotocephala) and Bacillus thuringiensis var. israelensis against Aedes taeniorhynchus: a laboratory bioassay.

The effectiveness of integrating Bacillus thuringiensis var. israelensis (B.t.i.) and the predatory planaria, Dugesia dorotocephala against Aedes taeniorhynchus was determined under controlled laboratory conditions. There was no significant effect (P greater than 0.05) of B.t.i. on D. dorotocephala either by direct association or through ingestion of B.t.i. dosed larvae. Planaria, alone, and B.t.i. combined with planaria, both provided significant (P less than 0.05) reduction of Ae. taeniorhynchus populations through the 12-week evaluation.

Field evaluation of four biorational larvicide formulations against Anopheles albimanus in Honduras.

Four biorational larvicide formulations: Teknar (B.t.i.), Arosurf MSF (Monomolecular Surface Film), Arosurf MSF combined with Teknar, and SAN-809-I ([s]-methoprene combined with B.t.i.), were evaluated against naturally occurring populations of the malaria vector mosquito Anopheles albimanus Wiedemann in Honduras. All formulations reduced the mean number of larvae per sample area to 0 within 48 h after treatment, and gave significant (P less than 0.05) control when compared with similar untreated areas for at least 10 days after treatment. It is concluded that each of these four formulations can be used effectively to control the larvae of An. albimanus in Honduras.

Comparison of ground and aerial ultra-low volume applications of malathion against Aedes aegypti in Santo Domingo, Dominican Republic.

Efficacy of ground and aerial ultra-low volume (ULV) applications of 91% malathion at 438 ml/ha against Aedes aegypti in the Dominican Republic was evaluated using indoor collections, oviposition trapping and adult sentinel mortality rates. Ground compared to aerial ULV applications in this study were found to have a greater effect on Ae. aegypti when measured by the described sampling techniques. Neither application method provided the level of Ae. aegypti suppression believed necessary for control in the event of a dengue virus epidemic.

Reduction of the Amblyomma americanum (Acari: Ixodidae) population at Fort A.P. Hill, Virginia, by aerial application of diazinon granules: correlation of percentage control with received dose.

Habitat (280 ha) of lone star tick, Amblyomma americanum (L.), was aerially treated with 14% diazinon granules. Concentration of acaricide reaching the forest floor ranged from 0.02 to 1.25 kg (AI)/ha. Greater than 85% control was achieved at study plots receiving the highest dose. A positive correlation was shown between dose received at the forest floor and percentage of control of adults (r = 0.91) and nymphs (r = 0.86).