Residual efficacy of three spinosad formulations against Psorophora columbiae larvae in small rice plots.

Experiments were conducted to determine the residual efficacy of both a briquette and a granular formulation (2 rates) of a numbered spinosad compound against Psorophora columbiae larvae in small rice plots. Comparisons were also made between the numbered compounds and labeled granular and briquette formulations of methoprene. Both rates of the spinosad granules had the highest initial efficacy (100% control), with the spinosad briquette being the least effective. However, 1 wk after treatment, the spinosad briquette was equally effective to both spinosad granules, suggesting a slow release in the briquette. The experimental briquette and the high rate of the experimental granules had the most residual activity, providing over 80% control for 33 days posttreatment. The granular methoprene formulation was the least residually effective compound, providing only 12% control at 7 days posttreatment.

Comparison of three residential mosquito traps against riceland mosquitoes in southeast Arkansas.

Field trials were conducted at 3 locations in Arkansas County, AR, to compare the effectiveness of 3 residential mosquito traps, the Stinger Mosquito Vacuum, the Mosquito Magnet Defender, and the Mosquito Deleto 2500 Active System, against riceland mosquitoes, specifically Anopheles quadrimaculatus and Psorophora columbiae. Both the Stinger Mosquito Vacuum and the Mosquito Deleto captured significantly more An. quadrimaculatus and total mosquitoes than did the Mosquito Magnet Defender. The Mosquito Deleto captured significantly more Ps. columbiae than did either of the other 2 traps.

Riceland mosquito management practices for Anopheles quadrimaculatus larvae.

Two separate but related studies were conducted regarding management of Anopheles quadrimaculatus larval populations in commercial rice fields near Cleveland, MS, in 2004. Study 1 was to evaluate the effectiveness of 2 treatments of aerially applied ultra-low volume applications of Bacillus thuringiensis var. israelensis (Bti) against An. quadrimaculatus larvae in dense, high-canopy mid- to late-season rice crop. Study 2 was to investigate the effect of preflood treatments of lambda-cyhalothrin (Karate), which is commonly used against rice water weevil (Lissorhoptrus oryzophilus), on An. quadrimaculatus larvae. Excellent initial, but short residual control (>99% control 1 day after treatment) was observed in the Bti-treated fields in both mid- and late-season rice. Little or no effect on mosquito larvae was observed in the lambda-cyhalothrin-treated fields. Results indicate that Bti can be effectively used by mosquito management personnel to control larval populations of An. quadrimaculatus in late-season rice fields; however, lambda-cyhalothrin did not effectively control larval An. quadrimaculatus when applied preflood to rice fields.

Comparison of dilute and neat formulations of Anvil by ultra-low volume ground application against Anopheles quadrimaculatus in Arkansas.

Neat (undiluted) and diluted ground-applied ultra-low volume (ULV) cold aerosol formulations of sumithrin (Anvil) were evaluated against Anopheles quadrimaculatus adults. Both formulations were applied at 1.938 g/AI/ha (0.00173 lb/AI/acre). Caged sentinel mosquitoes were placed on 1.5-m stakes 30.4, 60.9, and 91.0 m downwind and perpendicular to the line of spray. Mortality was observed at 1, 12, and 24 h posttreatment. Except for 1-h readings at 30.4 and 91.0 m the neat formulation was significantly more effective than the dilute. Droplet size and density averaged 13.6 microm and 422/cm2 for dilute formulation and 14.3 microm and 251/cm2 for the neat. There was no apparent relationship between droplet size and density when compared with mosquito mortality.

Ground ultra-low volume assessment of Aqua-Kontrol.

Against caged field-collected Anopheles quadrimaculatus Say adults, ultra-low volume (ULV) applications of 3.175 g a.i./0.40 ha (0.007 lb a.i.lac) of synergized permethrin (4% Aqua-Kontrol) gave excellent control (mean: 90%). Droplet collections on magnesium-oxide-coated (MGO) glass slides from 3 applications revealed mean deposition rate of 216 droplets/cm2 and 11-micron volume median diameter (VMD) (based on Aqua-Kontrol label spread factor of 0.61).

Efficacy of Biomist 30:30 and Aqua Reslin against Anopheles quadrimaculatus in Arkansas.

Aqua Reslin and Biomist 30:30 technical permethrin and piperonyl butoxide were applied via ground ultra-low volume at a rate of 237 ml/min and 0.00196 kg active ingredient/ha against wild-caught adult Anopheles quadrimaculatus. The 2 formulations did not differ significantly at 31 m from the spray path (P < or = 0.05). However, at 61 and 91 m, percent mortality for 30:30 was significantly higher than for Aqua Reslin at each time after treatment (P < or = 0.05). Between 12 and 24 h, about 8% recovery was observed in mosquitoes treated with Aqua Reslin at 31 m.

Efficacy of VectoLex WDG against Anopheles quadrimaculatus and Psorophora columbiae larvae in Arkansas and Mississippi rice.

In 1999, an aerial application of VectoLex WDG (water-dispersible granules) at 1.68 and 0.56 kg/ha, applied against sentinel 3rd-stage larvae of Psorophora columbiae installed in 0.42-ha rice plots 48 h after treatment, provided no control at 72 and 96 h after treatment. Less than 10% reduction was obtained at both rates 8 and 9 days after treatment against larvae of Ps. columbiae installed at 7 days after treatment. In a later test, VectoLex WDG manually applied at 5.04 and 1.68 kg/ha to small rice plots containing sentinel 3rd-stage larvae of Ps. columbiae and Anopheles quadrimaculatus obtained 90 and 97% control of Ps. columbiae at both rates, respectively, 24 h after treatment. A 2nd installation of Ps. columbiae at 24 h after treatment resulted in 7% and no control at both rates, respectively, even in the presence of larval carcasses from the 1st installation. VectoLex WDG was not effective against Ps. columbiae after 24 h atter treatment at either rate. Poor control was obtained at both rates against An. quadrimaculatus 24 h and 48 h after treatment for both installations. Two types of commercial rice fields containing native populations of larvae of An. quadrimaculatus were used for field tests in Cleveland, MS. In 1999, VectoLex WDG, aerially applied at 1.68 and 0.56 kg/ha to 0.2-ha plots in a contoured rice field, produced 81 and 85% reductions in early (neonate and 1st- and 2nd-stage) larvae and 94 and 76% reductions in late (3rd- and 4th-stage) larvae 2 days after treatment, respectively. At 2 days after treatment, means for all 4 developmental groupings (early larvae, late larvae, pupae, and combined stages) were significantly higher in untreated plots. Both VectoLex WDG rates did not differ significantly from one another. At 8 days after treatment, untreated plots contained significantly greater mean numbers of early larvae, late larvae, and combined stages, whereas both VectoLex WDG treatments were not significantly different. In 2000, VectoLex WDG applied at 1.68 kg/ha to two 0.40-ha plots in a precision-leveled field yielded 59 and 100% reductions of early and late larvae, respectively, 2 days after treatment. Reduction of late larvae remained 100% at 8 days after treatment. The numbers of late larvae, pupae, and combined stages were significantly greater in the untreated plot 2 days after treatment. At 8 days after treatment, numbers of early larvae and combined stages were significantly higher in the VectoLex WDG plot, whereas numbers of late larvae were significantly higher in the untreated plot. The differences in susceptibility of Ps. columbiae and An. quadrimaculatus to VectoLex WDG could be attributed to species differences in larval feeding behavior, body positioning in the water column, and developmental time. In tests in Arkansas, Ps. columbiae were controlled more quickly, usually within 24 h of exposure, whereas the percent reduction for An. quadrimaculatus in both tests in Cleveland, MS, suggests that control of this species within the region tested required from 48 h up to 8 days of exposure.

An aquatic light trap designed for live capture of predatory Tropisternus sp (Coleoptera: Hydrophilidae) larvae in Arkansas rice fields.

Construction of an aquatic light trap developed for the live capture of 3rd-stage larvae of predatory Tropisternus sp. for use in laboratory bioassays against larvae of Anopheles quadrimaculatus and Psorophora columbiae is described. On 10 occasions, an average of 5.2 traps was used per evening, resulting in 52 trap-nights that accumulated 106.7 h of trapping time, or an average of 10.6 h per trap. Use of 2 heavy-duty alkaline D-sized batteries and appropriate in-circuit resistance effectively increased bulb life and trap operating time, ranging from 22 to 36 h. During both seasons, approximately 3 wk after permanent flooding of large rice fields was the most productive period in which to capture larvae of Tropisternus sp. Live trapping worked well and provided numerous larvae of Tropisternus sp. for use in laboratory predation bioassays with An. quadrimaculatus and Ps. columbiae larvae. Six hundred fifteen 3rd-stage larvae of Tropisternus sp. and 740 adult Tropisternus lateralis were captured in aquatic light traps in 1999 and 2000. Of traps containing larval Tropisternus sp. and adult T. lateralis, average numbers of 15.3 and 19.4 were captured per trap, respectively. Among all traps, the largest nightly captures of larval Tropisternus sp. and adult T. lateralis consisted of 263 and 404 specimens, respectively. The largest single trap captures for larval Tropisternus sp. and adult T. lateralis were 94 and 184, respectively. Additionally, 478 rice water weevils (Lissorhoptrus oryzophilus) also were captured. Rice water weevils averaged 36.7 per trap, with the largest single trap capture of 102 weevils on an evening where 287 weevils were captured among all traps. Other predatory insect species were captured infrequently, consisting primarily of 3rd-stage larvae of Hydrophilus triangularis and adult belostomatids, dytiscids, and notonectids. Predatory larvae of H. triangularis may have been attracted to the traps by the presence of larval Tropisternus sp. Larval Tropisternus sp. may have been attracted by the light source and prey items that entered the trap, such as chironomid larvae.

Effectiveness of aerial- and ground-applied Bacillus formulations against Anopheles quadrimaculatus larvae in Arkansas rice plots.

Experimental Bacillus larvicides designed to float on or near the water surface were compared to labeled standard Bacillus corn-cob-based larvicides using sentinel Anopheles quadrimaculatus larvae in Arkansas rice plots during the 1998 growing season. Experimental floating formulations of Bacillus thuringiensis israelensis applied at 5.58 and 11.18 kg/ha provided up to 100% control of 3rd- and 4th-stage Anopheles larvae within 24-48 h, whereas the water-dispersible granule formulations containing Bacillus sphaericus required 48-72 h to yield >75% mortality in 0.16-ha plots at 11.18 kg/ha. Detecting and targeting the smaller developmental stages (1st- and 2nd-stage larvae) could increase the effectiveness of the tested compounds against An. quadrimaculatus in Arkansas and other rice-growing regions.

A simple technique for rapid colonization of Anopheles quadrimaculatus using adults aspirated from livestock barns.

A technique was developed for rapid colonization of Anopheles quadrimaculatus larvae in an improvised insectary using blood-fed mosquitoes aspirated from livestock barns. A novel device termed the mosquito aspiration transfer and ovipositional chamber (MATOC) is described. In 2 field seasons, 14 broods were successfully mass reared, yielding more than 28,500 vigorous 3rd- and 4th-stage larvae used in rice plot and other bioassays. Crowding the females over a natural ovipositional substrate induced oviposition as early as 12 h from introduction into the MATOCs.

Evaluation of methylated soy oil and water-based formulations of Bacillus thuringiensis var. Israelensis and Golden Bear Oil (GB-1111) against anopheles quadrimaculatus larvae in small rice plots.

The efficacy of formulations containing methylated soybean oil (MSO) alone and with technical-grade Bacillus thuringiensis var. israelensis (Bti) were compared to Golden Bear Oil (GB-1111) and a water-based Bti formulation against 3rd- to 4th-stage Anopheles quadrimaculatus larvae confined to sentinel cages in small rice plots. Three replicates each of MSO with 2% Pyroter added as a surfactant (MSO + PYR), MSO with 2% Pyroter and 4 g of Bti technical powder (MSO + PYR + Bti), GB-1111, a water-based formulation with 4 g of Bti technical powder (Bti + water), and untreated controls were performed. Mosquito larvae were introduced on the 1st day of treatment and at 4 days posttreatment. Mortality was recorded at 24 and 48 h posttreatment for the 1st installation and at 5 days posttreatment for the 2nd installation. The Bti + water formulation provided 71% control and the MSO + PYR + Bti formulation achieved 64% control, whereas MSO + PYR and GB-1111 produced 16 and 18% control, respectively, at 24 h posttreatment. With the exception of MSO + PYR + Bti, which decreased by 2%, the mean percent control increased slightly at 48h posttreatment across remaining treatments, with Bti + water obtaining 72% control. This was significantly higher than GB-1111, which achieved 23% control at 48 h posttreatment. The MSO + PYR and MSO + PYR + Bti formulations yielded 56 and 62% control, respectively, during the same interval and were not significantly different from one another. Formulations containing MSO + PYR exhibited delayed activity similar to GB-1111, with all formulations except MSO + PYR + Bti providing greatest control at 48 h posttreatment. Both MSO formulations (MSO + PYR + Bti and MSO + PYR) were statistically comparable to Bti + water and GB-1111, respectively, at 24 and 48 h posttreatment. None of the formulations exhibited a residual activity adequate enough to control An. quadrimaculatus larvae for up to 5 days.

Efficacy of Dibrom, Trumpet, and Scourge against four mosquito species in Louisiana.

Adult mortality of Anopheles quadrimaculatus, Culex quinquefasciatus, and the Aedes spp. complex (Aedes sollicitans and Aedes taeniorhynchus) was observed after aerial ultra-low volume (ULV) exposure to Dibrom, Trumpet, and Scourge. Dibrom was applied at 112 g active ingredient (AI)/ha, Trumpet at 112 g AI/ha, and Scourge at 1.96 g AI/ha. At all time intervals, Dibrom and Trumpet were significantly more effective against the Aedes spp. complex than against An. quadrimaculatus and Cx. quinquefasciatus. Scourge was significantly more effective against An. quadrimaculatus and Cx. quinquefasciatus than Dibrom or Trumpet. Trumpet was evaluated at lower labeled rates (28, 56, and 84 g AI/ha) against Cx. quinquefasciatus and the Aedes spp. complex. Adult mortality with Trumpet increased significantly at 1 and 24 h against Cx. quinquefasciatus. With the Aedes spp. complex, mortality increased with rate at 1 h, but at 12 and 24 h, the medium and high dosages were not significantly different from each other. Culex quinquefasciatus and the Aedes spp. complex were also subjected to ULV ground applications of Dibrom, Trumpet, and Scourge. Dibrom was applied at 22.4 g AI/ha, Trumpet at 22.4 g AI/ha, and Scourge as a 1:6 mineral oil mixture at 1.96 g AI/ha. Relative to Dibrom and Trumpet, mortality from Scourge differed greatly with mosquito species. Against Cx. quinquefasciatus, Scourge was significantly more effective than Dibrom and Trumpet at all times and distances, but against the Aedes spp. complex Scourge was significantly less effective.

Comparison of electrostatic versus nonelectrostatic ULV sprays of Aqua Reslin against Anopheles quadrimaculatus adults.

An electrostatic truck-mounted spray system (Spectrum, Houston, TX) and a nonelectrostatic spray system (Micro-Gen G-4, San Antonio, TX) were tested to determine the feasibility of electrostatically charging Aqua Reslin, a water-based permethrin insecticide, and ascertain whether an electrostatic charge would increase the efficiency of Aqua Reslin against Anopheles quadrimaculatus adults. Parameters tested for both machines included mean mass median diameter (MMD) of droplets, number of drops per cm2, and posttreatment percent mortality at 1, 12, and 24 h. Results indicated that the electrostatically charged droplets produced greater mortality at each distance and hour posttreatment. Correlation coefficients and linear equations were calculated for distance-mortality, MMD-mortality, drops per cm2-mortality, distance-drops per cm2, distance-MMD, and MMD-drops per cm2. Results indicated that the electrostatic drops demonstrated strong correlations between each paired variable, whereas the nonelectrostatic drops showed poor correlation between drops per cm2-mortality, distance-drops per cm2, and MMD-drops per cm2. However, from this trial, these differences cannot be attributed purely to the electrostatic charge because significant differences in droplet size can affect spray performance.

Efficacy of three synthetic pyrethroids against three mosquito species in Arkansas and Louisiana.

Adult mortality of Anopheles quadrimaculatus, Culex quinquefasciatus, and Aedes sollicitans was observed following ultra-low-volume (ULV) exposure to Responde, Permanone 31-66 RTU, and Scourge. Permanone 31-66 RTU (1:2.13, permethrin:PBO) and Scourge (1:3, resmethrin:PBO) were applied at 0.00175 lb AI/acre, while Responde (1:3, prallethrin:PBO) was applied at 0.001 lb AI/acre, and all were evaluated at 100, 200, and 300 ft. downwind of application. Significant mortality differences (P < or = 0.05) were observed among all compounds at 15 min and at 1, 12, and 24 h posttreatment against An. quadrimaculatus and Cx. quinquefasciatus. Responde exhibited significantly greater (P < or = 0.05) control (knockdown) against An. quadrimaculatus at both 15 min and 1 h posttreatment than did Permanone 31-66 RTU or Scourge; however, some recovery occurred by 12 h posttreatment. At 15 min posttreatment, Responde and Scourge were significantly (P < or = 0.05) more effective against Cx. quinquefasciatus than Permanone 31-66 RTU except at 300 ft. downwind, where Scourge was significantly (P < or = 0.05) more effective than either compound. No significant mortality differences (P < or = 0.05) were observed among the 3 compounds at 15 min, 1 h, 12 h, and 24 h posttreatment when tested against Ae. sollicitans. No significant mortality differences (P < or = 0.05) were observed between the 1:3 and 1:5 (prallethrin: piperonyl butoxide) formulations of Responde at any time posttreatment when tested against Ae. sollicitans.

Field trial efficacy of two formulations of Permanone against Culex quinquefasciatus and Anopheles quadrimaculatus.

Tests were conducted during the summer of 1996 to evaluate the effectiveness of different formulations of permethrin, Permanone 31-66 and Aquareslin, against Anopheles quadrimaculatus and Culex quinquefasciatus. Tests of both formulations were conducted at rates of 2.019 and 3.926 g AI/h with each formulation/rate replicated 3 times. Results indicate significantly greater control of both pest species at the higher application rate for both formulations. The high rate of Permanone 31-66 proved more effective than that of Aquareslin. Exposure at the low rate for both formulations provided inadequate adult control that was particularly pronounced against Cx. quinquefasciatus. Regardless, negligible recovery of exposed adults was observed at any formulations/rate. No significant differences in mortality were noted for any formulation/rate relative to distance downwind. However, volume median diameter and droplets/cm2 were significantly affected by distance downwind. Furthermore, volume median diameter and droplets/cm2 were both determined to significantly affect mortality in both mosquito species (P < or = 0.05). Overall, results indicate that Permanone 31-66 and Aquareslin applied at a rate of 3.926 g AI/h were effective.

Laboratory and field plot bioassay of Bacillus sphaericus against Arkansas mosquito species.

Bacillus sphaericus was evaluated in laboratory bioassays against larvae of 7 Arkansas mosquito species and in rice field plots against a single mosquito species. Laboratory-tested species included Aedes aegypti, Ae. albopictus, Ae. vexans, Anopheles punctipennis, Culex quinquefasciatus, Cx. restuans, and Psorophora columbiae. Field plot bioassays were evaluated against Ps. columbiae only. The laboratory formulation tested demonstrated activity against all 7 species. Mortalities were observed at 24 and 48 h posttreatment. Twenty-four-hour LC50 results ranged from 0.84 to 15.04 international toxic units (ITU)/ml for all species and 48-h LC50 results ranged from 0.38 to 9.27 ITU/ml. Twenty-four-hour LC90 results ranged from 1.90 to 48.21 ITU/ml for all species, whereas 48-h LC90 results ranged from 1.30 to 33.83 ITU/ml. Subsequent field plot evaluations yielded control at both dosages (0.45 and 0.9 g/ ha) during the initial 48-h exposure period. Mortalities at 48 h posttreatment for both dosages were 87 and 90%, respectively. Posttreatment mortalities never exceeded 16.7% after 24 h and none were significantly different from control mortality (P < or = 0.05).

Efficacy of a 1:1 and 1:5 mixture of technical permethrin and piperonyl butoxide against Anopheles quadrimaculatus and Psorophora columbiae.

Anopheles quadrimaculatus and Psorophora columbiae adults were treated with a 1:1 and 1:5 mixture of technical permethrin and piperonyl butoxide. These mixtures (0.00075 lb AI/acre) at 100, 200, and 300 ft. downwind of application killed a similar (P < or = 0.05) percentage of Ps. columbiae ranging from 45.1 to 68.8% and 85.7 to 100.0% after 1 and 24 h posttreatment, respectively. Similar results were obtained at 1 and 24 h posttreatment against An. quadrimaculatus (0.00075 lb AI/acre) where percentage mortality ranged from 42 to 62% and 63 to 78% after 1 and 24 h posttreatment, respectively. At 24 h posttreatment, significantly more mortality (P < or = 0.05) occurred in An. quadrimaculatus than in Ps. columbiae for both the 1:1 and 1:5 formulations above, except at 100 ft. downwind. A higher dosage against An. quadrimaculatus (0.001 lb AI/acre) resulted in a higher mean mortality at 1 h posttreatment (45.1-79.1%) and 24 h posttreatment (59.2-86.0%) than at the lower dosage. A 25% increase in permethrin (0.001 lb AI/acre) vs. a 400% increase in piperonyl butoxide alone gave increases in mortality of 30.4% vs. 8.6%, respectively.

Vector competence of Aedes albopictus from Pine Bluff, Arkansas, for a St. Louis encephalitis virus strain isolated during the 1991 epidemic.

The vector competence of Aedes albopictus from Pine Bluff, AR, was assessed for a St. Louis encephalitis (SLE) virus strain isolated during the 1991 epidemic. Aedes albopictus were fed on hamsters with viremia levels of 10(4.6)-10(4.9) Vero cell plaque-forming units (PFU)/ml. At 7 and 15 days postbloodfeeding, transmission trials were conducted using individual suckling mice. Three of 313 Ae. albopictus were determined to be infected with SLE virus with titers of 10(6.3)-10(7.0) PFU/mosquito. At 15 days postbloodfeeding, one of 209 Ae. albopictus that refed transmitted virus resulting in a 15-day population transmission rate of 0.5%. The infection threshold (i.e., the amount of virus required to infect from 1 to 5% of mosquitoes) was determined to be approximately 10(2.3) PFU/mosquito. Virus inoculated intracoelomically into Ae. albopictus replicated and reached mean titers above 10(6.0) PFU/mosquito on day 6. The combination of low susceptibility to infection and a mammalophilic bloodfeeding pattern suggests that Ae. albopictus is unlikely to play a significant role in SLE transmission.

Evaluation of aerial and ground-applied adulticides against mosquito species in Arkansas and Louisiana.

Mosquitoes were subjected to ultra-low volume (ULV) aerial applications of permethrin synergized with piperonyl butoxide (Biomist 30:30. Biomist 31:66) and Cythion and ULV ground applications of permethrin synergized with piperonyl butoxide (Biomist 30:30. Biomist 12:60), resmethrin (Scourge), and sumithrin (Solo 40-OS and Duets 8.8-OS). Permethrin compounds tested aerially against Anopheles quadrimaculatus were not significantly different. Biomist 30:30 tested aerially against Culex quinquefasciatus did provide significantly greater mortality compared to Cythion. Biomist 30:30 and Biomist 31:66 tested aerially against An. quadrimaculatus at 1 h did not provide a significant difference up to 600 ft. (182.9 m). Both products ground tested at 24 h revealed nonsignificant results. Biomist 30:30 and Biomist 12:60 ground tested against Cx. quinquefasciatus at 1 h did not provide a significant difference at 100 ft. (30.5 m) or 200 ft. (61.0 m); however, significantly greater mortality was observed at 300 ft. (61.0 m) and 600 ft. (91.4 m). At 24 h no significant mortality differences were observed at 300 ft. (61.0 m) and 600 ft. (91.4 m). Anopheles quadrimaculatus and Psorophora columbiae were treated with a 1:1 mixture of Solo 40-OS and Duet 8.8-OS (sumithrin+piperonyl butoxide). Significant mortality differences (P < or = 0.05) between species at 1 h posttreatment occurred at 300 ft. (91.4 m).

Assessment of Anopheles quadrimaculatus response to permethrin and resmethrin by topical application.

Topical applications with field-captured mosquitoes provided LD50 estimates ranging from 13.3 to 20.0 ppm for permethrin and 8.5 to 18.9 ppm for resmethrin in the Stuttgart, AR, area in 1993. Mosquitoes collected from the abatement area appeared to be more susceptible to resmethrin than those from outside the area (8.5 ppm vs. 18.9 ppm). The observed difference was not great enough to be of concern from an economic or control standpoint. The data provided a firm baseline for future assessment of changes in susceptibility to these 2 materials. Mosquitoes collected in Walnut Ridge, AR, were susceptible to permethrin and resmethrin within the same range as the Stuttgart populations, but the limited number of observations preclude firm LD50 estimates.