Evaluation of several novel alkynols, alkenols, and selected host odor blends as attractants to female Aedes albopictus and Culex quinquefasciatus.

The compound 1-octen-3-ol is a strong attractant for some mosquito species. Based on chemical structure, this may be due to a terminal site of unsaturation or high electron density, a structural capability for hydrogen bonding, e.g., -OH, -NH2, NHR, NR2, etc., a saturated hydrocarbon chain of a certain minimum length, and a certain relative distance between the region of high electron density and the alcohol (or other hydrogen-bonding) functional group. Based on this hypothesis, 4 novel alkynol (triple-bonded) analogs were synthesized and evaluated alone or in combination with acetone and dimethyl disulfide, and with and without carbon dioxide in Mosquito Magnet-X suction traps. Attraction of laboratory-reared adult Aedes albopictus and Culex quinquefasciatus to these analogs and combinations was compared to 1-octen-3-ol as a standard in semi-field trials. For both species none of the alkynols, with and without carbon dioxide or acetone and dimethyl disulfide, were significantly different from 1-octen-3-ol. The compounds 2-octyn-4-ol and 2-nonyn-4-ol alone and with carbon dioxide suppressed Cx. quinquefasciatus collections. An additional 6 alkenol (double-bonded) analogs were tested in mixtures with 3-n-propylphenol and 4-methylphenol in a ratio of 4:1:8, respectively. Using the same trapping methods, Cx. quinquefasciatus catches containing 3-decen-1-ol were increased nearly 3-fold when combined with carbon dioxide. Aedes albopictus collections in traps with the 3-decen-1-ol/phenol mixture and carbon dioxide were significantly greater than similar traps with 1-octen-3-ol. Traps baited with the phenol blends that incorporated (Z)-3-nonen-1-ol, (Z)-8-nonen-3-ol, or 1-octen-3-ol were considerably suppressed in the presence of carbon dioxide.

Efficacy of several commercially formulated essential oils against caged female Aedes albopictus and Culex quinquefasciatus when operationally applied via an automatic-timed insecticide application system.

The effectiveness of several commercially available products containing plant essential oils against caged female Aedes albopictus and Culex quinquefasciatus was studied. Products operationally applied via an automatic-timed insecticide application system (MistAway) at maximum label rates were EcoExempt MC (9.0 ml/liter, rosemary oil [18% AI], cinnamon oil [2% AI], lemongrass oil [2% AI], plus 78% "other ingredients" in wintergreen oil). Misting System Concentrate (4 ml/liter, oil of Juniperus virginiana [85% AI]), Mosquito Barrier (31.1 ml/liter, garlic oil [99.3% AI], and citric acid [0.5% AI]), and No-See-Um Organic Repellent (99.5 ml/liter, lemongrass [4% AI], citronella [3% AI], castor oil [3% AI], sodium laurate [3%], and garlic oil [1% AI] in an 86% [AI] mixture of wintergreen oil, lecithin, and water). All products were compared with a commercial formulation of synergized pyrethrins, Riptide (9.0 ml/liter, pyrethrins [5% AI], piperonyl butoxide [25% AI]), as a standard. Mortality was the greatest for Riptide to both mosquito species with effectiveness influenced by distance from the nozzle (ranging from > 80% at 3 m to > 10% at 20 m). The essential oil products resulted in < 10% mortality for each species regardless of application exposure distance with the exception of EcoExempt, which gave approximately 13% mortality of caged female Ae. albopictus 6 m from the nozzles.

Semi-field evaluation of several novel alkenol analogs of 1-octen-3-ol as attractants to adult Aedes albopictus and Culex quinquefasciatus.

The compound 1-octen-3-ol is a known attractant of some mosquito species, which has led to the hypothesis that olfactory stimulation by this alkenol may be associated with the following structural elements: a terminal site of unsaturation or high electron density; a structural capability for hydrogen bonding, e.g., -OH, -NH2, NHR, NR2, etc.; a saturated hydrocarbon chain of a certain minimum length; and a certain relative distance between the region of high electron density and the alcohol (or other hydrogen-bonding) functional group. Using this logic, we synthesized 20 alkenol analogs based on the octenol double-bonded carbon skeleton. The attraction of female Aedes albopictus and Culex quinquefasciatus to these analogs was compared with 1-octen-3-ol as a standard in semi-field trials. For both species, collections from Mosquito Magnet-X (MMX) suction traps baited with the alkenol analogs in the absence of carbon dioxide were not significantly different from octenol-only baited traps, with the exception of (Z)-3-hepten-1-ol which collected significantly more Ae. albopictus. In the presence of CO2, most of the collections from traps baited with an alkenol were considerably increased for both species but not different from octenol plus CO2, with the exception of Ae. albopictus where (Z)-3-decen-1-ol, (Z)-4-hexen-1-ol, 7-octen-2-ol, and 8-nonen-3-ol significantly depressed trap catches. Although no clearly identifiable structure-activity relationship could be determined from our collected data, we did find that MMX traps baited with carbon dioxide and 4-penten-2-ol or (E)-2-decen-4-ol significantly enhanced Cx. quinquefasciatus collections up to nearly 3-fold compared with octenol plus carbon dioxide.

Semi-field comparison of the BG Lure, nonanal, and 1-octen-3-ol to attract adult mosquitoes in northwestern Florida.

The relative attractiveness of Mosquito Magnet-X suction traps baited with various combinations of the BG Lure, nonanal, 1-octen-3-ol (octenol), and carbon dioxide was evaluated against laboratory-reared female Aedes albopictus and Culex quinquefasciatus in semi-field trials in northwestern Florida. In the absence of carbon dioxide, traps baited with the BG Lure (comprised of ammonia, caproic acid, and lactic acid) collected just as many mosquitoes as traps baited with carbon dioxide only. The numbers of mosquitoes caught in traps baited with no carbon dioxide and only nonanal, octenol, or their combination with or without the BG Lure were generally depressed compared with traps baited with carbon dioxide alone. When these chemicals were combined with carbon dioxide, no significant difference existed in the abundance of either mosquito species caught compared with traps baited only with carbon dioxide. However, in one trial, the combination of BG Lure plus octenol and carbon dioxide resulted in nearly a 4-fold depression in Ae. albopictus collections compared with carbon dioxide-only baited traps. The reason for this discordance remains to be investigated.

Residual effectiveness of three pyrethroids on vegetation against adult Aedes albopictus and Culex quinquefasciatus in screened field cages.

The residual effectiveness of pyrethroid-treated vegetation as a barrier against female host-seeking Aedes albopictus and Culex quinquefasciatus was evaluated in large screened-cage field tests for 12 wk. Individual potted southern wax myrtle (Myrica cerifera L.) plants were treated with either beta-cyfluthrin (Tempo SC Ultra), lambda-cyhalothrin (Demand CS), or tau-fluvalinate (Mavrik Perimeter) at maximum label rates. Suction mosquito traps (MMX) baited with carbon dioxide placed near plants treated with tau-fluvalinate provided significant overall reduction (approximately 62-80%) of mosquitoes through 2 wk compared with untreated plants. Overall percent knockdown/mortality from excised-leaf bioassays was similar to suction-trap reduction data. However, knockdown/mortality in leaf bioassays was greater for Ae. albopictus than for Cx. quinquefasciatus, whereas no such effect was observed in trap collections. Mosquito abundance in MMX collections near plants treated with beta-cyfluthrin provided similar levels of reduction as tau-fluvalinate-treated plants through 1 wk and 3-4 wk after treatment. Leaf toxicity generally provided approximately > 90% knockdown/mortality on beta-cyfluthrin treated leaves throughout the study. Generally, no consistent difference in trap reduction or weekly knockdown/mortality in leaf bioassays was observed between either mosquito species. Plants treated with lambda-cyhalothrin provided significantly greater overall reduction of mosquitoes (75-83%) from MMX collections for the first 5 wk compared with untreated plants. Knockdown/mortality levels and duration of leaf toxicity from lambda-cyhalothrin- treated leaves was similar to that of beta-cyfluthrin, with no consistent differences between mosquito species.

Evaluation of an automatic-timed insecticide application system for backyard mosquito control.

Several manufacturers and pest management companies have begun to market and install outdoor automatically timed insecticide application systems that claim to provide an envelope of protection against host-seeking mosquitoes within a defined area, e.g., residential backyards. A typical system consists of a multi-gallon reservoir attached to a continuous loop of plastic tubing with multiple single spray head nozzles. Nozzles are usually placed along the perimeter of a backyard in landscaping or other areas suitable for mosquito harborage. This array is then connected to a programmable electric pump set to automatically apply an insecticide at predetermined intervals. An operational field study was conducted to evaluate this technology using previously installed MistAway systems at.3 residences in northwestern Florida. This system applied a mist-like application of 0.05% AI synergized pyrethrins for 45 sec at dawn and again at dusk in each backyard. Twice-weekly collections from ABC suction light traps, baited with carbon dioxide, were used as the evaluation tool. Female mosquitoes from treatment backyards were compared with trap collections from 3 backyards without automatic misting systems used as controls. We found that weekly mosquito reduction was highly variable and ranged from 98% to 14% during the 35-wk study. Because the primary method of reduction by these application systems was not well understood, a MistAway system was installed in an outdoor simulated residential backyard to determine exposure pathway under controlled conditions with field cage and excised-leaf bioassays. Using laboratory-reared females of Aedes albopictus and Culex quinquefasciatus in those assays, we found that reduction by the MistAway system was primarily achieved by direct exposure of the mosquitoes to the insecticide application and not from residual deposits on treated vegetation.

Controlled release chamber for dispensing aromatic substances.

A novel device for the containment and precise release of aromatic substances is described. The device consists of a threaded-tubular polyvinyl chloride chamber (and screw-top cap) with ports for introduction and release of gaseous compounds. This chamber is inexpensive, easy to assemble, and useful for evaluating the combined release of carbon dioxide and aromatic hygroscopic substances as mosquito attractants in field studies.

Residual effectiveness of pyrethroid-treated foliage against adult Aedes albopictus and Culex quinquefasciatus in screened field cages.

The residual effectiveness of pyrethroid-treated foliage as a barrier against female Aedes albopictus and Culex quinquefasciatus was evaluated in large screened cage field tests. Individual potted southern wax myrtle, Myrica certifica, plants were treated with either Aqua Reslin 20 + 20 emulsifiable concentrate (EC) (20% active ingredient [AI] permethrin + 20% [AI] piperonyl butoxide), Permanone EC (10% [AI] permethrin), or Suspend suspension concentrate (SC) (4.75% [AI] deltamethrin) at maximum label rates. Generally, Aqua Reslin provided -83% overall reduction of mosquitoes during the week of treatment. After that time, mosquito reduction decreased to <50% and continued at this level for the remainder of the 12-wk study. Mosquito knockdown/mortality from excised Aqua Reslin-treated leaves revealed that this formulation quickly lost effectiveness after the initial week of treatment. Plants treated with Permanone provided =70% and 64% overall reduction during the week of, and first week after treatment, respectively. Knockdown/mortality from excised leaf bioassays of leaves treated with this formulation fell below 50% 2 wk after treatment where it remained for the rest of the study. Suspend generally provided 70 to approximately 80% overall mosquito reduction during the first 4 weeks after treatment and decreased to <50% thereafter. Residues on treated leaves provided >95% overall knockdown/mortality throughout the study and was not correlated with weekly reduction in the field cages. We believe this disparity was in part attributed to new plant growth. Newly formed leaves probably provided nontoxic surfaces for mosquito harborage.

The effectiveness of the Mosquito Magnet trap for reducing biting midge (Diptera: Ceratopogonidae) populations in coastal residential backyards.

This study evaluated the effectiveness of single Mosquito Magnet' traps to consistently reduce biting midge populations in a coastal northwest Florida residential neighborhood. Midge abundance from 5 backyards, each with a Mosquito Magnet trap, was compared with 3 backyards without traps (controls). Midge populations were sampled once weekly for 24 h in each backyard by using a Centers for Disease Control (CDC) suction trap baited with carbon dioxide. In addition, midge accumulations from Mosquito Magnet traps were collected once a week at the time of CDC trap operation while biting midge populations were manually sampled from each backyard by using a "sand fly bat" (i.e., a wire-handle flyswatter fitted with a 10.5-cm2 plastic 14 X 14 mesh screen). Eighteen midge species were collected during the study but the majority (99.9%) collected from all backyards were (in descending order): Culicoides mississippiensis, C. furens, and C. melleus. Midge populations from CDC traps in yards with Mosquito Magnets were significantly lower on 2 of 45 wk (March 28 and April 3) when compared with control backyards. Weekly reduction attributed to Mosquito Magnets was not consistent and ranged from 4.2 to 85.3%. No significant difference was found in mean midge abundance on sand fly bats from yards with Mosquito Magnets compared with control yards. On the average, cooperators with Mosquito Magnet traps reported that their seasonal level of midge reduction (as related to a monthly ranked degree of annoyance) was variable and often not consistently below their threshold.

Evaluation of a novel removal trap system to reduce biting midge (Diptera: Ceratopogonidae) populations in Florida backyards.

A removal trapping method that employed individual lure-baited insect suction traps for the reduction of adult biting midges (Culicoides spp.) was evaluated in a coastal residential neighborhood of northwestern Florida during 2000. Six backyards were used in the study. Lure-baited traps consisted of one ABC PRO insect suction trap (fitted with a 30 by 30-mesh polyester screen bag) baited with carbon dioxide (500 ml/min) and a 4:1:8 mixture of 1 octen-3-ol, 3-n-propylphenol, and 4-methylphenol (5.39 +/- 0.54 mg/h) placed in each of three backyards. Lure-baited traps ran continuously during the 4-mo study. Three backyards without lure-baited traps served as controls. Adult midge populations were monitored twice weekly for 24-h in each backyard using an additional ABC PRO trap baited with carbon dioxide (500 ml/min) only. Five species of biting midges were collected from all traps in each backyard (in descending order): Culicoides mississippiensis, C. barbosai, C. melleus, C. furens, and C. hollensis. Overall reduction was not consistent in lure-baited backyards and ranged from 2.3% to 70.6% on 16 of the 30 sample dates. But when biting midge populations seasonally declined to a weekly average of < 500 midges per lure-baited trap, reduction occurred more frequently. Midge reduction did not appear to be species specific.

Field trials of three concentrations of Laginex as biological larvicide compared to Vectobac-12AS as a biocontrol agent for Culex quinquefasciatus.

Laginex AS Biological Larvicide (Lagenidium giganteum) and Vectobac-12AS (Bacillus thuringiensis var. israelensis) were compared in plastic pools containing laboratory-reared Culex quinquefasciatus larvae located in a wooded area in Panama City, FL, in August and September 1997. The pools were dipped at 2-day intervals to assess larval control. Sentinel larvae in screen-sided cups were added to all treatment and control pools at 4-day intervals and evaluated for infection at 48 h. Laginex produced larval control up to 20 days as compared to the Vectobac-12AS compound, which required retreatment by the 10th day. The most effective control was attained by the Laginex 25 treatment, which reduced larvae in the pools by 100% for 22 days. Control in the Laginex 15 and Laginex 35 treatments dropped to 90% and 74% at day 13 and day 9, respectively. The numbers of infected larvae remained above 50% as larval control was assessed, but dropped and fluctuated when water temperatures were lowered at the onset of cold weather. Organic pollution did not prove to be a significant factor in the evaluations.

Effects of Mesocyclops longisetus (Copepoda:Cyclopidae) on mosquitoes that inhabit tires: influence of litter type, quality, and quantity.

A 59-week study was conducted to evaluate the impact of adult Mesocyclops longisetus populations on larval mosquito species inhabiting tires. Greater than 90% reduction of number of 1st and 2nd instars was recorded by 4 wk with 90% reduction of number of 3rd and 4th instars after 7 wk. Reduced control was noted with the onset of cooler winter water temperature. Overall. a 52% reduction in the number of 1st and 2nd instars was achieved, and a 57% reduction was noted in number of 3rd- and 4th-instar mosquito larvae. Cooler temperatures resulted in a decline of adult Mesocyclops, which resulted in reduced larval control. Significantly greater numbers of Mesocyclops adults were collected in tires with either new litter or heavy amounts of litter regardless of litter type. Lastly, litter type, either oak leaves or pine needles, did not influence mosquito reduction or abundance of Mesocyclops populations.

Downwind drift and deposition of malathion on human targets from ground ultra-low volume mosquito sprays.

Malathion was sprayed using a truck-mounted ultra-low volume (ULV) aerosol generator. The generator was operated at 41.4 kPa (6 psi) at flow rate of 128 ml (4.3 fl. oz.) per min. Malathion concentrations were measured at selected positions on live, stationary human subjects wearing protective clothing and placed along a transect at right angles to the path of the truck. Two standing subjects were exposed downwind to the malathion spray at 7.6 and 15.2 m. A third subject was exposed while jogging in the same direction as the spray vehicle and 1.5 m from the spray path. No significant differences (P > 0.05) in total amount of malathion deposited on subjects was demonstrated. During the last 4 sprays, average amounts of malathion deposited on ground level at 15.2, 30.4 and 91.2 m were not significantly different (P > 0.05). Malathion dermal residues were compared with the acute LD50 value (4,100 mg/kg) for a 70 kg adult male. Calculated malathion dermal exposures were less than the acute lethal dose for a human subject by 4 orders-of-magnitude or more.

Susceptibility of first instar Toxorhynchites splendens to malathion, naled and resmethrin.

Acute toxicity tests were conducted to measure the response of first instar Toxorhynchites splendens to commonly used mosquito adulticides: malathion, naled and resmethrin. The concentrations of pesticide causing 50% mortality (LC50) after 24 h was 2.87, 69.1 and 623 ppb for resmethrin, malathion and naled, respectively. Naled was determined to be the least toxic of the 3 compounds tested for integrated use with Tx. splendens. The latter assessments were based on comparisons between laboratory-derived dose-response curves and maximum concentrations reached in standing water calculated using standard application rates.

Effect of ULV malathion on automotive paint finishes.

The relationship between malathion droplet size (VMD) and degree of damage to 1990, 1K and 2K General Motors paint standards was investigated in the laboratory and field. Laboratory tests indicated a positive correlation between malathion droplet VMD and damage spot size. Laboratory settling chamber tests revealed that size-thresholds of droplets too small to cause visible damage averaged 8 and 11 mu on washed 1K and 2K paints, respectively. Field tests indicated malathion caused no visible damage to 1K or 2K paint panels under routine operating conditions, although droplet sizes (VMD) sampled on the automobile surface averaged 10.2 +/- 4.5 and 11.7 +/- 5.7 mu. Microscopic damage was found on paint panels placed on the hood, roof, trunk and doors of the automobile when parked parallel or perpendicular to the course of the spray truck and when driven through the spray of a stationary spray truck.

Acute toxicity of mosquitocidal compounds to young mosquitofish, Gambusia affinis.

Toxicity of Florida mosquito larvicides and adulticides to 3-5 day old Gambusia affinis was determined in the laboratory. After 24-h exposure, the larvicides, temephos, fenoxycarb and petroleum distillates had LC50 values of 5.60, 1.05 and 593.4 ppm, respectively. After 24 h the adulticides resmethrin, fenthion, naled and malathion had LC50 values of 0.007, 2.94, 3.50 and 12.68 ppm, respectively. The only compound toxic to young mosquitofish at maximum field application rates was resmethrin. However, in the light of earlier tests, aerially applied adulticides generally reach the water surface at reduced concentrations and thus probably pose little or no risk to mosquitofish populations.

Effects of pressure and flow rate on Cythion droplet size produced by three different ground ULV aerosol generators.

A study to determine the effects of machine pressure and insecticide flow rate on the size of aerosol droplets as they relate to the Cythion label was conducted with 3 different ground ULV aerosol generators. An increase in flow rate required a corresponding increase in blower pressure to maintain the labeled droplet mass median diameter of 17 microns or less. Droplets larger than 48 microns were frequently sampled at machine pressures less than 6 psi (41.4 kPa). At the highest labeled flow rate of 8.6 fl oz/min (254.3 ml/min), machine pressures of 7-8 psi (48.3-55.2 kPa) were required for each of the 3 aerosol generators tested to consistently conform to the droplet criteria of the Cythion label.