BVA 2 mosquito larvicide--a new surface oil larvicide for mosquito control.

BVA 2 mosquito larvicide was evaluated in laboratory pan tests against 3rd-instar Aedes taeniorhynchus (Wied.), Culex quinquefasciatus Say, and Culex nigripalpus Theobald larvae. BVA 2 was as effective as the standard, GB-1111, at 14 liters/ha (> 99.1% vs. 99.8%). In small field plot tests BVA 2 mosquito larvicide applied at 28 liters/ha was as effective as GB-1111 (99.0% vs. 99.8%) 24 h posttreatment. Operationally, applied by helicopter at 46.8 liters/ha, BVA 2 mosquito larvicide was more effective (> 90%) in the slightly less vegetated site than in the heavily vegetated site. As a pupicide applied at 14 liters/ha in laboratory pan tests, no significant differences were noted between BVA 2 mosquito larvicide and GB-1111 against Ae. taeniorhynchus, Cx. quinquefasciatus, and Cx. nigripalpus pupae.

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.

A comparison of Teflon slides and the Army Insecticide Measuring System for sampling aerosol clouds.

The effects of method of droplet analysis, reader of Teflon slides and distance on mass median diameter of a Cythion aerosol cloud were examined in the calibration of an Army Insecticide Measuring System (AIMS). There were no significant differences in results among readers and between the AIMS and readers. There were slight but statistically significant differences between readers of Teflon slides and between the methods of analysis. Data supports the manufacturer's recommendation that, for the AIMS, the distance at which an aerosol generator air blast is between 3 and 7 m3 s-1 must be determined.

Evaluation of three candidate cypermethrin-piperonyl butoxide formulations compared with Scourge against adult Culex quinquefasciatus.

Cypermethrin-piperonyl butoxide formulations (1:1, 1:5, 1:10) were evaluated in a laboratory wind tunnel against colony reared, susceptible adult Culex quinquefasciatus mosquitoes. Scourge (4% resmethrin:12% piperonyl butoxide) was used as the standard for comparison. Based on the LC90 data, the 3 cypermethrin-piperonyl butoxide formulations were 2.6-3.7x more toxic than Scourge 24-h posttreatment.

Control of Aedes taeniorhynchus and Culex quinquefasciatus emergence with sustained release Altosid sand granules and pellets in saltwater and freshwater test plots.

The efficacy of sustained release Altosid sand granules to control adult Aedes taeniorhynchus and Culex quinquefasciatus emergence was investigated. Sand granules applied at a 7-day preflood application rate of 5.6 kg/ha controlled 99% of the Ae. taeniorhynchus emergence in saltwater plots for 44 days posttreatment and 35% of Cx. quinquefasciatus in freshwater plots. A 5.6 kg/ha rate controlled 100% of the Ae. taeniorhynchus emergence for 30 days posttreatment in semi-permanent saltwater plots. Altosid pellets were used at the label rate for comparison. Sand granules applied at 11.2, 16.8 and 22.4 kg/ha against Cx. quinquefasciatus in freshwater plots gave 98% emergence inhibition at the 22.4 kg/ha rate 37 days posttreatment, 93% at 16.8 kg/ha for 22 days, and 100% at 11.2 kg/ha rate for 16 days.

Effects of Arosurf MSF on a variety of aquatic nontarget organisms in the laboratory.

Ninety-six-hour static acute toxicity tests were conducted in the laboratory to determine the effects of a 47 ml/m2 (50 gal/acre) application of Arosurf MSF (2 mole ethoxylate of isostearyl alcohol) on Fundulus similus, Palaemonetes pugio, Palaemonetes paludosus, Uca spp., Procambarus spp., Gammarus spp., Asellus spp., Streptocephalus seali, Physa spp., Laeonereis culveri and an unidentified amphipod. Test temperatures of 20-27 degrees C were based on the ambient water temperature for the season of the year when the desired life stages were more abundant. No acute toxicity was observed with any of the organisms exposed to this concentration of Arosurf MSF.

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.

A comparison of the mortality of caged adult mosquitoes to the size, number and volume of ULV spray droplets sampled in an open and a vegetated area.

A comparison of the mortality of caged adult mosquitoes to the size, number and volume of ULV spray droplets sampled in an open and vegetated area showed that 2.5-times more droplets with 3.24-times greater volume were sampled in the open area and resulted in 10-times greater mosquito mortality.