### Evaluation of Persistence and Accumulation for Mosqui to Adulticides Applied by Ultra Low Volume Spray (ULV)

The persistence of mosquito adulticides in water ha s been evaluated in several published studies. These can summarized briefly as follows:

Permethrin Persistence of permethrin following truck-mounted applications was evaluated by Pierce (2005). The material was undetectable in water samples taken 2-4 hr s after one applicatio n, and 12 hrs after another.

Pyrethrin and PBO Following aerial applications of pyr ethrin and PBO in Sacramento for West Nile virus, Larry Walker Assoc. (2006) reported results of wa ter testing on samples from 11 wate rways within the treatment area. Samples were taken immediately after applica tion (within 1 hour) and 12 to 16 hours after the application. Treated areas were sp rayed nightly for 3 to 4 days. Pyrethrins were undetectable at 12- 16 hours after each spray event . PBO was detected in 11 of 16 samples taken 12-16 hours after each spray event. Average concen tration was 0.853 ppb, maximum concentration detected was 4.2 ppb. Water samples were tested 8 days following aerial app lications, from 4 sites. No PBO could be detected in any of these. Therefore, the dur ation of persistence appears to be greater than 16 hours but less than 1 week

. Water testing was also carried out by Weston (2006) following the same applications. Pyrethrins were not detectable in any samples taken 10-34 hours after the spray applications . PBO was detected at low levels in water and sediment at 10-34 hours. Neither water nor sediment were tested at later intervals, so the duration of persistence could not be determined in this study.

Persistence of PBO was evaluated by Schleier et al in (2008). Water was sampled after aerial applications of pyrethrin and PBO in irrigation ditches at one site (Princeton) and in static ponds at another (Colusa). PBO concentration decreased exponentially at both sites with return to background levels or near background (0.004 ppb above) within 36 hours

.

Resmethrin and PBO Abbene et al (2005). Evaluated the persistence of resmethrin and PBO in ditch water following helicopter applications. Resmethrin returned to pretreatment levels by 9 hours after application, PBO persisted a little longer but also returned to background levels by 96 hours (4 days).

Naled Tucker (1987) reported that nale d applied aerially decreased to undetectable levels by 9 hours postapplication. In another test, na led was undetectable in samples ta ken 12 hours post-application. Truck applications of naled reached undetectable levels by 4 ho urs after the application

.

Malathion Persistence of malathion was also evaluated by tucker (1987). This material persisted longer than naled, being detectable for over 18 hours in some applications, but still became undetectable 48 hours after the application

.Absence of accumulation following multiple applications Several papers demonstrate that ULV-applied mo squito adulticides do not accumulate in water or sediment. Chemical testing was conducted follow ing multiple spray events in 2006 by Amweg et al. There was no increase in the level of pyrethrins or PBO following multiple daily spray events and the

concentration had returned to b ackground level when samples taken 1 week after the last application were tested. Similarly, Lawler et al (2008), reported that the concen tration of pyrethrins and PBO in

tanks within a treated area were not significantly higher afte r 11 applications than in samples taken after

the 5 th application. In many cases, the concentrations were actually lower following the 11 the spray than after the fifth spray event. Accumulation of PBO was evaluate d by Amweg et al, (2006). PBO did
not accumulate in water or sediment, even after 8 bi weekly applications by truck-mounted equipment,

over the course of 2 months.



### References

Amweg, EL, DP Weston, CS Johnson, J You and MJ Lydy. 2006. Effect of piperonyl butoxide on permethrin toxicity in the amphipod Hyalella azteca . Environmental Toxicology and Chemistry 25 (7):1817-1825

Abbene, I.J., S.C. Fisher, and S.A. Terracciano (U.S. Geological Survey). 2005. Concentrations of insecticides in selected surf ace water bodies in Suffolk County, New York, before and after mosquito spraying, 2002-04. Open-File Report 2005- 1384. New York, NY. 1-14.

Larry Walker and Associates 2006. SYMVCD Pyreth rin Water Quality Monitoring Data Summary. Larry Walker and Associates. 49 pp.

Lawler, S.P., D.A. Dritz, C.S. Johnson, and M. Wold er. 2008. Does synergized pyrethrin applied over wetlands for mosquito control affect Daphnia magna zooplankton or Callibaetis californicus mayflies? Pest Manag Sci 64: 843-847.

Schleier JJ III, RKD Peterson, PA Macedo, DA Brow n,. 2008. Environmental concentrations, fate, and risk assessment of pyrethrins and piperonyl butoxi de after aerial ultralow- volume applications for adult mosquito management. Environmental Toxicology and Chemistry, Vol. 27, No. 5, pp. 1063– 1068, 2008

Tucker, J.W., C.Q. Thompson, T.C. Wang, and R.A. Lenahan. 1987. Toxicity of organophosphorous insecticides to estuarin e copepods and young fish after field a pplications. Journa l of the Florida Anti-Mosquito Association 58: 1-6.Weston DP, EL Amweg, A Mekebri, RS Ogle, MJ Lydy. 2006. Aquatic effects of aerial spraying for mosquito control over an urban area. Environ Sci Technol 40:5817–582.