Evaluation of Persistence and Accumulation for Mosquito Adulticides Applied by 

Ultra Low Volume Spray (ULV) 

The persistence of mosquito adulticides in water has 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 hrs after one application, and 12 hrs after 

another.

Pyrethrin and PBO 

Following aerial applications of pyrethrin and PBO in Sacramento for West Nile virus, Larry Walker 

Assoc. (2006) reported results of water testing on samples from 11 waterways within the treatment area. 

Samples were taken immediately after application (within 1 hour) and 12 to 16 hours after the 

application. Treated areas were sprayed 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 concentration was 0.853 ppb, maximum concentration detected was 4.2 ppb. 

Water samples were tested 8 days following aerial applications, from 4 sites. No PBO could be detected 

in any of these. Therefore, the duration 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 naled applied aerially decreased to undetectable levels by 9 hours postapplication. In another test, naled was undetectable in samples taken 12 hours post-application. Truck 

applications of naled reached undetectable levels by 4 hours 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 mosquito adulticides do not accumulate in water 

or sediment. Chemical testing was conducted following 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 background level when samples taken 1 week after the last application 

were tested. Similarly, Lawler et al (2008), reported that the concentration of pyrethrins and PBO in 

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

the 5th application. In many cases, the concentrations were actually lower following the 11 the spray 

than after the fifth spray event. Accumulation of PBO was evaluated by Amweg et al, (2006). PBO did 

not accumulate in water or sediment, even after 8 biweekly 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 surface 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 Pyrethrin Water Quality Monitoring Data Summary. 

Larry Walker and Associates. 49 pp. 

Lawler, S.P., D.A. Dritz, C.S. Johnson, and M. Wolder. 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 Brown,. 2008. Environmental concentrations, fate, and 

risk assessment of pyrethrins and piperonyl butoxide 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 estuarine copepods and young fish after field applications. Journal 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.