Studies Assessing Persistence of Mosquito Adulticides Applied by Ultra Low Volum

Pyrethrins and Pyrethroids 

AI Product Sample 

Type 

Time 

sampled

Results Persistence Notes R

Resmethrin Scourge Water 

column 

0.5 h 

2 hr 9 hr 

48 h 

96 hr 

Spray # 1 

0.038 ppb @ 2 hr 

ND @ 9 hr 

Spray #2 

ND at any time 

>2h but <9 hr helicopter 

2 spray dates 1 site (tidal ditch) 

Abben

Pyrethrins Evergreen Water 2-

6 cm below surface 

1 hr 

12 hr 24 hr 36 hr 

No detect at Princeton site before or after Colusa site: ND 1, 12, 24h. Jasmolin 0.213 ppb @ 36 hrs, prob not from this applic since levels were higher at 36 hr than 1, 12, or 24 hrs post applic 

<1 h No pyrethrins 

detected at 1 site, prob from another applic at the other since levels were higher at 36 hrs than 1, 12 or 24 hrs 

Schleie

Pyrethrins Evergreen Water 

mid depth 10 sites 

1 h 

12-16 h 

8 days 

ND ND 

>1h but <16 h No signif 

increase after Multiple applics 

Larry WAssoc. SYVC

Pyrethrins Evergreen Water 10-34 

hrs PT 

ND in H2O <34 hrs No water caused 

signif mort in 7 days 

Westo

Pyrethrins Evergreen sediment 10-34 

hrs PT Sediment was before 

application was made 

PBO present at 34 hrs No signif dif betw 10 & 34 hr 

No water caused signif mort in 7 days 

Westo

In studies where repeated testing was done, pyrethroids and pyrethrins never persisted for 48 hours, and were often undeapplication
Piperonyl Butoxide (PBO) 

AI Product Sample 

Type 

Time 

sampled

Results Persistence Notes R

PBO in Pyrethrin mix 

Evergreen Crop Spray 

Water 2-6 cm below surface 

1 hr 

12 hr 24 hr 36 hr 

Colusa ponds Below back by 36 h Princ ditches 0.012 @ 36 h (0.004 above pre) 

~ 36 h Exp. decay w/ 

return to backgr by 36 h 

Schleie

PBO in Pyrethrins mix 

Pyrenone 25-5 

Water + sediment 

12 hr 

1 wk 

0-3 ppb in sediment 0-0.08 in water < report limit of 2 ppb 

>12h but <1 wk 

for sediment or 

water 

8 spray events Sampled 1 wk after last truck application 

Amwe

PBO in Pyrethrin mix 

Evergreen Crop Spray 

Water mid depth 10 sites 

1 hr 

12-16 hr 

8 days 

ND >16 h but < 8 d No signif 

increase after multiple aerial applications 

Larry WAssoc. SYVC

PBO in Pyrethrin mix 

Evergreen Crop Spray 

Water 10-34 

hrs postapplic 

0.44-3.92 ppb in H2O PBO present at 

34 hrs No signif dif betw 10 & 34 hr 

No water caused signif mort in 7 days 

Westo

PBO in Pyrethrin mix 

Evergreen Crop Spray 

Sediment 

10-34 

hrs postapplic 

< reporting limit (<1ppb) 15.9, 19.2, 34.0, 61.4 ppb 

>15.9 ppb @ 34 hrs 

No signif dif 

betw 10 & 34 hr 

Same aerial applications studied by Larry Walker Assoc 

Westo

PBO in Resmethrin mix 

Scourge Water 

1 site, 2 application dates 

0.5 h 

2 hr 9 hr 

48 hr 96 hr 

0.113 ppb @ 9 hr 

 ND at 48 

0.006 ppb @ 48 hr 

ND @ 96 h 

>48 h but <96 

hr 

Multiple samples after 2 helicopter applications over a tidal ditch 

Abben

ND = Not detected Jasmolin is one of the 6 materials making up natural pyrethrins Schleir et al. 2008 demonstrated that PBO became undetectable around 36 hours after aerial applications (residues were the level present before treatment). The four other papers reported on PBO concentrations following applications of PB

had fewer sample times at greater intervals. Results of these support the conclusions of Schleier et al. 2008. Taken toge

demonstrate that PBO does not persist in sediment or water for 4 days (96 hours).
Organophosphates

Active 

Ingredient 

Product Sample 

Type 

Time 

sampled

Results Persistence Notes R

Naled Water 12 times 

after, up 

to 48 h 

Worst case H2O conc 

peak = 20.15 ppb @ 

15 min 

ND in sample by 9 hr 

9 hrs after air 

applic 

4 hrs after truck 

applic 

 Tucker 

Malathion water 12 times 

after, to 

48 h 

Worst case H2O conc 

peak = 20.15 ppb @ 

45 min 

80% decrease by 8 h 20% persisted 24 h ND by 48 h 

>24 but <48 hr 1 applic by air, 

1 by truck 

Tucker 

Naled breaks down rapidly and is undetectable by 9 hours after applications by air or truck. Malathion persists longer than naled, but also decreases to undetectable levels by 48 hours following an application even

References 

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Schleier JJ III, RKD Peterson, PA Macedo, DA Brown,. 2008. Environmental concentrations, fate, and risk assessment 

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