UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

PC Code: 128965 

DP Barcode: 407817 

Date: March 28, 20123 

MEMORANDUM 

SUBJECT: 

TO:· 

FROM: 

Spray Drift Analysis for the Etofenprox Label Amendment (Petition No. 

1£7925) 

Andrew Ertman, Risk Manager Reviewer 

Barbara Madden, Risk Manager 

Minor Use Team 

Registration Division (7505P) 

Kristin Rury, Biologist 

Christine Olinger, Branch Chief 

Risk Assessment Branch III 

Health Effects Division (7509P) 

Chuck Peck, Environmental Engineer 

Environmental Risk Branch IV 

Environmental Fate and Effects Division (7507P) 

REVIEWI;J> Jim Carleton, Ph.D., Senior Scientist 

BY: x· ~ Environmental Risk Branch IV 

Environmental Fate and Effects Division (7~7P) f 

Faruque Khan, Ph.D., Senior Scientist / c:::v-~ C--t---3/ :2.& / I .J 

Environmental Risk Branch I 

Environmental Fate and Effects Division (7507P) 

APPROVED Marietta Echeverria, Branch Chief 

BY: Environmental Risk Branch IV 

Environmental Fate and Effects Division (7507P) 

This memorandum addresses the IR-4 submission in support of tolerance requests for etofenprox. 

In particular, IR-4 has requested to amend the labels for Zenivex E20 (Reg. No. 2724-791) to and 

Zenivex E4 RTU (Reg. No. 2724-807) allow for ultra-low volume (UL V) spray applications over 

"agricultural crops (including those intended for human consumption), pasture and rangeland." 

In support of this effort, IR-4 submitted a magnitude of residue study and modeling to evaluate 

residues over aerially applied crops. IR-4 also submitted information to support the supposition 

that residues resulting from ground UL V applications could be extrapolated from aerial UL V 

application deposition data. This memorandum addresses both aspects of the IR4 submission. 

Additionally, the results from this analysis are in good agreement with HED's assessment (DP 

Barcode 405380). 

1 
2 

Summary: A raw agricultural commodity (RAC) study was conducted by the IR-4 program in 

which a single treatment of etofenprox was completed using aerial equipment typical of mosquito 

adulticide applications.1

 Investigators used AGDISP to identify the locations outside of the 

treated area where residues were expected to be the highest, given the environmental conditions 

at the time of application. RACs were sampled in these locations. The submission addressed 

how the AGDISP computations were completed in order to define these sampling locations. 

In addition, IR-4 submitted rationale that the residues found in the RAC study, following aerial 

application, could be used as a basis for completing a risk assessment for ground-based mosquito 

adulticide applications (i.e., deposition from ground applications is similar to that from aerial 

applications). A number of literature studies were reviewed by the authors, as was a dissertation 

focused on the mechanistic aspects of drift from ground-based adulticide applications. The 

findings of these analyses indicated that deposition from ground-based applications were similar 

in to depositions monitored during aerial applications. 

However, there is some uncertainty as to how representative the deposition results were for 

minimum conditions specified on the etofenprox adulticide labels, based on the meteorological 

conditions and the number of applications occurring at the RAC study sites. Current labels 

stipulate that applications can occur during wind speed conditions ranging from 1 to 10 mph, and 

that up to 25 treatments can be completed within a single year. While the application conditions 

in the RAC studies were typical of what would be expected under normal application situations, 

only one application was performed rather than the maximum number allowed by the labels. As 

a result, the residue levels could be higher than those measured, as etofenprox deposition could 

potentially be higher than what occurred in the study. 

The results of the analysis conducted by EFED indicate that a deposition rate of 33% for sprays 

reaching agricultural crops is a conservative estimation for both ground (based on submitted 

literature data) and aerial (based on AGDISP modeling) ULV applications based on the label 

guidance for etofenprox. The maximum deposition value from the ground ULV literature was 

consistent with the modeling results also presented in the submission. The conservative 

deposition value helps account for some of the uncertainty associated with deposition values that 

could not be estimated from data provided in some of the studies. These values assume a 

minimum wind speed of 1 mph. If the wind speed was increased to 2 mph, the deposition rates 

would decrease to 20% (based on AGDISP modeling) for aerial ULV applications and 24% 

(based on Schleier model) for ground ULV applications. Table 1 depicts the deposition rates and 

estimated residues for aerial and ground ULV applications with minimum wind speeds of 1 and 2 

mph. 

Table 1. Deposition Rates and Residue Levels for Aerial and Ground ULV 

Applications of Etofenprox

 1 mph wind speed 2 mph wind speed 

Application Type Deposition (%) Residue (ppm) Deposition (%) Residue (ppm) 

Aerial 33 4.3 – 4.8 20 2.6 – 2.9 

Ground 33 4.3 – 4.8 24 3.1 – 3.5 

 

1

 MRID 48612201. 
3 

Introduction 

IR-4 has requested a label amendment for Zenivex E20 and Zenivex E4 RTU to allow for ultralow volume (ULV) spray applications over agricultural crops (including those intended for 

human consumption), pasture and rangeland. These end use products are insecticides used at low 

volumes to control adult mosquitoes, non-biting midges, and biting and non-biting flies. Zenivex 

E20 and Zenivex E4 RTU can be applied via aerial or ground ULV application at a rate of 0.007 

lbs a.i./A, 25 times per site per year, for a maximum annual application rate of 0.18 lbs 

a.i./A/year. These products do not have tolerances, however, nor are they currently allowed for 

use over general cropland areas. The purpose of this action is to evaluate the methodology and 

data submitted by IR-4 to support such a use pattern. When applied aerially, existing and the 

proposed label changes stipulate that spray equipment must be adjusted so that the volume 

median diameter (VMD) is less than 60 microns (Dv0.5< 60 μm) and 90% of the spray is 

contained in droplets smaller than 100 microns (Dv0.9< 100 μm). Aerial applications must occur 

at heights greater than 100 feet, preferably between 100 and 300 feet, and wind speeds must be 

between 1 and 10 mph. No swath width is specified, but based on the assessment conducted by 

IR-4, swath width for aerial applications is assumed to be 500 feet. For ground ULV applications 

via cold aerosol sprayers, the Zenivex E20 and Zenivex E4 RTU labels specify that spray 

equipment must be adjusted so that the VMD is between 10 and 30 microns (10 μm ≤ Dv0.5 ≤ 30 

μm) and 90% of the spray is contained in droplets smaller than 50 microns (Dv0.9< 50 μm). Wind 

speeds must be between 1 and 10 mph and a swath width of 300 feet is recommended. Per the 

Zenivex E20 label and Zenivex E4 RTU labels, thermal fogging equipment mounted on a truck 

can also be used with a VMD less than 60 microns (Dv0.5< 60 μm) and 90% of the spray is 

contained in droplets smaller than 100 microns (Dv0.9< 100 μm). 

Aerial ULV Application 

In order to support a label modification to allow for ULV applications of etofenprox over 

pastureland and crops, IR-4 conducted a magnitude-of-residue study, using aerial ultralow 

volume (ULV) applications of etofenprox (Zenivex E20) over pasture grass, leaf lettuce, alfalfa, 

and snap beans in California and Florida (MRID 48612201). In each case, a single application at 

0.007 lbs a.i./A was made. The maximum residue reported for an application at a 100-foot 

release height (required by the label for aerial ULV applications) was 0.17 ppm on leaf lettuce at 

the Florida site. The maximum residue reported for an application at a much lower release height 

(50 feet) was 0.39 ppm on pasture grass at the California site. It should be noted that the 50-foot 

release height is not allowed under the current Zenivex E20 and Zenivex E4 RTU labels2

. 

To estimate the residues resulting from multiple applications, IR-4 used the TREX model. The 

model uses the Kenaga Nomagram to calculate the residues on avian and mammalian food items, 

using the application rate and the dissipation rate of a chemical applied to foliar surfaces. 

Assuming a single application rate of 0.007 lbs a.i./A, a default dissipation rate of 35 days, and 

that 100% of the applied pesticide deposited on the crop, TREX estimates a maximum residue 

level (short grass) of 1.68 ppm, roughly 10 times higher than the residues measured at the Florida 

site in the study. To achieve the levels observed at the Florida site in the residue study, an 

application rate of 7.08x10-4 lbs a.i./A, or 10% of the application rate, would need to be used in 

TREX. Given that the wind speed at the Florida site ranged from 0 to 2.5 mph, the observed 

application efficiency of approximately 10% appears reasonably consistent with AGDISP 

predictions for aerial ULV application (see discussion below). Therefore, use of an application 

 

2

 MRID 48612201. 
4 

rate of 7.08x10-4 lbs a.i./A for etofenprox in TREX is consistent with both observed and predicted 

deposition data. 

 

EFED evaluated aerial ULV applications of etofenprox using the model AGDISP version 8.25 

(Appendix A). Given the same application parameters (e.g., drop size distribution, application 

material, application height), model results indicate that deposition is sensitive to wind speed as 

an input parameter. Etofenprox can be applied when wind speeds range from 1 to 10 mph. For a 

wind speed of 1 mph, the application efficiency, or the percent of pesticide depositing on the 

crop, is 33%. As wind speed increases, the deposition within the swath decreases. The 

deposition inside the swath drops to 2.2% and 0% at a wind speeds of 2.5 and 3 mph, 

respectively. It should be noted that in running AGDISP, two warning messages occurred: (1) the 

spray volume (0.005 gal/A) was beyond the recommended range of 0.25 to 30 gal/A, and (2) the 

swath width (500 ft) was beyond the recommended range of 15 to 100 ft. While the values for 

spray volume and swath width were taken from the study (MRID 48612201) and appear to 

generate deposition residues in line with the study results, they are outside the recommended 

range of the model and the modeled deposition estimates are characterized as uncertain. 

IR-4 then used this application rate (7.08x10-4 lbs a.i./A) in TREX to model multiple applications. 

Per their submission (pg. 19), the IR-4 proposed the following: 

Four applications, at the maximum label rate, per 30‐day period (i.e. 4 applications + a 

26‐day rest period), would be unlikely to exceed 1.5 ppm peak residue using reasonably 

conservative assumptions. Restricting the label to 3 applications per week (i.e. no more 

than 3 applications at any site in any 7 day period, and no more than 4 applications at 

any site in any 30 day period) would provide a greater safety margin. 

EFED evaluated the proposed multiple application scenarios using TREX and confirmed the 

calculation of estimated residues predicted by IR-4. For the proposed four applications scenario, 

the maximum residue level (short grass) from TREX was 1.46 ppm. For the proposed three 

applications scenario, the maximum residue level (short grass) from TREX was 1.32 ppm. 

For comparison purposes, EFED also evaluated the residues for deposition rates of 33% (worst 

case wind speed of 1 mph) and 20% (wind speed of 2 mph). The application rates increased from 

7.08x10-4 lbs/A to 2.31x10-3 and 1.4x10-3 lbs/A for deposition rates of 33 and 20%, respectively. 

For the proposed four applications scenario, the maximum residue levels (short grass) from 

TREX increased to 4.77 and 2.89 ppm for deposition rates of 33 and 20%, respectively. For the 

proposed three applications scenario, the maximum residue levels (short grass) from TREX 

increase to 4.32 and 2.62 ppm for deposition rates of 33 and 20%, respectively. In both cases, the 

increases were proportional to the increases in application efficiency. 

Ground ULV Application 

IR-4 has suggested that the surface deposition of pesticide residues following ground ULV 

application will be similar to that resulting from aerial ULV application. IR-4 has also suggested 

that to reduce the risk of exceeding proposed tolerances, label requirements of a minimum wind 

speed of 2 mph during application, and a 25 foot buffer zone between the spray equipment and 

the agricultural commodities for ground-based ULV application of etofenprox may be warranted. 

To support these arguments, IR-4 submitted the following: a literature review on deposition from 

ground ULV applications; a review of aerial deposition using the AGDISP spray drift model; a 

summary of model results for ground ULV deposition from a recent dissertation (Schleier, 2012); 

and, worst-case deposition estimates based on physics-based modeling. A discussion of each of 

these supporting arguments is provided below. It should be noted that while EFED evaluated the 
5 

deposition of ground ULV applications at wind speeds of 2 mph, it may not be feasible to 

implement this as a label condition. 

According to communications with IR-4 (email from Dr. Karl Malamud-Roam, Public Health 

Pesticides Program Manager, IR-4 Project Headquarters, 2/8/2013), ground-based ULV 

applications typically occur in neighborhoods on the fringe of agricultural areas, with potential 

drift occurring onto agricultural areas. Mosquito control districts treating neighborhoods 

typically drive up each street, then turn and make a pass on the next street (i.e., one pass per 

block-wide swath). Drift from more distant passes is possible into agricultural areas, but is 

assumed to be attenuated by the buffering distance of the block (typically assumed to be 300 feet) 

and by the houses, trees, and other obstacles typical of urban/suburban areas. While ground ULV 

applications can occur in more rural areas (e.g., larger fields devoid of obstacles hindering drift) 

as well as suburban areas with smaller blocks (e.g., OPP’s Health Effects Division currently uses 

50 feet wide lawns for their residential spray drift assessments), as the purpose of ground ULV 

applications is to maintain the adulticide in the air, a 300-foot swath was considered a typical 

value for this assessment. 

Literature Review 

IR-4 submitted eight published studies on ground ULV application, in which pesticide deposition 

was measured. IR-4 concluded that, based on the results of these studies, ground ULV deposition 

values are similar to results that have been reported for aerial ULV applications. 

EFED has reviewed these studies (DP Barcode 407817, 03/11/2013) and has determined that up 

to 33% of the nominal application rate of an active ingredient may be deposited on surfaces. 

However, it should be noted that in three of the studies the deposition rate, as a percentage of the 

application rate, could not be determined, as an accurate application rate could not be ascertained 

from the study. The highest deposition rates, obtained in the Knepper et al. (1996) study, were 1-

2 orders of magnitude higher than those in the other studies. The study used grass clippings to 

evaluate deposition, unlike the other studies that typically employed flat cloth, paper, or metal 

dosimeters. As the grass has the ability to capture droplets in the horizontal and vertical 

directions, unlike flat coupons which collect deposition only in the horizontal direction, this may 

explain why the Knepper deposition results are higher. Additionally, wind speeds were low (1 

mph), increasing the likelihood of deposition rates higher than the other studies. An application 

rate could not be determined from the study, so it is unclear what percentage of the applied 

pesticide was deposited on the grass. A summary of the deposition values is provided in Table 2. 

An analysis of the available deposition percentages indicates that the 90 percent upper confidence 

limit on the mean value is 8.7% (average of 7.1%, n=94). 

Table 2. Peak deposition rates reported in ground ULV literature studies 

Reference / 

Number Material 

Peak 

deposition 

(ng/cm2

) 

Peak 

deposition (% 

applied)1

Distance from 

application source 

to peak deposition 

(m) 

Wind speed 

(mph) 

Tucker et al

1987 

Fenthion 2.92 2 8 Not reported 

Malathion 85.8 15 8 Not reported 

Naled 57.3 20 8 Not reported 

Moore et al

1993 Malathion 84.1 14 30.4 0.9 – 3.4 

Tietze et al

1994 Malathion 50 9 5 2.1 – 4.0 
6 

Reference / 

Number Material 

Peak 

deposition 

(ng/cm2

) 

Peak 

deposition (% 

applied)1

Distance from 

application source 

to peak deposition 

(m) 

Wind speed 

(mph) 

Knepper et al

1996 

Malathion 9,222 NA 7.6 1 

Permethrin 14,389 NA 7.6 1 

Tietze et al

1996 Malathion 473 NA Unknown 0 – 2.5 

Schleier and 

Peterson 2010 

Naled 74 33 50 1.5 

Permethrin 4.6 5.9 25 4.3 

Pierce et al

2005 Permethrin 5.1 10 Unknown 6 - 12 

Preftakes et al

2011 Permethrin 8 10 25-50 m 4.8 

1. NA – insufficient information to assess. 

AGDISP Modeling 

In an effort to depict the impact of meteorological conditions on deposition, IR-4 conducted a 

number of model runs using the AGDISP version 8.15. In prior work, IR-4 used the AgDISP 

model to predict potential aerial ULV deposition for use in establishing flight-lines for their 

magnitude-of-residue study. Using the results of this analysis (Figure 1), IR-4 concluded that the 

relationship between deposition and distance from the application source was strongly dependent 

on wind speed, with peak deposition decreasing dramatically as wind speed increases from 0.5 

mph to 1.0 mph, and a less dramatic decrease as wind speed increases from 1 to 2 mph. While 

the analysis was conducted for aerial ULV applications, and EFED does not use the AgDISP 

model for estimating deposition from ground applications, nevertheless IR-4 concluded that the 

impact in changing wind speeds would be similar for ground ULV applications. 

Figure 1. Deposition from Aerial ULV Applications, IR-4 AGDISP Modeling 
7 

Using the input parameters provided by IR-4 (Appendix A of the IR-4 submission, Appendix B

in this document), EFED ran AGDISP, but was not able to replicate the deposition pattern 

depicted in Figure 1. Results from EFED modeling using IR-4’s input parameters and AGDISP 

version 8.25 are depicted in Figures 2 (g/m2

 versus distance, similar to units depicted in Figure 

1) and 3 (percent applied versus distance). While the EFED modeled deposition rates are higher 

than those obtained by IR-4, the general trend that deposition in the application area (-500 to 0 ft) 

decreased with increased wind speed was observed. As wind speed increased, the amount that 

deposited from the point of application to the distance of the swath width (500 ft) also decreased, 

with a deposition rate of 46% at 0.5 mph to 9% at 1 mph to 0% at wind speeds greater than 3 

mph. It should be noted that the application efficiency for the 1 mph wind speed run (9%) is 

lower than the 33% modeled in the Aerial ULV Application section above. The Dv0.5 in these 

model runs was set to 28 microns, per IR-4 parameters, as opposed to the maximum aerial Dv0.5 of 

60 microns specified on the label, which was used in the Aerial ULV Application model runs. 

0.00E+00

1.00E‐04

2.00E‐04

3.00E‐04

4.00E‐04

5.00E‐04

6.00E‐04

‐500 ‐300 ‐100 100 300 500 700 900

Deposition (g/m2)

Distance from Downwind Edge of Swath (ft)

Figure 2. Deposition in Application Area and Beyond

0.5 mph 1.0 mph 2.0 mph 2.5 mph 3.0 mph
8 

ULV Spray Drift Modeling (Schleier 2012) 

In addition to the studies cited in the literature review described above for ground-based ULV 

applications, additional information was submitted to support the premise that ground ULV 

deposition rates can be conservatively estimated using aerial ULV deposition estimates of 10-

30% of the amount applied. IR-4 submitted a recent dissertation (Schleier, 2012) on ground ULV 

applications and a model developed based on the study results. A brief summary of Schleier 

2012 is provided in Appendix C. IR-4 used the model developed in the dissertation paper to 

estimate deposition of etofenprox following ground ULV applications in different wind speeds. 

The range of model deposition results for a typical 300 foot swath downwind of spray equipment 

was 8 to 18 ng/cm2

, or 10-23% deposition rate of an application of etofenprox at 0.007 lbs/A 

(0.007 lb/A = 78.5 ng/cm2

). This is similar to the rate estimated from the magnitude of residue 

study following an aerial application of etofenprox. 

Using the parameters specified in the IR-4 submission (Table 3 and Appendix C), EFED ran the 

Schleier model and was able to duplicate the deposition results estimated by IR-4 (Figure 4) for a 

Dv0.5 of 22 μm. Deposition rates ranged from 11 to 22% across the 300 foot (90 meter) swath, 

with an average deposition rate across the swath of 16% for all wind speeds. If the Dv0.5 was 

increased to 30 μm (the maximum Dv0.5 specified on the label) and all other input parameters 

were held constant, deposition rates would range from 16 to 33% across a 300 foot swath, with an 

average deposition rate of 24% for wind speeds ranging from 1 to 10 mph. For both 1 and 2 mph 

wind speeds, deposition rates ranged from 21 to 27%. It should be noted that, based on the data 

0%

10%

20%

30%

40%

50%

60%

70%

‐500 ‐300 ‐100 100 300 500 700 900

Deposition (%)

Distance from Downwind Edge of Swath (ft)

Figure 3. Deposition in Application Area and Beyond

0.5 mph 1.0 mph 2.0 mph 2.5 mph 3.0 mph
9 

in Schleier 2012, there did not appear to be a clear relationship between the count median 

diameter (CMD) and VMD, so the CMD was not changed. 

 

Table 3. Input Parameters Used in IR-4 Modeling 

Parameter Application 

Rate (g/ha) 

Flow 

Rate 

(ml/min) 

Density 

(g/ml) 

CMD 

(μm) 

VMD 

(μm) 

Temperature 

(oC) 

RH 

(%) Stability 

Value 7.846 192 0.891 1.36 22 22 50 2 (neutral) 

Physics-based Modeling 

As the current spray drift models (AGDISP and AgDRIFT) employed by EFED are not capable 

of estimating deposition from ground-based ULV applications, IR-4 used a simple Newtonian 

model to estimate downwind travel distance for the ground ULV applications. Using the 

following equation, based on Stoke’s Law, (USEPA 2010), the terminal velocity of a particle can 

be estimated, which in turn can be used to estimate travel time and downwind distance for the 

particle, assuming relatively stable atmospheric conditions 

0.00E+00

2.00E+00

4.00E+00

6.00E+00

8.00E+00

1.00E+01

1.20E+01

1.40E+01

1.60E+01

1.80E+01

2.00E+01

0 50 100 150 200

Deposition (ng/cm2)

Distance (m)

Figure 4. ULV Deposition, Shleier Model 2012

1 mph 2 mph 3 mph 4 mph 5 mph

6 mph 7 mph 8 mph 9 mph 10 mph
10 

௦௣݀ ݔ௣ߩ ݔ ݃ ൌ ௧ݒ௖ܥ ݔ ଶ

ߤ ݔ 18

 Where 

 vt = terminal settling velocity (cm/s) 

 g = acceleration due to gravity (980 cm/s2

) 

ρp = density of particle (0.891 g/cm3

) 

 dps = Stokes particle diameter (cm) 

 Cc = Cunningham slip correction factor (unitless, 1) 

 μ = viscosity of air (1.82x10-4 g/cm-s) 

For a 1 meter release height, IR-4 estimated the downwind travel distance for a number of 

particle sizes that encompass the size of particles in ground ULV sprays (Table 4). EFED verified 

these calculations, and concurs that this would be representative of worst case settling conditions, 

as more unstable conditions would cause the adulticide aerosol to dilute and ascend out of the 

target area (Bonds, 2012). According to Bonds, 2012, “neutral to weakly stable conditions are 

considered ideal for ULV spraying”. As such, EFED would expect these estimations, modeled 

during steady state wind flow, to be similar to those estimates derived in the literature studies, 

which were primarily conducted at dusk, when neutral to stable conditions are expected to exist 

(Bonds, 2012). 

The cumulative drop size distribution (DSD) column reflects the percentage of droplets below the 

specified drop diameter, assuming a DSD where the Dv0.5 was 30 microns and the relative span 

(e.g., the breadth of the drop size distribution, or [Dv0.9-Dv0.1]/Dv0.5) was 1.14. These 

specifications closely match the specifications on the Zenivex E20 label, where the Dv0.5 must be 

less than or equal to 30 microns and 90% of the particles must be less than 50 microns in 

diameter. The deposition rate column is 100% minus the cumulative DSD. Based on the 

deposition rates, EFED estimated the percentage of droplets settling within 300 feet (or the swath 

width) of the application source using the above equation. 

Table 4. Newtonian Modeling Results of Ground ULV Deposition, Release Height 1 

Meter

Drop 

Diameter 

(μm) 

Diameter 

(cm) 

Velocity 

(cm/s) 

Time 

(s) 

Distance (ft) Cumulative 

DSD % 

Deposition 

Rate 

(%) 

Wind speed (mph) 

1 2 3 5 10 

8 0.0008 0.171 586.22 859.8 1719.6 2579.4 4299.0 8598.1 1.6 98.4 

10 0.001 0.267 375.18 550.3 1100.6 1650.8 2751.4 5502.8 2.9 97.1 

15 0.0015 0.600 166.75 244.6 489.1 733.7 1222.8 2445.7 9.7 90.3 

20 0.002 1.066 93.80 137.6 275.1 412.7 687.8 1375.7 20.8 79.2 

25 0.0025 1.666 60.03 88.0 176.1 264.1 440.2 880.4 34.9 65.1 

30 0.003 2.399 41.69 61.1 122.3 183.4 305.7 611.4 50.0 50.0 

40 0.004 4.265 23.45 34.4 68.8 103.2 172.0 343.9 75.5 24.5 

50 0.005 6.663 15.01 22.0 44.0 66.0 110.1 220.1 90.2 9.8 

60 0.006 9.595 10.42 15.3 30.6 45.9 76.4 152.9 96.8 3.2 

70 0.007 13.060 7.66 11.2 22.5 33.7 56.2 112.3 99.1 0.9 

80 0.008 17.058 5.86 8.6 17.2 25.8 43.0 86.0 99.8 0.2 
11 

% DSD Settling within 200 ft of application 86 69 53 30 8 

% DSD Settling within 300 ft of application 92 81 69 49 19 

Assuming a wind speed of 2 mph, a Dv0.5 of 22 microns (approximate midpoint of Dv0.5

requirements for etofenprox), and a release height of 1 meter, IR-4 estimated that 10% of the 

etofenprox deposits in the first 44 feet (the red value in Table 4) and 50% in the first 200 feet (the 

approximate midpoint of the two blue values in Table 4). The Zenivex E20 label requires the 

Dv.09 (or 10% of the drops) to be less than or equal to 50 microns for ground spray. Using Table 

4, the distance at the intersection of 50 microns and a wind speed of 2 mph is 44 feet. Likewise, 

if the Dv50 (or 50% of the drops) equals 22 microns, the distance for a wind speed of 2 mph lies 

approximately midway between 176 and 275 feet, or around 200 feet. 

Assuming a wind speed of 2 mph, a Dv0.5 of 30 microns, and a release height of 1 meter, EFED 

confirmed that approximately 10% of the etofenprox residue deposits in the first 44 feet (the red 

value in Table 4), but that 69% deposits in the first 200 feet and 81% in the first 300 feet (the 

green values in Table 4). The 69% is estimated by interpolating between the deposition rate for 

176.1 feet (65.1%) and the deposition rate for 275.1 feet (79.2%) to determine the deposition 

estimate at 200 feet. Likewise, the 81% is estimated by interpolating between deposition rate for 

275.1 feet (79.2%) and the deposition rate for 489.1 feet (90.3%) to determine the deposition 

estimate at 300 feet. 

For comparison purposes, a release height of 10 feet (3.05 m), the minimum height of the adult 

mosquito habitat cited by IR-4 (page 23 of submission), was also modeled (Table 5). Assuming 

a wind speed of 2 mph and Dv0.5 of 30 microns, EFED estimated that that 23% of the etofenprox 

deposits in the first 200 feet and 39% in the first 300 feet (the green values reported in Table 5), 

which is slightly higher than the 33% reported in the literature studies. Values were estimated as 

discussed above. 

It should be noted that the percentages developed above are deposition rates for the entire 

distance specified and do not reflect the deposition at any particular point. For instance, the 39% 

reported in Table 5 is the deposition over the entire 300 foot width, and not the deposition 

specifically at the 300 foot distance, which would be expected to be smaller. 

Table 5. Newtonian Modeling Results of Ground ULV Deposition, Release Height 

3.05 Meter (10 feet)

Drop 

Diameter 

(μm) 

Diameter 

(cm) 

Velocity 

(cm/s) 

Time 

(s) 

Distance (ft) 

Cumulative 

DSD % 

Deposition 

Rate 

(%) 

Wind speed (mph) 

1 2 3 5 10 

8 0.0008 0.171 1787 2620.7 5241.4 7862.1 13103.5 26206.9 1.6 98.4 

10 0.001 0.267 1144 1677.2 3354.5 5031.7 8386.2 16772.4 2.9 97.1 

15 0.0015 0.600 508.2 745.4 1490.9 2236.3 3727.2 7454.4 9.7 90.3 

20 0.002 1.066 285.9 419.3 838.6 1257.9 2096.6 4193.1 20.8 79.2 

25 0.0025 1.666 183.0 268.4 536.7 805.1 1341.8 2683.6 34.9 65.1 

30 0.003 2.399 127.1 186.4 372.7 559.1 931.8 1863.6 50.0 50.0 

40 0.004 4.265 71.47 104.8 209.7 314.5 524.1 1048.3 75.5 24.5 

50 0.005 6.663 45.74 67.1 134.2 201.3 335.4 670.9 90.2 9.8 

60 0.006 9.595 31.77 46.6 93.2 139.8 233.0 465.9 96.8 3.2 
12 

70 0.007 13.060 23.34 34.2 68.5 102.7 171.1 342.3 99.1 0.9 

80 0.008 17.058 17.87 26.2 52.4 78.6 131.0 262.1 99.8 0.2 

% DSD Settling within 200 ft of application 53 23 10 2 0 

% DSD Settling within 300 ft of application 68 39 23 8 1 

Discussion and Conclusions 

IR-4 has requested a label amendment for Zenivex E20 and Zenivex E4 RTU (Reg. No. 2724-

807) to allow for ultra-low volume (ULV) spray applications over agricultural crops (including 

those intended for human consumption), pasture and rangeland. Zenivex E20 and Zenivex E4 

RTU can be applied via aerial or ground ULV application at a rate of 0.007 lbs a.i./A, 25 times 

per site per year, for a maximum annual application rate of 0.18 lbs a.i./A/year. These products 

do not have tolerances, however, nor are they currently allowed for use over general cropland 

areas. The purpose of this action is to evaluate the methodology and data submitted by IR-4 to 

support such a use pattern. IR-4 has submitted a residue study for aerial ULV applications over 

pasture grass, leaf lettuce, alfalfa, and snap beans in California and Florida. The maximum 

residue levels corresponded to approximately 10% of the amount of pesticide applied. Aerial 

ULV deposition data from the residue study and AGDISP modeling suggests that deposition 

values will typically be in the range from 10 to 33% of the amount of pesticide applied for wind 

speeds between 1 and 3 mph. IR-4 has posited that pesticide deposition resulting from ground 

ULV applications will be similar to that resulting from aerial ULV applications, but has also 

proposed that, to reduce the risk of exceeding proposed tolerances, for ground-based ULV 

applications a minimum wind speed of 2 mph and a 25 foot buffer zone between the spray 

equipment and the agricultural commodities may be warranted. EFED has evaluated the 

supporting documentation (e.g., literature studies, AGDISP modeling, dissertation modeling, and 

physics-based modeling) and agrees that they support the contention that ground ULV deposition 

rates at wind speeds greater than 2 mph are comparable to those associated with aerial ULV 

application (e.g., deposition ≤ 33% of the amount applied). However, not all of the deposition 

rates could be estimated for the submitted literature studies (e.g., Knepper et al., 1996), so it is 

possible that the maximum deposition rate could be higher than 33%. In cases where the 

application height of etofenprox is lower than 10 feet (the minimum mosquito habitat), there is 

also the potential for more material to deposit (50-70%, 200 feet from the application source, 

based on simple Newtonian modeling at a 1 meter high release height). 

Overall Conclusions 

Based on the current label specifications, EFED concludes that 33% (based on AGDISP 

modeling) is a conservative estimation for deposition resulting from aerial ULV applications and 

that 33% (maximum value reported in the submitted literature studies) is a conservative 

estimation for deposition resulting from ground ULV applications. The maximum value from the 

ground ULV literature was consistent with the modeling results also presented in the submission. 

The conservative value helps account for some of the uncertainty associated with deposition 

values that could not be estimated from data provided in some of the studies. These values 

assume a minimum wind speed of 1 mph. If the wind speed was increased to 2 mph, the 

deposition rates would drop to 20% (based on AGDISP modeling) for aerial ILV applications and 

24% for ground ULV applications (based on Schleier model). Residue estimates based on these 

deposition rates were determined using the TREX model and are presented in Table 1 of this 

report. 
13 

References 

MRID 48612201-01. Dorschner, K. 2011. Etofenprox: Magnitude of residue on alfalfa, bean 

foliage, pasture grass, and leaf lettuce. IR-4 Project Headquarters, Princeton, NJ. 

Bonds, J.A.S. 2012. Ultra-low volume space sprays in mosquito control: a critical review. 

Medical and Veterinary Entomology 26:121-130 

(http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.2011.00992.x/pdf)

Knepper, R.G., Walker, E.D., et al. 1996. Deposition of malathion and permethrin on sod grass 

after single, ultra-low volume applications in suburban neighborhood in Michigan. J Am Mosq 

Control Assoc 12:45-51 

Moore, J.C., Dukes, J.C., Clark, J.R., Malone, J., Hallmon, C.F., Hester, P.G. 1993. Downwind 

drift and deposition of malathion on human targets from ground ultralow volume mosquito 

sprays. J Am Mosq Control Assoc 9:138-142 

Pierce, M.C., R.H., Henry, M.S., Blum, T.C., Mueller, E.M. 2005. Aerial and tidal transport of 

mosquito control pesticides into the Florida Keys National Marine Sanctuary. Revista de 

Biologia Tropical. 53:117-125 

Preftakes, C.J., Schleier, J.J. III, Peterson, R.K.D. 2011. Bystander exposure to ultra-low volume 

insecticide applications used for adult mosquito management. International Journal of 

Environmental Research and Public Health, 8:2142-2152

Schleier, J. III and Peterson, R. 2010. Deposition and air concentrations of permethrin and naled 

used for adult mosquito management. Archives of Environmental Contamination and Toxicology. 

58(1):105-111 

Schleier, J. III. 2012. Development of an environmental fate model for risk assessment of ultralow volume insecticides. Dissertation submitted in partial fulfillment of the requirements for the 

degree of Doctoral of Philosophy in Ecology and Environmental Sciences, Montana State 

University. April 2012 

Tietze, N.S., Hester, P.G., and Shaffer, K.R.. 1994. Mass recovery of malathion in simulated open 

field mosquito adulticide tests. Archives of Environmental Contamination and Toxicology 

26:473-477 

Tietze, N.S., Hester, P.G., Shaffer, K.R., and Wakefield, F.T. 1996. Peridomestic deposition of 

ultra-low volume malathion applied as a mosquito adulticide. Bulletin of Environmental 

Contamination and Toxicology. 56:210-218 

Tucker, J., Thompson, C., Wang, T., and Lenahan, R. 1987. Toxicity of organophosphorus 

insecticides to estuarine copepods and young fish after field applications. J Florida AntiMosquito Association 58:1-6 

USEPA. 2010. Basic Concepts in Environmental Sciences, Module 3: Characteristics of Particles 

- Collection Mechanisms (http://www.epa.gov/apti/bces/module3/collect/collect.htm). USEPA’s 

Office of Air and Radiation, Air Quality Planning and Standards, Air Pollution Training Institute. 

Updated January 29, 2010. 
14 

Appendix A. EPA Input Parameters used in AGDISP Modeling 

AGDISP Input Data Summary 

Title: Etofenprox aerial copter ULV 1 mph 

Notes: 

Calculations Done: Yes 

Run ID: AGDISP etofenprox aerial copter ulv 1 mph.ag 8.25 01-29-2013 14:29:40 

--APPLICATION METHOD-- ---------------------------- 

Method Aerial 

--Aircraft-- ---------------------------- 

Name Aerodyne Wasp 

Type Library 

Wing Type Helicopter 

Rotor Radius (ft) 17.4 

Weight (lbs) 2090 

Typical Speed (mph) 61.99 

Rotor RPM 320 

--Spray Lines-- ---------------------------- 

Release Height (ft) 100 

Spray Lines 1 

Optimize Spray Reps No 

Spray Line Reps # Reps 

 1 1 

--APPLICATION TECHNIQUE-- ---------------------------- 

Application Technique Liquid 

--Nozzles-- ---------------------------- 

Boom Length (%) 0 

Nozzle Locations # Hor(ft) Ver(ft) Fwd(ft) 

 1 0 0 0 

--Drop Size Distribution-- ---------------------------- 

Name ULV 

Type User-defined 

Drop Categories # Diam (um) Frac 

 1 5.09 0.0010 

 2 10.22 0.0036 

 3 15.38 0.0092 

 4 20.58 0.0183 

 5 25.81 0.0303 

 6 31.08 0.0435 

 7 36.38 0.0563 

 8 41.72 0.0673 

 9 47.10 0.0759 

 10 52.51 0.0815 

 11 57.96 0.0830 

 12 63.45 0.0803 

 13 68.98 0.0763 

 14 74.54 0.0692 

 15 80.14 0.0608 

 16 85.78 0.0521 

 17 91.46 0.0436 

 18 97.18 0.0357 

 19 102.94 0.0286 

 20 108.73 0.0224 

 21 114.57 0.0171 

 22 120.45 0.0128 

 23 126.36 0.0094 

 24 132.32 0.0067 

 25 138.32 0.0048 
15 

 26 144.36 0.0033 

 27 150.44 0.0023 

 28 156.56 0.0016 

 29 162.73 0.0011 

 30 168.93 0.0007 

 31 175.18 0.0005 

--SWATH-- ---------------------------- 

Swath Width 500 ft 

Swath Displacement 0 ft 

--METEOROLOGY-- ---------------------------- 

Wind Speed (mph) 1 

Wind Direction (deg) -90 

Temperature (deg F) 65 

Relative Humidity (%) 50 

--SPRAY MATERIAL-- ---------------------------- 

Name Etofenprox 

Spray Material Evaporates No 

Spray Volume Rate (gal/ac) 0.005 

Active Fraction 0.2 

Nonvolatile Fraction 0.99 

Active Fraction of Tank Mix 0.2 

Fraction of Active Solution that is Nonvolatile 1 

Additive Fraction of Tank Mix 0.79 

Fraction of Additive Solution that is Nonvolatile 1 

--ATMOSPHERIC STABILITY-- ---------------------------- 

Atmospheric Stability Overcast 

--SURFACE-- ---------------------------- 

Upslope Angle (deg) 0 

Sideslope Angle (deg) 0 

--Canopy-- ---------------------------- 

Type None 

Surface Roughness (ft) 0.0246 

--TRANSPORT-- ---------------------------- 

Flux Plane Distance (ft) 0 

--ADVANCED SETTINGS-- ---------------------------- 

Wind Speed Height (ft) 6.56 

Max Compute Time (sec) 600 

Max Downwind Dist (ft) 2608.24 

Vortex Decay Rate (OGE) (mph) 0.3355 

Vortex Decay Rate (IGE) (mph) 1.25 

Aircraft Drag Coeff 0.1 

Propeller Efficiency 0.8 

Ambient Pressure (in hg) 29.91 

Ground Reference (ft) 0 

Save Trajectory Files No 

Half Boom No 

Default Swath Offset 0 Swath 

Specific Gravity (Carrier) 0.891 

Specific Gravity (Active/Additive) 0.891 

Evaporation Rate (μm2/deg C/sec) 84.76 

 
16 

AGDISP Input Data Summary 

Title: Etofenprox Aerial 1 mph 

Notes: 

Calculations Done: Yes 

Run ID: AGDISP aerial ulv 1 mph.ag 8.25 01-30-2013 13:07:51 

--APPLICATION METHOD-- ---------------------------- 

Method Aerial 

--Aircraft-- ---------------------------- 

Name Hiller FH-1100 

Type Library 

Wing Type Helicopter 

Rotor Radius (ft) 17.7 

Weight (lbs) 2073 

Typical Speed (mph) 68.99 

Rotor RPM 394 

--Spray Lines-- ---------------------------- 

Release Height (ft) 50 

Spray Lines 1 

Optimize Spray Reps No 

Spray Line Reps # Reps 

 1 1 

--APPLICATION TECHNIQUE-- ---------------------------- 

Application Technique Liquid 

--Nozzles-- ---------------------------- 

Boom Length (%) 50 

Nozzle Locations # Hor(ft) Ver(ft) Fwd(ft) 

 1 -8.85 0 0 

--Drop Size Distribution-- ---------------------------- 

Name ULV 

Type User-defined 

Drop Categories # Diam (um) Frac 

 1 2.49 0.0010 

 2 4.99 0.0038 

 3 7.49 0.0099 

 4 10.01 0.0199 

 5 12.54 0.0328 

 6 15.07 0.0468 

 7 17.61 0.0600 

 8 20.17 0.0711 

 9 22.73 0.0792 

 10 25.30 0.0839 

 11 27.88 0.0839 

 12 30.48 0.0805 

 13 33.08 0.0752 

 14 35.69 0.0673 

 15 38.30 0.0584 

 16 40.93 0.0495 

 17 43.57 0.0410 

 18 46.22 0.0333 

 19 48.88 0.0264 

 20 51.55 0.0205 

 21 54.22 0.0156 

 22 56.91 0.0116 

 23 59.61 0.0085 

 24 62.31 0.0061 

 25 65.03 0.0043 

 26 67.76 0.0030 

 27 70.49 0.0021 
17 

 28 73.24 0.0014 

 29 76.00 0.0010 

 30 78.76 0.0007 

 31 81.54 0.0005 

 32 84.32 0.0010 

--SWATH-- ---------------------------- 

Swath Width 500 ft 

Swath Displacement 0 ft 

--METEOROLOGY-- ---------------------------- 

Wind Speed (mph) 1 

Wind Direction (deg) -90 

Temperature (deg F) 77.9 

Relative Humidity (%) 55.44 

--SPRAY MATERIAL-- ---------------------------- 

Name Etofenprox 

Spray Material Evaporates No 

Spray Volume Rate (gal/ac) 0.005 

Active Fraction 0.2 

Nonvolatile Fraction 1 

Active Fraction of Tank Mix 0.2 

Fraction of Active Solution that is Nonvolatile 1 

Additive Fraction of Tank Mix 0.8 

Fraction of Additive Solution that is Nonvolatile 1 

--ATMOSPHERIC STABILITY-- ---------------------------- 

Atmospheric Stability Slight 

--SURFACE-- ---------------------------- 

Upslope Angle (deg) 0 

Sideslope Angle (deg) 0 

--Canopy-- ---------------------------- 

Type None 

Surface Roughness (ft) 0.0246 

--TRANSPORT-- ---------------------------- 

Flux Plane Distance (ft) 0 

--ADVANCED SETTINGS-- ---------------------------- 

Wind Speed Height (ft) 6.56 

Max Compute Time (sec) 600 

Max Downwind Dist (ft) 2608.24 

Vortex Decay Rate (OGE) (mph) 0.3355 

Vortex Decay Rate (IGE) (mph) 1.25 

Aircraft Drag Coeff 0.1 

Propeller Efficiency 0.8 

Ambient Pressure (in hg) 29.91 

Ground Reference (ft) 0 

Save Trajectory Files No 

Half Boom No 

Default Swath Offset 0 Swath 

Specific Gravity (Carrier) 0.8 

Specific Gravity (Active/Additive) 0.8 

Evaporation Rate (μm2/deg C/sec) 84.76 

 
18 

Appendix B. AGDISP Input Parameters for IR-4 Modeling 

 
19 
20 

Appendix C. Summary of Schleier, J. 2012. Development of an Environmental Fate Model 

for Risk Assessment of Ultra-low Volume Insecticides. Dissertation, Montana State 

University. April 2012 

The objectives of the dissertation were to perform field studies to measure environmental 

concentrations of insecticides applied using ground ultra-low volume spray in order to develop a 

validated model to predict the deposition of ULV insecticides, and use the data generated from 

the field study to perform refined human and aquatic ecological risk assessments. A regression 

model selected by a Bayesian Information Criterion and k-fold cross validation was used to 

validate the selected model. 

Deposition experiments were conducted near Elk Grove, California, Bozeman, Montana, and 

Baton Rouge, Louisiana during the summers of 2009 to 2011. Sites with little vegetative 

structure and flat topography were chosen for all experiments, to minimize vegetation affects on 

air movement and subsequent deposition. Sites were 200-m long with two lines of horizontal 

drift collectors positioned 25 m to the left and right of the center of the plot to capture variability 

of deposition within the spray plot (Figure C-1). Samples were averaged together at each 

distance from the spray source for statistical analysis. Sampling occurred at distances of 5, 10, 

15, 20, 30, 35, 40, 50, 60, 65, 70, 75, 80, 90, 95, 100, 110, 120, 125, 130, 135, 140, 155, 160, and 

180 m from the spray source. 

During all applications, the truck speed was 16.1 km/h (10 mph). Applications occurred when the 

prevailing wind was blowing perpendicular to the collection site (Figure C-1). Sprays were 

conducted using a Guardian 95 ES (ADAPCO, Sanford, FL, USA) in Montana and a London 

Fogger model 18 (London Fog Inc., Long Lake, MN, USA) in California and Louisiana. Nozzle 

orientation of the sprayers was +45° angle compared to the horizon which is the most commonly 

used angle for mosquito management. Between each spray replication the nozzle, pump, and 

hoses were rinsed with 300 ml of D.I. H2O followed by 300 ml of a 1:1 mixture of high pressure 

liquid chromatography acetone (99.7% purity; EMD Chemicals, Gibbstown, NJ, USA) and 

American Chemical Society (ACS) grade toluene (99.5% purity, Mallinckrodt Baker, Inc., 

Phillipsburg, NJ, USA) (Schleier III et al. 2010). 
21 

Figure C-1. Plot Layout for Schleier 2012 Study 

The oil-based insecticides Permanone® 30-30 (30% permethrin), Scourge® 18+54 (18% 

resmethrin), Permanone® 31-66 (31% permethrin) (Bayer Environmental Science, Research 

Triangle Park, NC, USA), Zenivex® E20 (20% etofenprox) (Central Life Sciences®, 

Schaumburg, IL, USA), and PyronylTM Crop Spray (6% pyrethrins) (Prentiss Inc., Alpharetta, 

GA, USA) were used. The water-based formulations Aqua-Reslin® (20% permethrin) (Bayer 

Environmental Science, Research Triangle Park, NC, USA) and Aqua-Kontrol (20% permethrin) 

(Univar®, Redmond, WA, USA) were used. The active ingredients were applied at the 

maximum rate of 7.85 g/ha of active ingredient according to label for all insecticides, except for 

Pyronyl Crop Spray which was applied at the maximum rate of 2.8 g/ha of active ingredient. 

The experimental design was a complete randomized design with each formulation randomly 

selected for the order when it was sprayed. Replications were performed over time within the 

same night and over different nights with a total of 96 spray events occurring during the three 

field seasons. Applications began no earlier than 18:00 h at all locations, with most applications 

occurring after 20:00 h. Glass Petri dishes (15-cm diameter) were used to collect deposition at 

ground level. Cardboard was staked to the ground to provide a level surface for the glass Petri 

dishes. One glass Petri dish was placed on each piece of cardboard at ground level and collected 

10 minutes after the application. Fluorescent tracers were used to determine the concentrations of 

insecticide. The oil-soluble tracer Tinopal OB (BASF Corp., Florham Park, NJ, USA) was mixed 

with all oil-based formulations at a rate of 11 g/L and the water-soluble tracer Fluorescein (Aqua 

Solutions, Deer Park, TX, USA) was mixed with all water-based formulations at a rate of 14 g/L. 

For all applications, a maximum of 1-L of formulation was mixed with the tracer in a Nalgene 1-

L narrow mouth high density polyethylene bottle (Fischer Scientific, Pittsburgh, PA, USA) to 

ensure that the tracer was adequately mixed into the formulation. 
22 

Petri dishes were extracted with 15 ml of toluene or D.I. H2O for Tinopal OB and Fluorescence, 

respectively. The liquid was decanted into analysis vials which were wiped with KimWipes 

(Kimberly-Clark® Global Sales, LLC, Roswell, GA, USA) to remove fingerprints and dry the 

vials before analysis. After extraction, Petri dishes were rinsed with toluene or D.I. H2O, 

depending on the tracer used, then rinsed with high pressure liquid chromatography acetone. 

A GFL-1A fluorometer (Opti-Sciences, Inc., Hudson, NH, USA) was used to detect the amount 

of light absorbed at a specific wavelength which represented the amount of tracer present in the 

sample. For the detection of Fluorescence, the source filter was 465 nm and the detection filter 

was 530 nm. For the detection of Tinopal OB, the source filter was 370 nm and the detection 

filter was 430 nm. Standard curves were prepared using serial dilutions prepared in toluene and 

D.I. H2O for Tinopal OB and fluorescence, respectively. Absorbance was recorded for each 

sample representing the concentration of the insecticide. The detection limits for Tinopal OB and 

Fluorescence were 0.00012 and 0.000015 μg/cm2

, respectively. The detection limits for waterand oil-based insecticides were 0.00076 and 0.0002 μg/cm2

, respectively. 

A DC-III portable droplet measurement system (KLD Labs, Inc., Huntington Station, NY, USA) 

was used to measure droplet spectra of each formulation at all locations. The DC-III probe was 

held 2 m from the nozzle in the center of the spray plume and sampling was terminated at 15 

seconds or when 10,000 droplets were sampled. Two subsamples were taken for each spray 

formulation and combined. Distributions were fit using MATLAB® R2010a distribution fitting 

tool to determine the count median diameter (CMD; μm) and the volume median diameter 

(VMD; μm) using the Hatch-Choate conversion equations. 

Wind speed, air temperature, wet-bulb depression, and relative humidity were measured with 

sensors positioned 2.5 m above the ground. Temperature and relative humidity readings were 

also taken 10 m above the ground. Meteorological measurements were taken upwind of the spray 

site. Wind speed, wet bulb depression, temperature, and relative humidity at both 2.5 and 10 m 

above the ground were averaged over a 5 minute interval. 

Using 1,067 data points from three years of sampling, a linear regression model was developed 

relating the natural logarithm of deposition (C) to wind speed (WS), temperature (T), relative 

humidity (RH), stability (SC), distance from the spray source (D), application rate (AR), flow rate 

(FR), density (DEN), count median diameter (CMD), and volume median diameter (VMD), as 

well as a number of terms which were the products of the aforementioned terms. The regression 

is depicted below 

C = -3.71 + 0.008D - 1.15AR -0.005FR - 24.57DEN + 3.95CMD + 1.13VMD -0.014WS + 0.34T 

+ 0.15RH + 1.44SC - 0.007(D * CMD) - 0.00002(D * WS) + 18.95 (DEN * CMD) - 0.007(DEN 

* WS) - 1.66(DEN * SC) - 0.16(CMD * T) - 0.064(CMD * RH) - 0.32 (CMD * SC)- 0.78(CMD 

* VMD)- 0.004(VMD * T) + 0.034(VMD * SC) + 0.001(WS * T) + 0.0001(WS * RH) + 

0.0004(WS * SC) - 0.003(T * RH) 

Figure C-2 shows the estimated prediction line for Aqua-Reslin for an application rate of 7.85 

g/ha, a flow rate of 197 mL/min, a density of 0.996 g/mL, a CMD of 1.66 μm, a VMD of 20 μm, 

a wind speed of 316 cm/s, a temperature of 23oC, a relative humidity of 43%, and stability 

category of 2 (neutral). The selected model inputs were the average for all variables measured 

during experiments for Aqua-Reslin. Table C-1 depicts the parameters used in the Schleier 

model for etofenprox. 
23 

Figure C-2. Example Depiction of Schleier 2012 Model Prediction for Aqua-Reslin 

 
24 

Table C-1. Input Parameters for Schleier 2012 ULV Model for Etofenprox