1

APPENDIX A

Environmental Fate and Transport Data
2

(1) Laboratory degradation in soil systems

Aerobic soil systems

Degradation of sulfoxaflor was studied in 4 US and 4 EU soils. The results for the US 

soils are summarized in Figure 1 and those for EU soils in Figure 2.

Figure 1 Fate of sulfoxaflor in Aerobic Soil systems (average for 4 US soils) 

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

20%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 100 200 300

% of Applied (All others)

% of Applied (Parent & X117194-74

Time (days)

Aerobic Soil System (4 US soils)

X11579457

X11719474

X11519540

Sulfoxaflor

Others including CO2

Non-extractable residue
3

0%

2%

4%

6%

8%

10%

12%

14%

16%

18%

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 20 40 60 80 100 120

% of Applied (All others)

% of Applied (Parent & X117194-74

Time (days)

Aerobic Soil System (4 EU soils)

X11579457

X11719474

X11519540

Sulfoxaflor

Others including CO2

Figure 2 Fate of sulfoxaflor in Aerobic Soil systems (average for 4 EU soils) 

Under aerobic conditions and 25 °C, sulfoxaflor parent degraded rapidly to one major 

degradate (X-474) and was below the limit of detection (LOD= ) within 3 – 14 days after 

treatment (DAT). Calculated half-life values (t1⁄2) for the parent ranged from 0.3 to 0.6 

days (MRID 478655-78). Similar results, with more rapid degradation, were observed for 

sulfoxaflor parent in four EU soils (three from the UK and one from Germany; MRID 

478320-13). In these EU soils, residues of the parent compound dropped below the LOD 

within 1 - 4 DAT. Calculated half lives, for the parent, ranged from 0.1 to 0.3 days.

The overall degradation profiles in U.S. and European Union (EU) soil systems suggest 

that parent rapidly transforms into degradate X-474 which appears to transform into 

another two degradation products X-540 and X457, CO2 and bound residues. Parent 

chemical is expected to be non-persistent in the soil systems of the natural environment 

and important exposure, in these systems, is expected to be mainly associated with X-74; 

just after one to few days following parent application.

Effect of low temperature and sterility were also studied using one EU soil “the UK 

Aberford soil” by incubating the samples at 10 °C for the temperature effects and by 

sterilizing the test soil for the sterilization effects. Data suggest that low temperature/ 

sterility reduces the bio-transformation rate due to the reduction/elimination of biological 

activity. In addition sterility appears to inhibit transformation of the major degradate 

X474 into X457 and X540 (Table 1).

Table 1 Summary of observed effects of temperature and sterilization on the degradation 

rate/profile of sulfoxaflor

Non-extractable residues
4

Affected Parameters

Characteristics of the Aberford soil

Guideline Conditions (viable 

soil, incubation at 20 °C for 

123 days

Low Temperature Effects: 

(viable soil, incubation at 

10 °C for 120 days)

Soil Sterility Effects (Sterilized 

soil incubation at 20 °C for 120 

days)

Profile for parent concentration 

decrease

Reached “No detection” 

after 1 day

Reached “No detection” 

after 3 days

Decreased to 15% at study 

termination

Parent half-life 0.1 day 0.14 days 18

Profile for major degradate 

X117194-74

Reached a max. of 98% 

within only one day; then 

declined to 36% at at study 

termination

Reached a max. of 97% 

within only one day; then 

declined to 68% at at 

study termination

Reached a max. of 83% after 

90 days; then declined to 77% 

at study termination

X117194-74 half-life 85 184

Can not calculate (only two 

intervals) but appear to be 

Highly persistent

Profile for X115794-57 and 

X115795-40 degradates

Max. observed 9% and 12%,

respectively with no clear 

formation/decline profile

Max. observed 8% for 

both with no clear 

formation/decline profile Non detected

Evolved CO2 32% max at 123 days 6% max at 120 days <1% max at 120 days

Non-extractable Residues 15% 9% 6%

Anaerobic soil systems

Sulfoxaflor degradation was studied in one clay loam Texas soil (MRID 478322-79) under the 

following conditions:

• Aerobic incubation for 8 hours (which is equivalent to the half-life estimated under 

aerobic conditions); followed by

• Anaerobic (flooding/purging with nitrogen) conditions for 113 days

Examination of aerobicity data suggest that anaerobic conditions were met for the system 

as a whole although the soil was much more anaerobic compared to the water layer above. 

Data also show the following:

• The presence of O2 at detectable level at all intervals suggesting slightly aerobic 

conditions which appear to decrease with time (O2 decreased from 5 to 0.2 ppm)

• Water pe+ pH decreased from 8.58 to 5.89 indicating sub-oxic conditions 

(considered by EFED to be anaerobic), and 

• Soil pe+ pH decreased from 4.50 to 3.00 (Oxic conditions= anaerobic)

Similarly, sulfoxaflor degradation was studied in one EU soil “the UK Aberford soil”

under the following conditions:

• Aerobic incubation for 2 hours (which is equivalent to the half-life estimated under 

aerobic conditions). Followed by

• Anaerobic (flooding/purging with nitrogen) conditions for 120 days
5

Examination of aerobicity data suggest that anaerobic conditions were met for the system 

as a whole and that the soil reached true anaerobic conditions after 32 days. Data also 

show the following:

• The presence of O2 at detectable level at all intervals suggesting higher level of 

aerobicity as compared to conditions for Texas soil above. However aerobicity 

appears to decrease with time (O2 decreased from 8 to 2 ppm)

• Water pe+ pH decreased from 11.00 to 8.83 indicating sub-oxic conditions 

(considered by EFED to be anaerobic), and 

• Soil pe+ pH decreased from 9.71 to 7.19 indicating sub-oxic conditions 

(considered by EFED to be anaerobic) from time zero to 14 days, then decreased 

further to a range from 4.27 to 3.25 suggesting oxic or anaerobic conditions.

The results for the US and EU soils are summarized in Figure 3.

Figure 3 Sulfoxaflor degradation profile under aerobic followed by anaerobic conditions

In the US soil, more than half of sulfoxaflor transformed into its major degradate X-474 

during the aerobic incubation period. Samples were analyzed at 1 day (i.e., few hours 

after the start of the anaerobic phase) and results indicated that 32% of the parent 

remained in the soil along with 62% of its major degradate X-474. Therefore, data for 

bio-degradation under anaerobic conditions starts at 1 day (nearly the start of the 

anaerobic conditions) and ends at 120 days (study termination). During this anaerobic 

period, parent reached no detection at 20 DAT while the degradate X-474 continued to 

increase to a maximum of 95% at day 20 and then decrease to 75% by 113 days (study 

termination). No other degradates were identified and the un-extracted residue reached 

nearly 25% at study termination with a maximum of <1% CO2 evolved. Estimation of 

reliable half-lives for Sulfoxaflor in aerobic and anaerobic phases is difficult because of 

the rapid degradation within only one interval. However, data suggest that degradation 

rate in both aerobic and anaerobic phases are relatively fast with a noticeable decrease in 

the rate for the anaerobic phase. In contrast, formation and decline data were available to 

 Time (days)

Aberford Soil, UK

 Time (days)

Clay Loam Soil, TX
6

estimate half-lives for main degradate (X-474) in anaerobic conditions. In the same soil, 

estimated anaerobic soil half-life for X-474 were much shorter than that in aerobic 

conditions (t1⁄2= 320 days in anaerobic conditions compared >1000 days in aerobic 

conditions). However, it is noted that estimated short anaerobic half-life was a result of 

formation of relatively high bound residues (25% of the applied). 

In the EU soil, results indicated that, at the end of the aerobic phase, 29% of the parent 

remained in the soil along with 66% of its major degradate X-474. During the anaerobic 

phase of the study, residues of the parent compound dropped below the LOD by 1 DAT 

while the degradate X-474 increased to a maximum of 97-98% 4 to 7 DAT then 

decreased to 84% at study termination (120 DAT). No other degradates were identified 

and the un-extracted residue reached nearly 12% at study termination with a maximum of 

<1% CO2 evolved. Estimation of reliable half-lives for sulfoxaflor in the aerobic and 

anaerobic phases is difficult to differentiate because of the rapid degradation within only 

two intervals. However, data suggest that degradation rate in both aerobic and anaerobic 

phases are relatively fast with a noticeable decrease in the rate for the anaerobic phase. In 

contrast, formation and decline data were available to estimate the half-life of the main 

degradate X-474 under anaerobic conditions. Estimated anaerobic soil half-life for X-474 

was 532 days compared to a half-life of 85 days estimated for the same soil under aerobic 

conditions. 

Comparison of data from US and EU soils suggest similarity in reduction of parent 

degradation rate due to change from aerobic to anaerobic soil conditions. This observed 

reduction, in the rate, appeared to be more pronounced in US soil compared to EU soil 

possibly due to the more stable anaerobic conditions in the former. Estimated anaerobic 

half-life for the degradate X-474 in the US soil was much lower than the aerobic halflives. In contrast, the results for the EU soil suggest an opposite conclusion. Data do not 

suggest a clear conclusion for the effect of anaerobic soil conditions on the rate of 

degradation of the main degradate X-474. 

No an anaerobic soil study, in which the main degradate is used as a test substance, was 

executed although such as study could have helped in drawing conclusions on the 

anaerobic degradation profile for this major degradate. 

(2) Laboratory degradation in water/sediment systems

Aerobic water/sediment systems

The aerobic degradation of 14C radiolabel sulfoxaflor was studied in two pond watersediment systems from England, one from Derbyshire (system-1) and the other from 

Staffordshire (system-2) for 103 days (MRID 478320-14) in the dark at 20 °C.

Parent, in the total pond system, declined to an average of 39 to 56% and 13 to 31% in 

systems 1 and 2, respectively (total system t1⁄2= 88 days and 37 days in systems 1 and 2, 

respectively). The decline occurred between 76 and 103 DAT. Parent transformed mainly 
7

into the one major degradate, X-474, with maximums ranging from 25 to 71% in system1 and 47 to 66% in system-2 occurring at 61-103 DAT with no apparent decline (system 

t1⁄2 cannot be determined). Mineralization to CO2 and other degradates (maximums were 

low with a range: CO2: 6 to 1.5% and other degradates: <1 to 2.4%). At study termination 

(100 DAT), relatively high amounts of un-identified bound residues were observed only 

in system-2 (maximum of 26%) compared to lower amounts in system 1 (maximum of 

6%). The observed high amounts of of un-identified bound residues in system-2 may be 

related to insufficient extraction and/or degradation. Examination of the aerobicity data 

for both water/sediment systems, suggest that they were outside guideline recommended 

values (Eh of -80 to -190 mV in sediment layer and oxygen concentration from 7 to 10 

mg/L in water layer). Conditions were reducing to moderately reducing in the water layer 

and strongly reducing in the sediment. 

Anaerobic water/sediment systems

Anaerobic biotransformation of 14C radiolabel sulfoxaflor parent and major degradate 

X117194-74 was studied separately in two pond water sediment systems from the United 

States. The first “sand” system (system-3) was obtained from Virginia and the second 

“sandy clay loam” system (system-4) was obtained from Iowa. The duration of the 

studies were up to 100 days and were incubated in the dark at 25 °C. Samples were 

treated with 14C-sulfoxaflor at the rate of 0.019 mg a.i. /L and 14C-X-474 at the rate of 

0.015 mg/L. The sediment/water ratios used were approximately 1:3 (MRID 478322-77).

Data from parent study show that radioactivity partitioned between water and sediment 

with a steady increase in the un-identified bound residue (up to maximums ranging from 

12 to 37%, in systems 3 and 4, respectively). Only very limited amounts of CO2 evolved 

(maximums were <1% in systems 3 and 4). Parent, in the total pond systems, declined 

with a total system t1⁄2= 382 days and 103 days in systems 3 and 4, respectively. The 

reason for parent decline may not be related to the formation of the degradate X-474 

(max. 3% to 8%” in systems 3 and 4) but is related to the formation of the un-identified 

bound residue (maximum 12 and 37% in system-3 and 4, respectively). Un-identified 

bound residue may not be related to partitioning of the degradate X-474 as it has very low 

infinity to partition into the sediment (Koc = 25 L/Kg). Also the reduced tendency of 

parent to partition into the sediment is inferred from its low Koc (Koc = 30 L/Kg) and the 

observed higher concentration of parent in the water column compared to that in 

sediment layer. 

Degradate X-474 data show that the radioactivity partitioned between water and sediment 

and the steady increase in un-identified bound residue reaching relatively low levels 

compared to parent study (maximums of 2 to 5%, in systems 3 and 4, respectively). Only 

very limited amounts of CO2 evolved (maximums were <1% in systems 3 and 4). 

Degradate X-474, shows relatively high, though variable persistence (total system t1⁄2= 

1,090 days in system 4 and 5,270 days in system-3). Examination of data on actual study 

conditions suggests that the conditions met EFED criteria for anaerobic studies in the two 

systems as a whole. However, the extent of anaerobic conditions appears to vary widely 

between the two systems and within each system (water phase and sediment phase). 
8

Based on the observed parameters, anaerobic conditions were maintained much better in 

VA pond system (system-3) compared to IA pond system (system-4). In addition, 

anaerobic conditions appear to have been difficult to maintain in the overlying water 

column compared to the sediment for both systems. 

(3) Field Dissipation in Terrestrial Systems

Extensive data were collected from the terrestrial field dissipation (TFD) studies for 

sulfoxaflor (MRID 47832282). These data are summarized hereunder.

(1) Conceptual Design

The terrestrial field dissipation (TFD) study for sulfoxaflor was designed based on the 

results of laboratory studies. These studies showed that sulfoxaflor degraded rapidly in 

soil, forming a major degradation product (X-474), and two minor degradation products 

(X-540 and X-457). Adsorption/desorption studies indicated that both parent sulfoxaflor 

and major/minor degradate (X-474, X-540 and X-457) are expected to be mobile. 

Additionally, sulfoxaflor and it degradate X-474 are systemic and were found to be stable 

to hydrolysis at pH 5, 7, or 9. Therefore, the TFD study design included leaching and 

plant uptake modules. Due to the low vapor pressure and Henry’s law constant of 

sulfoxaflor, volatility in the field was not measured.

(2) Selection of sites

Five sites were selected for conducting bare and cropped-plots in California (CA), 

Florida (FL), North Dakota (ND), Ontario, Canada (ON), and Texas (TX). Sulfoxaflor 

soluble concentrate formulation (242 g active ingredient per litre of product or 22% w/w) 

was surface applied one to three times at nominal single rates ranging from 100g a.i./ha 

(equivalent to 0.089 lb a.i/A) to 200 g a.i./ha. 

Information about application and soils are as follows:

• The first application rates in spinach and bell peppers were higher than proposed 

label rate ;

• Label rates were not followed in the other crops (wheat the total rate was applied 

one time instead of two; soybeans received one application of 200 g a.i/ha instead 

of three at 100 g a.i/ha; and cotton received only one application at 100 g a.i/ha 

instead of three at 100 g a.i/ha each). It is noted that terrestrial field dissipation 

studies guideline calls for application of the pesticide as per the label.

• The top soil of the cropped plots show that soils chosen for conducting the studies 

represent a wide range of soil properties. Soil textural classes include two loamy 

sand soils from CA and FL; one loam to sandy loam soil from Ontario, Canada 

(ON), and two clay to clay loam soils from ND and TX. Top soil horizons were 

acidic in CA, FL and ON (pH range from 5.3 to 6.4) and near neutral in ND and 

TX (pH range from 6.9 to 7.9); and
9

• Characteristics of top soil for associated bare soil plots were the same for CA and 

TX soils, contains higher clay contents (by 7-10%) for FL and ON soils and 

contains lower clay content (by 10%) in ND soil.

(3) Study design and sampling

The study design consisted of two treated plots (one cropped and one bare soil) and an 

untreated control plot at each study location (located at least 30 m from the treated plot). 

Treated and rotational crops representative of the geographical location of each test site 

were planted on areas designated for cropped plots over the course of the study. The 

California and Florida test sites were equipped with soil-suction lysometers for the 

collection of soil-pore water samples. 

As required, supplemental irrigation (type not specified) was supplied to maintain at least 

110% of long term average rainfall. The monthly target moisture input was set at 400% 

of the local historical average monthly precipitation in California and 120% in other sites. 

Other normal agronomic practices were followed.

Soil core samples were collected, for all sites, immediately after the first application to a 

depth of 6”. Additionally, soil samples were collected from the soil profile to a depth of 

36 inches at various sampling dates up to and including the end of the study (18 months 

in California, 15 months at other sites). The soil samples were extracted with 90:10 

acetonitrile: 1.0 N hydrochloric acid (v: v) on a flat-bed shaker and extracts were 

concentrated prior to analysis. Soil pore-water samples were collected at depths of 3, 6, 

and 8 ft. in FL or 9 ft. in California at 1, 6, 13, 28 days and 2, 4, 6, 9, 12 and 15 months 

after the first treatment. Water samples were analyzed directly. Soil and water samples 

were analyzed for sulfoxaflor and its aerobic soil metabolite (X474, X540 and X457) 

using HPLC) with positive-ion electro-spray (ESI) tandem mass spectrometry 

(HPLC/MS/MS).

For at least one sampling event at each site, a set of transit stability samples were 

prepared to evaluate the stability of sulfoxaflor and its transformation products during 

shipment and storage. Soil samples were spiked at 1x and 100x the limit of quantification. 

Pore water samples were spiked at 1x and 40x the LOQ. Spiked samples were subjected 

to the same procedures as the field samples. Average recovery in transit stability soil 

samples ranged between 82 and 97% for sulfoxaflor, 94 and 125% for X4-4, 77 and 

101% for X457, and 81.0 and 111% for X540. Recovery in transit stability pore water 

samples was 88 and 88% for Sulfoxaflor, 95 and 88% for X117194-74, 85 and 84% for 

X5-0, and 99 and 93% for X457, in California and Florida, respectively.

Crop samples were collected at various crop growth stages during the first and second 

growing seasons and analyzed for sulfoxaflor, X-474 (i.e., the major soil metabolite)and 

X-061 (i.e., the plant metabolite) using a reverse-phase polymeric solid-phase extraction 

(SPE) cartridge on-line system using HPLC/MS/MS.

(4) Method of Analysis: Limits of Detection/Quantification LOD/ LOQ and Performance
10

Data show that the method of analysis LODs and LOQs are reasonable when compared to 

the lowest expected concentrations in soils, plants and pore water samples. The range of 

sulfoxaflor, that may go un-quantified in all media, is from <0.1 to 2.3%. The efficiency 

(or performance) of the analytical method was determined for:

• Soil, water, tank mix and saturation pads samples: Data suggest efficient 

performance over the concentration range of 0.001 to 0.2 ppm for spiked soils 

with a LOQ of 0.001 ppm and LOD of 0.0003 ppm; 0.05- 2 ng/mL for spiked 

pore-water and the tank mix samples with LOQ of 0.05 ng/mL and LOD of 

0.015 ng/mL; and 2.00 to 100 μg/pad for the saturation pads with a LOQ of 

2.00 μg/pad and LOD of 0.667 μg/pad; 

• Freshly spiked and field spiked soils with parent sulfoxaflor, X-474, X-457 and 

X-540 degradate: Data suggest that the method’s recoveries for freshly spiked 

soils had a wide range of concentrations suggesting possible problems in 

preparation /analysis in at least some of the samples. Mean recovered 

concentrations for the freshly spiked soils were within a very narrow range from 

100% for sulfoxaflor parent, X-474, and X-540 but wider ranges were obtained 

for X457 (85-105%: a wide range around 100%, mostly below 100%). Based on 

these data, it can be stated that the analytical method performed “well” for 

sulfoxaflor and its main degradate X-474, may “slightly over-estimate” or “underestimate” X457, and may give a “good” or “under-estimate” of X540.

• Field spiked reagents with parent sulfoxaflor, X-474, X-457 and X-540 

degradates: with three exceptions, these data indicate that both the average and 

the range of concentrations found in field spiked reagents were within a very 

narrow margin of 100% which indicate very limited effects on concentrations of 

parent and it’s degradates as a result of transport and storage. The exceptions 

include X-440 concentrations found in reagents transported/stored with ND and 

TX samples and concentrations of X-457 found in reagents transported/stored 

with TX samples. It appears that concentrations found for X-40 in reagents 

transported/stored with ND were probably a result of errors in reagent preparation. 

In general, data suggest stability of parent sulfoxaflor and its degradates X-474, 

X-440, and X-457 during transport and storage; and

• Freshly spiked and field spiked pore-water with parent sulfoxaflor and degradates 

X-474, X-457 and X-540: Data suggest that the method’s recoveries for freshly 

spiked pore-water had a wide range of concentrations suggesting possible 

problems in preparation/analysis in at least some of the samples. Mean recovered 

concentrations for the freshly spiked pore-water were within a narrow range from 

100% for sulfoxaflor parent, X-474, and X-540 but wider ranges were obtained 

for X-457 in CA samples (over 115%). Based on these data, it can be stated that 

the analytical method performed “well” for sulfoxaflor and its main degradates X474 and X-540 but may “slightly over-estimate” X-457 in CA samples. 
11

(5) Verification of application

Application was verified by analysis of the tank mix, soil deposition trays/saturated pads, 

and time-zero data. The following is a summary of the results:

 Tank-mix data: The nominal application rates were verified by analyzing tank 

mix samples. A summary of the data is included in Figure 4.

Figure 4 Tank-mix data for the purpose of verification of application rates

Data in Figure 4 suggest that concentrations, found in most of the tank-mix spray 

materials, were within reasonable limits of the target nominal concentrations (overall 

average 92%, range of averages 83-104%, and range of individual samples 80-147% of 

nominal). It is noted however that three sulfoxaflor degradates (X-474, X-540 and X-457) 

were present as impurities in the formulation with an average total of 3% and range of 3 

to 4% of nominal. The suite of these degradates, in the tank mix, consisted mainly of X540 (overall average of 99% and range of 96-100% of the total degradates) with minor 

amounts of X-474 and X-457 (overall averages of 0.9% and 0.2% and ranges of 0.2-4% 

and 0.2-0.3% of the total degradates, respectively);

 Soil deposition trays/saturated pads: soil deposition trays were used to verify the 

application rates for all site including the Ontario cropped plots in which saturated 

pads were also used. The measured concentration of parent equivalents in the tank 

mix samples were between 86 and 108% of the nominal application rate. The 

average deposition tray recoveries (parent equivalents expressed as a percentage 

of nominal applied) ranged between 84 and 126% in California, 77 and 115% in 

0%

20%

40%

60%

80%

100%

120%

140%

160%

CA-1-Min

Max

CA-2-Min

Max

CA-3-Min

Max

FL-1-Min

Max

FL-2-Min

Max

FL-3-Min

Max

ND-Min

Max

ON-Min

Max

TX-Min

Max

Parent (78-147% )

X1175194-40 (2.4-4.1% )

X117194-74 (0.01-0.28% )

X115794-57 (0-0.01% )
12

Florida, 85 and 98% in North Dakota, 33 and 114% in Ontario, and 93 and 97% 

in Texas. The low recovery in the deposition tray samples observed for the 

Ontario cropped plot (33%) was associated with crop canopy interception 

(soybean) because the deposition trays at this site were placed on the ground 

below the soybean crop canopy. Saturation pads, placed over the soybean crop 

canopy during application, showed 75% recoveries; and

 Day-zero soil concentrations: For the first application, samples were taken from 

the top 6” of the soils at all sites just after the first application to determine dayzero concentrations (i.e., the actual rate applied). TFD guidance emphasizes that 

“day zero concentration lays the foundation for all subsequent sampling and is 

used to build confidence that the pesticide was applied uniformly and accurately”. 

Day-zero data suggest that “average” concentrations of the pesticide residues 

(including the impurity of degradation products) are within the reasonable limits 

of 10-20% of nominal (i.e., 80- 120% of nominal) of the expected at CA, FL, ND, 

and ON bare plots and at the FL cropped plot. In contrast, relatively high average 

found concentrations were observed at TX bare plot (154% of nominal) and CA 

and FL cropped plots (138 and 151% of nominal) with relatively low average 

concentrations observed at ON and ND cropped plots (16-75% of nominal). This 

indicates that the pesticide was accurately and uniformly applied at CA, FL, ND, 

and ON bare plots and at the FL cropped plot. However, hot spots (areas receiving 

more pesticide) appear to be present at TX bare plot and the CA and FL cropped 

plots and cold spots (areas receiving less pesticide) appear to be present at ON 

and ND cropped plots. No analysis can be performed for the multiple applications 

at CA and FL because day-zero samples were taken only just after the second and 

third applications with no samples taken just before these applications. The TFD 

guideline states that “For multiple applications, each application should be treated 

as time zero, and concentrations prior to and immediately after application should 

be determined”.

(6) TFD Half-lives: Parent Sulfoxaflor parent, X-474, X-457 and X-540

(1) Parent Sulfoxaflor: Sulfoxaflor dissipation half-lives (DT50) were calculated for 

residues in the top 6” of the soil and the whole 0-36” soil profile. In all half-life 

calculations, the highest observed residue value was used as the initial data point. 

Residue data for the 0-6 inch soil layer were plotted for all sites and data for the 

entire soil profile were plotted for ND, ON, and TX (data from deeper soil layers 

were not consistently available in CA and FL). To determine the DT50 in the 

entire soil profile based on the total mass of parent sulfoxaflor throughout the soil 

profile was calculated using the bulk density and volume of each core segment at 

every sampling depth1. The data were analysed by using single first order (SFO), 

double first order in parallel (DFOP) and indeterminate order rate equation (IORE) 

models and best fit was chosen. When more than one application was made (i.e., 

for CA and FL), data collected after the first, second and third application were 

 1 Total chemical mass= concentration (mg/kg soil) x core volume (m3

) x mean bulk density (kg soil/m3)
13

analysed separately. Furthermore, it is noted that the first data point below LOD 

was replaced with 1⁄2 the LOD and subsequent points less than the LOD were 

omitted from the curve fitting unless positive detections were determined at a later 

sampling points. Results are summarized in Table 2.

Table 2 A summary of field dissipation half-lives (DT50 in days) for sulfoxaflor from the 

top 6” of the soil and the entire soil profile (0-36”)

Chemical Considered Depth 

CALIFORNIA* FLORIDA*

NORTH 

DAKOTA* ONTARIO* TEXAS*

Bare Cropd Bare Cropd Bare Cropd Bare Cropd Bare Cropd

Sulfoxaflor 

Parent

0-6” (top soil) 2.0 1.9 0.7 1.6 0.3 0.1 0.6 0.9 8.1 1.5

0-36” (entire 

profile) ND ND ND ND ND 0.2 0.6 ND 8.1 1.5

* Kinetic models used to fit data for dissipation half-life: SFO (values in red)= Single First Order; DFOP (Values in blue)= 

Double First Order in Parallel; IEORE= Indeterminate Order Rate Equation (values in black)

Bare= Bare soil plots; cropd= cropped plots; ND= Not determined due to lack of data

Sulfoxaflor rapidly dissipated in the field from the top 6”, the chemical dissipated 

in soil bare-plots with half-lives in the range of 0.3 to 2 .0 days in CA, FL, ND, 

ON. Relatively longer dissipation half-life of 8.1 days was observed in TX baresoil plots. Calculated DT50 for the same soil layer in the cropped plots ranged 

from 0.1 to 1.9 days.

These DT50 results confirm data obtained from aerobic soil studies (t1⁄2= 0.3 to 0.6 

days) although it appears that the chemical persists slightly longer in the field 

compared to the laboratory. The observed low amounts of the chemical that 

leached below 6” is probably a result of the slightly longer field half-life and high 

mobility (Koc= 12 to 71 mL/g). Sulfoxaflor was detected within 1 to 28 days after 

application at depths of 6-18” with concentrations ranging from 0.8 to 6% of the 

applied in CA bare/cropped plots and FL cropped plots. Lower concentrations of 

<1% of the applied were observed, at same depth, in ND, ON (Ontario, Canada), 

and TX bare/cropped plots and in FL bare-plots. In CA only, the chemical 

reached concentrations ranging from <0.5% to 0.7% of the applied to depths of 18 

to 36”. The relatively high leaching observed in CA soil was attributed to 

excessive irrigation. Therefore, leaching of sulfoxaflor parent is possible if heavy 

rain occurred just after application. The possibility of sulfoxaflor reaching very 

shallow ground water may not be discounted because sulfoxaflor is mobile, less 

vulnerable to anaerobic degradation in lower soil horizons and is stable for 

hydrolysis. 

Field leaching was also tested using soil pore water suction lysometers to collect 

soil-pore water samples in two of terrestrial field dissipation studies: CA and FL. 
14

soil-suction lysometers were installed at sampling depths of 3, 6, and 8 (FL) or 9 

(CA) feet below ground surface. Soil-pore water samples were collected at -1, 6, 

13, 28 days and 2, 4, 6, 9, 12 and 15 months after the first treatment. Although 

sulfoxaflor was not detected in pore water at any time/depth sampled in the high 

leaching profile in CA, it was concluded that non-detection was related to time of 

sampling rather than absence of leaching (i.e., samples missed the leaching 

events). In FL, the low leaching site, sulfoxaflor was detected, in only 6% of the 

samples, at low sporadic levels at all times/depths with maximum concentration 

of 0.0001 ppb (≈ 0.1% of applied) at a depth of 3 ft, 28 days after the 1st treatment. 

It is noted that SCIGROW predicts a very low ground water expected 

concentration for parent sulfoxaflor (EECs= 0.0001 ppb).

(2) Major Degradate: Consistent with laboratory studies, X-474 was the major 

transformation product in the field dissipation studies. Data for the top 6” of the 

soil indicate the rapid formation of X-474 as its concentration of 13-54% of the 

applied parent was observed immediately following the first application. This was 

the case also following the second and third applications in CA and FL sites. It is 

interesting to note that concentrations reached more than 100% of the applied 

parent after each of the single applications in bare/cropped plots in ND (112-

185%), ON (101-350%), and FL (150-100%) and in bare plots in TX (129%). 

This may indicate mass balance issues or may indicate that X4-74 is accumulating 

in hot spots possibly as a result of lateral movement if it can be assumed that 

parent was uniformly applied; however, X4-74 hot-spots may also result from 

parent hot-spots if parent was not distributed uniformly during application. 

Furthermore, data suggest that X-474 has the potential to carryover especially if 

leaching is limited (concentrations ranging from 1 to 18% of the applied parent 

were left in the soil after a year). Dissipation half-lives (DT50) for X-474 were 

calculated for residues in the top 6” of the soil and the whole 0-36” soil profile 

following the same procedure described for above for parent. Results are 

summarized in Table 3.

Table 3 A summary of field dissipation half-lives (DT50) for major degradate X4-74 

from the top 6” of the soil and the entire soil profile (0-36”)

Chemical Considered Depth 

CALIFORNIA* FLORIDA* NORTH DAKOTA* ONTARIO* TEXAS*

Bare Cropd Bare Cropd Bare Cropd Bare Cropd Bare Cropd

X117194-74

Degradate

0-6” (top soil) 27.2 52.3 48.8 62.1 217 39.7 248 109 50.8 58.2

0-36” (entire profile) 5.9 9.9 49.4 59.9 200 36.4 114 58.5 45.1 51.9

* Kinetic models used to fit data for dissipation half-life: SFO (values in red)= Single First Order; DFOP (Values in 

blue)= Double First Order in Parallel; IEORE= Indeterminate Order Rate Equation (values in black)

Bare= Bare soil plots; cropd= cropped plots; ND= Not determined due to lack of data Bare= Bare soil plots; cropd= 

cropped plots; ND= Not determined due to lack of data
15

Data summarized in Table 3 indicate that X-474 is much more persistent than its 

parent. Dissipation half-lives ranged from 49 to 248 days and from 40 to 109 days 

in bare soil and cropped plots, respectively.

Additionally, X-474 leached below the top 6” soil layers at all terrestrial field 

dissipation sites reaching 36, 30, 24, and 18” below the surface. At CA and FL 

sites, residues of X-474 reached a depth of 36” with maximum concentrations of 

19.5 to 20.6 ppb (≈19-20% of the applied parent) at 28 days after the 1st

application in CA and maximum concentrations of 1.7 to 2.5 ppb (≈2-4% of the 

applied parent) at 2-15 months after the 1st application in FL. In ND, X474 

reached a depth of 30” with maximum concentrations of 1.0 to 2.3 ppb (≈2-4% of 

the applied parent) at 2-11 months after the 1st application. At ON (Canada) site, 

it reached a depth of 18” with maximum concentrations of 0.5-1.6 ppb (≈0.6-10% 

of the applied parent) at 9 months after the 1st application. At TX site, it reached a 

depth of 12” below the soil surface with maximum concentrations of 14.7 to 17.5 

ppb (≈18-22% of the applied parent) at 4-9 months after the 1st application. 

Observed data confirm that field dissipation of X117194-74, from the top soil, is 

mainly related to transport (Koc= 7 to 74 mL/g) rather than degradation.

Field leaching was also tested using soil pore water suction lysometers to collect 

soil-pore water samples in two of the terrestrial field dissipation studies: CA and 

FL. Soil-suction lysometers were installed at sampling depths of 3, 6, and 8/9 ft 

(FL/CA) below ground surface. Soil-pore water samples were collected at -1, 6, 

13, 28 days and 2, 4, 6, 9, 12 and 15 months after the first treatment. The range of 

X-474 concentrations, in pore water, was from 108 to 218 ppb (≈120-242% of the 

applied) at depths ranging from 3 to 9 ft in CA at 2-6 months after the 1st

application. Lower peak concentrations were observed in FL as they were in the 

range of 0.096 to 5.89 ppb (≈0.1-5.9% of the applied) after the 1st application and 

at the same depths. Based on this field and laboratory data, high leaching is 

expected for X-474 and is expected to reach ground water at high concentrations. 

Other Degradates: X-540 and X-457: Degradates X-540 and X-457 were minor 

transformation products in the field. In most field sites, both degradates dissipated 

from the 0-6 inch soil layer before the end of the study. The observed formation of 

minor quantities of degradates X-457 and X-540 is probably related to the relative 

high persistence of its most probable parent (the major degradate X-474). A kinetic 

analysis was not performed for X115195-40 and X115794-57.

(7) Crop Residues: Target and rotational Crops

Crop residue results for all five test sites were monitored for parent sulfoxaflor and its 

major transformation product X11719474, as well as X11721061 (a plant metabolite). 

Field plant data can be used to characterize foliage interception of applied parent and 

nature/concentration of residues in target and rotational crops (foliage uptake).

Plant Interception
16

Plant residue concentration data (in ppm) were collected but no data were collected for 

the total crop mass (g) / unit area (m2

). Therefore, data on the amount intercepted by 

foliage could not be related to the amount applied. In another words, the amount of the 

pesticide intercepted by foliage could not be calculated as % of the applied parent. 

Additionally, for this systemic pesticide, found concentrations in plant samples may be 

interpreted as follows:

• Whole plant concentration, just after the first application represents the amount of 

sulfoxaflor intercepted by the plant foliage. Amounts intercepted at any other 

application may only be determined if plant samples are taken just before and just 

after each of these applications and the amount is equal to concentration just after 

the application minus concentration just after the application.

• For systemic pesticides, the observed change in whole plant concentration 

between applications is the result of many competing processes, namely:

o Degradation that might occur on the surface of the foliage. This process is 

not expected to have a major effect on sulfoxaflor as it is stable for 

hydrolysis and photolysis;

o Plant interaction with applied pesticide including how much of the 

pesticide enters the plant tissues and how much is affected by plant 

metabolism. 

o Wash-off due to rainfall and/or irrigation which is expected to reduce 

concentrations that might remain on foliage (i.e., didn’t enter the plant). 

This process is expected to have minimum impact on systemic sulfoxaflor 

which is expected to enter the plant tissues; and

o Plant up-take from sulfoxaflor reaching the soil. This process is not 

expected to impact sulfoxaflor due to its rapid soil degradation. 

(8) TFD: Nature and concentration of residues in target and rotational crops

In California, spinach (treated crop), cantaloupe and wheat (rotational crops) were 

planted over the course of the study. Sulfoxaflor in spinach whole plant samples was 

detected at a maximum of 7.4 ppm immediately after the 2nd application and then 

declined to non detectable levels by 46 days after the 1st application (1st order half-life 

ranging from 1.1 to 2.8 days). X-474 and X-061were detected at a maximum of 2.7 ppm 

(3 days after the 2nd application) and 0.3 ppm (immediately after the 3rd application), 

respectively.

In Florida, peppers (treated crop), radishes and lettuce (rotational crops) were planted 

over the course of the study. In pepper whole plant samples, sulfoxaflor was detected at a 

maximum of 11.2 ppm immediately following the 1st application and then declined to non 

detectable levels by 63 days after the 1st application (1st order half-life ranging from 1.5 

to 4.7 days). The X-474 and X-061 degradates in whole plant samples were detected at a 

maximum of 2.0 ppm and 0.8 ppm, respectively at 63 days after the first application. In 

pepper fruit only X474 was detected (0.1 ppm) at 63 days after the first application.
17

In North Dakota, wheat (treated crop) and cabbage (rotational crop) were planted over the 

course of the study. In wheat whole plant samples, sulfoxaflor was detected at a 

maximum of 6.3 ppm immediately following application and then declined to 

nondetectable levels by 7 DAT (1st order half-life 0.6 day). Degradate X-474 was 

detected at a maximum of 0.03 ppm immediately following application and X-061 was 

detected at a maximum of 0.05 ppm at 3 DAT. Residues of sulfoxaflor, X-474, and X061 were not detected in wheat grain and wheat straw. 

In Ontario, soybeans (treated crop) and corn (rotational crop) were planted over the 

course of the study. In soybean whole plant samples, sulfoxaflor was detected at a 

maximum of 11ppm immediately following application and then declined to non 

detectable levels by 99 DAT (1st order half-life 7.9 days). X-474 and X-061 were found 

in the whole plant at a maximum of 0.53 ppm (14 DAT) and 0.28 ppm (1 DAT). 

Sulfoxaflor was not detected in the soy bean itself. In contrast, degradates X-474 and X061 were found at 0.08 and 0.007 ppm, respectively.

In Texas, cotton (treated) and melon (rotational crop) were planted over the course of the 

study. In cotton whole plant samples, sulfoxaflor was detected at a maximum of 7.1 ppm 

immediately following application and then declined to nondetectable levels by 14 DAT 

(1st order half-life 10.7 days). Degradates X-474 and X-061 were found in the whole 

plant at a maximum of 0.11 ppm immediately following application and 1 DAT, 

respectively. Parent, X-474 and X-061 were not detected in cotton seed proper. 

In summary, data indicate that sulfoxaflor parent is the most relevant residue observed in 

the whole plants (in terms of concentration). The highest concentrations of the parent 

compound appear to occur just after applications. After reaching a maximum, parent 

sulfoxaflor appears to decline rapidly in CA spinach, FL peppers, and ND wheat (1st

order half-lives range from <1 to 5 days). In contrast, the parent compound declines much 

slower in ON soybeans and TX cotton (1st order half-life range from 8-11 days). The 

second relevant compound is X-474 (plant and environmental metabolism product of 

parent sulfoxaflor) with maximum concentrations ranging from 2.0 to 2.7 ppm in CA 

spinach and FL peppers, and 0.03 to 0.53 ppm in ND wheat, ON soybean and TX cotton. 

The plant only metabolism product (X-061) appears to form at low concentrations with 

peak residue levels ranging from 0.8 to 1.3 ppm in CA spinach and FL peppers and 0.05 

to 0.28 ppm in ND wheat, ON soybean and TX cotton. Residue profiles in spinach in CA 

and peppers in FL suggest that peaks residues of sulfoxaflor parent appear to coincide 

with application (chemical source) which is followed by peaks in X-474. Both 

compounds appear to decline within two months following a multiple reapplication with 

two weeks intervals.

(9) Nature and concentration of residues in rotational crops

With only one exception, data indicate that parent sulfoxaflor was not detected in any 

sample from any of the rotational crops examined. Only the degradate X-474 and X-061 

were detected. The degradate X-061 is expected to be present as it is a known plant 
18

metabolite, however, the presence of X474 in rotational crops suggests its uptake from 

soil (i.e., X-474 is systemic as parent). 

The following is a summary of the residues profile for the two degradates in rotational 

crops:

 In CA, cantaloupe was the first crop planted in rotation with spinach (77 days 

after the initial application to spinach). The degradate X-474 was found in whole 

plant samples at a maximum of 0.55 ppm at123 days after the 1st application and

remained at roughly similar levels until the end of the cantaloupe sampling period; 

X474 in melon samples was found at 0.07 ppm at 182 days after the 1st

sulfoxaflor application. The degradate X061 was detected at 0.17 ppm in the 

cantaloupe whole plant samples at 182 days after the 1st sulfoxaflor application; 

no X061 residues were detected in the fruit itself. Additionally, wheat was the 

second crop planted in the rotation (planted 245 days after the initial application 

to spinach). The degradate X-474 was found in the wheat whole plant samples at 

0.004 ppm (<LOQ of 0.01 ppm) at 368 days after the 1st application and in the 

wheat straw at 0.007 ppm (<LOQ) at 425 days after the 1st application; X-474 was 

not detected in wheat grain itself. The degradate X061 was not detected in the 

wheat whole plant, wheat grain, and wheat straw samples.

 In FL: radish was the first crop planted as a rotational crop (planting date was not 

reported) following an initial application to peppers. The degradate X-474 was 

found in whole plant samples at 0.01 ppm at 180 days after the 1st application and 

was found in radish tops at 0.01 ppm (<LOQ) at 203 days after the 1st application; 

X474 was not detected in radish root. No X061 residues were detected in the 

radish whole plant, root, and top samples. Additionally, leaf lettuce was the 

second rotational crop to be planted 315 days after the initial application to 

peppers. The degradate X-474 was found at a maximum of 0.01 ppm at 363 days 

after the 1st application to wheat. The degradate X-061 was not detected in leaf 

lettuce.

 In ND: Cabbage was planted 380 days after application to wheat. X-474 was 

found at a maximum of 0.01 ppm (<LOQ) at 426 DAT while X61 was not 

detected. 

 In ON: Corn was planted 327 days after an initial application to soybeans. 

Degradates X-474 and X-061 were not detected in the corn whole plant, corn ears, 

or corn stover samples. 

 In TX: Melons were planted 309 days after an initial application to cotton. The 

degradate X-474 and X-061 were detected at 0.004 and 0.005 ppm (both < LOQ), 

respectively, but were not detected in the melon fruit proper. 

(10) Dissipation Pathways for Parent and Degradates

The major dissipation pathways for parent sulfoxaflor and transformation products were 

tracked and included degradation and leaching. Runoff and volatilization were not 

tracked as both are not expected to be factors in dissipation due to the study area (flat 

plots with limited possibility for runoff) and the low vapor pressure and Henry’s law 
19

constant for sulfoxaflor. Other minor pathways that were tracked include plant uptake 

and residue carryover. Two major properties of sulfoxaflor were the drivers for its 

dissipation in terrestrial systems, i.e., its ability to enter the plant through foliage 

(systemic distribution) following application and its high vulnerability to degradation in 

the soil system. Factors affecting dissipation for degradates were persistence and 

mobility.

(11) TFD: Residues Carryover

In California, the DT90 for sulfoxaflor was 6.6 and 6.1 days (from the 3rd application to 

the end of the study; based on single first order kinetics) for the bare soil and cropped 

plot, respectively. Approximately one year after the 1st application and including the two 

subsequent applications, sulfoxaflor was no longer detected and has a low potential for 

carryover into the next growing season. When considering the 0-6 inch soil layer, 

carryover of the transformation products at the beginning of the next growing season 

ranged from 0 to <1%of the Time 0 parent-equivalent concentration for X-474, X-457 

and X-540, respectively. When considering the entire soil profile, carryover of the 

transformation products at the beginning of the next growing season ranged from 0 to 2% 

of the Time 0 parent-equivalent concentration for X-474, X-457 and X-540.

In Florida, the DT90 for sulfoxaflor was 22 days for the bare soil plot (from the 3rd

application to the end of the study; based on double first order (in parallel) and 23 days 

for the cropped plot (from the 3rd application to the end of the study; based on an 

indeterminate order rate equation). Approximately one year after the 1st application, 

sulfoxaflor was detected at 1% and less than 1% of the Time 0 parent-equivalent 

concentration in the bare soil and cropped plots, respectively. Based on these data, parent 

sulfoxaflor appears to have a low potential for carryover into the next growing season. 

When considering the 0-6 soil layer, carryover of the transformation products at the 

beginning of the next growing season was 14-15%, less than 1% and 1% of the Time 0 

parent-equivalent concentration for X-474, X-457 and X-540, respectively. When 

considering the entire soil profile, carryover of the transformation products at the 

beginning of the next growing season was 22-25%, less than 1% and 3% of the time zero 

parent-equivalent concentration for X-474, X-457 and X-540, respectively.

In North Dakota, the DT90 for sulfoxaflor was <1 day for bare soil and cropped plots. 

Parent sulfoxaflor was no longer detected well before the growing season had ended and 

thus is considered to have a low potential for carryover into the next growing season. 

When considering the 0-6 soil layer, carryover of the transformation products at the 

beginning of the next growing season was 28-39%, 1% and 3-4% of the Time 0 parentequivalent concentration for X-474, X-457 and X-540, respectively. When considering 

the entire soil profile, carryover of the transformation products at the beginning of the 

next growing season was 32-52%, 1-2% and 7% of the Time 0 parent-equivalent 

concentration for X-474, X-457 and X-540, respectively. The degradate X-474 is 

expected to carry over into the following season.
20

In Ontario, the DT90 for sulfoxaflor was approximately 1 day for the bare soil and 

cropped plots. Parent sulfoxaflor was no longer detected well before the growing season 

had ended and thus has a low potential of carryover into the next growing season. When 

considering the 0-6 inch soil layer, carryover of the transformation products at the 

beginning of the next growing season was 36-40%, <1% and 0-3% of the Time 0 parent 

equivalent concentration for X-474, X-457 and X-540, respectively. When considering 

the entire soil profile, carryover of the transformation products at the beginning of the 

next growing season was 50-131%, 0-1% and 4-6% of the Time 0 parent-equivalent 

concentration for X-474, X-457 and X-540, respectively. The degradate X-474 is 

expected to carry over into the following season. 

In Texas, the DT90 for parent sulfoxaflor was 8.1 and 1.5 days for the bare soil and 

cropped plots, respectively. Parent sulfoxaflor was no longer detected before the growing 

season had ended and thus has a low potential of carryover into the next growing season. 

When considering the 0-6 inch soil layer, carryover of the transformation products at the 

beginning of the next growing season was 44-46%, <2% and 3-5% of the Time 0 parent 

equivalent concentration for X-474, X-457 and X-540, respectively. When considering 

the entire soil profile, carryover of the transformation products at the beginning of the 

next growing season was 65-76%, 1-3% and 4-8% of the Time 0 parent-equivalent 

concentration for X-474, X-457 and X-540, respectively. The degradate X-474 is 

expected to carry over into the following season.

In conclusion, top soil carryover is not expected for sulfoxaflor parent but is expected for 

X-474, X-457 and X-540. Estimated carryover for all of the three degradates were 

minimal (0-<1%) for CA site while it was significantly higher for FL, ND, ON and TX 

sites. For X-474, the maximum top soil carryover is estimated to be 15% for FL, 39% for 

ND, 40% for ON and 46% for TX. This is a reflection of the high formation/persistence 

of the degradate X-474. For X-540, the maximum top soil carryover is estimated to be 

1% for FL, 4% for ND, 3% for ON and 5% for TX. For X-457, the maximum top soil 

carryover is estimated to be <2% in FL, ND, ON and TX.