MRID 49090502 CDPR IMI Strawberry

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Reference

Gould, T.; Dallstream, K.; Beedle, E. (2012) Determination of the Residues of Imidacloprid and its 

Metabolites 5-Hydroxy Imidacloprid and Imidacloprid Olefin in Bee Relevant Matrices Collected from 

Strawberries, Grown at Locations Treated with Imidacloprid at Least Once Per Year During Two 

Successive Years. Project Number: EBTNL056/04, M/445207/01/2. Unpublished study prepared by 

Bayer Cropscience LP and California Agricultural Research Inc. 186p. MRID 49090502, CDPR Study ID 

268742, Data Volume 51950-0812, Tracking ID# 256590

1. STUDY INFORMATION

Chemical: Imidacloprid PC Code 129099

Test Material: 1) Admire Pro 

2) Alias 4F

Percent Active 

Ingredient:

1) 42.8%

2) 40% 

Study Type:

Non-Guideline field residue study to establish imidacloprid and metabolite levels 

in blossoms, anthers, pollen and leaves from strawberry in site locations that 

have been previously treated with imidacloprid at least once for two successive 

years.

Sponsor:

Bayer CropScience

2T.W. Alexander Drive

Research Triangle Park, NC 

USA 27709

Experiment Start and

End Date:

September 2011 –

December 13, 2012

Sponsor Study 

ID: EBNTL056-04

Study Locations:

Seven treated fields 

sites within California 

that consist of either 

sand or loam soil. 

Study 

Completion 

Date:

December 27, 2012

GLP Status: Non-GLP; protocol reviewed by CDPR. 

[CDPR study ID 260012, Data Volume 51950-0791, Tracking ID# 247269]

2. REVIEWER INFORMATION

Study Reviewed by: 

California Department 

of Pesticide Regulation 

Richard Bireley, Sr. Environmental Scientist (Specialist) 

John Troiano, Ph.D., Research Scientist III

Alexander Kolosovich, Environmental Scientist 

Brigitte Tafarella, Environmental Scientist

Denise Alder, Sr. Environmental Scientist (Specialist) 

Russell Darling, Environmental Scientist 

3. EXECUTIVE SUMMARY

Blossom and leaf samples were collected from seven treated field sitesin Santa Barbara County, California 

to determine the residues of imidacloprid and its metabolites (5-hydroxy imidacloprid and imidacloprid 

olefin) in blossoms, anthers, pollen and leaves collected from strawberry plants grown at locations treated 

with imidacloprid at least once per year for two years. The site locations consisted of either a sand soil (3 

sites, “light”) or a loam soil (4 sites, “medium”), which had all previousreceived applications of either Alias 

4F or Admire Pro at a rate of 0.5 lb. a.i./acre in the prior year as well as an application of imidacloprid in 

2010.
MRID 49090502 CDPR IMI Strawberry

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Duplicate composite samples of strawberry blossoms for direct analysis, strawberry blossoms for anther 

samples, strawberry blossoms for pollen samples and strawberry leaves were collected at a BBCH ranging 

from 61 to 69 (flowering) at each field site.

The residues of imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin were quantitated by high 

performance liquid chromatography/triple stage quadrupole mass spectrometry (LC/MS/MS) using stable 

isotopically labeled internal standards. The individual analyte residues were summed to give a total 

imidacloprid residue.

4. STUDY VALIDITY

Guideline Followed: Non-guideline study (protocol was reviewed by U.S. EPA/PMRA/CDPR)

Guideline Deviations: N/A

Other Deviations: N/A

Classification: Supplemental

Rationale: N/A

Reparability: N/A

5. MATERIALS AND METHODS

Test Material Characterization

Test item: Admire Pro, Alias and 

Unknown Formulations

pH (24°C) 7.8 

Description: Unknown Density (20°C): 1.54 g/mL

CAS #: 138261-41-3 Solubility: 0.51 to 0.61 g/L

5A. STUDY DESIGN

Seven treated field sites in California representing two soil categories classified as either 'light,' generally 

sand soil, or 'medium,' generally loam soil, were selected based on previous application(s) of 

imidacloprid according to grower interviews. Classification of the soils was obtained from the Soil Survey 

Geographic (SSURGO) Database provided by the Natural Resources Conservation Service. All test sites 

had received applications of imidacloprid in the preceding years (2011, 2010). 

The field sampling phase of this study occurred in September, 2011, and was not conducted under GLP. 

The GLP experimental start date was August 22, 2012 (leaf sample homogenization), and the 

experimental end date was December 13, 2012 (last analysis). The field sampling phase of the study was 

conducted by California Agricultural Research, Inc. (CAR).

The sampling of blossoms and leaves, as well as the separation of the pollen and anthers, were 

performed at the test site. Homogenization of the leaves and blossoms for direct analysis from this 

study were performed at the Bayer Research Park (BRP) located in Stilwell, KS. Sample analysis and 

report preparation was performed at Bayer CropScience located in Research Triangle Park, NC. All raw 

data associated with this study are retained along with the protocol, protocol amendments and the final 

report under Notebook Number EBNTL056-04 at locations specified by Bayer CropScience.

5B. APPLICATION TIMING AND RATES
MRID 49090502 CDPR IMI Strawberry

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In 2011, one application of either Alias 4F or Admire Pro was made to the soil at a rate of 0.5 lb. a.i./acre

in each of the seven field sites. In 2010, one soil application of an imidacloprid product (the subject

products were not identified for four out of seven of the sites) was made at a rate of 0.5 lb. a.i./acre in 

each of the seven field sites. Method, timing or growth stage, and spray volume of these applications 

were not reported by the study authors. Thus, it is uncertain when the sampling was conducted in 

relation to the imidacloprid applications.

The test substance use pattern for imidacloprid in 2011 and 2010 for each site is described in Table 1. All 

site locations were in Santa Barbara county in California, NAFTA Region 10. For the applications in 2011, 

either Alias 4F or Admire Pro were applied at a rate of 0.5 lb ai/A.

Table 1. Study Use Pattern for 2011 Application of Imidacloprid on Strawberry.

Trial 

Identification

Location Year End Use 

Product a

Timing/Grow

th Stage

Spray 

Volume b

Rate (lb. 

a.i./A) a

NT031-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Alias 4F

Alias 4F

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT032-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Alias 4F

Alias 4F

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT033-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Alias 4F

Alias 4F

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT035-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Alias 4F

Not Available c

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT037-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Admire Pro

Not Available c

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT038-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Admire Pro

Not Available c

Unknown

Unknown

Unknown

Unknown

0.5

0.5

NT039-11ZA Santa 

Maria, CA 

Region 10

2011

2010

Admire Pro

Not Available c

Unknown

Unknown

Unknown

Unknown

0.5

0.5

a imidacloprid use was obtained from verbal communications with the growers or pest control advisors. b Rates and spray volumes that were provided in the application order/recommendation. See Appendix 2 of the 

study report for field trial summary data. c imidacloprid use was confirmed by the grower, but no documentation was available .

5C. STUDY SITE LOCATION AND CHARACTERISTICS 

The trial site conditions including soil characteristics are listed in Table 2. All sites used agronomic 

practices typical for commercial production of strawberries. A chronological listing of significant study

dates is given in Appendix 1 of the study report. 
MRID 49090502 CDPR IMI Strawberry

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Temperatures and rainfall recorded during the field phase of the study were similar to average historical 

records, with no significantly unusual weather conditions that would affect the conclusions of the study.

Temperature and precipitation data for each trial were obtained from the nearest National Climatic Data 

Center (NCDC) weather station. Application, sampling and climatic data are located in Appendix 2 of the 

study report.

Table 2. Trial Site Conditions for Imidacloprid on Strawberry. 

Trial 

Identification

Trial Location Soil Type a Rainfall (in) b Temperature 

Range (°F) b

NT031-11ZA Santa Maria, CA 

Region 10

Batteravia Loamy 

Sand, Light

0.1 58-78

NT032-11ZA Santa Maria, CA 

Region 10

Oceano Sand, 

Light

0.1 58-78

NT033-11ZA Santa Maria, CA 

Region 10

Batteravia Loamy 

Sand, Light

0.1 58-78

NT035-11ZA Santa Maria, CA 

Region 10

Sorento Sandy 

Loam, Medium

0.1 58-78

NT037-11ZA Santa Maria, CA 

Region 10

Sorrento Loam, 

Medium

0.1 58-78

NT038-11ZA Santa Maria, CA 

Region 10

Sorrento Loam, 

Medium

0.1 58-78

NT039-11ZA Santa Maria, CA 

Region 10

Sorento Sandy 

Loam, Medium

0.1 58-78

a Classification of the soils was obtained from the Soil Survey Geographic (SSURGO) Database provided by the 

Natural Resources Conservation Service.

b Data is for the interval of the month of sampling. Meteorological data were obtained from nearby government 

weather stations.

5D. SAMPLE COLLECTION, HANDLING, PROCESSING

At each sampling interval, duplicate samples of strawberry blossoms, strawberry blossoms for anther 

samples, strawberry blossoms for pollen samples, and strawberry leaves were collected from the 

treated sites during flowering.

Strawberry blossoms and leaves were placed into coolers with dry ice directly after sampling. Strawberry 

blossoms for anther samples were processed by removing the anthers from the blossom with 

tweezers/small scissors and transferred to a sampling jar and frozen. Strawberry blossoms for pollen 

samples were allowed to dry overnight, and the pollen was removed by vacuum and frozen.

Untreated (control) blossom and leaf samples used for validation of the analytical method and for 

transit stability samples were obtained from a nearby farm that was believed to have no recent 

imidacloprid application.

All samples were placed in frozen storage at CAR Samples were shipped to BRP frozen via Agricultural 

Chemicals Development Services (ACDS) and were placed in frozen storage upon receipt and remained 

frozen throughout the storage period at BRP.
MRID 49090502 CDPR IMI Strawberry

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The anther and pollen samples, along with the transit stability samples, were shipped frozen to Bayer 

CropScience, Research Triangle Park (RTP), NC, via ACDS. Homogenization of the leaf and blossom 

samples was conducted at BRP and shipped frozen via FedEx to RTP. During storage at RTP, the anther 

and pollen samples, along with the transit stability samples, reached room temperature for

approximately three days due to freezer failure. Transit stability samples accompanied the field samples 

during all sample handling and preparation steps to ensure the validity of the sampling practices.

Sample Storage.

Upon arrival at BRP, all samples were immediately transferred to frozen storage. The leaf samples were 

homogenized with dry ice using a Robot Coupe chopper (Jackson, MS). The leaf samples were returned 

to frozen storage immediately following homogenization. Samples were transferred to Bayer 

CropScience, Research Triangle Park, NC, for analysis. Samples remained frozen at all times except 

during preparation for analysis A summary of collection, shipment, and homogenization dates for the 

trials is given in Appendix 1 of the study report.

Additionally, freezer storage stability studies have indicated the imidacloprid residues are stable (<30%

decomposition) for 24 months (728 to 769 days) of freezer storage in the following representative crops: 

an oilseed (cottonseed), a non-oily grain (wheat), a leafy vegetable (lettuce), a root crop (potato), a tree 

fruit (apple), and a fruiting vegetable (tomato). 7-11

Demonstrated freezer stability in the transit stability samples from this study, as well as stability 

demonstrated in the above crops is representative of the freezer stability of imidacloprid residues to be 

expected in the blossoms, anthers, pollen, and leaves collected in this study.

5E. ANALYTICAL METHODS

The analytical method used in this study measured the residues of imidacloprid, 5-hydroxy imidacloprid, 

and imidacloprid olefin in strawberry blossoms, anthers, pollen and leaves.4

All neat analytical reference standards were stored frozen when not in use and all solutions were stored 

refrigerated or frozen. Analytical standard solutions used in this study were not stored for longer than 

approximately 2 months and have been shown to be stable for this period of time. 5 All reference 

standard solutions were prepared in parent imidacloprid equivalents and corrected for purity during 

initial preparation.

Samples of anthers, blossoms, leaves, and pollen were analyzed for residues of imidacloprid,

imidacloprid olefin, and imidacloprid 5-hydroxy. For anthers, blossoms, and leaves, a sample was 

extracted by blending samples with 2:1 acetonitrile/water (ACN/H20). The mixture was amended with 

MgS04, NaCI, and isotopically labeled internal standards, mixed well, and centrifuged. An aliquot of the 

supernatant was transferred to a 15-mL centrifuge tube containing MgS04 and Bondesil-PSA. The 

contents of the tube were mixed well and centrifuged. About 1.2 ml of the supernatant was percolated 

through a C18 SPE cartridge (50 mg Bond Elut) into a 20x150mm culture tube. The eluate was 

evaporated to dryness and the residue was reconstituted with 1:9 methanol/water (MeOH/H20) for 

analysis by high performance liquid chromatography/tandem mass spectrometry (LC/MS/MS).

For pollen a sample was extracted by shaking with water for 10 minutes, adding ACN and shaking for an 

additional 55 minutes. The mixture was amended with isotopically labeled internals standards, mixed 
MRID 49090502 CDPR IMI Strawberry

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well and centrifuged. The supernatant was drawn off, evaporated to an aqueous remainder, amended 

with water and applied to a Chern Elute cartridge (3-ml). The analytes were extracted from the cartridge 

with 3 x 5 ml of hexane/ethyl acetate (1:1 v/v). The eluate was evaporated to dryness and the residue 

was reconstituted with 1:9 methanol/water (MeOH/H20) for analysis by LC/MS/MS.

Quantitation of each analyte was based on the daughter ion transitions of the analytes and the 

respective internal standard analogs. The responses of LC/MS/MS system to each analyte and its 

internal standard were measured in samples and in standards, and a relative response was calculated as 

the ratio of the analyte and the stable isotopically labeled internal standard responses. The relative 

response of the analyte in each sample was compared to the relative response of the analyte in the 

standards (Appendix 3 of the study report).

The relative responses of imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin in solvent were 

measured over the range of 3 ppb to 3000 ppb for each analyte. The coefficients of determination (r2

) 

were calculated using linear regression analysis (Microsoft Excel 2010; Appendix 3 of the study report).

The total imidacloprid residue is the sum of the individual measured residue values of imidacloprid, 5-

hydroxy imidacloprid, and imidacloprid olefin in parent equivalents. For the purpose of calculating total 

imidacloprid residues where individual analyte residue values were less than the limit of detection 

(LOD), the residues were assigned a finite value of 1⁄2 the value of the respective LOD. This value is only 

an estimate of potential residue in a sample, not a measured value.

Blossoms and leaves were collected from the control test site and were used for validation, LOD 

determination, and concurrent recoveries. Commercially obtained bee pollen was also used for 

validation and recovery. Because only small, untreated control samples of anthers and pollen were 

generated in the field phase of this study, surrogate anther and pollen controls were used for validation, 

LOD determination, and concurrent recoveries. Blossom validation LOD data was used for anthers while

the control strawberry blossoms were used for anther concurrent recoveries. Commercial bee pollen 

was obtained from a local health food store and stored at room temperature. The bee pollen was used 

without any preparation. The commercial pollen was used for pollen validation, LOD determination, and 

for concurrent recoveries.

The method for determining imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin residues 

in/on strawberry blossoms, anthers, pollen and leaves was validated by measuring the recovery of these 

analytes from control matrices fortified at their respective LOQs.

Additional recoveries at higher fortification levels validated the method for the highest residues 

observed in individual matrices. Concurrent recoveries of imidacloprid, 5-hydroxy imidacloprid, and 

imidacloprid olefin were measured with each set of samples to verify method performance.

5F. QUALITY ASSURANCE RESULTS

The responses of the LC/MS/MS system to imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin 

were linear in solvent over the range of 3 ppb to 3000 ppb for each analyte. The coefficients of 

determination were >0.99. 

All recoveries were corrected for any interferences in corresponding controls. The overall mean values 

of the recoveries for each matrix were within the acceptable range of 70% to 120%, and the standard 
MRID 49090502 CDPR IMI Strawberry

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deviation values were below 20%, except for 5-hydroxy imidacloprid recovery from blossoms which had 

a percent recovery standard deviation of 24%.

The limit of quantitation (LOQ) is defined as the lowest fortification level of an analyte at which 

acceptable recovery has been achieved. The LOQ for total residue is the highest of the LOQ values 

assigned to the individual analytes for a particular matrix.

The limit of detection (LOD) is defined as the lowest concentration of an analyte that can be determined 

to be statistically different from a blank. The LODs were determined from method validation data 

obtained from control samples fortified at the respective analyte LOQs. The LODs were calculated by 

multiplying the standard deviation of recovery measurements at the LOQ by t0.99 [where t0.99 is the onetailed t-statistic at the 99% confidence level for the number of replicates (n)] 6

. The LOD for the total 

imidacloprid residue in each matrix is the highest LOD value of any individual analyte for that particular

matrix.

The LOQs and LODs are summarized in the table below.

Summary of LOQs and LODs

Matrix Analyte LOQ (ppb, parent equivalents) LOD (ppb, parent equivalents)

Strawberry 

Blossom

Imidacloprid 5.0 0.87

5-hydroxy Imidacloprid 5.0 3.9

Imidacloprid olefin 5.0 1.3

Total Imidacloprid 5.0 3.9

Strawberry 

Anthers

Imidacloprid 5.0 0.87

5-hydroxy Imidacloprid 5.0 3.9

Imidacloprid olefin 5.0 1.3

Total Imidacloprid 5.0 3.9

Strawberry 

Pollen

Imidacloprid 10 1.1

5-hydroxy Imidacloprid 10 2.6

Imidacloprid olefin 10 2.2

Total Imidacloprid 10 2.6

Strawberry 

Leaves

Imidacloprid 10 2.2

5-hydroxy Imidacloprid 10 3.0

Imidacloprid olefin 10 4.6

Total Imidacloprid 10 4.6

Any individual analyte or total residue measured to be less than the Limit of Quantitation (LOQ) was 

reported as <5 ppb for blossoms and anthers and <10 ppb for leaves and pollen. In Appendix 3 of the 

study report, any residue value that was below the LOD was reported as less than the LOD and 

measured residue values between the LOQ and LOD are also provided.

6. RESULTS:

Summary statistics for concentration of total imidacloprid in strawberry blossoms, anthers, pollen and 

leaves are contained in Table 3. The individual analyte residues were summed to give a total 
MRID 49090502 CDPR IMI Strawberry

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imidacloprid residue. The study authors stated that when individual analyte residue values were less 

than the LOD, the residues were assigned a finite value of half the value of the respective LOD.

Table 3. Magnitude of total imidacloprid residues in strawberry blossoms, anthers, pollen, and leaves.

Commodity

Soil Texture 

Categorya

Total Imidacloprid Residue Levels (ppb)b

N Min Max

Highest 

Avg. Site 

Residue Median Mean

Standard 

Deviation

Strawberry Blossoms Coarse 6 210 530 500 380 360 130

Strawberry Anthers Coarse 6 81 300 250 200 180 82

Strawberry Pollen Coarse 6 78 320 280 210 190 95

Strawberry Leaves Coarse 6 1700 2800 2400 2100 2200 410

Strawberry Blossoms Medium 8 <5.0 31 18 6.4 9.4 9.1

Strawberry Anthers Medium 8 11 33 23 13 18 7.9

Strawberry Pollen Medium 8 <10.0 <10.0 <10.0 <10.0 <10.0 <10.0

Strawberry Leaves Medium 8 <10.0 18 17 11 11 <10.0 a Classification of the soils was obtained from the Soil Survey Geographic (SSURGO) Database provided by the 

Natural Resources Conservation Service and converted to soil texture categories.

b Abbreviations used are as follows: Min is the lowest treated residue value; Max is the highest treated residue 

value; Median is the geometric median of the treated residue values; Mean is the mathematical average of the 

treated residue values; Standard Deviation is the standard deviation for a small population of “N” samples.

The total imidacloprid residue data for strawberry blossoms, anthers, pollen and leaves are provided in 

Table 4.

Table 4. Imidacloprid Residue Data from Strawberry. Trial Identification Location (City, State, Region) Plot Name Commodity

Rate, lb a.i./A

Residue Sample Collection 

DAT (Days after 2010 

Imidacloprid Olefin Residue 

(ppb)

5-Hydroxy Imidacloprid 

Residue (ppb)

Imidacloprid Residue (ppb)

Total Imidacloprid Residue 

(ppb)

Blossoms Residue (ppb) a

NT031-1ZA Santa Maria, 

CA, Region 10

Sand 1 Blossom 0.5 NA 10

12

46

33

470

420

530

470

Average

500

NT032-1ZA Santa Maria, 

CA, Region 10

Sand 2 Blossom 0.5 NA 8.7

8.2

31

27

340

350

380

380

Average

380
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Trial Identification

Location (City, State, 

Region)

Plot Name

Commodity

Rate, lb a.i./A

Residue Sample Collection 

DAT (Days after 2010 

Imidacloprid Olefin Residue 

(ppb)

5-Hydroxy Imidacloprid 

Residue (ppb)

Imidacloprid Residue (ppb)

Total Imidacloprid Residue 

(ppb)

NT033-1ZA Santa Maria, 

CA, Region 10

Sand 3 Blossom 0.5 NA 8.5

10

38

40

160

170

210

220

Average

220

NT035-1ZA Santa Maria, 

CA, Region 10

Loam 1 Blossom 0.5 NA <5.0

<5.0

7.0

<5.0

22

<5.0

31

<5.0

Average

18

NT037-1ZA Santa Maria, 

CA, Region 10

Loam 3 Blossom 0.5 NA <5.0

<5.0

7.4

<5.0

<5.0

<5.0

11

6.0

Average

8.6

NT038-1ZA Santa Maria, 

CA, Region 10

Loam 4 Blossom 0.5 NA <5.0

<5.0

5.1

6.8

<5.0

<5.0

6.7

8.8

Average

7.7

NT039-1ZA Santa Maria, 

CA, Region 10

Loam 5 Blossom 0.5 NA <5.0

<5.0

<5.0

<5.0

<5.0

<5.0

<5.0

<5.0

Average

<5.0

Anthers Residue (ppb) a

NT031-1ZA Santa Maria, 

CA, Region 10

Sand 1 Anthers 0.5 NA 19

9.5

43

26

240

170

300

210

Average

250

NT032-1ZA Santa Maria, 

CA, Region 10

Sand 2 Anthers 0.5 NA 7.5

9.5

24

35

160

180

190

220

Average

210

NT033-1ZA Santa Maria, 

CA, Region 10

Sand 3 Anthers 0.5 NA 5.5

7.6

26

20

64

54

96

81

Average

89

NT035-1ZA Santa Maria, 

CA, Region 10

Loam 1 Anthers 0.5 NA <5.0

<5.0

13

7.6

38

<5.0

19

11

Average

15

NT037-1ZA Santa Maria, 

CA, Region 10

Loam 3 Anthers 0.5 NA <5.0

<5.0

13

22

<5.0

<5.0

14

25

Average

19

NT038-1ZA Santa Maria, 

CA, Region 10

Loam 4 Anthers 0.5 NA <5.0

8.8

8.7

23

<5.0

<5.0

13

33

Average

23
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Trial Identification

Location (City, State, 

Region)

Plot Name

Commodity

Rate, lb a.i./A

Residue Sample Collection 

DAT (Days after 2010 

Imidacloprid Olefin Residue 

(ppb)

5-Hydroxy Imidacloprid 

Residue (ppb)

Imidacloprid Residue (ppb)

Total Imidacloprid Residue 

(ppb)

NT039-1ZA Santa Maria, 

CA, Region 10

Loam 5 Anthers 0.5 NA <5.0

<5.0

11

11

<5.0

<5.0

12

13

Average

13

Pollen Residue (ppb) a

NT031-1ZA Santa Maria, 

CA, Region 10

Sand 1 Pollen 0.5 NA 17

14

42

33

260

200

320

250

Average

280

NT032-1ZA Santa Maria, 

CA, Region 10

Sand 2 Pollen 0.5 NA 14

10

32

25

190

150

240

190

Average

210

NT033-1ZA Santa Maria, 

CA, Region 10

Sand 3 Pollen 0.5 NA <10

<10

21

18

57

54

87

78

Average

83

NT035-1ZA Santa Maria, 

CA, Region 10

Loam 1 Pollen 0.5 NA <10

<10

<10

<10

<10

<10

<10

<10

Average

<10

NT037-1ZA Santa Maria, 

CA, Region 10

Loam 3 Pollen 0.5 NA <10

<10

<10

<10

<10

<10

<10

<10

Average

<10

NT038-1ZA Santa Maria, 

CA, Region 10

Loam 4 Pollen 0.5 NA <10

<10

<10

<10

<10

<10

<10

<10

Average

<10

Leaves Residue (ppb) a

NT031-1ZA Santa Maria, 

CA, Region 10

Sand 1 Leaves 0.5 NA 14

17

50

64

1600

2200

1700

2300

Average

2000

NT032-1ZA Santa Maria, 

CA, Region 10

Sand 2 Leaves 0.5 NA 27

18

53

48

2300

1900

2400

1900

Average

2200

NT033-1ZA Santa Maria, 

CA, Region 10

Sand 3 Leaves 0.5 NA 42

25

100

70

2700

1800

2800

1900

Average

2400
MRID 49090502 CDPR IMI Strawberry

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Trial Identification

Location (City, State, 

Region)

Plot Name

Commodity

Rate, lb a.i./A

Residue Sample Collection 

DAT (Days after 2010 

Imidacloprid Olefin Residue 

(ppb)

5-Hydroxy Imidacloprid 

Residue (ppb)

Imidacloprid Residue (ppb)

Total Imidacloprid Residue 

(ppb)

NT035-1ZA Santa Maria, 

CA, Region 10

Loam 1 Leaves 0.5 NA <10

<10

<10

<10

14

<10

18

16

Average

17

NT037-1ZA Santa Maria, 

CA, Region 10

Loam 3 Leaves 0.5 NA <10

<10

<10

<10

<10

<10

<10

10

Average

<10

NT038-1ZA Santa Maria, 

CA, Region 10

Loam 4 Leaves 0.5 NA <10

<10

<10

<10

<10

<10

12

13

Average

13

NT039-1ZA Santa Maria, 

CA, Region 10

Loam 5 Leaves 0.5 NA <10

<10

<10

<10

<10

<10

<10

<10

Average

<10

a See Appendix 3 of the study report for analytical data summaries and refined data used to prepare this summary. 

Total

imidacloprid is the sum of imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin .

In coarse-textured soils, mean residues of total imidacloprid were 360, 180, 190, and 2200 ppb in 

blossoms, anthers, pollen, and leaves, respectively and, maximum residues were 530, 300, 320, and 

2800 ppb in blossoms, anthers, pollen, and leaves respectively. In medium-textured soils, mean residues 

of total imidacloprid were 9.4, 18, <0.010 (LOQ), and 11 ppb in blossoms, anthers, pollen, and leaves, 

respectively, and maximum residues were 31, 33, <0.010 (LOQ), and 18 ppb in blossoms, anthers, pollen, 

and leaves respectively. Thus, in all matrices (blossoms, anthers, pollen, and leaves) mean 

concentrations of total imidacloprid were approximately ten times higher in strawberries grown in 

coarse-textured soil than in medium-textured soil.

7. STUDY VALIDITY/CLASSIFICATION AND STUDY LIMITATIONS 

Classification/Utility for Bee Risk Assessment. The study is SUPPLEMENTAL for considering the level of 

residues of imidacloprid in pollen after soil application in strawberry. The level of imidacloprid residues 

appeared to be much higher in strawberries grown in coarse-textured sandy soil than in mediumtextured loamy soil. In sandy soil, soil application at 0.5 lb ai/A of imidacloprid for two consecutive years 

resulted in maximum total imidacloprid residues of 320 ppb (mean ± SEM, 190 ± 95), 300 ppb (180±82), 

530 ppb (360±130) and 2800 ppb (2200±410) respectively in strawberry pollen, anthers, blossoms and 

leaves. Residues in strawberry nectar, another bee-relevant matrix, were not measured. Another 

concern is that the date of the last soil application was not provided, thus the duration from the soil 

application to the collection of the samples could not be estimated.
MRID 49090502 CDPR IMI Strawberry

12

Temporal Variability in Residues. This study was not designed to measure temporal variability in 

residues. All samples were taken in 2011, within five days of each other. Thus, this study was designed 

to analyze imidacloprid residues at a single time point. In addition, time of sampling in relation to the 

imidacloprid applications, is unknown. 

Spatial Variability in Residues. All seven sites for this strawberry study were located in Santa Maria, CA. 

As expected, reported weather conditions (temperature and precipitation) were the same across all 

seven sites. As a result of the close proximity of trial sites, this study provides very limited information 

on how differences in environmental conditions across different areas of the US may affect 

accumulation of total imidacloprid in bee-relevant matrices. However, because there are different soil 

types represented (3 sand soil sites and 4 loam soil sites), this study may offer insight to how soil type 

may affect accumulation of total imidacloprid in bee-relevant matrices. In all matrices (blossoms, 

anthers, pollen, and leaves) mean concentrations of total imidacloprid were higher in strawberries 

grown in sandy soil than in loam soil.

Pesticide Carryover. This study was not designed to measure pesticide carryover. All samples were 

taken in 2011, within five days of each other. This this study is designed to analyze imidacloprid residues 

at a single time point.

8. CONCLUSION

Samples were obtained from 7 field sites where soil in 3 of the sites was classified as coarse-textured 

and the other 4 classified as medium-textured. The cultivar of strawberry was not reported that was 

grown in each field. Parent imidacloprid and 2 breakdown products, the 5-Hdroxy and Olefin residues, 

were measured. Concentrations were measured for whole blossoms, anthers and pollen separated from

the blossom, and leaves. Chemical analysis was conducted on samples stored for more than 1 year.

Samples were purported to store well over this period but storage data were only referenced and not 

provided.

In coarse-textured soils, mean residues of total imidacloprid were 360, 180, 190, and 2200 ppb in 

blossoms, anthers, pollen, and leaves, respectively and, maximum residues were 530, 300, 320, and 

2800 ppb in blossoms, anthers, pollen, and leaves respectively. In medium-textured soils, mean residues 

of total imidacloprid were 9.4, 18, <0.010 (LOQ), and 11 ppb in blossoms, anthers, pollen, and leaves, 

respectively, and maximum residues were 31, 33, <0.010 (LOQ), and 18 ppb in blossoms, anthers, pollen, 

and leaves respectively. Thus, in all matrices (blossoms, anthers, pollen, and leaves) mean 

concentrations of total imidacloprid were approximately ten times higher in strawberries grown in 

coarse-textured soil than in medium-textured soil.

9. REFERENCES

1. Hoelscher, A. 1998. Physical and chemical properties of the active ingredient imidacloprid. 

Bayer CropScience Report No. M0-03-006885, M-105510-01-1.

2. Talbott, T. D. 1991. Product Chemistry of BAY NTN 33893 Technical. Bayer CropScience Report 

No. MRID M004227-01-1.
MRID 49090502 CDPR IMI Strawberry

13

3. Krohn, J. 1993. Vapour Pressure Curve of lmidacloprid. Bayer CropScience Laboratory Project ID 

14 200 0804. Report No. M-004042-01-1.

4. Brungardt, Jaime 201 0. An Analytical Method for the Determination of Residues of lmidacloprid 

and its Metabolites lmidacloprid Olefin and 5-Hydroxy lmidacloprid in Bee Relevant Matrices 

Using LC/MS/MS. Bayer Report No. NT-005-P10-01.

5. Schoning, R. 1999. Residue Analytical Method for the Determination of Residues of lmidacloprid, 

Hydroxy-lmidacloprid, Olefin-lmidacloprid, YRC 2894, YRC 2894-Amide, and 4-Hydroxy-YRC 

2894-Amide in Plant Material by HPLC with Electrospray MS/MS Detection. Method No. 00573. 

Report No. MR-853/98.

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pesticide residues in human health food exposure assessments. EPA Docket #OPP-00570A.

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10. Lenz, C.A. 1993. Addendum 2. lmidacloprid and metabolites- freezer storage stability study in 

crops (what matrices, cottonseed, tomato, cauliflower, and lettuce). Bayer CropScience Report 

No. 103949-2. MRID 43197201.

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crops (what matrices, cottonseed, tomato, cauliflower, and lettuce). Bayer CropScience Report 

No. 103949-3. MRID 43487301.