MRID 49090504 CDPR IMI Citrus (2011)

1 1. STUDY INFORMATION

Sponsor: Bayer CropScience
2T.W. Alexander Drive Research Triangle Park,

NC USA 27709 Study Completion Date : March 30, 2011 Study Location: 1) Hemet, California 2) Lindcove Research and Extension Center 3) Ventura County, California 4) Temecula, California 5) Tulare County, California 6) University of California, Riverside Sponsor Study ID: EBNTL056

- 7 PC Code: 129099

GLP Status: Non

- GLP; Final protocol was submitted to CDPR for review. [CDPR study ID 253951 , Data Volume 51950

- 0756 , Tracking ID# 240317 ] Study Type: Non

- Guideline field residue study on Southern California Citrus Groves that had been previously treated with Imidacloprid to evaluate bee exposure.

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. STUDY VALIDITY

Guideline Followed: Non

- guideline study (final protocol submitted by CDPR)

Guideline Deviations: N/A

Other Deviations: N/A

Classification: Supplemental
Rationale: N/A Reparability: N/A

4. TEST MATERIAL CHARACTERIZATION

Test Material : 1) Admire Pro 2) Unknown Formulations Percent Active Ingredient: 1) 42.8% A.I. 2) Unknown

Description: 1) Suspension concentrate (SC) 2) Unknown Density: 1.41

- 1.54 g/mL

Material Source: Bayer Corporation Solubility: 0.51 to 0.61 g/L

CAS #: 138261

- 41

- 3 pH (24°C): 7.8

5. EXECUTIVE SUMMARY Reference Byrne, F.; Morse, J.; Visscher, P.; Grafton

- Cardwell, E.; Leimkuehler, W. (2011) Determination of exposure levels of honey bees foraging on flowers of citrus trees previously treated with imidacloprid. Project Number: EBNTL056/7, M/408424/012. Unpublished study prepared by University of California, Riverside. 70p. MRID 49090504 , CDPR Study I D 259131 , Data Volume 51950

- 0787 , Tracking ID# 246252MRID 49090504 CDPR IMI Citrus (2011)

2 A series of field investigations were conducted between 2008 and 2011 to determine to what extent honey bees foraging on citrus blossoms may be exposed to imidacloprid when citrus trees are treated with systemic applications (soil treatments) of this insecticide

.

The approach that was taken was to compare the imidacloprid residues in floral nectar with nectar extracted from the crops

, foraging honey bees and from stored nectar within their hives. Two experimental systems were established. First, honey bee colonies were confined within large t unnel cage enclosures where foraging access to treated trees was limited. S econd, honey bee colonies were situated in an open

- field system, in which hives were placed in a large acreage of commercial citrus that
had been treated with imidacloprid. In this second system, the foraging activity of the honey bees was not limited to any specific trees or to citrus.

In addition to the honey bee studies, the study quantifies the levels of imidacloprid in nectar from trees
that had been treated under a number of d ifferent scenarios. The intent was to d etermine residues in
trees treated in successive years to test for potential imidacloprid accumulation and persistence. For this, groves that were growing in different soil types were included because of the impact th at soil has on the availability of imidacloprid for uptake. The effect of differing application rate s were also
evaluated on imidacloprid residues in nectar.

The subject study report consists of five different trials that will make up the composition of this Data Evaluation Report. Detailed findings, study limitations , study validity and results from each trial are
found below.

6. 

### S AMPLE 

### C OLLECTION 

### , H ANDLING 

### , P ROCESSING

Nectar Collections by Hand

Nectar was sampled from individual flowers using a micro

- capillary tube inserted into a bulb dispenser. After insertion of the tip of the tube into the nectar at the base of the flower, the nectar was drawn into the tube by capillary action. The nectar was then transferred to an autosampler vial. The targe t volume for each sample was 150 μl. During field trips to collect the nectar, the samples were kept in an ice chest containing dry ice until they were stored in a

- 20°C freezer.

Nectar collections by Honey Bees

Nectar was collected from the crops of hon ey bees returning to their hives from foraging trips to determine the concentrations of imidacloprid and metabolites. Bees were intercepted at the entrance to the hives using a small net and were immediately transferred to a cooler containing dry ice to

an esthetize them. After 30 seconds in the cooler, individual bees were forced to regurgitate the contents of their crops by pressing gently on the lateral sides of their abdomen region (the gaster) with paddle forceps. The nectar formed a droplet at the top of their mandibles where it was collected using a

micro

- capillary tube. The nectar was transferred to an autosampler vial and then placed in a cooler with dry ice. For each sample it was necessary to composite nectar from several bees in order to meet the minimum target volume of 75 μl. At least 5 bees were used to prepare 1 sample and a maximum of 20 samples from each hive were collected.

Stored NectarMRID 49090504 CDPR IMI Citrus (2011)

3 In addition to the stomach nectar, nectar was also collected from deposits made to new comb within

eac h hive. A sample consisted of pooled nectar from comb cells near each other. Sufficient nectar was collected for residue analysis and to measure sugar concentration using a refractometer to provide information on possible changes in imidacloprid concentrat ion during conversion from nectar to honey. The target sample number was 10 samples from each hive.

7. 

### A NALYTICAL 

### M ETHODS

Nectar

Nectar collected from citrus trees (orange, mandarins and grapefruit) was analyzed by dilution with mobile phase containing the stable isotope internal standards. 50 μL of nectar was pipetted into an autosampler vial containing a 300 μL conical insert. 50 μL of mobile phase (9:1 water/methanol containing 10 mM NH 4 HCO 3 ) containing 10 ng/mL of the stable isotope internal standards was added and the sample mixed a couple times by pulling up and down with the Gilson Microman pipette. The final concentration in the diluted nectar of the internal standard was 5 ng/mL. The sa mples were analyzed by LC/MS/MS. Response ratios (NA/IS) were directly compared to a calibration curve having concentrations of 5 ng/mL for the internal standards and native analyte concentrations ranging from 0.1 to 100 ng/mL and adjusted for dilution, i. e., 50 μL of nectar diluted to 100 μL (2X dilution). Recoveries (QC) samples were prepared by diluting control nectar with the QC dilution solution as described.

Pollen

A 0.05 to 0.5 g sample of pollen was weighed into a 13 mL polypropylene conical scre w cap centrifuge tube. 1.5 mL of HPLC grade water (pesticide residue grade) was added and the pollen dissolved. 20 ng of the stable isotope internal standard mixture of imidacloprid, imidacloprid olefin and 5

- hydroxy imidacloprid was added followed by 4 mL of ACN. The tube was then shaken vigorously for one minute. Then 1 g of MgSO 4 (anhydrous) and 0.5 g NaCl was added and the tube again shaken and vortexed vigorously for 1 minute. The tubes were then centrifuged at 4000 RPM for 5 minutes using an Eppendorf 5810 R centrifuge.

The supernatant, nominally 4 mL, was decanted into another 13 mL centrifuge tube containing, 0.040 g

BONDESIL

- PSA and 170 g Mg SO 4 (anhydrous). The tube was shaken and vortexed vigorously for 1 minute. The tubes were centrifuged as be fore. A 1.0 mL portion of the supernatant (ACN) was transferred to a LC autosampler vial and the ACN was avaporated to dryness using a N

- Evap or Tubovap.
The residue was re

- dissolved in 1.0 mL of HPLC mobile phase (9:1 water/MeOH containing 10 mM

NH 4 HCO 3 ) in preparation for analysis by LC/MS/MS.

Recoveries (QC) samples (5 ppb) were prepared by fortifying control pollen (500 mg) with mixed native stds (25 μL of the 0.1 μg/mL mixed standard).

Imidacloprid, imidacloprid olefin and 5

- hydroxy imidacloprid wer e measured in nectar and pollen. Nectar was measured directly by dilution with HPLC mobile phase and the pollen was extracted using QuEChERS methodology. The final extracts were analyzed by LC/MS/MS employing stable isotope
internal standards. The Limit o f Detection (LOD) and Limit of Quantitation (LOQ) were calculated based on 3X and 10X, respectively, of the standard deviation of 4 QC recovery samples from stomach nectar atMRID 49090504 CDPR IMI Citrus (2011)

4 1 ppb. From this evaluation, the LOD and LOQ were calculated to be 0.018, 0.36 and 0.30 ppb (LOD) and 0.6, 1.2 and 1 ppb (LOQ) for imidacloprid, 5

- hydroxy imidacloprid, and imidacloprid olefin, respectively.

8. TRIALS

8 A

. TRIAL INFORMATION

Title: Tunnel Cage Trial Application Date : September 3, 2009 Sampling Date: April 24, 2010

Section of Study : Section 2 Trial Location: Lindcove Research and Extension Center (LREC)

TRIAL SUMMARY

The objective of this component of the study was to examine citrus groves that were treated with a soil application of imidacloprid systemic insecticide, to understand the levels of imidacloprid that occurred in (a) nectar extracted by hand from citrus flowers, (b) nectar collected by forager honey bees and transported back to the hive, and (c) nectar or "uncapped honey" deposited by bees in ce lls of the
Brood comb

.

Honey bee colonies were confined within tunnel cage enclosures, each containing 3 flowering citrus trees that had been treated with soil applications of systemic imidacloprid (Admire Pro®). Nectar was collected by hand from each tr ee within each tunnel cage. In addition, nectar was extracted from the stomachs of honey bees foraging within the tunnels so that a comparison could be made between hand

collected and honey bee

- collected nectar. At the end of the confinement period within the tunnels,
stored nectar was sampled from new comb that had been placed within each hive at the start of the exposure period. Four tunn els were constructed, providing three imidacloprid

- treated and one untreated control data set.

METHOD

A PPLICATION T IMING AND R ATES

Admire Pro® was applied at the maximum label rate of 14 fl oz per acre (0.104 fl oz per tree) on Sept. 3, 2009. Trees were pre

- irrigated for 2 hours prior to applications. The insecticide was applied to each tree using a watering can, taking care to apply the solution evenly within the irrigated area defined by the

s prinklers. Watering cans were used to administer the insecticide to the trees in order to ensure that the correct amount of active ingredient, as defined by the insecticide label, was delivered to each tree. Trees were irrigated for another 4 hours following completion of th e applications, and then subjected to the standard 8 hour, once

- per

- week irrigation regime during the first 4 weeks post

- treatment. Thereafter, trees were irrigated according to tensiometer measurements.

S TUDY S ITE L OCATION AND C HARACTERISTICS

This tria l was conducted at the Lindcove Research and Extension Center (LREC) in Exeter, California. The trees were Washington Parent Navels on C35 rootstock, which were planted in June 1992 (17 years old at the time of the study). The soil type at LREC is a loam s oil consisting of 15

- 25% clay and 00.5

- 1% organic matter. There were 134 trees per acre with a tree spacing of 18’ x 18’ in the 3.9 acre block. EachMRID 49090504 CDPR IMI Citrus (2011)

5 tree was irri gated by 2 sprinklers located on opposite sides of the trunk with 10.3 gph output on a weekly schedule.

The enclosures were constructed from transparent netting with a maximum light exclusion of 13%. The netting was supported on a frame constructed from 1" PVC tubing to provide a semi cylindrical tunnel that fully enclosed 3 citrus trees . There was sufficient clearance to allow movement of personnel between the citrus trees and the netting so that all sections of the trees could be used for nectar sampling. Tunnel dimensions were 26' x 96' x 16'.

The Italian honey bee, Apis mellifera ligustica, was used in the subject trial . When the trees were in full bloom, one small colony of bees (a nuclear hive consisting of 5 frames of comb, a queen, developing brood, and workers to cover about 4 frames) was introduced into each tunnel. Hives were initially placed in the tunnels at 8.00 a.m. on April 20 , 2010 . Due to heavy rainfall, bees were confined within the hives until the morning of April 22 , 2010 when the bees were released to begin foraging.

S AMPLING M ETHOD

Nectar was sampled directly from the flow er by hand using a micro

- capillary tube. The target volume for each sample was 150 μl, with nine composite nectar samples collected, three from each tree. Samples were also collected using honey bees that were contained over the three trees by a tunnel con structed from transparent netting (Combined Clear Net 13%) with 1” PVC tube frames. The bees were intercepted at the hive entrance and chilled with dry ice for 30 seconds. A composite sample from at
least 5 bees was collected. In addition, stored nectar wa s collected from new combs within each hive. A pooled sample was collected from cells near each other with a target of ten samples per hive. Nectar sugar analysis was measured by refractometry.

RESULTS: The mean residues of total imidacloprid in hand or bee collected citrus nectar ranged from 13.97

- 21.19 ppb, while mean residues in hive stored nectar ranged from 44.65

- 72.81 ppb. The highest residues were found in hive stored nectar, corresponding with the highest sugar concentration.

Table 1. Summary of imidacloprid residues in nectar collected from orange trees within four tunnel enclosures that had been treated the previous two years as a soil drench at the maximum labelled rate. Maximum application rate applied to individual trees on 9/3/2009.

Lindcov e Research and Extension Center (LREC) Spring 2010 Loam Soil [15

- 25% clay, 0.5

– 1% organic matter] Mean Residue Concentration (ppb) (minimum

– maximum)

Tunnel Hand Collected Nectar

N 1 = 9 [3 samples from each tree, 3 trees per tunnel] Sampling occurred 4/22/2010 Bee Collected Nectar

N 1 = 20 [one hive per tunnel, mean of 20 samples] Sampling occurred 4/22/2010 Uncapped Stored Nectar

N 1 = varies [one hive per tunnel, mean of up

to 10 samples] Sampling occurred 4/24/2010

IMI Total IMI 2 IMI Total IMI 2 IMI Total IMI 2

Control <1.0 <1.0 <1.0 <1.0 <1.0 <1.0

1 8.3 13.96 10.61 (5.6

– 21.22) 17.55 (9.17

– 37.12) 25.49 (19.71

– 36.06) 44.65 (35.40

– 62.75)MRID 49090504 CDPR IMI Citrus (2011)

6 Lindcov e Research and Extension Center (LREC) Spring 2010 Loam Soil [15

- 25% clay, 0.5

– 1% organic matter] Mean Residue Concentration (ppb) (minimum

– maximum)

Tunnel Hand Collected Nectar

N 1 = 9 [3 samples from each tree, 3 trees per tunnel] Sampling occurred 4/22/2010 Bee Collected Nectar

N 1 = 20 [one hive per tunnel, mean of 20 samples] Sampling occurred 4/22/2010 Uncapped Stored Nectar

N 1 = varies [one hive per tunnel, mean of up

to 10 samples] Sampling occurred 4/24/2010

IMI Total IMI 2 IMI Total IMI 2 IMI Total IMI 2 (2.86

– 13.64) (5.30

– 22.73)

2 7.64 (4.38

– 12.38) 14.01 (8.06

– 22.84) 8.97 (3.02

– 16.17) 15.08 (4.92

– 29.75) 27.33 (24.81

– 30.83) 49.65 (42.52

– 57.58)

3 12.81 (8.72

– 21.91) 21.19 (9.18

– 34.64) 8.00 (1.66

– 18.99) 13.38 (2.81

– 34.15) 40.12 (27.14

– 54.14) 72.81 (48.75

– 95.18)

Mean for
Tunnels 1

- 3 9.58 (7.64

– 12.81) 16.39 (13.96

– 21.19) 9.23 (8.00

– 10.61) 15.40 (13.38

– 17.55) 30.98 (25.49

– 40.12) 55.70 (44.65

– 72.81)

1 “N” is the total number of samples collected 2 “Total IMI” combines magnitude of residues of imidacloprid plus degradants IMI

- olefin and IMI

- 5

- OH

CONCLUSION TO TUNNEL CAGE

In this first trial, oranges (Washington Parent Navels on C35 rootstock) in a 3.9 acre block were treated

in the fall of 2009 with 14 fl oz per acre (the maximum current U.S. label rate). The trial was located at

the Lindcove Research and Extension Center (LREC) in Exeter, CA. The soil type at LREC is a loam soil consisting of 15

- 25% clay and 0.5

- 1% organic matter. Honey bee colonies were confined within tunnel cage enclosures, each containing 3 flowering citrus trees

.

Nectar was collected by hand from eac h tree within each tunnel cage. In addition, nectar was extracted from the stomachs of honey bees foraging within the tunnels so that a comparison could be made

between hand

- collected and honey bee

- collected nectar. At the end of the confinement period wit hin
the tunnels, stored nectar was sampled from new comb that had been placed within each hive at the

start of the exposure period.

The mean residues of total imidacloprid in hand or bee collected citrus nectar ranged from 13.97

- 21.19 ppb, while mean residues in hive stored nectar ranged from 44.65

- 72.81 ppb. The highest residues were found in hive stored nectar, corresponding with the highest sugar concentration.MRID 49090504 CDPR IMI Citrus (2011)

7 8 B . TRIAL INFORMATION

Title: Open Field Trial Application Date : Fall 2009 Sampling Date: April 25, 2010

Section of Study : Section 3 Trial Location: Lindcove Research and Extension Center (LREC)

TRIAL SUMMARY

Honey bee colonies were situated within a large area of treated commercial citrus. Within the area,
there were multiple citrus varieties, some weeds, but no other commercial crops. The bees were allowed to forage freely. Nectar was collected by hand from trees within several different blocks within the perceived foraging area. In addition, nectar was extracted from the stomachs of honey bees foraging within the citrus region so that a comparison could be made between hand

- collected and honey bee

collected nectar. Whereas in the tunnel study, hand

- collected and honey bee

- collected sources were controlled, the foragin g range of the honey bees was not controlled . At the end of the 3

- day foraging period, nectar was sampled from new comb that had been placed within each hive at the start of the
trial . Pollen traps were also included in the hives and these were operated fo r a 24

- hour period prior to the completion of the experiment.

The Italian honey bee Apis mellifera ligustica was also used in this study. Five large colonies consisting of
10 frames were situated in the citrus area on the evening of April 22. The bees wer e confined within the hives until the morning of April 23 when the bees were released to begin foraging. The larger hives used for the open field study were equipped with pollen traps that were set into operation for 24 hours beginning on April 24 , 2010 an d concluding on April 25 , 2010

.

Hand

- collect nectar, bee

- collected nectar, and stored nectar were collected in the same way as in the tunnel trial. Pollen samples were also collected from pollen traps within a 24

- hour collection period prior to the comple tion of the experiment. Pollen samples from only two hives were available for residue analysis. It was found that the pollen load in each trap was very low given the 24

- hour collection period.

Pollen sources were not distinguished for residue analysis. U pon visual examination, there were clearly several pollen sources within the traps indicating that the bees were not foraging exclusively on citrus
flowers.

METHOD

A PPLICATION T IMING AND R ATES

All citrus groves in a radius of 1

- 2 miles on and around the LREC were treated for aphids with imidacloprid in the fall of 2009. A very large contiguous area of citrus had been treated in 2009 with various imidacloprid commercial formulations at half the m aximum field rate (0.25 lb. a.i. per acre regardless of the commercial formulations used). A large block of citrus was selected in the center of such treatments for this honey bee study with the knowledge that bees can forage very long distancesMRID 49090504 CDPR IMI Citrus (2011)

8 from their hives. Although there were other blooming plants in the vicinity of this block that honey bees could have foraged from, there were no nearby agricultural crops other than citrus. All nearby citrus
within 1 mile had been treated with the half rate of imida cloprid the previous fall.

S TUDY S ITE L OCATION AND C HARACTERISTICS

The Lindcove Research and Extension Center (LREC) contains much of the collection of important rootstock and scions for the Citrus Clonal Protection Program (CCPP) and research projects for the S tate of California. In 2009, a higher than normal number of trees in the region became infected with Citrus tristeza virus (CTV). CTV is a pathogen vectored by several species of aphids. The LREC has soils
characterized as l oam soils (15

- 25% clay, 0.5

- 1% organic matter).

RESULTS:

In this trial, the mean residues of total imidacloprid in hand collected citrus nectar ranged from 1.81

- 9.42 ppb while the mean residues in nectar extracted from foraging honey bees ranged from 1.11

- 7.59 ppb. Also, the mean residues of total imidacloprid in hive stored nectar ranged from 6.95

- 11.63 ppb. Moreover, the maximum mean residues for hive pollen we re found to be 10.2 ppb while the average residue measurement was 9.39 ppb.

There appears to be large variations in the level of residues among citrus varieties. Due to the limited samples and information provided, it is unknown if this variation was due to citrus varieties or other factors, including age of the trees or level or irrigation.

Table 2. Summary of imidacloprid residues in hand collected nectar randomly selected within six blocks of citrus surrounding the location of five honey bee hives. Co mmercial citrus trees were treated in the Fall of 2009 at half (1⁄2X) the labelled rate.
Lindcove Research and Extension Center (LREC) Spring 2010 Loam Soil [15

- 25% clay, 0.5

– 1% organic matter] Mean Residue Concentration (ppb) (minimum

– maximum)

Citrus Variety Hand Collected Nectar

N 1 IMI 5

- OH Olefin Total IMI 2

Valencia Oranges

– South East 10 <1.0 (<1.0

– 1.18) <1.0 <1.0 1.81 (1.15

– 2.48)

Valencia Oranges

– South West 5 2.73 (1.53

– 3.55) <1.0 <1.0 (<1.0

– 2.22) 5.18 (3.17

– 6.21)

Navel Oranges

– North East 4 1.79 (<1.0

– 2.48) <1.0 <1.0 (1.02

– 1.95) 3.51 (2.11

– 4.42)

Navel Oranges

– South East 4 3.51 (2.03

– 6.15) <1.0 <1.0 (<1.0

– 1.73) 4.87 (2.64

– 8.42)

Tangerines 10 6.82 (2.84

– 13.26) <1.0 1.99 (<1.0

– 3.67) 9.42 (4.03

– 18.28)

Young Oranges 5 2.76 (1.34

– 4.21) <1.0 <1.0 (<1.0

– 1.11) 3.73 (1.76

– 5.88)

Means 3.29 (<1.0

– 6.82) <1.0 1.19 4.75 (1.81

– 9.42)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues o f imidacloprid plus degradates IMI

- olefin and IMI

- 5

- OHMRID 49090504 CDPR IMI Citrus (2011)

9 Table 3. Summary of imidacloprid residues in nectar collected from free

- ranging honey bees in
commercial citrus trees treated in the fall of 2009 at half the labelled rate.
Lindcove Research and Extension Center (LREC) Spring 2 010 Loam Soil [15

- 25% clay, 0.5

– 1% organic matter] Mean Residue Concentration (ppb) (minimum

– maximum)

Hive Bee Collected Nectar

N 1 = varies [mean of up to

20 samples] Sampling occurred 4/23/2010 Uncapped Stored Nectar

N 1 = varies [mean of up to

10 samples] Sampling occurred 4/25/2010 Hive Pollen [Each value represents a single measurement for the analysis of the entire pollen retrieved from traps within individual hives] Sampling occurred 4/25/2010

IMI Total IMI 2 IMI Total IMI 2 IMI Total IMI 2

1 1.05 (<1.0

– 2.43) 2.11 (<1.0

– 5.07) 6.25 (4.73

– 8.67) 11.63 (9.31

– 15.53) N/A

2 3.77 (<1.0

– 9.31) 7.59 (1.16

– 16.02) N/A N/A

3 1.94 (<1.0

– 7.56) 3.59 (<1.0

– 12.16) N/A N/A

4 <1.0 (<1.0

– 2.69) 1.11 (<1.0

– 3.71) 3.23 (2.47

– 4.98) 6.96 (4.47

– 9.25) 6.58 8.57

5 1.94 (<1.0

– 4.2) 3.23 (<1.0

– 7.29) 5.98 (3.81

– 8.18) 10.60 (8.13

– 13.98) 5.84 10.2

Mean for

Hive 1

- 5 1 .88 (<1.0

– 3.77) 3.53 (1.11

– 7.59) 5.15 (3.23

– 6.25) 9.72 (6.96

– 11.63) 6.21 9.39

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues o f imidacloprid plus degradates IMI

- olefin and IMI

- 5

- OH

CONCLUSION TO OPEN FIELD TRIAL

The second trial, also at the LREC, consisted of an open field area with multiple citrus varieties. A very large contiguous area of citrus had been treated in 2009 with various imidacloprid commercia l

formulations at 0.25 lbs. a

. i

. /acre (half the maximum label rate).

Five large 10

- frame colonies were situated in the citrus orc hard area. Pollen was successfully collected from only two of five hives via pollen traps that were operated for 24 hours. Nectar was either hand collected from randomly selected citrus trees, extracted from honey stomachs of honey bees allowed to forage i n the treated orchard and intercepted at the hive, and from the hive as uncapped honey. Nectar sugar analysis was measured by refractometry.

In this trial, the mean residues of total imidacloprid in hand collected citrus nectar ranged from 1.81

- 9.42 ppb w hile the mean residues in nectar extracted from foraging honey bees ranged from 1.11

- 7.59 ppb. Also, the mean residues of total imidacloprid in hive stored nectar ranged from 6.95

- 11.63 ppb.MRID 49090504 CDPR IMI Citrus (2011)

10 Moreover, the maximum mean residues for hive pollen were found to be 10.2 ppb while the average residue measurement was 9.39 ppb.

8 C . TRIAL INFORMATION

Title: One Year Nectar Collections Application Date : September 3 and 9, 2009 Sampling Date: Spring 2010

Section of Study: Section 4 Trial Location: Lindcove Research and Extension Center (LREC) and Bakersfield, CA

TRIAL SUMMARY

As research into the potential uses of imidacloprid for the management of Asian Citrus Psylliid ( Diaphorina citri ), different imidacloprid rates at several locations within the citrus producing areas of
southern and central California were evaluated. Nectar from trees treated with either the maximum
la b el rate (1X) or double the maximum label rate (2X) of imidacloprid (Admire Pro) were evaluated to
determine whether there was a r elationship between application rates and residue levels. For this component of the trial, all data were derived from analysis of hand

- collected nectar.

METHOD

A PPLICATION T IMING AND R ATES

The treatments were applied by water can on September 3, 2009 and September 8, 2009 at the LREC
and B akersfield sites, respectively. Citrus trees were treated with Admire Pro at the maximum label rate (1X=14 fl oz/ acre) and double the maximum label rate (2X= 28 fl oz/acre) in the Fall of 2009. Residues of imidacloprid, 5

- hydroxy imidacloprid, and imidacloprid olefin were then analyzed from hand

- collected nectar samples.

S TUDY S ITE L OCATION AND C HARACTERISTICS

For this trial, Lindcove Resear ch and Extension Center (LREC) and a commercial citrus farm in Bakersfield were used to collect data from. The LREC trees were in the same block of navel oranges that were used for the honey bee trial. At the commercial citrus farm in Bakersfield, a 3.9 ac re block of Valencia oranges that were planted in 1985 were provided. There were 100 trees per acre compared to the 134 trees
were acre at the LREC site. The LREC has soils classified as loam soil (15

- 25% clay, 0.5

- 1% organic matter). Soil characteristics were not provided in the study for Bakersfield.

RESULTS:

The 1X label rate treatments resulted in an average residue measurement of 19.30 ppb in nectar at the Bakersfield grove and 16.30 ppb at the LREC. While the 2X label rate treatments resulted in an average residue measurement of 47.36 ppb at the Bakersfield grove and 35.83 ppb at the LREC.MRID 49090504 CDPR IMI Citrus (2011)

11 Residues of imidacloprid, 5

- hydroxy Imidacloprid and imidacloprid olefin were higher in nectar sampled from the trees treated with the 2X label rate compared with the 1X label rate, with the ca

. two fold difference in residue levels reflecting the twofold difference in application rates. The imidacloprid and total residues were lower at the LREC site. The most likely reason for this difference is the higher tree

den sity at the LREC site. Since the insecticide was applied on a per acre basis (1X=14 fl oz./acrea and 2X=28 fl oz./acre), the amount of active ingredient per tree would have been higher at the Bakersfield site and
this could, therefore, account for the high er residues in the nectar.

Table 4. Summary of imidacloprid residues in hand collected nectar resulting from a soil treatment at maximum label rate (1X) and twice maximum label rate (2X). Application made by watering can to
individual trees in Bakersfield on 9/8/2009 and LREC on 9/3/09.

Spring 2010 Mean Residue Concentration (ppb) (minimum

– maximum)

Location Citrus Variety Rate Hand Collected Nectar (N 1 = 10)

IMI 5

- OH Olefin Total IMI 2

Bakersfield Valencia Oranges (soil type unknown) 1X 12.13 (3.62

– 18.82) 2.53 (1.10

– 3.61) 4.64 (1.58

– 6.93) 19.30 (6.30

– 29.10)

2X 31.10 (9.70

– 92.05) 5.67 (1.88

– 15.95) 10.60 (3.12

– 31.15) 47.36 (14.70

– 139.15)

LREC Navel Oranges

[Loam Soil] 1X 9.51 (3.31

– 15.49) 3.09 (1.18

– 5.39) 3.70 (1.56

– 6.04) 16.30 (6.81

– 26.45)

2X 22.23 (5.98

– 43.94) 6.70 (2.25

– 11.74) 6.89 (1.70

– 13.06) 35.82 (9.93

– 68.30)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues of imidacloprid plus degradates IMI

- olefin and IMI

- 5

- OH.

CONCLUSION TO ONE YEAR NECTAR COLLECTIONS

The third trial was conducted at the LREC and a commercial citrus farm in Bakersfield, CA. Navel oranges (LREC) and Valencia oranges (Bakersfield) were treated with either 1X (the maximum label rate) or 2X the label rate in Fall 2009. Hand collected nectar was quantified in Spring 2010.

Residues of imidacloprid, 5

- hydroxy Imidacloprid and imidacloprid olefin were higher in nectar sampled from the trees treated with the 2X label rate compared with the 1X label r ate, with the ca

. two fold difference in residue levels reflecting the twofold difference in application ratesMRID 49090504 CDPR IMI Citrus (2011)

12 8 D. TRIAL INFORMATION

Title: Citrus Nectar Collected from Field Sites Treated in Successive Years

Application Years: 2008 & 2009 Sampling

Date: Spring 2010

Section of Study: Section 5 Trial Location: 1) Hemet, California 2) Temecula, California 3) Lindcove Research and Extension Center (LREC)

TRIAL SUMMARY

The objective of this trial was to determine if imidacloprid residues in nectar could persist and/or accumulate in situations where the insecticide was used on the same trees in successive years. Residues in nectar sampled from citrus trees that had been t reated in 2 successive years were quantified. Sites were chosen with different soil types for the sampling program. Imidacloprid uptake into trees can be affected by soil type and this could potentially affect the residues in nectar. All analyses were cond ucted on nectar that was extracted by hand.

METHOD

A PPLICATION T IMING AND R ATES

Hemet. The first treatments with Admire Pro were applied in Fall 2008 and the second treatments were applied in Fall 2009. The intent was to evaluate both the 1X label rate and the 2X label rate in all possible application sequences. In order to do this, the block was subdivided into four 2.5 acre plots so that the following sequences of treatments could be established: 1X (Fall 2008) followed by 1X (Fa ll 2009), 1X (Fall 20

. 08) followed by 2X (Fall 2009), 2X (Fall 2008) followed by 1X (Fall 2009), and 2X (Fall 2008) followed by 2X (Fall 2009). Nectar Samples were taken from trees chosen at random from within each plot.

Temecula. Six commercial orchards in Temecula, California that had been treated both years of 2008
and 2009 in an area

- wide control program were used in this study. The sites consisted of five Grapefruit
and one Valencia orange orchard , which were first treated bet ween June 7 and June 16, 2008 and then treated a second time between April 7 and May 27, 2009. The maximum label rate (1X) for Admire Pro
was used i n both treatment year s.

Lindcove Research and Extension Center. Five citrus blocks at the LREC had been tre ated with imidacloprid for two successive years ( 2008 and 2009 ) . The sites consisted of four navel oranges and one Valencia orange orchard, which were first treated on September 17 and September 18, 200 8 and then
treated a second time between September 10 and September 16, 2009. The maximum label rate (1X) for Admire Pro was used in both treatment years.

S TUDY S ITE L OCATION AND C HARACTERISTICSMRID 49090504 CDPR IMI Citrus (2011)

13 Hemet. The trial was conducted in a 10 acre block of 50 year old Ruby Red Grapefruit trees on Troyer Rootstock. Soil type was sandy loam and irrigation was scheduled weekly according to tensiometer

measurements. Nectar samples were collected from treated trees at random within the commercial grapefruit orchard.

Temecula. A total of 68.25 acres of Star Ruby Grapefruit and 1.65 acres of Valencia oranges were treated with imidacloprid for two successive years. The soil type at all six site locations is considered to be Sandy

Loam. At each site, two trees were randomly selected for hand

- collected nectar sampling.

Lindcove Research and Extension Center. Five citrus blocks with 2 successive years of imidacloprid applications were chosen from the LREC. These blocks were independent from the block used for the tunnel study. The soil type at all five site locations is considered to be Loam Soil. A total of 15.44 acres of navel oranges and 2.5 acres of Valencia oranges were treated with imidacloprid. Within each block, 2 trees were randomly selected for hand

- collected nectar sampling

.

RESULTS:

Imidacloprid nectar residues in Hemet were lowest in the 1X

– 1X label rate treatment with an average residue measurement of 23.84 ppb and highest in the 2X

– 2X label rate treatment with an average residue measurement of 58.66 ppb. Following the 1X

– 1X label rate treatments in two succes sive years at Temecula and LREC, an average residue measurement of the nectar residues were 5.15 ppb and 11.16 ppb, respectively . The maximum mean residues of 21.65 ppb were measured at LREC.

The imidacloprid and total residues measured in the nectar sampled from trees treated with the 1X

- 2X label rate sequence were approximately 2

- fold higher than those measured for the 1X

- 1X la bel rate treatments, suggesting that the residue levels reflected the rate of imidacloprid used in the most recent application. Thus, residues for the 1X

- 1X and 2X

- 1X rate sequences were not significantly different, and

data for the 1X

- 2X and 2X

- 2X rate s equences were not significantly different. While the means for the 2X treatments exceeded the 1X measurements by more than twofold, the statistical analysis shows that imidacloprid and its metabolites did not accumulate significantly from one year to the n ext.

Data from six commercial groves in Temecula that were treated in two successive years (2008 and 2009) with the maximum label rate of imidacloprid (1X

- 1X) were completed by June each year. The highest total residues (9.56 ppb and 15.53 ppb for the two trees sampled) were measured at Site 6, where the youngest trees (seven years of age) used in the sampling program was located. The overall means for the Temecula samples were lower than those measured for the Hemet site where the 1X rate was applied for two successive years.

Data from five blocks at the LREC that were treated in two successive years (2008 and 2009) with the label rate of imidacloprid (1X

- 1X) had higher residues than those measured at the Temecula site, possibly reflecting the later timin g of treatments. Despite the higher values at the LREC site, the residues were still lower than those measured for trees at Hemet. The major difference between the LREC and Hemet sites is the soil type and it seems that the lighter and sandier soil at Heme t allowed better uptake of imidacloprid into the trees resulting in higher residues in nectar the following spring.MRID 49090504 CDPR IMI Citrus (2011)

14 Table 5

. Summary of imidacloprid residues in hand collected nectar of Ruby Red grapefruit trees resulting from two successive year soil treatments at maximum label rate (1X) and twice maximum label rate (2X) in Fall 2008/Fall 2009.

Hemet Site Spring 2010 [Sandy Lo am] Mean Residue Concentration (ppb) (minimum

– maximum)

Rate Hand Collected Nectar

N IMI 5

- OH Olefin Total IMI 2

1X

– 1X 10 16.07 (9.88

– 25.67) 5.05 (3.62

– 6.43) 2.72 (1.57

– 4.00) 23.84 (15.57

– 35.47)

1X

– 2X 9 35.13 (13.28

– 63.60) 9.70 (6.70

– 12.33) 6.04 (3.77

– 9.31) 50.87 (27.54

– 85.03)

2X

– 1X 7 14.50 (11.77

– 22.66) 4.78 (3.63

– 7.49) 2.44 (1.73

– 3.66) 21.73 (17.62

– 33.81)

2X

– 2X 7 41.41 (28.62

– 62.67) 10.78 (7.14

– 13.56) 6.47 (4.38

– 10.48) 58.67 (40.14

– 86.71)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues of imidaclopr id plus degradates IMI

- olefin and IMI

- 5

- OH

.

Table 6

. Summary of imidacloprid residues in hand collected nectar sampled in Spring 2010 from citrus

trees receiving a soil treatment at maximum label rate (1X) in successive years 2008 and 2009.
Spring 2010 Mean Residue Concentration (ppb) (minimum

– maximum) Sampling occurred 4/2010

Location Rate N 1 Hand Collected Nectar

IMI 5

- OH Olefin Total IMI 2

Temecula 1X

– 1X 11 3.17 (<1.0

– 10.60) <1.0 (<1.0

– 1.18) 1.48 (<1.0

– 3.76) 5.15 (<1.0

– 15.54)

LREC 1X

– 1X 9 6.51 (<1.0

– 13.65) 1.80 (<1.0

– 5.40) 2.86 (<1.0

– 8.42) 11.17 (1.53

– 21.64)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues o f imidacloprid plus degradates IMI

- 5

- OH and IMI

- olefin

CONCLUSION FOR FIELD SITES TREATED IN SUCCESSIVE YEARS

The fourth trial was conducted to determine if imidacloprid residues in nectar could accumulate from year to year following successive year applications at three different locations (Hemet, Temecula, and LREC). Hand collected nectar samples were obtained with either 1X or 2X soil applications were made in two successive years (2008, 2009) prior to sa mpling during bloom 2010.

I midacloprid residues at the Hemet site appear to be a function of the rate applied at the most recent application only, with no evidence of carryover from previous years

. The overall means for the Temecula samples were lower than those measured for the Hemet site where the 1X rate was applied for two
successive years. Data from five blocks at the LREC that were treated in two successive years (2008 and 2009) with the label rate of imidacloprid (1X

- 1X) had higher residues than those measured at theMRID 49090504 CDPR IMI Citrus (2011)

15 Temecula site, possibly reflecting the later timing of treatments. Despite the higher values at the LREC site, the residues were still lower than those measured for trees at Hemet. The major difference

between the LREC and Hemet sites is the soil type and it seems that the lighter and sandier soil at Hemet allowed better uptake of imidacloprid into the trees resulting in higher residues in nectar the following spring.

8 E . TRIAL INFORMATION

Title: Citrus Nectar Collection from Field Sites Treated in Successive Years

Application Years: 2008, 2009 and 2010 Sampling

Date: Spring 2011

Section of Study : Appendix B (Supplemental) Trial
Location: 1) Tulare County, California 2) Temecula, California 3) Lindcove Research and Extension Center (LREC) 4) Ventura County, California 5) University of California,
Riverside 6) Hemet, California

TRIAL SUMMARY

The objective of this trial was to determine if residues of imidacloprid and its important metabolites could persist and/or accumulate in nectar in situations where the insecticide was used on the same

trees in successive years. Also, because imidacloprid uptake into trees can be affected by soil type, sites were chosen to reflect the variety of soil types where citrus is gown in California. In section 3 of this Data Evaluation Report, data and information was provided for several sites where citrus was gro wn in soils that ranged from sandy loam to loam. To expand on the previous trial, this study will include data
and information on heavi er clay soils and lighter soils. Nectar was extracted from flowers by hand at all sites during bloom and imidacloprid, im idaclop rid olefin and 5

- hydroxy imidacloprid were quantified by LC/MS/MS.

METHOD

A PPLICATION T IMING AND R ATES

Tulare County. Five of the citrus sites had been treated with the full label rate of imidacloprid for at least 3 previous years. The sixth citrus site was treated with the full label rate of imidacloprid for 2 successive years. Two composite nectar samples were collected fro m each grove and all nectar samples were hand

collected.

Temecula Valley. Nectar samples were hand

- collected from six groves where the trees have been treated for three successive years with the full label rate of imidacloprid.

Lindcove Research and Extension Center. Nectar samples were hand

- collected from five citrus blocks at the LREC that had been treated with the full label rate of imidacloprid for three successive years ( September 2008, 2009, and 2010).MRID 49090504 CDPR IMI Citrus (2011)

16 Ventura County. Nec tar samples were hand

- collected from a lemon grove where the trees had been treated with the full label rate of imidacloprid at different timings during the season. The treatment timings were in May, July and September of 2010. The subject grove had not be en treated in 2009. Two composite nectar samples were collected from trees treated at application timing 1 and 3, while one composite nectar sample was collected from trees treated at application 2.

University of California, Riverside. In October of 2010, n ectar samples were collected from a citrus block where the trees had been treated with the full label rate of imidacloprid. Sixteen composite samples
were collected from the trees.

Hemet. In the previous trial titled “ Citrus Nectar Collected from Field Sites Treated in Successive Years” (Section 5 of study report), data was provided for a grapefruit grove that had been treated in successive years (Fall 2008 nad Fall 2009) with different combinations of application rates. The initial trial began
with eit her a 1X label rate of imidacloprid (Admire Pro at 14 fl oz/ acre) or a 2X label rate (Admire Pro at 28 fl oz/ acrea). In 2009, the same trees were treateed to give different treatment rate scenarios. To expand on the subject trial, an additional year of t reatment was provided to the trees in 2010.

S TUDY S IT E L OCATION AND C HARACTERISTICS

Table 7

. Site location with information regarding soil type and treated commodity.

S ITE AND C OMMODITY I NFORMATION
T EMELCULA S OIL T YPE C OMMODITY
1 F ALLBROCK R OCKY S ANDY L OAM S TAR R UBY G RAPEFRUIT
2 F ALLBROCK R OCKY S ANDY L OAM S TAR R UBY G RAPEFRUIT
3 F ALLBROCK R OCKY S ANDY L OAM V ALENCIA O RANGE
4 F ALLBROCK R OCKY S ANDY L OAM S TAR R UBY G RAPEFRUIT
5 F ALLBROCK R OCKY S ANDY L OAM S TAR R UBY G RAPEFRUIT
6 G REENFIELD S ANDY L OAM S TAR R UBY G RAPEFRUIT
T ULARE C OUNTY
1 P ORTERVILLE C LAY T ANGELOS
2 C ENTERVILLE C LAY N AVEL O RANGES
3 P ORTERVILLE C LAY N AVEL O RANGES
4 P ORTERVILLE C LAY N AVEL O RANGES
5 P ORTERVILLE C LAY N AVEL O RANGES
6 P ORTERVILLE C LAY V ALENCIA O RANGES
O THER S ITES
L INDCOVE R ESEARCH AND E XTENSION
C ENTER S AN J OAQUIN L OAM N AVEL AND V ALENCIA O RANGES

U NIVERSITY OF C ALIFORNIA
, R IVERSIDE A RLINGTON L OAM V ALENCIA O RANGES

V ENTURA C OUNTY M OCHO L OAM L EMON

RESULTS:

Total mean residues in nectar of imidacloprid from trees treated three years in a row at the Temecula site ranged from 1.02 to 5.91 ppb with an average residue measurement of 2.57 ppb. Mean nectar residues from Tulare County ranged from 0.29 to 4.21 ppb with an average residue measurement ofMRID 49090504 CDPR IMI Citrus (2011)

17 1 .54 ppb. Total mean nectar residues from trees at the LREC with a loam soil ranged from 0.52 to 23.95 ppb with an average residue measurement of 4.55 ppb. Total mean nectar residues from the UCR site with a loam soil ranged from 0.83 to 13.88 ppb with an average residue measurement of 3.68 ppb. Imidacloprid nectar residues from Ventura County sites treated at various times during 2010 were all less than 1 ppb regardless of the application timing. Following three years of treatments at the Hemet site at various application rates, the average residue measurement in nectar for the 1X

- 1X

- 1X treatment regimen was 24.40 ppb. The average residue measurement following the third year of treatment for sites treated once per year with 2X the label rate (2X

- 2X

- 2X) was 44.81 ppb. For t he 1X

- 2X

- 0X and 2X

- 1X

0X treatments the average residue measurement was 31.67 and 32.97 ppb. The residues following three years of applications at 2X the maximum label rate were slightly lower than residues after just two

years.

Table 8 . Summary of imidacl oprid residues in hand collected nectar sampled in Spring 2011 from citrus trees receiving a soil treatment at maximum label rate (1X) in successive years 2008, 2009, and 2010.
Spring 2011 Mean Residue Concentration (ppb) (minimum

– maximum)

Location Rate N 1 Hand Collected Nectar

IMI 5

- OH Olefin Total IMI 2

Temecula 1X

– 1X

– 1X 12 1.68 (<1.0

– 3.48) <1.0 <1.0 (<1.0

– 1.62) 2.58 (1.01

– 5.91)

LREC 1X

– 1X

– 1X 10 3.50 (<1.0

– 16.87) <1.0 (<1.0

– 3.88) <1.0 (<1.0

– 3.20) 4.95 (<1.0

– 23.95)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues of imidacloprid plus degradates IMI

- olefin and IMI

- 5

- OH

Table 9

. Supplement to Table E

- 10. Summary of imidacloprid residues in hand collected nectar resulting
fro m successive year soil treatments at maximum label rate (1X), twice maximum label rate (2X), and no application (0X) in Fall 2008/Fall 2009/Fall 2010.

Hemet Site Spring 201 1 [Sandy Loam] Mean Residue Concentration (ppb)

( minimum

– maximum )

Rate Hand Collected Nectar (N 1 = 10)

IMI 5

- OH Olefin Total IMI 2

1X

– 1X

– 1X 19.68
( 12.26

– 33.82 ) 3.13
( 2.02

– 4.31 ) 1.59
( <1.0

– 4.96 ) 24.40
( 17.56

– 39.86 )

1X

– 2X

– 0X 26.01
( 23.05

– 30.00 ) 3.93
( 3.35

– 4.37 ) 1.73
( 1.44

– 1.92 ) 31.67
( 28.97

– 36.27 )

2X

– 1X

– 0X 27.02
( 20.01

– 33.45 ) 3.87
( 2.28

– 5.43 ) 2.08
( 1.51

– 3.11 ) 32.97
( 25.12

– 41.99 )

2X

– 2X

– 2X 36.86
( 26.67

– 41.92 ) 5.18
( 3.86

– 5.76 ) 2.77
( 2.27

– 3.16 ) 44.81
( 32.80

– 50.35 )

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues of imidacloprid plus degradates IMI

- olefin and IMI

- 5

- OHMRID 49090504 CDPR IMI Citrus (2011)

18 Table 10 . Information on trees used for hand collected nectar collected from six commercial orchards in Tulare County during bloom in Spring 2011 afte r three successive years of imidacloprid application for control of glassy

- winged sharpshooter 2008, 2009, 2010.

T ulare County [ Porterville Clay

– 40% clay ]

S pring 2011

Site Citrus Variety 2008

Treatment

Date 2009

Treatment

Date 2010

Treatment

Date

1 Tangelos Not treated 6/16/2009 5/21/2010

2 Navel Oranges 5/22/2008 6/29/2009 6/18/2010

3 Navel Oranges 7/8/2008 6/18/2009 6/9/2010

4 Navel Oranges 5/17/2008 6/18/2009 6/6/2010

5 Navel Oranges 5/21/2008 6/29/2009 6/15/2010

6 Valencia Oranges 7/3/2008 6/26/2009 6/16/2010

Table 11 . Information on trees used for hand collected nectar collections during bloom in Spring 2011 after three successive years of imidacloprid application at the label rate 2008, 2009, 2010.

Temecula [Sandy Loam] Spring 2011

Site Citrus Variety 2008

Treatment

Date 2009

Treatment

Date 2010

Treatment

Date

1 Star Ruby Grapefruit 6/7/2008 5/27/2009 5/22/10

2 Star Ruby Grapefruit 6/9/2008 4/13/2009 6/11/10

3 Valencia Orange 6/6/2008 4/7/2009 6/12/10

4 Star Ruby Grapefruit 6/9/2008 4/21/2009 5/17/10

5 Star Ruby Grapefruit 6/7/2008 4/10/2009 6/2/10

6 Star Ruby Grapefruit 6/16/2008 4/17/2009 5/14/10

LREC [Loam Soil] Spring 2011

Site Citrus Variety 2008

Treatment

Date 2009

Treatment

Date 2010

Treatment

Date

1 Atwood Navel 9/18/2008 9/10/2009 9/13/2010

2 Atwood Navel 9/17/2008 9/10/2009 9/10/2010

3 Caracara Navel 9/18/2008 9/16/2009 9/09/2010

4 Parent Navel 9/18/2008 9/16/2009 9/09/2010

5 Red Valencia 9/17/2008 9/14/2009 9/13/2010MRID 49090504 CDPR IMI Citrus (2011)

19 Table 12. Summary of imidacloprid residues in hand collected nectar sampled in Spring 2011 from citrus trees receiving a soil treatment at maximum labelled rate as part of the area side control program for glassy

- winged sharpshooter in successive years 2008, 2009 and 2010. Spring 2011

Mean Residue Concentration (ppb)

(minimum

– maximum)

Location Rate N 1 Hand Collected Nectar

IMI 4/5

- OH Olefin Total IMI 2

Tulare County 1X 3

– 1X

– 1X 12 1.29
(<1.0

– 3.31) <1.0 <1.0 1.70
(<1.0

– 4.21)

1 “N” is the total number of samples collected

2 “Total IMI” combines magnitude of residues of imidacloprid plus IMI

- olefin and IMI

- 5

- OH

3 One site did not receive an application in 2008.

CONCLUSION

In 2011, the researchers followed up with a third year of treatments at the Temecula, LREC, and Hemet sampling sites. Nectar was again collected from six groves previously treated in Temecula where the soil type is sandy loam and five citrus blocks at the LREC with a loam soil (20% clay).

In addition, sites were added at University of California, Riversid e (UCR), Ventura County and Tulare County to address different soil types not previously represented. Nectar was collected from six citrus groves in Tulare County grown in Porterville clay (clay content 40%). Of these six sites, five had been

treated with 1X imidacloprid for the past three years and the remaining site was treated similarly the past two years. A new site in Ventura County with a soil consisting of 23% clay/35% sand was sampled following applications at the full label rate of imidacloprid at different times during the season. The treatment timings for this site were May, July and September 2010 and untreated in 2009. Also, a citrus block from the farm at UCR, where the soil type is loam, was treated in October 2010 and sampled in

2011.

In Tem ecula and Tulare County, the 2010 treatments at the 1X label rate were made in mid

- May to mid

June. The LREC and UCR 2010 treatments at 1X label rate were made in September and October.

Treatments at the four Hemet sites were 1X

- 1X

- 1X, 1X

- 2X

- 0X, 2X

- 1X

- 0X, or 2X

- 2X

- 2X representing years 2008, 2009 and 2010, where 1X

- 1X

- 1X represents a single application at the maximum label rate per year for three consecutive years.

9. STUDY VALIDITY/CLASSIFICATION AND STUDY LIMITATIONS

Classification/Utility for Bee Risk Assessment . This study is classified as supplemental for use in risk

assessment d ue to no pollen data available and a potential underestimation of a worst case scenario due to current labels not restricting pre bloom and during bloom applications whereas t his study done post bloom. The study results characterize expected imidacloprid residues in citrus nectar from applications in various soils ranging from fine to coarse and following different application rates andMRID 49090504 CDPR IMI Citrus (2011)

20 application timing in California. These r esults may not extrapolate directly to expected results in other regions of the U.S.

Concentrations in nectar extracted from the stomachs of free

- ranging bees (open field study) were somewhat lower than samples collected directly from flowers of nearby trees

. This may reflect a

" dilution effect " from bees foraging on other (untreated) flower types

. The few pollen samples obtained during the open field study had imidacloprid concentrations roughly equal to the nectar sampled from

the same hives. Concentra tions in flower nectar samples appear to be linearly related to the application
rate, based on ca. twofold increases in residue levels with doubling the application rate in the Hemet

trials.

Temporal Variability in Residues. Nectar samples were obtained f rom two locations (citrus blocks in the Temecula region and at LREC) where the 1X soil application rate of imidacloprid had been made in two successive years (2008, 2009) prior to sampling in April 2010. Residue levels at these 11 sites averaged 8 ppb and ranged from 1 to 18 ppb. The application timing (May, July, September, October) appears to be an important factor in determining residue levels in flower nectar the following year particularly for sites planted to coarse soils which consistently yielded t he higher imidacloprid residues. Fall (Sept) applications resulted in about twofold higher residue concentrations than spring (April

- June) applications

.

Spatial Variability in Residues. The six locations for the citrus trials were in relatively close prox imity. Soil types reflect sandy loam, loam or clay compositions (20

- 40% clay) and low organic carbon content (0.35

- 1.9%). Weather conditions (temperature and precipitation) were similar across the three trials. 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 U.S. may affect accumulation of total imidacloprid in pollen and nectar.

Pesticide Carryover. The authors speculated that imid acloprid residues at the Hemet site appear to be a function of the rate applied at the most recent application only, with no evidence of carryover from previous years. However, following the third year of application at the Hemet site, residues were higher at the two sites receiving no treatment in 2010 than at the site treated all three years with 1X. This indicates some degree of carryover from previous application years, at least for sites treated with the 2X rate during one of the two years prior to the no treatment year. This was the only site where samples were collected following a year without treatment.