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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND

 POLLUTION PREVENTION

MEMORANDUM

Date: March 17, 2016

Subject: Abamectin. Petition for the Establishment of a Permanent Tolerance and 

Registration for Use on the Caneberry Subgroup 13-07A. Summary of Analytical 

Chemistry and Residue Data.

PC Code: 122804 DP Barcode: D412860

Decision No.: 478520 Registration Nos.: 100-898, 100-1154

Petition No.: 3E8175 Regulatory Action: Section 3 Registration

Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 71751-41-2

MRID No.: See Below 40 CFR: 180.449

From: Nancy Dodd, Chemist

Risk Assessment Branch III (RAB3)

Health Effects Division (HED; 7509P)

Through: Christine Olinger, Chief

RAB3/HED (7509P)

To: Barbara Madden/Sidney Jackson, RM# 5

Registration Division (7505P)

Summary of Submitted Residue Chemistry Studies

OCSPP 860 Series 

Guideline

MRID 

Number

Title

860.1500 49080101 Dorschner, K. (2012) Abamectin: Magnitude of the Residue on Caneberry 

(Raspberry or Blackberry). Project Number: 06475/OCR, 06475/00/BER01. 

Unpublished study prepared by Interregional Research Project No. 4, 

Washington State University and North Carolina State University. 230 p.
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Table of Contents

1.0 Executive Summary............................................................................................................. 4

2.0 Regulatory Recommendations............................................................................................. 4

2.1 Data Deficiencies/Data Needs.......................................................................................... 5

2.2 Tolerance Considerations................................................................................................. 5

2.2.1 Enforcement Analytical Method............................................................................... 5

2.2.2 Recommended Tolerances........................................................................................ 5

2.2.3 Revisions to Petitioned-For Tolerances.................................................................... 5

2.2.4 International Harmonization ..................................................................................... 5

2.3 Label Recommendations.................................................................................................. 5

3.0 Introduction.......................................................................................................................... 6

3.1 Chemical Identity ............................................................................................................. 6

3.2 Physical/Chemical Characteristics................................................................................... 7

3.3 Pesticide Use Pattern/Directions for Use (860.1200)....................................................... 7

4.0 Metabolite/Degradate Residue Profile................................................................................. 8

4.1 Nature of the Residue....................................................................................................... 8

4.1.1 Summary of Plant Metabolism (860.1300)............................................................... 8

4.1.2 Summary of Livestock Metabolism (860.1300)....................................................... 9

4.1.3 Summary of Confined Rotational Crops (860.l850)................................................. 9

4.1.4. Summary of Metabolites and Degradates................................................................. 9

4.2 Comparison of Metabolic Pathways ................................................................................ 9

4.3 Residues of Concern Summary and Rationale............................................................... 10

5.0 Residue Profile................................................................................................................... 12

5.1 Residue Analytical Methods (860.1340)........................................................................ 12

5.1.1 Data Collection Methods ........................................................................................ 12

5.1.2 Multi-Residue Methods (860.1360)........................................................................ 12

5.1.3 Tolerance Enforcement Methods............................................................................ 12

5.1.4 Submittal of Analytical Reference Standards (860.1650) ...................................... 13

5.2 Storage Stability (860.1380) .......................................................................................... 13

5.3 Residue Data .................................................................................................................. 13

5.3.1 Crop Field Trials (860.1500) .................................................................................. 13

5.3.2 Field Rotational Crops (860.1900) ......................................................................... 15

5.3.3 Processed Food and Feed (860.1520)..................................................................... 15
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5.3.4 Meat, Milk, Poultry and Eggs (860.1480) .............................................................. 15

5.3.5. Food Handling (860.1460)...................................................................................... 15

5.3.6. Water, Fish, and Irrigated Crops (860.1400).......................................................... 15

5.4. Food Residue Profile...................................................................................................... 15

6.0 Tolerance Derivation ......................................................................................................... 15

Appendix A. Field Trial Geographic Distribution....................................................................... 17

Appendix B. International Residue Limits Table ........................................................................ 18

Appendix C. OECD MRL Calculation Procedure Inputs/Outputs.............................................. 19
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1.0 Executive Summary

The Interregional Research Project No. 4 (IR-4), on behalf of the Agricultural Experiment 

Stations of CA, SC, AR, NC, WA, and DE, has submitted a petition to propose use of abamectin 

to control mites on caneberries and to establish a tolerance for the caneberry subgroup 13-07A. 

The petitioner proposes addition of the use on caneberries to the Agri-Mek® 0.15 EC and EpiMek® 0.15 EC labels.

The petitioner has proposed a tolerance for residues of abamectin (avermectin), including its 

metabolites and degradates, in/on the caneberry subgroup 13-07A at 0.20 ppm. Compliance with 

the tolerance levels specified is to be determined by measuring only avermectin B1 [a mixture of 

avermectins containing greater than or equal to 80% avermectin B1a (5-O-demethyl avermectin 

A1) and less than or equal to 20% avermectin B1b (5-O-demethyl-25-de(1-methylpropyl)-25-(1-

methylethyl) avermectin A1)] and its delta-8,9-isomer.

Tolerances are established under 40 CFR §180.449 for residues of abamectin (avermectin), 

including its metabolites and degradates, in or on various crop and livestock commodities at 

levels ranging from 0.005 ppm to 1.0 ppm. Compliance with the tolerance levels is to be 

determined by measuring only avermectin B1 [a mixture of avermectins containing greater than 

or equal to 80% avermectin B1a (5-O-demethyl avermectin A1) and less than or equal to 20% 

avermectin B1b (5-O-demethyl-25-de(1-methylpropyl)-25-(1-methylethyl) avermectin A1 )] and 

its delta-8,9-isomer.

Agri-Mek® 0.15 EC (EPA Reg. No. 100-898) and Epi-Mek® 0.15 EC (EPA Reg. No. 100-

1154) are to be applied to caneberries as broadcast foliar sprays using ground or aerial 

equipment. Multiple applications can be made with a retreatment interval of 7 days. The 

maximum application rates are 0.019 lb ai/A/application and 0.056 lb ai/A/season. The 

preharvest interval is 7 days. 

The residue chemistry database is adequate for tolerance assessment and for registration of the 

two EC formulations of abamectin on the caneberry subgroup 13-07A. Residues of concern in 

plants are parent (avermectin B1a and B1b) and the 8,9-Z isomers. The field trials reflect the 

proposed use pattern. The number of field trials and the geographic representation are adequate. 

An adequate method was used for data collection. Field trial residues in caneberries (raspberries 

and blackberries) were low but quantifiable as combined residues. Residues in blackberries

decline with increasing preharvest intervals (PHIs). Adequate storage stability data are available 

to support the field trials. No processed commodities or livestock feed items are associated with 

caneberries. Caneberries are not considered to be rotated.

2.0 Regulatory Recommendations

There are no residue chemistry considerations that would preclude granting the requested 

registrations and establishing the recommended tolerance for abamectin on the caneberry 

subgroup 13-07A. The specific tolerance recommendations are discussed in Section 2.2. There 

are no recommended label modifications.
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2.1 Data Deficiencies/Data Needs

There are no data deficiencies.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

Adequate enforcement methods for abamectin in plant and livestock commodities are available 

in the Pesticide Analytical Manual, Volume II (PAM II). The methods have been validated for 

citrus and processed fractions (Method I), ginned cottonseed (Method IA), and bovine tissues 

and milk (Method II). These methods determine residues in plant and livestock commodities at 

limits of quantitation (LOQs) of 0.02 ppm for meat and meat byproducts and ≤0.01 ppm for 

other plant/livestock commodities. The limit of detection (LOD) of the methods for plant and 

livestock commodities is 0.001 ppm for each analyte, equivalent to 0.002 ppm for two analyte 

peaks (i.e., avermectin B1a and its delta-8,9-isomer in one peak and avermectin B1b and its delta8,9-isomer in the other peak).

2.2.2 Recommended Tolerances

The current tolerance expression in 40 CFR §180.449 is consistent with the S. Knizner memo 

dated 5/27/09.

Table 2.2.2. Tolerance Summary for Abamectin.

Commodity Established

Tolerance 

(ppm)

IR-4-

Proposed 

Tolerance

(ppm)

HEDRecommended 

Tolerance 

(ppm)

Comments 

(correct commodity definition)

Caneberry, subgroup 13-07A none 0.20 0.20 Caneberry subgroup 13-07A

2.2.3 Revisions to Petitioned-For Tolerances

None.

2.2.4 International Harmonization

The tolerance definitions for plants are essentially the same for the US, Codex, and Canada. 

There are no Codex maximum residue limits (MRLs) for abamectin on caneberries. Canada and 

the US are concurrently establishing the new tolerance on the caneberry subgroup 13-07A at 

0.20 ppm. Therefore, there are no harmonization issues at this time. 

2.3 Label Recommendations

None.
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3.0 Introduction

Abamectin is an insecticide/miticide used to control mites, leaf miners, and other insects in 

commercially important crops. Avermectins are macrocyclic lactones produced as natural 

fermentation products of the soil bacterium Streptomyces avermitilis. Abamectin is a mixture of 

avermectin B1 [a mixture of avermectins containing greater than or equal to 80% avermectin B1a

(5-O-demethyl avermectin A1) and less than or equal to 20% avermectin B1b (5-O-demethyl-25-

de(1-methylpropyl)-25-(1-methylethyl) avermectin A1)] and its delta-8,9-isomer. Abamectin has 

limited plant systemic activity, but does exhibit some translaminar movement. Abamectin acts 

as an insecticide by interfering with the nervous system of the insect, causing the insect to 

become paralyzed. Available mechanistic data indicate a neurotoxic mechanism of action, 

related to interference with GABA-mediated neurotransmission. 

3.1 Chemical Identity

Table 3.1. Abamectin Nomenclature

Compound

Abamectin

Chemical Structure

Common Names abamectin, avermectin B1

Company experimental name MK-0936

IUPAC name mixture of (10E,14E,16E)-(1R,4S,5 'S,6S,6 'R,8R,12S,13S,20R,21R,24S)-6 '-[(S)-

sec-butyl]-21,24-dihydroxy-5 ',11,13,22-tetramethyl-2-oxo-(3,7,19-
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Table 3.1. Abamectin Nomenclature

trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene)-6-spiro-2 '-(5 

',6 '-dihydro-2 'H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-α-Larabino-hexopyranosyl)-3-O-methyl-α-L-arabino-hexopyranoside and 

(10E,14E,16E)-(1R,4S,5 'S,6S,6 'R,8R,12S,13S,20R,21R,24S)-21,22-dihydroxy-6 

'-isopropyl-5 ',11,13,22-tetramethyl-2-oxo-(3,7,19-

trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene)-6-spiro-2 '-(5 

',6 '-dihydro-2 'H-pyran)-12-yl 2,6-dideoxy-4-O-(2,6-dideoxy-3-O-methyl-α-Larabino-hexopyranosyl)-3-O-methyl-α-L-arabino-hexopyranoside

CAS name Avermectin B1

CAS # Avermectin B1 - 71751-41-2; Avermectin B1a - 65195-55-3; Avermectin B1b -

65195-56-4

End-use products/EPs

Agri-Mek® 0.15 EC Miticide/Insecticide, EPA Reg. No. 100-898 (contains 0.15 

lb ai per gallon);

Epi-Mek® 0.15 EC Miticide/Insecticide, EPA Reg. No. 100-1154 (contains 0.15 

lb ai per gallon).

3.2 Physical/Chemical Characteristics

Avermectin is a crystalline powder with very low vapor pressure. It has very low water 

solubility but is soluble in organic solvents. Residues do not readily leach to groundwater due to 

their affinity for soil particles. Abamectin is stable to abiotic hydrolysis. Refer to Table 3.2 for 

the table of physical/chemical properties.

TABLE 3.2. Physicochemical Properties of the Technical Grade of Abamectin

Parameter Value Reference

Molecular weight 873.1 MRID 48758002

Melting point/range 161.8-169.4°C (with thermal decomposition)

pH 8-9 at 25°C

Density 1.18 x 103 kg/m3 at 22°C

Water solubility at 25oC 1.21 μg/mL at pH 7.57

Solubility in organic solvents Acetone 72 g/L

Dichloromethane 470 g/L

Ethyl acetate 160 g/L

Hexane 0.110 g/L

Methanol 13 g/L

Octanol 83 g/L

Toluene 23 g/L

Vapor pressure at 25oC <3.7 x 10-6 Pa 

Dissociation constant (pKa) no dissociation constant in aqueous solution

Octanol/water partition coefficient, 

Log Pow

4.4 at pH 7.2

UV/visible absorption spectrum Absorbance maxima

Neutral: 32,549 l/mol•cm at 245 nm

18,983 l/mol•cm at 255 nm

Acidic: 34,515 l/mol•cm at 245 nm

20,977 l/mol•cm at 255 nm

Basic: 29,551 l/mol•cm at 245 nm

3.3 Pesticide Use Pattern/Directions for Use (860.1200)
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IR-4 has submitted a petition to add use on the caneberry subgroup13-07A to the Agri-Mek®

0.15 EC (EPA Reg. No. 100-898) and Epi-Mek® 0.15 EC (EPA Reg. No. 100-1154) labels. 

Both labels are emulsifiable concentrate (EC) formulations containing 0.15 lb ai/gal.

Table 3.3. Summary of Proposed Directions for Use of Abamectin on Caneberry.

Applic. Timing, 

Type, and 

Equip.

Formulation

[EPA Reg. 

No.]

Applic. 

Rate 

(lb ai/A)

Max. No. 

Applic. 

per 

Season

Max. Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and 

Limitations

Caneberry (Crop Subgroup 13-07A)

(blackberry, loganberry, raspberry ( black and red), wild raspberry and cultivars/varieties, and/or hybrids of 

these)

Postemergence; 

Broadcast foliar 

spray; Ground 

or aerial 

equipment

Agri-Mek®

0.15 EC

[100-898]

Epi-Mek®

0.15 EC

[100-1154]

0.0094-

0.019

not 

stated*

0.056 7 Restricted Use Pesticide

Apply when spider mites 

are first observed and 

repeat as needed.

Do not apply with 

aircraft in NY state.

Apply in a minimum of 

10 gals. water by ground 

or 5 gal water by air.

The retreatment interval 

is 7 days. 

Do not make more than 

2 sequential applications 

of an abamectincontaining product.

A nonionic activator 

type wetting, spreading, 

and/or penetrating 

adjuvant can be used. 

Do not use binder 

sticker type adjuvants.

* The maximum number of applications at the maximum rate is 3.

Caneberry samples were analyzed for residues of avermectin B1a, 8,9-Z avermectin B1a, and 

avermectin B1b using a high performance liquid chromatography (HPLC) method with 

fluorescence detection based on analytical method M-073.

Conclusions. The Agri-Mek® 0.15 EC Miticide/ Insecticide label (EPA Reg. No. 100-898) and 

the Epi-Mek® 0.15 EC Miticide/ Insecticide label (EPA Reg. No. 100-1154) are adequate to 

allow evaluation of the residue data relative to the proposed use.

4.0 Metabolite/Degradate Residue Profile

4.1 Nature of the Residue

4.1.1 Summary of Plant Metabolism (860.1300)

DP Barcode D380523, N. Dodd, 7/18/11
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No new plant metabolism data were submitted with this registration request. The qualitative 

nature of the abamectin residues in the caneberry subgroup13-07A is adequately understood 

based on metabolism studies on cotton, citrus, and celery (PP#'s 5G3500, 5G3287, and 8F3649, 

respectively), as well as a report titled "Comparative Degradation of Avermectin B1a in Cotton 

Leaf, Citrus Fruit, Celery, and In Vitro" (PP#9F3703, S. Willett, 12/15/89). The available 

studies indicate that the metabolism of abamectin in plants results in a complex mixture of 

residues. The majority of the terminal residue is composed of several unidentified polar 

degradates. The parent compound, its delta-8,9-isomer, and the alpha 8-OH degradate have been 

identified in plants, with only the parent and its delta-8,9-isomer each accounting for at least 

10% of the total residue. The polar degradates generated on citrus (7-day PHI) and in vitro (30 

hour sample) have been tested for toxicity (in the developmental toxicity study in CF-1 mice) 

and were found to be of no toxicological significance at the levels tested (TOX memos 7080 and 

7081, W. Dykstra, 3/15/89; PP#8F3592, F. Boyd, 6/21/89; D203373, G. J. Herndon, 3/29/95). 

As stated in The Pesticide Manual, Eleventh Edition, British Crop Protection Council (1997), 

abamectin has limited plant systemic activity, but does exhibit some translaminar movement. 

For the tolerance expression and risk assessment, the residues of concern in these crops are the 

parent compounds (avermectin B1a and B1b) and their delta-8,9-isomers (also known as 8,9-Z

avermectin B1a and 8,9-Z avermectin B1b).

4.1.2 Summary of Livestock Metabolism (860.1300)

No livestock feed items are associated with use on caneberries (Table 1 Feedstuffs, June 2008).

4.1.3 Summary of Confined Rotational Crops (860.l850)

Caneberries are not considered to be rotated (OCSPP 860.1850).

4.1.4. Summary of Metabolites and Degradates

4.2 Comparison of Metabolic Pathways

DP Barcode D380523, N. Dodd, 7/18/11

Metabolism studies on cottonseed, citrus, and celery indicate that the metabolism of abamectin in 

plants results in a complex mixture of residues. The majority of the terminal residue is 

composed of several unidentified polar degradates. The parent compound, its delta-8,9-isomer, 

and the alpha 8-OH degradate have been identified in plants, with only the parent and its delta8,9-isomer each accounting for at least 10% of the total residue. In citrus, the majority of the 

residue remained in the peel but a small amount translocated into the pulp. For the tolerance 

assessment and risk assessment, the residues of concern in these crops are the parent compounds 

(avermectin B1a and B1b) and their delta-8,9-isomers (also known as 8,9-Z isomers).
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4.3 Residues of Concern Summary and Rationale

DP Barcode D380523, N. Dodd, 7/18/11

DP Barcode D357192, T. Morton, 1/27/09

DP Barcode D402677, N. Dodd, 12/20/12

Metabolism in Primary Crops: The qualitative nature of abamectin residues in cotton and 

strawberry is adequately understood based on metabolism studies on cotton, citrus, and celery 

(PP#'s 5G3500, 5G3287, and 8F3649, respectively), as well as a report titled "Comparative 

Degradation of Avermectin B1a in Cotton Leaf, Citrus Fruit, Celery, and In Vitro" (PP#9F3703, 

S. Willett, 12/15/89). The available studies on cotton, citrus, and celery indicate that the 

metabolism of abamectin in plants results in a complex mixture of residues, with the majority of 

the terminal residue composed of several unidentified polar degradates. The parent compound, 

its delta-8,9-isomer, and the alpha 8-OH degradate have been identified in plants, with only the 

parent and its delta-8,9-isomer each accounting for at least 10% of the total residue. The polar 

degradates generated on citrus [7-day preharvest interval (PHI)] and in vitro (30 hour sample) 

have been tested for toxicity (in the developmental toxicity study in CF-1 mice) and were found 

to be of no toxicological significance at the levels tested (TOX memos 7080 and 7081, W. 

Dykstra, 3/15/89; PP#8F3592, F. Boyd, 6/21/89; D203373, G. J. Herndon, 3/29/95). As stated in 

The Pesticide Manual, Eleventh Edition, British Crop Protection Council (1997), abamectin has 

limited plant systemic activity, but does exhibit some translaminar movement. For the tolerance 

expression and risk assessment, the residues of concern in these crops are the parent compounds 

(avermectin B1a and B1b) and their delta-8,9-isomers (also known as 8,9-Z avermectin B1a and 

8,9-Z avermectin B1b).

Metabolism in Rotational Crops: The qualitative nature of the residue in rotational crops is 

adequately defined. The confined rotational crop study indicated that avermectin residues 

accumulated in some rotational crops at levels up to 10-12 ppb. However, the radioactivity was 

due to polar degradates that were of little toxicological concern as compared to the parent 

compound avermectin B1 and/or the delta-8,9-isomer (Memo, P. Mastradone, 4/24/88).

 

Metabolism in Ruminants: The qualitative nature of abamectin residues in ruminants as a result 

of application to crops is adequately understood based on a goat metabolism study (PP#7G3468, 

L. Cheng, 2/11/87; PP#9F3703, S. Willett, 12/15/89). The residues of concern in ruminants for 

the tolerance expression and risk assessment are the parent compounds (avermectin B1a and B1b) 

and their delta-8,9-isomers. An additional metabolite (24-hydroxymethyl avermectin B1a) was 

identified and is potentially of toxicological significance, but was not included in the tolerance 

expression because of its presence at low levels (PP#8F3592, F. Boyd, 6/21/89; DP#203373, G. 

J. Herndon, 3/29/95). If the tolerances for residues in meat and milk need to be raised at some 

future time due to registration of abamectin on additional feed items, the 24-hydroxymethyl 

metabolite may need to be included in the tolerance expression and appropriate enforcement 

methods developed.

The qualitative nature of the residue in ruminants from use of the cattle ear tag is adequately 

understood based on sufficient non-guideline data. The residues of concern are the parent 

compounds (avermectin B1a and B1b) and their delta-8,9-isomers.
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Metabolism in Poultry: No poultry metabolism study has been submitted. Since no significant 

poultry feed items are associated with the proposed uses, as indicated in Table 1 Feedstuffs (June 

2008), no poultry metabolism study is required. (Note: The tolerances for meat and meat 

byproducts of poultry and swine of 0.02 ppm were established for residues in food handling 

establishments.) 

Metabolism in Rats: Avermectin B1a does not bioaccumulate in rat tissues. Avermectin B1a in 

rats is metabolized to 24-hydroxy-methyl B1a (i.e., 24-OH-Me-B1a), which accounts for most of 

the radiolabeled residues. 

Residues of concern for the risk assessment and tolerance expression are summarized in Table 

4.3 below.

Table 4.3. Summary of Metabolites and Degradates to be included in the Risk Assessment 

and Tolerance Expression

Matrix Residues included in Risk 

Assessment

Residues included in 

Tolerance Expression

Plants Primary Crop Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z isomers)

Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z isomers)

Rotational Crop Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z isomers)

Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z

isomers)**

Livestock Ruminant* Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z isomers)

Parent (avermectin B1a and 

B1b) and the delta-8,9-isomers 

(also known as 8,9-Z isomers)

Poultry Not applicable Not applicable

Drinking Water Parent (avermectin B1a and 

B1b)***

Not applicable

* Residues of concern in ruminants include both use on crops and use in cattle ear tags.

** No rotational crop tolerances have been established.

*** The delta-8,9-isomers (also known as 8,9-Z isomers) are not included in the drinking water assessment because 

they were not identified in the fate studies. The major soil degradate included in the previous assessment (a mixture 

of an 8-alpha-hydroxy and a ring opened aldehyde derivative) was not included in the current assessment based on 

an assumption of stability of parent until acceptable environmental fate data are submitted (D380524, G. Orrick, 

1/31/11). 
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5.0 Residue Profile

5.1 Residue Analytical Methods (860.1340)

5.1.1 Data Collection Methods

49080101.der caneberry

Caneberry

Caneberry samples were analyzed for residues of avermectin B1a, 8,9-Z avermectin B1a, and 

avermectin B1b using an HPLC method with fluorescence detection based on analytical method 

M-073. The limit quantitation (LOQ) for each analyte is 0.002 ppm, the lowest level of method 

validation (LLMV). The method was validated prior to sample analysis by spiking control 

blackberry samples with 0.002-0.1 ppm avermectin B1a, 0.002-0.008 ppm avermectin B1b, and 

0.002-0.1 ppm 8,9-Z avermectin B1a. All method validation recoveries were within the 

acceptable 70-120% range. Adequacy of the method was also confirmed during sample analysis 

by spiking control blackberry and raspberry samples with 0.002-0.12 ppm avermectin B1a, 0.002-

0.01 ppm avermectin B1b, and 0.002-0.12 ppm 8,9-Z avermectin B1a. Four low concurrent 

recoveries were attributed to spiking errors. The remaining recoveries, with the exception of one 

concurrent recovery of 68%, were all within the acceptable range of 70-120%. Given that the 

majority of recoveries were within the acceptable range, the working method based on Method 

M-073 is adequate for the determination of residues in blackberries and raspberries. 

Conclusions. Caneberry samples were analyzed for residues of avermectin B1a, 8,9-Z avermectin 

B1a, and avermectin B1b using an HPLC method with fluorescence detection based on analytical 

method M-073. The method has been adequately validated as data collection methods based on 

acceptable concurrent recovery data. Method M-073 quantitates the sum of avermectin B1a and 

8,9-Z avermectin B1a as a single value, with residues of avermectin B1b determined as a separate 

peak. The LOQ, determined as LLMV, was 0.002 ppm for each analyte in each matrix. 

5.1.2 Multi-Residue Methods (860.1360)

DP Barcode D380523, N. Dodd, 7/18/11

The Pestrak database indicates that abamectin and its metabolites are not recovered or not likely 

to be recovered by FDA multiresidue methods. Therefore, the multiresidue methods cannot be 

used to determine residues for dietary exposure assessment and cannot be used as the primary 

enforcement method.

5.1.3 Tolerance Enforcement Methods

DP Barcode D380523, N. Dodd, 7/18/11

DP Barcode D230333, G. Jeffrey Herndon, 1/10/97

DP Barcode D198491, Jerry Stokes, 2/2/94

Adequate enforcement methods for abamectin in plant and livestock commodities are available 

in the Pesticide Analytical Manual, Volume II (PAM II). The methods have been validated for 
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citrus and processed fractions (Method I), ginned cottonseed (Method IA), and bovine tissues 

and milk (Method II). These methods determine residues in plant and livestock commodities at 

limits of quantitation (LOQs) of 0.02 ppm for meat and meat byproducts and ≤0.01 ppm for 

other plant/livestock commodities. The limit of detection (LOD) of the methods for plant and 

livestock commodities is 0.001 ppm for each analyte, equivalent to 0.002 ppm for two analyte 

peaks (i.e., avermectin B1a and its delta-8,9-isomer in one peak and avermectin B1b and its delta8,9-isomer in the other peak).

5.1.4 Submittal of Analytical Reference Standards (860.1650)

Analytical reference standards are available at the EPA National Pesticide Standards Repository 

[Source: e-mail from Gregory Verdin of the Analytical Chemistry Branch/Biological and 

Economic Analysis Division (ACB/BEAD)].

5.2 Storage Stability (860.1380)

49080101.der

Caneberry samples were stored frozen (≤ -20 °C) from collection to analysis (33.4 months). 

Adequate storage stability data are available demonstrating that residues of avermectin B1a, 

avermectin B1b, and 8,9-Z avermectin B1a are stable under frozen storage conditions for 33

months in blackberries.

TABLE 5.2. Summary of Storage Conditions.

Matrix 

(RAC)

Storage 

Temperature

(°C)

Actual Storage 

Duration1

Interval of Demonstrated Storage Stability

(months)

Blackberry and 

raspberry

≤ -20 1016 days 

(33.4 months)

Residues of avermectin B1a, avermectin B1b and 8,9-Z 

avermectin B1a were stable when stored frozen for 33 

months in blackberries. 1 From harvest to extraction. Residues were determined within 5 days of extraction.

Conclusions. The storage stability data are adequate to support the storage intervals and 

conditions for the caneberry residue samples from the submitted field trials. 

5.3 Residue Data

5.3.1 Crop Field Trials (860.1500)

49080101.der (caneberries)

Caneberries:

The Interregional Research Project No. 4 (IR-4) has submitted field trial data for abamectin on 

blackberries and raspberries. Four field trials were conducted on blackberries in Zones 1 (1 in 

NY), 2 (1 in NC; 1 in NJ), and 12 (1 in OR). Three field trials were conducted on raspberries in 

Zones 5A (1 in MI) and Zone 12 (1 trial in WA; 1 in OR). The geographic representation and 
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number of field trials are adequate. Refer to Appendix A for the geographic distribution table. 

At each trial site, abamectin, formulated as an emulsifiable concentrate (Agri-Mek® 0.15EC) was 

applied to caneberries in three foliar broadcast or directed applications at rates of 19.4 – 23.1 g 

ai/ha (0.017-0.021 lb ai/A), for total rates of 61.3 – 67.9 g ai/ha (0.055-0.061 lb ai/A). A nonionic surfactant was included in the spray mixture for all applications. The re-treatment interval 

(RTI) was 6 – 8 days, and commercially mature blackberries and raspberries were harvested at a 

PHI of 7 days at all trial sites. Additional samples were harvested at PHIs of 0, 3, and 9 days at 

one of the blackberry trial sites to determine residue decline behavior. There was one untreated 

control plot and one treated plot at each trial site.

As shown in Table 5.3.1 below, total combined residues of avermectin B1a + 8,9-Z avermectin 

B1a and avermectin B1b + 8,9-Z avermectin B1b in blackberries and raspberries following a total 

application of 61.3 – 67.9 g ai/ha (0.055-0.061 lb ai/A) ranged from <0.0062 – 0.1215 ppm when 

samples were harvested at a PHI of 7 days. Total abamectin residues declined with increasing 

PHI when blackberry samples were harvested at PHIs of 0, 3, 7, and 9 days.

An acceptable method was used for residue quantitation, and adequate storage stability data are 

available to support sample storage intervals and conditions for all analytes.

TABLE 5.3.1. Summary of Residue Data from Caneberry Field Trials with Abamectin

Commodity Total Applic. 

Rate,

g ai/ha

(lb ai/A)

PHI 

(days)

Residue Levels1,2

(ppm)

n Min. Max. LAFT3 HAFT3 Median

(STMdR)

Mean

(STMR)

Std. Dev.

CANEBERRIES Proposed Use = 0.056 lb ai/acre/season total application rate, 7-day PHI

Blackberry 62.8 – 66.1

(0.056-0.059)

7 4 <0.0164 0.0632 <0.0171 0.0535 <0.0233 <0.029 0.017

Raspberry 61.3 – 67.9

(0.055-0.061)

7 3 <0.0062 0.1215 <0.0067 0.1184 0.0084 0.045 0.064

Blackberry 

and 

Raspberry

61.3-67.9

(0.055-0.061)

7 7 <0.0062 0.1215 <0.0067 0.1184 <0.0204 <0.0358 0.040

1 Residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b were reported. 2 Except for sample min/max, values reflect per trial averages; n = no. of field trials. For calculation of median, 

mean, and standard deviation, the LOQ (0.002 ppm for each analyte in each matrix) was used for any results 

reported as <LOQ.

3 LAFT = lowest average field trial; HAFT = highest average field trial.

Conclusions. Adequate field trials were submitted for abamectin on caneberries. Seven field 

trials were conducted on blackberries and raspberries in Zones 1 (1 in NY), 2 (1 in NC; 1 in NJ), 

5A (1 in MI), and 12 (2 in OR; 1 in WA). Abamectin, formulated as an emulsifiable concentrate, 

was applied to caneberries as three foliar broadcast or directed applications at total rates of 61.3 

– 67.9 g ai/ha (0.055-0.061 lb ai/A), and a non-ionic surfactant was included in the spray mixture 

for all applications. Total combined residues of avermectin B1a + 8,9-Z avermectin B1a and 

avermectin B1b in blackberries and raspberries ranged from <0.0062 – 0.1215 ppm when samples 

were harvested at a PHI of 7 days. Total abamectin residues declined with increasing PHI when 

blackberry samples were harvested at PHIs of 0, 3, 7, and 9 days.
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The studies reflect the proposed use patterns. The number of trials and the geographic 

representation are adequate. The residue data are adequately supported by the storage stability 

studies. The analytical methods are adequate for the analysis of the residues of concern. The 

residue data adequately address the residues of concern.

5.3.2 Field Rotational Crops (860.1900)

Caneberries are not considered to be rotated.

5.3.3 Processed Food and Feed (860.1520)

There are no processed commodities associated with caneberries.

5.3.4 Meat, Milk, Poultry and Eggs (860.1480)

There are no livestock feed items associated with caneberries.

5.3.5. Food Handling (860.1460)

There are no proposed uses that are relevant to this guideline topic.

5.3.6. Water, Fish, and Irrigated Crops (860.1400)

There are no proposed uses that are relevant to this guideline topic.

5.4. Food Residue Profile

The residue chemistry database is adequate for tolerance assessment and for registration of the 

two EC formulations of abamectin on caneberries. 

Crop field trials: The caneberry (blackberry and raspberry) field trials adequately reflect the 

proposed use pattern. The number of trials and the geographic representation are adequate. 

Field trial residues were low but quantifiable in caneberries. Residues in blackberries decline 

with increasing PHI. 

Processing Studies: There are no processed commodities associated with caneberries.

Storage Stability: Adequate storage stability data are available to support the field trials.

Meat, Milk, Poultry, and Eggs: There are no livestock feed items associated with caneberries.

Rotational Crops: Caneberries are not considered to be rotated.

6.0 Tolerance Derivation

As shown in Appendix C, the Organization for Economic Cooperation and Development 

(OECD) tolerance calculation procedures were used for calculating the recommended tolerance 
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for caneberries. The statistical goal of the tolerance calculation procedures is to produce an 

MRL proposal in the region of the 95th percentile of the underlying residues distribution. 

Caneberry (MRID 49080101)

The dataset used to establish a tolerance for abamectin consisted of field trial data on 

blackberries and raspberries representing application rates of 0.056 lb ai/A abamectin with a 7-

day PHI. The combined dataset of blackberries and raspberries (seven field trials) was used 

since the representative crop for the caneberry subgroup 13-07A is either blackberry or 

raspberry. The field trial application rates and PHIs are within 25% of the maximum label 

application rate and minimum label PHI, respectively. The average residue values used to 

calculate the tolerance are provided below. Combined residues of avermectin B1a, 8,9-Z 

avermectin B1a, and avermectin B1b were quantifiable in/on samples from all seven field trials. 

Using the OECD tolerance calculation procedures, the recommended tolerance is 0.20 ppm for

combined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b in caneberries.
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Appendix A. Field Trial Geographic Distribution

TABLE A. Trial Numbers and Geographical Locations.

NAFTA Growing 

Zones

Caneberry

Submitted Requested (DIR98-02)* Requested by US**

Blackberry Raspberry Raspberry

1 1 -- -- 1R

2 2 -- -- 1B

5 -- -- 1 1R

5A -- 1 --

5B -- -- 1

6 1B

12 1 2 3 3B,3R

Total 4 3 5 5

*Since trials were conducted prior to January 2012, trials are required as indicated in DIR98-02. DIR98-02 does not 

specify trial requirements for blackberries.

** Table 4, OCSPP 860.1500 indicates that 5 trials (on any one blackberry (B) or any one raspberry (R)) should be 

conducted for the caneberry crop group. The five sites can be chosen from the requested locations for blackberry 

and raspberry (Table 5, OCSPP 860.1500).
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Appendix B. International Residue Limits Table

Abamectin (122804; 9/19/2013)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex

40 CFR §180.449: avermectin B1 [a 

mixture of avermectins containing 

greater than or equal to 80% avermectin 

B1a (5- O -demethyl avermectin A1 ) and 

less than or equal to 20% avermectin B1b

(5- O -demethyl-25-de(1-methylpropyl)-

25-(1-methylethyl) avermectin A1 )] and 

its delta-8,9-isomer

avermectin B1 (a mixture of 

avermectins containing 

greater than or equal to 80% 

avermectin B1a (5-Odemethyl avermectin A1a) 

and less than or equal to 

20% avermectin B1b (5-Odemethyl-25-de(1-

methylpropyl)-25-(1-

methylethyl) avermectin 

A1a) and its delta-8,9-

isomer)

Plants: sum of 

avermectin B1a, 

avermectin B1b, 

8,9-Z-avermectin 

B1a and 8,9-Zavermectin B1b. 

Animal 

commodities: 

sum of 

avermectin

B1a and 8,9-Zavermectin B1a.

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex

Caneberry subgroup 13-07A 0.20 0.20 (pending)

Completed: M. Negussie; 9/19/2013

1 Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
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Appendix C. OECD MRL Calculation Procedure Inputs/Outputs

Blackberry and Raspberry (MRID 49080101)

0.056 lb ai/A; 7-day PHI

Residues (mg/kg) n

0.0067 1

0.0084 1

0.0171 1

0.0204 1

0.0262 1

0.0535 1

0.1184 1

Abamectin

Blackberry/Raspberry

USA

0.056 lb ai/A; 7-day PHI

Total number of data (n) 7

Percentage of censored data 0%

Number of non-censored data 7

Lowest residue 0.007

Highest residue 0.118

Median residue 0.020

Mean 0.036

Standard deviation (SD) 0.040

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.118

- Mean + 4 SD 0.194

- CF x 3 Mean 0.107

Unrounded MRL 0.194

Rounded MRL 0.2

High uncertainty of MRL estimate.

[Small dataset]