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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 Permanent Tolerances and Registration 

for Use on Sweet Corn and Soybeans. Summary of Analytical Chemistry and 

Residue Data.

PC Code: 122804 DP Barcode: D414022

Decision No.: 480190 Registration Nos.: 100-1350, 100-1351, 100-

1408, and 100-1439

Petition No.: 3F8184 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: Steve Funk, Senior Chemist

RAB3/HED (7509P)

To: Venus Eagle/Jessica Rogala, RM #1

Registration Division (7505P)
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Summary of Submitted Residue Chemistry Studies

OCSPP 860 Series 

Guideline

MRID 

Number

Title

860.1500 49071008 Carringer, S. (2013) Abamectin 500 FS (A14006B) and Abamectin SC (A15368D) 

– Magnitude of the Residues in or on Sweet Corn Resulting from Seed Treatment 

followed by Foliar Applications - USA, 2011. Final Report. Report Number: 

TK0056923. Morse Study Number: 67392. SGS Study Number: G1112BK. Unpublished study prepared by Syngenta Crop Protection, LLC. 360 p.

860.1500/860.1520 49071010 Carringer, S. (2013). Abamectin 500 FS (A14006B) and Abamectin SC 

(A15368D) – Magnitude of the Residues in or on Soybean Resulting from Seed 

Treatment followed by Foliar Applications – USA, 2011. Report Number: 

TK0040391. Morse Study Number: 67391. SGS Study Number: G1110BK. Unpublished study prepared by Syngenta Crop Protection, LLC. 621 p.

860.1380 49071012 Rees, S. (2013) Stability of Abamectin Residues in Representative Crop Raw 

Agricultural and Processed Commodities Under Freezer Storage Conditions. Final 

Report. Report Number: 69101, Task Number: TK0167413. Unpublished study 

prepared by Syngenta Crop Protection, LLC. 175 p.

860.1380 49071016 Kwiatkowski, A. (2007) Abamectin - Storage Stability in Crops Stored Deep 

Frozen for up to Two Years - Final Report. Report Number: T022438-04-REG, 

Study Number: 05-S504. Unpublished study prepared by Syngenta Crop 

Protection, LLC. 71 p.
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Table of Contents

1.0 Executive Summary............................................................................................................ 5

2.0 Regulatory Recommendations............................................................................................ 6

2.1 Data Deficiencies/Data Needs.......................................................................................... 6

2.2 Tolerance Considerations................................................................................................. 6

2.2.1 Enforcement Analytical Method............................................................................... 6

2.2.2 Recommended Tolerances........................................................................................ 6

2.2.3 Revisions to Petitioned-For Tolerances.................................................................... 7

2.2.4 International Harmonization ..................................................................................... 7

2.3 Label Recommendations.................................................................................................. 8

3.0 Introduction......................................................................................................................... 8

3.1 Chemical Identity ............................................................................................................. 9

3.2 Physical/Chemical Characteristics................................................................................. 10

3.3 Pesticide Use Pattern/Directions for Use (860.1200)..................................................... 11

4.0 Metabolite/Degradate Residue Profile.............................................................................. 13

4.1 Nature of the Residue..................................................................................................... 13

4.1.1 Summary of Plant Metabolism (860.1300)............................................................. 14

4.1.2 Summary of Livestock Metabolism (860.1300)..................................................... 14

4.1.3 Summary of Confined Rotational Crops (860.l850)............................................... 15

4.1.4. Summary of Metabolites and Degradates............................................................... 15

4.2 Comparison of Metabolic Pathways .............................................................................. 15

4.3 Residues of Concern Summary and Rationale............................................................... 16

5.0 Residue Profile.................................................................................................................. 16

5.1 Residue Analytical Methods (860.1340)........................................................................ 16

5.1.1 Data Collection Methods ........................................................................................ 17

5.1.2 Multi-Residue Methods (860.1360)........................................................................ 17

5.1.3 Tolerance Enforcement Methods............................................................................ 17

5.1.4 Submittal of Analytical Reference Standards (860.1650) ...................................... 18

5.2 Storage Stability (860.1380) .......................................................................................... 18

5.3 Residue Data .................................................................................................................. 19

5.3.1 Crop Field Trials (860.1500) .................................................................................. 19

5.3.2 Field Rotational Crops (860.1900) ......................................................................... 23

5.3.3 Processed Food and Feed (860.1520)..................................................................... 23
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5.3.4 Meat, Milk, Poultry and Eggs (860.1480) .............................................................. 27

5.3.5. Food Handling (860.1460)...................................................................................... 33

5.3.6. Water, Fish, and Irrigated Crops (860.1400).......................................................... 33

5.4. Food Residue Profile...................................................................................................... 33

6.0 Tolerance Derivation ........................................................................................................ 34

Appendix A. Field Trial Geographic Distribution....................................................................... 36

Appendix B. International Residue Limits Tables....................................................................... 38

Appendix C. OECD MRL Calculation Procedure Inputs/Outputs.............................................. 40
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1.0 Executive Summary

Syngenta Crop Protection LLC has submitted a petition to propose use of abamectin on soybeans 

and sweet corn. The petitioner proposes addition of the uses on soybeans and sweet corn to the 

labels for Agri-Flex® Miticide/Insecticide, Agri-Mek® SC Miticide/Insecticide, Epi-MekTM SC 

Miticide/Insecticide, and Epi-MekTM SCL Miticide/Insecticide. 

The petitioner has proposed tolerances for the combined residues of the insecticide avermectin 

B1 (a mixture of avermectins containing greater than or equal to 80% avermectin B1a (5-Odemethyl 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 in or on sweet corn 

commodities (forage, kernel plus cob with husk removed, and stover) and soybean commodities 

(forage, hay, and seed).

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-Flex® Miticide/Insecticide, Agri-Mek® SC Miticide/Insecticide, Epi-MekTM SC 

Miticide/Insecticide, and Epi-MekTM SCL Miticide/Insecticide are to be applied to sweet corn 

and soybeans as broadcast foliar sprays using ground or aerial equipment. Applications can be 

made with a retreatment interval of 7 days. The application rates are 0.018/0.019 lb 

ai/A/application (0.037/0.038 lb ai/A/season) for sweet corn and 0.014/0.019 lb ai/A/application 

(0.028/0.038 lb ai/A/season) for soybeans. The preharvest intervals are 7 days for sweet corn 

forage and ears, either 7 or 14 days for sweet corn stover, and 28 days for soybean seed. The 

preharvest interval for soybean forage and hay is either 7 days or is restricted from 

feeding/grazing. 

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

four formulations of abamectin on sweet corn and soybeans. Residues of concern in primary 

(treated) plants, rotational crops, and ruminants are parent (avermectin B1a and B1b) and the 8,9-Z 

isomers. The sweet corn and soybean field trials adequately reflect the proposed use patterns. 

The number of field trials and the geographic representation are adequate. An adequate method 

was used for data collection. Adequate concurrent storage stability data are available to support 

the field trials.

Field trial residues in sweet corn forage and stover and soybean forage and hay were small (low 

level) but quantifiable as combined residues; these combined residues generally decreased with 

increasing PHIs. Combined residues in sweet corn kernel plus cob with husk removed and in 

soybean seed were all less than the limit of quantitation (<LOQ; <0.006 ppm). 
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No processed commodities are associated with sweet corn. The processed commodities for 

soybean are meal, hulls, refined oil, and aspirated grain fractions (AGF). A processing study on 

soybeans indicated that combined residues of avermectin B1a, avermectin B1b, and 8,9-Z 

avermectin B1a may concentrate in/on AGF (average processing factor of 59x), meal (1.1x), and 

hulls (1.2x). A processing factor could not be calculated for refined oil because residues were 

below the LOQ in both the raw agricultural commodity (RAC) and processed commodity; 

however, additional processing data are not required and a separate tolerance for refined oil is 

not needed since the processing study was conducted at an exaggerated rate (~5x the proposed 

foliar rate). 

A confined rotational crop study indicated that avermectin residues of significant toxicological 

concern are not expected to occur in rotational crops. 

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 sweet corn and 

soybeans. The specific tolerance recommendations are discussed in Section 2.2. There are no 

recommended label modifications.

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 

the 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 delta-8,9-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.
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The petitioner must propose a tolerance of 0.40 ppm for grain, aspirated grain fractions and 

increase some of the established livestock tolerances, as indicated in Table 2.2.2 below.

Table 2.2.2. Tolerance Summary for Abamectin.

Commodity Established

Tolerance 

(ppm)

SyngentaProposed 

Tolerance

(ppm)

HEDRecommended 

Tolerance 

(ppm)

Comments 

(correct commodity definition)

Cattle, fat 0.03 none 0.05

Cattle, meat 0.02 none 0.02

Cattle, meat byproducts 0.06 none 0.09

Corn, sweet, forage none 0.2 0.20

Corn, sweet, kernel plus cob 

with husk removed

none 0.01 0.01

Corn, sweet, stover none 0.5 0.50

Goat, fat 0.01 none 0.03

Goat, meat 0.02 none 0.02

Goat, meat byproducts 0.02 none 0.04

Grain, aspirated grain 

fractions

none none 0.40

Hog, fat 0.01 none 0.01

Hog, meat 0.02 none 0.02

Hog, meat byproducts 0.02 none 0.02

Horse, fat 0.01 none 0.03

Horse, meat 0.02 none 0.02

Horse, meat byproducts 0.02 none 0.04

Milk 0.005 none 0.015

Poultry, meat 0.02 none 0.02

Poultry, meat byproducts 0.02 none 0.02

Sheep, fat 0.01 none 0.03

Sheep, meat 0.02 none 0.02

Sheep, meat byproducts 0.02 none 0.04

Soybean, forage none 0.3 0.30

Soybean, hay none 1 1.0

Soybean, seed none 0.01 0.01

2.2.3 Revisions to Petitioned-For Tolerances

The petitioner must propose a tolerance of 0.40 ppm for grain, aspirated grain fractions since 

residues in soybean seed (<0.006 ppm) concentrate 59x in aspirated grain fractions.

Since the proposed uses on sweet corn and soybeans include livestock feed items, higher 

tolerances are needed for the fat of cattle (0.05 ppm), meat byproducts of cattle (0.09 ppm), fat of 

goat, horse, and sheep (0.03 ppm), meat byproducts of goat, horse, and sheep (0.04 ppm), and 

milk (0.015 ppm). 

2.2.4 International Harmonization

The plant tolerance definitions are essentially the same for the US, Codex, and Canada, all 

including avermectin B1a, avermectin B1b, and the 8,9-Z isomers. There are no Codex or 
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Canadian maximum residue limits (MRLs) for abamectin on sweet corn or soybean 

commodities. Therefore, there are no harmonization issues at this time for plant commodities.

The livestock residue definitions are essentially the same for the US and Canada; the Codex 

residue definition includes only avermectin B1a and its 8,9-Z isomer, whereas the US and Canada 

include both avermectin B1a and avermectin B1b and their 8,9-Z isomers. There are no Canadian 

tolerances set on livestock commodities. There are some Codex maximum residue limits 

(MRLs) on livestock commodities, but fewer than US tolerances. None of the Codex MRLs are 

set at the same level as the US recommended tolerance levels.

An International Residue Limits Status sheet is attached (Appendix B.)

2.3 Label Recommendations

None.

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. 
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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-

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 
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Table 3.1. Abamectin Nomenclature

'-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-Flex® Miticide/Insecticide, EPA Reg. No. 100-1350, contains 0.277 lb 

abamectin and 1.27 lb thiamethoxam per gallon.

Agri-Mek® SC Miticide/Insecticide, EPA Reg. No. 100-1351, contains 0.7 lb 

abamectin per gallon.

Epi-MekTM SC Miticide/Insecticide, EPA Reg. No. 100-1408, contains 0.7 lb 

abamectin per gallon.

Epi-MekTM SCL Miticide/Insecticide, EPA Reg. No. 100-1439, contains 0.35 lb 

abamectin 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
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3.3 Pesticide Use Pattern/Directions for Use (860.1200)

IR-4 has submitted a petition to add uses on sweet corn and soybeans to the following labels: 

Agri-Flex® Miticide/Insecticide, Agri-Mek® SC Miticide/Insecticide, Epi-MekTM SC 

Miticide/Insecticide, and Epi-MekTM SCL Miticide/Insecticide. 

Agri-Flex® Miticide/Insecticide (EPA Reg. No. 100-1350) is a suspension concentrate which 

contains 0.277 lb abamectin and 1.27 lb thiamethoxam per gallon. It contains 3.0% abamectin 

and 13.9% thiamethoxam. 

Agri-Mek® SC Miticide/Insecticide (EPA Reg. No. 100-1351) is a suspension concentrate 

which contains 0.7 lb abamectin per gallon. It contains 8.0% abamectin.

 

Epi-MekTM SC Miticide/Insecticide (EPA Reg. No. 100-1408) is a suspension concentrate which 

contains 0.7 lb abamectin per gallon. It contains 8.0% abamectin.

Epi-MekTM SCL Miticide/Insecticide (EPA Reg. No. 100-1439 is a suspension concentrate 

which contains 0.35 lb abamectin per gallon. It contains 4.2% abamectin.

Table 3.3. Summary of Proposed Directions for Use of Abamectin on Corn (Field, Pop, Seed, and Sweet) 

and Soybean.

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 

Limitations1,2

Corn (Sweet)

Postemergence;

Broadcast foliar 

spray;

Ground or 

aerial 

equipment

Agri-Flex® 

Miticide/

Insecticide

[100-1350]

0.012 

–0.018 

not stated 0.037 7 

(forage 

or ears)

14

(stover)

Apply to thoroughly cover the 

crop to control spider mites 

and insects.

Apply when spider mites first 

appear. Repeat as needed to 

maintain control.

Do not apply more than 0.018 

lb ai/A of Agri-Flex® or more 

than 0.019 lb ai/A of any 

other foliar applied abamectin 

containing product or more 

than 0.086 lb ai/A of any 

other foliar applied 

thiamethoxam containing 

product per application.

Do not apply more than 0.037 

lb ai/A of Agri-Flex® or more 

than 0.038 lb ai/A of any 

other foliar applied abamectin 

containing product or more 

than 0.172 lb ai/A of any 

other foliar applied 

thiamethoxam containing 

product per season.
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Table 3.3. Summary of Proposed Directions for Use of Abamectin on Corn (Field, Pop, Seed, and Sweet) 

and Soybean.

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 

Limitations1,2

Postemergence;

Broadcast foliar 

spray;

Ground or 

aerial 

equipment

Agri-Mek® 

SC Miticide/

Insecticide

[100-1351]

Epi-MekTM 

SC Miticide/

Insecticide

[100-1408]

Epi-MekTM 

SCL 

Miticide/

Insecticide

[100-1439]

0.0096

-0.019

not stated 0.038 7 

(forage, 

ears, or 

stover)

Apply to thoroughly cover the 

crop to control spider mites.

Apply when spider mites first 

appear. Repeat as needed to 

maintain control.

Do not apply more than 0.019 

lb ai/A of Agri-Mek® 

SC/Epi-MekTM SC/EpiMekTM SCL or any other 

foliarly applied abamectincontaining product per 

application.

Do not apply more than 0.038 

lb ai/A of Agri-Mek® SC/ 

Epi-MekTM SC/Epi-MekTM 

SCL or any other foliarly 

applied abamectin-containing 

product in a growing season.

Soybeans

Postemergence;

Broadcast foliar 

spray;

Ground or 

aerial 

equipment

Agri-Flex® 

Miticide/

Insecticide

[100-1350]

0.011-

0.014

not stated 0.028 28 Apply to thoroughly cover the 

crop to control spider mites 

and insects. Apply when

spider mites first appear. 

Repeat as needed to maintain 

control.

Do not apply more than 0.014 

lb ai/A of Agri-Flex® or more 

than 0.019 lb ai/A of any 

other foliar applied abamectin 

containing product or more 

than 0.063 lb ai/A of any 

other foliar applied 

thiamethoxam containing 

product per application.

Do not apply more than 0.028 

lb ai/A of Agri-Flex® or more 

than 0.038 lb ai/A of any 

other foliar applied abamectin 

containing product or more 

than 0.125 lb ai/A of any 

other foliar applied 

thiamethoxam containing 

product per season.

Do not allow livestock to 

graze in treated areas or 

harvest treated soybean 

forage, straw or hay as feed 

for meat or dairy animals.
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Table 3.3. Summary of Proposed Directions for Use of Abamectin on Corn (Field, Pop, Seed, and Sweet) 

and Soybean.

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 

Limitations1,2

Do not feed treated soybean 

fodder or silage to meat or 

dairy animals.

Postemergence;

Broadcast foliar 

spray;

Ground or 

aerial 

equipment

Agri-Mek® 

SC Miticide/

Insecticide

[100-1351]

Epi-MekTM 

SC Miticide/

Insecticide

[100-1408]

Epi-MekTM 

SCL

Miticide/

Insecticide

[100-1439]

0.0096

-0.019 

not stated 0.038 7 

(forage 

or hay)

28 

(seed)

Apply to thoroughly cover the 

crop to control spider mites.

Apply when spider mites first 

appear. Repeat as needed to 

maintain control.

Do not apply more than 0.019 

lb ai/A of Agri-Mek® 

SC/Epi-MekTM SC/ EpiMekTM SCL or any other 

foliarly applied abamectincontaining product per 

application.

Do not apply more than 0.038 

lb ai/A of Agri-Mek® 

SC/Epi-MekTM SC/ EpiMekTM SCL or any other 

foliarly applied abamectincontaining product in a 

growing season. 1 Restrictions that apply to all the above labels and all the above crops:

Restricted Use Pesticide

To avoid illegal residues, Agri-Flex®/Agri-Mek® SC/ Epi-MekTM SC/Epi-MekTM SC must be mixed with a nonionic activator type wetting, spreading and/or penetrating spray adjuvant. Do not use binder or sticker type 

adjuvants.

Do not apply with aircraft in NY state.

Do not apply in less than 10 gal water /A by ground or 5 gal water/A by air.

The retreatment interval is 7 days.

For resistance management, do not make more than 2 sequential applications of Agri-Flex®/Agri-Mek® SC/ EpiMekTM SC/ Epi-MekTM SCL or any other foliar applied abamectin containing product. 2 Unless specifically restricted in the individual Crop Use Directions on the Agri-Mek® SC, Agri-Flex®, 

Epi-MekTM SC, or Epi-MekTM SCL labels, those products may be used in the same year abamectin is used as an atplant seed treatment. Abamectin is registered as a seed treatment on the Avicta® 500 FS label (EPA Reg. No. 100-

1204) at rates of 0.20-0.25 mg ai/seed for corn and 0.10-0.15 mg ai/seed for soybean.

Conclusions. The labels 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
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4.1.1 Summary of Plant Metabolism (860.1300)

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

No new plant metabolism data were submitted with this registration request. The qualitative 

nature of the abamectin residues in sweet corn and soybeans 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)

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

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

No new livestock metabolism data were submitted with this registration request.

The qualitative nature of abamectin residues in ruminants as a result of application to crops is 

adequately understood based on a goat metabolism study which was previously submitted 

(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 significantly 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.

No poultry metabolism study has been submitted and none is required. Based on dietary burden 
Abamectin Summary of Analytical Chemistry and Residue Data Barcode D414022

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calculations using Table 1 Feedstuffs (June 2008), no secondary residues are expected to occur in 

poultry commodities. (Note: The tolerances for meat and meat by-products of poultry and swine 

were established for residues from use in food handling establishments.)

4.1.3 Summary of Confined Rotational Crops (860.l850)

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

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

No confined rotational crop studies were submitted with this registration request. The qualitative 

nature of the residue in rotational crops is adequately defined. Review of the results of the 

previously submitted 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). 

4.1.4. Summary of Metabolites and Degradates

4.2 Comparison of Metabolic Pathways

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).

The results of a 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. It is not likely that residues of concern will occur in 

rotational crops.

Based on the goat metabolism study, 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. The 24-hydroxy-methyl metabolite is a minor metabolite in ruminants 

(goats). 

A poultry metabolism study has not been conducted. Based on dietary burden calculations using 

Table 1 Feedstuffs (June 2008), no secondary residues are expected to occur in poultry 

commodities; therefore, 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.) 

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

4.3 Residues of Concern Summary and Rationale

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

As shown in Table 4.3 below, the residues of concern for primary crops, rotational crops, and 

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

and the delta-8,9-isomers (also known as 8,9-Z isomers). 

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). 

5.0 Residue Profile

5.1 Residue Analytical Methods (860.1340)
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5.1.1 Data Collection Methods

49071008.der (sweet corn)

49071010.de1 (soybean field trials)

49071010.de2 (soybean processing study)

Sweet Corn and Soybean: Samples of sweet corn forage, K+CWHR, and stover and soybean 

forage, hay, and seed from the field trials and soybean processing study were analyzed for 

residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b using a high performance 

liquid chromatography method with tandem mass spectrometric detection (HPLC/MS/MS), 

Morse Analytical Method Meth-192/Revision #2. The LOQ (determined as the lowest level of 

method validation, LLMV) was 0.002 ppm for each analyte in each sweet corn and soybean 

matrix, for a combined LOQ of 0.006 ppm. The method was adequate for data collection based 

on acceptable concurrent recovery data. The fortification levels used in concurrent method 

recovery were adequate to bracket expected residue levels. Concurrent recoveries were 

corrected for apparent residues in controls; residues in the treated samples were not corrected for 

apparent residues in controls. 

Conclusions. An adequate HPLC/MS/MS data collection method was used to determine 

residues in sweet corn and soybean field trials and the soybean processing study. The method

separately determined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b. The 

LOQ was 0.002 ppm for each analyte in each sweet corn and soybean matrix, for a combined 

LOQ of 0.006 ppm. 

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 

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 

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 delta-8,9-isomer in the other 

peak).
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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)

49071008.der (sweet corn field trials)

49071010.de1 (soybean field trials)

49071010.de2 (soybean processing study)

49071012.der (corn and soybean storage stability)

49071016.der (storage stability on various crops)

Sweet corn field trial samples were stored frozen (<0 °C at the field sites and -25 to -10 °C at the 

analytical laboratory) from collection to analysis for 242-357 days (8.0-11.7 months) for forage, 

232-342 days (7.6-11.2 months) for K+CWHR, and 278-380 days (9.1-12.5 months) for stover. 

Samples were analyzed within 0-14 days of extraction.

Soybean field trial samples were stored frozen (<0 °C at the field sites and -25 to -10 °C at the 

analytical laboratory) from collection to analysis for 299-350 days (9.8 – 11.5 months) for 

forage, 362-440 days (11.9-14.5 months) for hay, and 317-360 days (10.4-11.8 months) for seed. 

Samples were analyzed within 0-6 days of extraction.

 

Soybean seeds for processing were stored frozen after harvest for 2 days at the Richland, IA site 

and at ambient temperatures for 6 days at the Bagley, IA site, after which they were shipped 

frozen from the field sites to the processing facility, where they were stored frozen (<-10 °F) 

until processing. Processing took place within 232-276 days (7.6-9.1 months) of harvest. 

Samples were stored frozen (generally <-10 °F at the processing facility and -25 to -10 °C at the 

analytical laboratory) from harvest/processing to analysis for 339-351 days (11.1-11.5 months) 

for seed (RAC), 93-119 days (3.1-3.9 months) for AGF, and 47-79 days (1.5-2.6 months) for the 

processed commodities. Samples were analyzed within 1-4 days of extraction. 

Acceptable 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 in/on 

cottonseed (avermectin B1a only) for 14 months; in/on celery, tomato, and strawberries for 24 

months; in/on oranges, lemons, and grapefruits for 29 months; and in/on pears for 35 months 

(DP# 191433, G. J. Herndon, 5/19/94). In addition, acceptable storage stability data have been 

submitted demonstrating that residues of avermectin B1a, avermectin B1b, and 8,9-Z avermectin 

B1a are stable in/on corn grain and forage during frozen storage for up to 6 months (refer to 

49071012.der) and in/on tomato, bean, sunflower seed, and potato for up to 24 months (refer to 

49071016.der)
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TABLE 5.2. Summary of Storage Conditions.

Matrix Storage Temperature (°C) Actual Storage Duration1 Limit of Demonstrated Storage Stability

Sweet corn, 

forage

<0 °C at field sites;

-25 to -10 at analytical 

laboratory

242-357 days

(8.0-11.7 months)

Acceptable 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 

in/on cottonseed (avermectin B1a only) for 14 

months; in/on celery, tomato, and 

strawberries for 24 months; in/on oranges, 

lemons, and grapefruits for 29 months; and 

in/on pears for 35 months (DP# 191433, G. J. 

Herndon, 5/19/94). 

In addition, acceptable storage stability data 

have been submitted demonstrating that 

residues of avermectin B1a, avermectin B1b, 

and 8,9-Z avermectin B1a are stable in/on 

corn grain and forage during frozen storage 

for up to 6 months (refer to 49071012.der)

and in/on tomato, bean, sunflower seed, and 

potato for up to 24 months (refer to 

49071016.der).

In addition, acceptable storage stability data 

have been submitted demonstrating that 

residues of avermectin B1a, avermectin B1b, 

and 8,9-Z avermectin B1a are stable in corn

and soybean meal and oil during frozen 

storage for up to 6 months (refer to 

49071012.der).

Sweet corn, 

K+CWHR

232-342 days

(7.6-11.2 months)

Sweet corn, 

stover

278-380 days

(9.1-12.5 months)

Soybean, forage Frozen at field sites;

-25 to -10 at analytical 

laboratory

299-350 days

(9.8 – 11.5 months)

Soybean, hay 362 - 440 days

(11.9-14.5 months)

Soybean, seed 317-360 days

(10.4-11.8 months)

Soybean seed for 

processing 

(RAC)

Frozen at field sites;

-25 to -10 at analytical 

laboratory

339-351 (11.1-11.5)

AGF 93-119 (3.1-3.9)

Meal 51-79 (1.7-2.6)

Hulls 57-66 (1.9-2.2)

Refined oil 47-63 (1.5-2.1)

1 Interval from harvest or processing to analysis. Sweet corn samples were analyzed within 0-14 days of extraction. Soybean 

samples were analyzed within 0-6 days of extraction. Samples of soybean seeds for processing and soybean processed 

fractions were analyzed within 1-4 days of extraction.

Conclusions. Acceptable storage stability data are available demonstrating that residues of 

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

least 24 months in five different crop types: high water (celery and pear), high acid (orange, 

lemon, grapefruit, strawberry, and tomato), high protein (bean), high fat (sunflower seed), and 

high starch (potato). The available and submitted storage stability data are adequate to support 

the storage conditions and durations of samples of corn forage, K+CWHR, and stover from the 

submitted sweet corn field trials, soybean forage, hay, and seed from the submitted soybean field 

trials, and soybean seed and processed commodities from the soybean processing study.

5.3 Residue Data

5.3.1 Crop Field Trials (860.1500)

49071008.der (sweet corn field trials)

49071010.de1 (soybean field trials)

Sweet Corn: 
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Syngenta Crop Protection, LLC has submitted field trial data for abamectin on sweet corn. 

Twelve field trials were conducted in the United States during the 2011 growing season in the 

North American Free Trade Agreement (NAFTA) Growing Zones 1 (NY and PA; 2 trials), 2 

(NC; 1 trial), 3 (FL; 1 trial), 5 (IA, KS, MN, WI; 5 trials), 10 (CA; 1 trial), 11 (OR; 1 trial), and 

12 (OR; 1 trial).

Each trial consisted of one untreated plot and one treated plot reflecting a combination of seed 

treatment and two foliar applications of abamectin. A 4.17 lb ai/gal flowable concentrate for 

seed treatment (FS) formulation (Abamectin 500FS; A14006B) was applied to sweet corn seed 

before planting. The nominal seed treatment rate was 0.25 mg ai/seed, which is 1X the 

registered rate on the Avicta 500 FS label (EPA Reg. No. 100-1204). Application rates of 

~0.013-0.041 lb ai/A for seed treatment were based on approximate seeding rates (23,478-79,746 

seeds/A) and actual seed treatment rates (0.262-0.234 mg ai/seed) as reported for each field trial.

Each treated plot received two foliar broadcast applications of a 0.70 lb ai/gal suspension 

concentrate (SC) formulation (Abamectin SC; A15368D) at 0.0184-0.0197 lb ai/A/application. 

The first applications were made 51-103 days after planting, and the second foliar applications 

were made at retreatment intervals (RTIs) of 6-8 days. All foliar applications were made using 

ground equipment in spray volumes of 2.5-31 gal/A. A nonionic surfactant (NIS) or crop oil 

concentrate (COC) was added to the foliar spray mixture for each trial. Total application rates 

including seed treatment and foliar applications were 0.0504-0.0795 lb ai/A. Samples of sweet 

corn forage, kernel + cob with husk removed (K+CWHR), and stover were harvested from all 

trials at preharvest intervals (PHIs) of 6-7 days. Additional samples were collected at PHIs of 1, 

3, 10, and 14 days from two trials to assess residue decline. Stover samples were allowed to dry 

for 4-12 days prior to collection.

Following a combination of seed treatment with the 4.17 lb ai/gal FS formulation and two foliar 

broadcast applications of the 0.70 lb ai/gal SC formulation at total application rates of 0.0504-

0.0795 lb ai/A, residues (and per trial averages) of avermectin B1a, 8,9-Z avermectin B1a, and 

avermectin B1b, respectively, in sweet corn harvested at PHIs of 6-7 days were: 0.00890-0.111 

(0.0106-0.0975), <0.002-0.002 (<0.002), and <0.002 (<0.002) ppm in/on forage; <0.002

(<0.002) ppm for all analytes in/on K+CWHR; and 0.0118-0.355 (0.0181-0.322), <0.002-

0.00293 (<0.002-0.00259), and <0.002-0.0296 (<0.002-0.0168) ppm in/on stover. Combined 

residues (and per trial averages) of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b

were <0.0129-<0.115 ppm (<0.0146-<0.102 ppm) in/on forage, <0.006 ppm (<0.006 ppm) in/on 

K+CWHR, and <0.0158-0.363 (<0.0221-0.329) ppm in/on stover.

In the residue decline trials, combined residues of avermectin B1a, 8,9-Z avermectin B1a, and

avermectin B1b generally decreased with increasing PHIs in/on sweet corn forage and stover. 

Residues of all analytes were below the LOQ (<0.002 ppm) in/on all samples of K+CWHR; 

therefore, residue decline could not be evaluated.

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.
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TABLE 5.3.1. Summary of Residue Data from Sweet Corn Crop Field Trials with Abamectin.

Commodity Analyte Total Rate

(lb ai/A)

PHI

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

SWEET CORN Proposed Use = max 0.038 lb ai/acre/season total application rate, min 7-day PHI for forage, ears and stover

Sweet corn, 

forage

Combined 

Residues3

0.0504-

0.0795

6-7 12 <0.0129 <0.115 <0.0146 <0.102 0.063 0.056 0.029

Sweet corn, 

K+CWHR

Combined 

Residues3

0.0504-

0.0795

6-7 12 <0.006 <0.006 <0.006 <0.006 0.006 0.006 N/A

Sweet corn, 

stover

Combined 

Residues3

0.0504-

0.0795

6-7 12 <0.0158 0.363 <0.0221 0.329 0.065 0.101 0.094

1 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) was used for any results reported as <LOQ in Table C.3. N/A = Not applicable. 2 LAFT = lowest average field trial; HAFT = highest average field trial. 3 Combined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b.

Conclusions. Adequate field trials were submitted for abamectin on sweet corn. Following a 

combination of seed treatment with the 4.17 lb ai/gal FS formulation and two foliar broadcast 

applications of the 0.70 lb ai/gal SC formulation at total application rates of 0.0504-0.0795 lb 

ai/A (approximately 1x the maximum registered seed treatment rate plus 1x the maximum

proposed seasonal foliar application rate), combined residues (and per trial averages) of 

avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b were <0.0129-<0.115 ppm (<0.0146-

<0.102 ppm) in/on forage, <0.006 ppm (<0.006 ppm) in/on K+CWHR, and <0.0158-0.363 

(<0.0221-0.329) ppm in/on stover. Combined residues of avermectin B1a, 8,9-Z avermectin B1a, 

and avermectin B1b generally decreased with increasing PHIs in/on sweet corn forage and stover. 

Residues of all analytes were below the LOQ (<0.002 ppm) in/on all samples of K+CWHR; 

therefore, residue decline could not be evaluated.

The studies adequately 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.

Soybeans:

Syngenta Crop Protection, LLC has submitted field trial data for abamectin on soybeans. 

Twenty field trials were conducted in the United States during the 2011 growing season in the 

North American Free Trade Agreement (NAFTA) Growing Zones 2 (VA and NC; 2 trials), 4

(AR, LA, MO; 3 trials), and 5 (IA, IL, MO, MN, ND, WI; 15 trials). Refer to Appendix A for 

the geographic distribution table. 

Each trial consisted of one untreated plot and one treated plot reflecting a combination of seed 

treatment and two foliar applications of abamectin. A 4.17 lb ai/gal flowable concentrate for 

seed treatment (FS) formulation (Abamectin 500FS; A14006B) was applied to soybean seed 

before planting. The nominal seed treatment rate was 0.15 mg ai/seed, which is 1X the 

registered rate on the Avicta 500 FS label (EPA Reg. No. 100-1204). Seed treatment rates of 

~0.0402-0.0884 lb ai/A were based on approximate seeding rates (124,069-260,282 seed/A) and 

actual seed treatment rates (0.135-0.158 mg ai/seed) as reported for each field trial. Each treated 
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plot received two foliar broadcast applications of a 0.70 lb ai/gal suspension concentrate (SC) 

formulation (Abamectin SC; A15368D) at 0.0181-0.0199 lb ai/A/application, except for the 

forage plot of Trial -10 (MN), where the second foliar application was made at 0.0223 lb ai/A.

The first foliar applications were made to forage and hay plots 25-80 days after planting and to 

seed plots 75-117 days after planting; the second foliar applications were made at retreatment 

intervals (RTIs) of 6-9 days. All foliar applications were made using ground equipment in spray 

volumes of 2.5-35 gal/A. A nonionic surfactant (NIS) or crop oil concentrate (COC) was added 

to the foliar spray mixture for each trial. Total application rates including seed treatment and 

foliar applications were 0.077-0.127 lb ai/A. The highest combined application rates occurred at 

Trial -01 (VA), where the seed treatment rate was 0.0884 lb ai/A for both plots. Excluding this 

trial, the maximum combined application rate was 0.102 lb ai/A. 

Samples of soybean forage and hay were harvested from all trials at preharvest intervals (PHIs) 

of 6-8 days, and samples of seed were harvested from all trials at PHIs of 27-29 days. Additional 

forage and hay samples were collected at PHIs of 1, 3, 10, and 14 days, and additional seed 

samples were collected at PHIs of 20/21, 23/24, 31/32, and 34/35 days from two trials to assess 

residue decline. Hay samples were allowed to dry for 2-10 days prior to collection.

Residues following a combination of seed treatment with the 4.17 lb ai/gal FS formulation and 

two foliar broadcast applications of the 0.70 lb ai/gal SC formulation at total application rates of

0.077-0.127 lb ai/A are shown in Table 5.3.2 below. Combined residues (and per trial averages) 

of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b were <0.0121-0.165 (<0.0138-

<0.158) ppm in/on forage, <0.0420-0.741 (<0.0448-0.607) ppm in/on hay, and <0.006 (<0.006) 

ppm in/on seed. The highest residues in hay were observed in the trial which received the 

highest second foliar application (Trial -10). 

In the residue decline trials, combined residues of avermectin B1a, 8,9-Z avermectin B1a, and

avermectin B1b generally decreased with increasing PHIs in/on soybean forage and hay. In one 

trial, however, residues in/on hay increased from the 1- to the 3-day PHI and declined thereafter. 

Residues of all analytes were below the LOQ (<0.002 ppm) in/on all samples of seed; therefore, 

residue decline could not be evaluated.

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 5.3.2. Summary of Residue Data from Soybean Crop Field Trials with Abamectin.

CommodityAnalyte Total 

Rate

(lb ai/A)

PHI

(days)

Residue Levels (ppm)1

n Sample 

Min.

Sample 

Max.

LAFT2 HAFT2 Median Mean Std. 

Dev.

SOYBEAN Proposed Use =max 0.038 lb ai/acre/season total application rate; min 7-day PHI for forage and hay; 

28-day PHI for seed

Forage Combined 

Residues3

0.0776-

0.127

6-8 20 <0.0120 0.165 <0.0138 <0.158 0.037 0.059 0.047

Hay Combined 

Residues3

0.0776-

0.127

6-8 20 <0.0420 0.741 <0.0448 0.607 0.200 0.240 0.174

Seed Combined 

Residues3

0.0770-

0.127

27-29 20 <0.006 <0.006 <0.006 <0.006 <0.006 <0.006 N/A

1 Except for sample min/max, values reflect per trial averages; n = no. of field trials. N/A = Not Applicable.
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2 LAFT = lowest average field trial; HAFT = highest average field trial. 3 Combined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b.

Conclusions. Adequate field trials were submitted for abamectin on soybeans. Following a 

combination of seed treatment with the 4.17 lb ai/gal FS formulation and two foliar broadcast 

applications of the 0.70 lb ai/gal SC formulation at total application rates of 0.077-0.127 lb ai/A

(approximately 1x the maximum registered seed treatment rate plus 1x the maximum proposed 

seasonal foliar application rate), combined residues (and per trial averages) of avermectin B1a, 

8,9-Z avermectin B1a, and avermectin B1b were <0.0121-0.165 (<0.0138-<0.158) ppm in/on 

forage, <0.0420-0.741 (<0.0448-0.607) ppm in/on hay, and <0.006 (<0.006) ppm in/on seed. 

The highest residues in hay were observed in the trial which received the highest second foliar 

application (Trial -10). Combined residues of avermectin B1a, 8,9-Z avermectin B1a, and

avermectin B1b generally decreased with increasing PHIs in/on soybean forage and hay. In one 

trial, however, residues in/on hay increased from the 1- to the 3-day PHI and declined thereafter. 

Residues of all analytes were below the LOQ (<0.002 ppm) in/on all samples of seed; therefore, 

residue decline could not be evaluated.

The studies adequately 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)

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

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

No field rotational crop studies were submitted with this registration request. Review of the 

results of the confined rotational crop study indicated that field rotational crop studies are not 

required (PP#7F3500, PP#8F3592, and PP#5E4566, DP#s 230333, 230352, and 230880, G. 

Herndon, 1/10/97).

5.3.3 Processed Food and Feed (860.1520)

No processed commodities are associated with sweet corn. The processed commodities for 

soybeans are meal, hulls, refined oil, and aspirated grain fractions (AGF).

Syngenta CropScience, LLC has submitted a processing study with abamectin on soybean. Two 

trials were conducted during the 2011 growing season in Richland, IA and Bagley, IA reflecting 

a combination of seed treatment and two foliar applications of abamectin. A 4.17 lb ai/gal 

flowable concentrate for seed treatment (FS) formulation (Abamectin 500FS; A14006B) was 

applied to soybean seed before planting. Application rates of ~0.0413-0.0455 lb ai/A for seed 

treatment were based on approximate seeding rates and actual seed treatment rates. Each treated 

plot received two foliar broadcast applications of a 0.70 lb ai/gal suspension concentrate (SC) 

formulation (Abamectin SC; A15368D) at exaggerated rates of 0.0938-0.0949 lb 

ai/A/application (~5x the application rate used in the corresponding field trials). The first 

applications were made 96-81 days after planting, and the second foliar applications were made 
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at retreatment intervals (RTIs) of 6 days. A nonionic surfactant (NIS) or crop oil concentrate 

(COC) was added to the foliar spray mixture for each trial. Total application rates including seed 

treatment were 0.231-0.234 lb ai/A. Soybean seed was harvested at commercial maturity at 

preharvest intervals (PHIs) of 27-37 days and processed into aspirated grain fractions (AGF), 

meal, hulls, and refined-bleached deodorized oil using simulated commercial procedures.

 

Following a combination of seed treatment with the 4.17 lb ai/gal FS formulation and two foliar 

broadcast applications of the 0.70 lb ai/gal SC formulation at total application rates of 0.231-

0.234 lb ai/A, residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b were below 

the LOQ in/on all samples of soybean seed and refined oil from both trials and in all samples of 

processed commodities from the Richland, IA trial except AGF, in which average residues of 

avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b, and combined residues of the three 

analytes, respectively, were 0.193, 0.00332, 0.00256, and 0.198 ppm. In the Bagley, IA trial, 

residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b, respectively, were: 0.496, 

0.00456, 0.00635, ppm in/on AGF; <0.00233, <0.002, and <0.002 ppm in meal; and 0.00292, 

<0.002, and <0.002 ppm in hulls. Combined residues of the three analytes were 0.507, 

<0.00633, and <0.00692 ppm in/on AGF, meal, and hulls, respectively. 

The processing data indicate that combined residues of avermectin B1a, avermectin B1b, and 8,9-

Z avermectin B1a may concentrate in/on AGF (average processing factor of 59x), meal (1.1x), 

and hulls (1.2x). For all other matrices, processing factors could not be calculated because 

residues were below the LOQ in both the RAC and processed commodities.

The observed processing factors are less than the theoretical concentration factor of 11.3x in 

soybean hulls, 2.2x in soybean meal, and 12x in soybean oil (based on separation into 

components; OCSPP 860.1520, Table 3).
Page 25 of 45

TABLE 5.3.3. Residue Data from Soybean Processing Study with Abamectin.

RAC Processed 

Commodity

Total 

Rate

(lb 

ai/A)

PHI

(days)

Residues1 (ppm) [Average] Processing Factor3

Avermectin B1a 8,9-Z

Avermectin B1a

Avermectin B1b Combined 

Residues2

Avermectin 

B1a

8,9-Z

Avermectin 

B1a

Avermectin 

B1b

Combined 

Residues2

Richland, IA; 2011 (TK0040391-19)

Soybean Seed (RAC) 0.231 27 <0.002, <0.002, 

<0.002

[<0.002]

ND, ND, ND

[<0.002]

ND, ND, ND

[<0.002]

<0.006, <0.006, 

<0.006 

[<0.006]

-- -- -- --

AGF 0.196, 0.189

[0.192]

0.00344, 

0.00320 

[0.00332]

0.00246, 

0.00266

[0.00256]

0.202, 0.195 

[0.198]

≥96 ≥1.7 ≥1.3 ≥33

Meal <0.002, ND

[<0.002]

ND, ND

[<0.002]

ND, ND

[<0.002]

<0.006, <0.006 

[<0.006]

NC4 NC NC NC

Hulls <0.002, <0.002

[<0.002]

ND, ND

[<0.002]

ND, ND

[<0.002]

<0.006, <0.006 

[<0.006]

NC NC NC NC

Refined oil ND, ND

[<0.002]

ND, ND

[<0.002]

ND, ND

[<0.002]

<0.006, <0.006 

[<0.006]

NC NC NC NC

Bagley, IA;2011 (TK0040391-20)

Soybean Seed (RAC) 0.234 37 <0.002, <0.002, 

<0.002

[<0.002]

ND, ND, ND

[<0.002]

ND, ND, ND

[<0.002]

<0.006, <0.006, 

<0.006 

[<0.006]

-- -- -- --

AGF 0.498, 0.494

[0.496]

0.00492, 

0.00420 

[0.00456]

0.00615, 

0.00655

[0.00635]

0.509, 0.505 

[0.507]

≥248 ≥2.3 ≥3.2 ≥84.5

Meal ND, 0.00265

[<0.00232]

ND, ND 

[<0.002]

ND, ND 

[<0.002]

<0.006, 

<0.00665 

[0.00632]

1.2 NC NC 1.1

Hulls 0.00281, 

0.00302

[0.00292]

ND, ND 

[<0.002]

ND, ND 

[<0.002]

<0.00681, 

0.00702 

[0.00692]

1.5 NC NC 1.2

Refined oil ND, ND 

[<0.002]

ND, ND 

[<0.002]

ND, ND 

[<0.002]

<0.006, <0.006 

[<0.006]

NC NC NC NC
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TABLE 5.3.3. Residue Data from Soybean Processing Study with Abamectin.

RAC Processed 

Commodity

Total 

Rate

(lb 

ai/A)

PHI

(days)

Residues1 (ppm) [Average] Processing Factor3

Avermectin B1a 8,9-Z

Avermectin B1a

Avermectin B1b Combined 

Residues2

Avermectin 

B1a

8,9-Z

Avermectin 

B1a

Avermectin 

B1b

Combined 

Residues2

Average Processing Factors (for Trials TK0040391-19 and TK0040391-20)

Soybean Seed (RAC) -- -- -- --

AGF 172 2.0 2.2 59

Meal 1.2 NC NC 1.1

Hulls 1.5 NC NC 1.2

Refined oil NC NC NC NC

1 The LOQ was 0.002 ppm for each analyte in each corn matrix; the LOD was not reported. <0.002 ppm represents values <LOQ. ND = not detected (no observable 

chromatographic response) as reported by the petitioner. Average residues and combined residues were calculated by the study reviewer using the LOQ for values reported as 

<LOQ.

2 Combined residues of avermectin B1a, avermectin B1b, and 8,9-Z avermectin B1a. 3 Processing Factor = [Measured residue for analyte in the processed fraction] / [Measured residue for analyte in the grain RAC]. 4 NC = Not calculated; residues were below the LOQ in both the RAC and processed fraction.
Page 27 of 45

Conclusions. No processed commodities are associated with sweet corn. The processed 

commodities for soybean are meal, hulls, refined oil, and aspirated grain fractions (AGF). A 

processing study on soybeans indicated that combined residues of avermectin B1a, avermectin 

B1b, and 8,9-Z avermectin B1a may concentrate in/on AGF (average processing factor of 59x),

meal (1.1x), and hulls (1.2x). A processing factor could not be calculated for refined soybean oil 

because residues were below the LOQ in both the RAC and the processed commodity; however, 

additional processing data are not required and a separate tolerance for refined oil is not needed 

since the processing study was conducted at an exaggerated rate (~5x the proposed foliar rate). 

Based on the average residues in soybean seed and the concentration factor of 1.1x for meal and 

1.2x for hulls (i.e., 0.006 ppm x 1.2x = 0.0072 ppm), no separate tolerances are needed for 

soybean meal and hulls since residues in those commodities will be less than the recommended 

tolerance of 0.01 ppm on soybean seed.

The residue data are adequately supported by the storage stability studies. The analytical method 

is adequate for the analysis of the residues of concern. The residue data adequately address the 

residues of concern.

5.3.4 Meat, Milk, Poultry and Eggs (860.1480)

Livestock feed items are associated with the proposed uses on sweet corn and soybeans (Table 1 

Feedstuffs, June 2008). Because there are feed items associated with the proposed uses, the 

established livestock tolerances have been reassessed. Residues in livestock commodities 

calculated below include residues from uses on proposed/registered crops and from beef and 

dairy cattle ear tags.

Livestock Feeding Studies

RCB #1568, L. Cheng, 2/11/87

No poultry feeding studies have been submitted or required. No additional ruminant feeding 

studies have been submitted with this petition. 

Feeding studies on lactating dairy cattle were reviewed in PP#7G3468 (RCB #1568, L. Cheng, 

2/11/87; MRID #164157; Accession #265585). Each feeding level included three treated 

animals. A control group was also included.
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Table 5.3.4.a. Abamectin Residues in Cow Milk from a 28-Day Feeding Study

Day

Avermectin B1a 1 Levels (ppb) in Milk at 3 Dosing Levels

10 ppb 30 ppb 100 ppb

1 ND2 ND ND

2 ND ND ND - 1

3 ND ND ND - 1

5 ND ND - 1 ND - 1

7 ND ND 1 - 2

14 ND ND 1 - 4

28 ND ND 1 1 Abamectin was fed. Avermectin B1a was determined. 2 ND = not detectable down to the lower limit that adequate method recoveries were achieved (0.5 ppb).

Table 5.3.4.b. Abamectin Residues in Dairy Cattle Tissues from a 28-Day Feeding Study

Dose (ppb)

Avermectin B1a 1 Levels in Various Tissues and Organs (ppb)

Liver Muscle Fat Kidney

10 3 - 4 1 - 2 2 1 - 2

30 5 - 8 2 4 - 6 2

100 18 - 20 2 10 - 14 4 - 5

1 Abamectin was fed. Avermectin B1a was determined. The data were validated at 5 ppb avermectin B1a.

Table 5.3.4.c. Summary of Livestock Feeding Studies with Abamectin.

Commodity Feeding Level, ppm Residue in Tissue, ppm1 Tissue-to-Feed Ratio

Milk 0.010 ND2 --

0.030 0.001 0.033

0.100 0.004 0.040

Muscle 

(cattle)

0.010 0.002 0.20

0.030 0.002 0.067

0.100 0.002 0.02

Fat (cattle)2 0.010 0.002 0.20

0.030 0.006 0.20

0.100 0.014 0.14

Liver (cattle) 0.010 0.004 0.40

0.030 0.008 0.27

0.100 0.020 0.2

Kidney 

(cattle)

0.010 0.002 0.2

0.030 0.002 0.067

0.100 0.005 0.05 1

maximum residue 2 ND = not detectable.
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5.3.4.1 Dietary Burden

A summary of the livestock feeds considered in a more balanced diet (MDB) is presented in 

Table 5.3.4.1.1., and the estimated dietary burden is presented in Table 5.3.4.1.2.

Table 5.3.4.1.1 Feeds Considered in More Balanced Diet

Crop Commodity Type input %DM Max 

%Diet % Diet Used

Beef Cattle

Cotton Hulls R 0.006 Median 90 10 10

Citrus Pulp, dried R 0.02 Median 91 10 0

Cotton Gin byproducts R 0.018 Median 90 5 0

Pineapple Process residue R 0.016 Median 25 10 0

Grain Aspirated grain fractions CC 0.4 Median 85 5 5

Potato Culls CC 0.0027 HR 20 30 0

Potato Process Waste CC 0.0027 Median 12 30 0

Cotton Meal PC 0.006 Median 89 5 5

Soybean Seed PC 0.006 Median 89 5 0

Dairy Cattle

Corn, sweet Stover R 0.329 HR 83 15 15

Corn, sweet Forage R 0.102 HR 48 45 30

Almond Hulls R 0.039 Median 90 10 0

Citrus Pulp, dried R 0.02 Median 91 10 0

Pineapple Process residue R 0.016 Median 25 10 0

Corn, sweet Cannery waste CC 0.063 Median 30 10 10

Apples Pomace, wet CC 0.02 Median 40 10 0

Potato Process Waste CC 0.0027 Median 12 10 0

Potato Culls CC 0.0027 HR 20 10 0

Cotton Undelinted seed PC 0.006 Median 88 10 10

Cotton Meal PC 0.006 Median 89 10 0

Soybean Seed PC 0.006 Median 89 10 0

Poultry

Cotton Meal PC 0.006 Median 89 20 20

Soybean Seed PC 0.006 Median 89 20 5

Swine

Cotton Meal PC 0.006 Median 89 15 15

Soybean Seed PC 0.006 Median 89 15 0
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Table 5.3.4.1.2 More Balanced Diet (MBD)

Crop Commodity Type Residue %DM %Diet Dietary Contribution

ppm input ppm

Beef Cattle

Cotton Hulls R 0.006 Median 90 10 0.0007

Grain Aspirated grain fractions CC 0.4 Median 85 5 0.02

Cotton Meal PC 0.006 Median 89 5 0.0003

Untreated feed NA NA NA NA NA 80 0

Total NA NA NA NA NA 100 0.02

Dairy Cattle

Corn, sweet Stover R 0.329 HR 83 15 0.06

Corn, sweet Forage R 0.102 HR 48 30 0.06

Corn, sweet Cannery waste CC 0.063 Median 30 10 0.02

Cotton Undelinted seed PC 0.006 Median 88 10 0.0007

Untreated feed NA NA NA NA NA 35 0

Total NA NA NA NA NA 100 0.14

Poultry

Cotton Meal PC 0.006 Median 89 20 0.001

Soybean Seed PC 0.006 Median 89 5 0.0003

Untreated feed NA NA NA NA NA 75 0

Total NA NA NA NA NA 100 0.002

Swine

Cotton Meal PC 0.006 Median 89 15 0.0009

Untreated feed NA NA NA NA NA 85 0

Total NA NA NA NA NA 100 0.0009 1 R: Roughage; CC: Carbohydrate concentrate; PC: Protein concentrate. 2 Table 1 Feedstuffs (July 2008). 3 Contribution = ([tolerance /% DM] X % diet) for beef and dairy cattle; contribution = ([tolerance] X % 

diet) for poultry and swine.

4 LOQ tolerance (i.e., <0.002 ppm x 3 analytes = <0.006 ppm).

5.3.4.2. Estimated Secondary Residues in Livestock

Estimated Secondary Residues in Livestock from Crops

Table 5.3.4.2.1. Estimation of Secondary Residues in Cattle Commodities from Use of Abamectin on 

Crops

Commodity Tissue-to-Feed Ratio1 Dietary Burden (ppm) Expected Residue

Milk 0.040 0.14 0.0056

Muscle 0.02 0.14 0.0028

Fat 0.14 0.14 0.020

Liver 0.2 0.14 0.028

Kidney 0.05 0.14 0.007 1 The 0.100 ppm feeding level is used because it is closest to the dietary burden of 0.14 ppm.
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Table 5.3.4.2.2. Estimation of Secondary Residues in Swine Commodities from Use of Abamectin on 

Crops

Commodity Tissue-to-Feed Ratio1 Dietary Burden (ppm) Expected Residue

Muscle 0.02 0.00090 0.000018

Fat 0.14 0.00090 0.00013

Liver 0.2 0.00090 0.00018

Kidney 0.05 0.00090 0.000045 1 The 0.100 ppm feeding level.

Residues in Meat, Fat, and Meat Byproducts from Use of Ear Tags on Beef Cattle and Nonlactating Dairy Cattle

D357192, T. Morton, 1/27/09

Quantifiable residues of abamectin (>0.005 ppm) were found in some liver, kidney, and fat 

samples from beef cattle/non-lactating dairy cattle treated with the cattle ear tag according to 

label directions (1x). Based on these data, the tolerances for cattle fat and cattle meat byproducts 

were increased to from 0.01 to 0.03 ppm and from 0.02 to 0.06 ppm, respectively. No change 

was required to the established tolerance for ruminant meat as a result of the ear tag use.

 

Residues in Milk from Use of Ear Tags on Lactating Dairy Cattle

D410993, N. Dodd, 5/14/14

Maximum residues of abamectin in milk from use of ear tags on lactating dairy cattle were 

0.0046 ppm.

Comparison of Established Tolerances to Expected Residues

The table below compares the total expected residues in livestock commodities to the established 

tolerances. 

Table 5.3.4.2.3. Comparison of Expected Residues to Established Tolerances, and Tolerance 

Recommendations.

Commodity

Expected Residue 

from Dietary 

Burden (ppm)

Expected 

Residue from 

Cattle Ear Tag 

Use1 (ppm)

Total 

Expected 

Residue

(ppm)

Established 

Tolerance3

(ppm)

Recommended 

Tolerance

(ppm)4

Cattle, fat 0.020 0.018 + (0.0036) 0.042 0.03 0.05

Cattle, meat 0.0028 <0.005 +

(<0.001) 0.0088 0.02 0.02

Cattle, meat byproducts 

(Liver) 0.028 0.043 + (0.0086) 0.080

0.06 0.09 Cattle, meat byproducts

(Kidney) 0.0070 0.017 + (0.0034) 0.027

Milk 0.0064 0.0046 0.011 0.005 0.015

Goat, Horse, Sheep, fat 0.020 0.020 0.01 0.03

Goat, Horse, Sheep, meat 0.0028 0.0028 0.02 0.02

Goat, Horse, Sheep, meat 

byproducts;(Liver) 0.028 0.028

0.02 0.04 Goat, Horse, Sheep, meat 

byproducts (Kidney)

0.0070 0.0070

Hog, fat 0.00013 0.00013 0.01 0.01
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Table 5.3.4.2.3. Comparison of Expected Residues to Established Tolerances, and Tolerance 

Recommendations.

Commodity

Expected Residue 

from Dietary 

Burden (ppm)

Expected 

Residue from 

Cattle Ear Tag 

Use1 (ppm)

Total 

Expected 

Residue

(ppm)

Established 

Tolerance3

(ppm)

Recommended 

Tolerance

(ppm)4

Hog, meat 0.000018 0.000018 0.02 0.02

Hog, meat byproducts

(Liver)

0.00018 0.00018 0.02 0.02

Hog, meat byproducts

(Kidney)

0.000045 0.000045

Poultry, meat 0.005 0.00 0.025 0.02

Poultry, meat byproducts

( Liver)

0.005 0.00 0.025 0.02

1 Maximum residues of avermectin B1a/8,9-Z avermectin B1a from D357192(T. Morton, 1/27/09) are reported in the 

table. The LOQ of 0.005 ppm in cattle muscle, fat, kidney, and liver for the method (an HPLC method with 

fluorescence detection; Method AATM-R-53) was supported by acceptable method validation recoveries. Residues 

of avermectin B1b/8,9-Z avermectin B1b were not determined; they comprise ≤20% of the active ingredient. Residues 

of avermectin B1b/8,9-Z avermectin B1b are included in the table (in parenthesis) as 20% of the reported avermectin 

B1a/8,9-Z avermectin B1a residue and are included in the total. 2 The maximum residue of abamectin (total avermectin B1a/8,9-Z isomer and avermectin B1b/8,9-Z isomer) in milk 

from the dairy cattle ear tag use (pending) is reported as 0.0046 ppm (D416280, N. Dodd, 5/15/14). 3 Tolerances on cattle fat and meat byproducts are higher than other ruminant tolerances because they were raised 

upon establishment of the abamectin ear tag use on beef cattle. The established tolerances for meat and meat byproducts of poultry and swine were established at the LOQ of the enforcement method for residues in food handling 

establishments. In connection with D310414 (N. Dodd, 12/1/04), the LOQs of the enforcement methods for the 

combined residues of avermectin B1a and 8,9-Z-avermectin B1a (one peak on the chromatogram) and the combined 

residues of avermectin B1b and 8,9-Z-avermectin B1b (one peak on the chromatogram) were determined to be 0.005 

ppm for milk, 0.02 ppm for meat and meat byproducts, and ≤0.01 ppm for other food items in food handling 

establishments. 

4 Recommended changes are bolded.

5 No poultry metabolism or feeding studies have been submitted. Based on dietary burden calculations using Table 

1 Feedstuffs (June 2008), no secondary residues are expected to occur in poultry commodities; therefore, no poultry 

metabolism or feeding studies are required. The tolerances for meat and meat by-products of poultry and swine 

were established for residues in food handling establishments and were set at the enforcement method LOQs.

 

Conclusions. Because there are livestock feed items associated with the proposed uses on sweet 

corn and soybeans, the established livestock tolerances have been reassessed. The calculated 

residues in livestock commodities include residues from uses on proposed/registered crops, from 

use in food handling establishments, and from beef and dairy cattle ear tags.

Higher tolerances are needed for the fat of cattle (0.05 ppm), meat byproducts of cattle (0.09 

ppm), fat of goat, horse, and sheep (0.03 ppm), meat byproducts of goat, horse, and sheep (0.04 

ppm), and milk (0.015 ppm). The established tolerances on the remaining livestock commodities 

are adequate. Refer to Table 2.2.2 for all the recommended livestock tolerances.

No poultry feeding studies have been submitted or required. Based on dietary burden 

calculations using Table 1 Feedstuffs (June 2008), no secondary residues are expected to occur in 

poultry commodities; therefore, no poultry feeding studies are required.
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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 

four formulations of abamectin on sweet corn and soybeans. 

Crop field trials: The sweet corn and soybean field trials adequately reflect the proposed use 

patterns. The number of trials and the geographic representation are adequate. Field trial 

residues in sweet corn forage and stover and soybean forage and hay were small (low level) but 

quantifiable as combined residues; these combined residues generally decreased with increasing 

PHIs . Combined residues in sweet corn kernel plus cob with husk removed and in soybean seed 

were all <LOQ (<0.006 ppm). 

Processing studies: No processed commodities are associated with sweet corn. The processed 

commodities for soybean are meal, hulls, refined oil, and aspirated grain fractions (AGF). A 

processing study on soybeans indicated that combined residues of avermectin B1a, avermectin 

B1b, and 8,9-Z avermectin B1a may concentrate in/on AGF (average processing factor of 59x),

meal (1.1x), and hulls (1.2x). A processing factor could not be calculated for refined oil because 

residues were below the LOQ in both the RAC and processed commodities; however, additional 

processing data are not required and a separate tolerance for refined oil is not needed since the 

processing study was conducted at an exaggerated rate (~5x the proposed foliar rate). 

Storage Stability: Acceptable storage stability data are available demonstrating that residues of 

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

least 24 months in five different crop types: high water (celery and pear), high acid (orange, 

lemon, grapefruit, strawberry, and tomato), high protein (bean), high fat (sunflower seed), and 

high starch (potato). The available and submitted storage stability data are adequate to support 

the storage conditions and durations of samples from the residue studies.

Meat, Milk, Poultry, and Eggs: Because there are livestock feed items associated with the 

proposed uses on sweet corn and soybeans, the established livestock tolerances have been 

reassessed. The calculated residues in livestock commodities include residues from uses on 

proposed/registered crops and beef and dairy cattle ear tags. Higher tolerances are needed for 

some livestock commodities.

No poultry feeding studies have been submitted or required. Based on dietary burden 

calculations using Table 1 Feedstuffs (June 2008), no secondary residues are expected to occur 

in poultry commodities; therefore, no poultry feeding studies are required.
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Rotational Crops: A confined rotational crop study indicated that avermectin residues of 

significant toxicological concern are not expected to occur in rotational crops. 

6.0 Tolerance Derivation

Based on residues <LOQ (<0.006 ppm) in soybean seed and sweet corn kernel plus cob with 

husk removed, the proposed tolerances of 0.01 ppm for those commodities are adequate. Based 

on the average residues in soybean seed and the concentration factor of 1.1x for meal and 1.2x 

for hulls (i.e., 0.006 ppm x 1.2x = 0.0072 ppm), no separate tolerances are needed for soybean 

meal and hulls since residues in those commodities will be less than the recommended tolerance 

of 0.01 ppm on soybean seed. Based on residues of <0.006 ppm in soybean seed and a 

concentration factor of 59x in aspirated grain fractions, a tolerance is needed for grain, aspirated 

grain fractions at 0.40 ppm. 

Since livestock feed items are associated with sweet corn and soybean, the established livestock 

tolerances have been re-evaluated. Higher tolerances are needed for the fat of cattle (0.05 ppm), 

meat byproducts of cattle (0.09 ppm), fat of goat, horse, and sheep (0.03 ppm), meat byproducts 

of goat, horse, and sheep (0.04 ppm), and milk (0.015 ppm). The established tolerances on the 

remaining livestock commodities are adequate. Table 2.2.2 lists all the recommended livestock 

tolerances.

As shown in Appendix C, the OECD tolerance calculation procedures were used for calculating 

the recommended tolerance for sweet corn forage and stover and soybean forage and hay. 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. 

Sweet Corn Forage and Stover (MRID 49071008)

The datasets used to establish tolerances for abamectin consisted of field trial data on sweet corn 

forage and stover representing application rates of 0.0504-0.0795 lb ai/A abamectin with PHIs of 

6-7 days. The field trial application rates are approximately 1x the maximum registered seed 

treatment rate plus 1x the maximum proposed seasonal foliar application rate. The PHIs are 

within 25% of the minimum label PHI. The average residue values used to calculate the 

tolerances are provided below. Combined residues of avermectin B1a, 8,9-Z avermectin B1a, and 

avermectin B1b were quantifiable in/on samples from all twelve field trials. Using the OECD 

tolerance calculation procedures, the recommended tolerances are 0.2 ppm and 0.5 ppm for 

combined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b in sweet corn 

forage and stover, respectively.

Soybean Forage and Hay (MRID 49071010)

The datasets used to establish tolerances for abamectin consisted of field trial data on soybean 

forage and hay representing application rates of 0.0776-0.127 lb ai/A abamectin with PHIs of 6-8

days. The field trial application rates are approximately 1x the maximum registered seed 

treatment rate plus 1x the maximum proposed seasonal foliar application rate. The PHIs are 

within 25% of the minimum label PHI. The average residue values used to calculate the 
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tolerances are provided below. Combined residues of avermectin B1a, 8,9-Z avermectin B1a, and 

avermectin B1b were quantifiable in/on samples from all twenty trials. Using the OECD 

tolerance calculation procedures, the recommended tolerances are 0.3 ppm and 1 ppm for 

combined residues of avermectin B1a, 8,9-Z avermectin B1a, and avermectin B1b in soybean 

forage and hay, respectively.
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Appendix A. Field Trial Geographic Distribution

Sweet Corn

TABLE A.1.3. Trial Numbers and Geographical Locations.

NAFTA Growing Regions Sweet Corn

Submitted Requested1

Canada U.S.

1 2 -- 2/2

1A -- -- --

2 1 -- 1

3 1 -- 1

4 -- -- --

5 5 -- 5/3

5A -- -- --

5B -- -- --

6 -- -- --

7 -- -- --

7A -- -- --

8 -- -- --

9 -- -- --

10 1 -- 1

11 1 -- 1

12 1 -- 1

13 -- -- --

14 -- -- --

15 -- -- --

16 -- -- --

17 -- -- --

18 -- -- --

19 -- -- --

20 -- -- --

21 -- -- --

Total 12 12 (9)

1 As per Table 5 of 860.1500 for sweet corn; the second number reflects a 25% reduction in the number of field trials allowed for 

the crop as a representative commodity in support of a crop group/subgroup tolerance or when application results in no 

quantifiable residues. 
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Soybeans

TABLE A.1.3. Trial Numbers and Geographical Locations.

NAFTA Growing Regions Soybean

Submitted Requested1

Canada U.S.

1 -- -- --

1A -- -- --

2 2 -- 2/2

3 -- -- --

4 3 -- 3/2

5 15 -- 15/11

5A -- -- --

5B -- -- --

6 -- -- --

7 -- -- --

7A -- -- --

8 -- -- --

9 -- -- --

10 -- -- --

11 -- -- --

12 -- -- --

13 -- -- --

14 -- -- --

15 -- -- --

16 -- -- --

17 -- -- --

18 -- -- --

19 -- -- --

20 -- -- --

21 -- -- --

Total 20 20/15

1 As per Table 5 of 860.1500 for soybean. The second number reflects a 25% reduction in the number of field trials allowed for 

the crop as a representative commodity in support of a crop group/subgroup tolerance or when application results in no 

quantifiable residues. 
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Appendix B. International Residue Limits Tables

Plants:

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

Corn, sweet, forage 0.20

Corn, sweet, kernel plus cob with 

husks removed 0.01

Corn, sweet, stover 0.50

Soybean, forage 0.30

Soybean, hay 1.0

Soybean, seed 0.01

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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Livestock:

Abamectin (122804; 9/19/2013)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

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-O-demethyl 

avermectin A1a) and less than or 

equal to 20% avermectin B1b

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

methylpropyl)-25-(1-

methylethyl) avermectin A1a) 

and its delta-8,9-isomer)

Animal 

commodities: sum 

of avermectin

B1a and 8,9-Zavermectin B1a.

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

US Canada Mexico2 Codex3

Cattle, fat 0.05 0.14

Cattle, meat 0.02 0.01 (*)

Cattle, meat byproducts 0.09

0.054 cattle 

kidney

0.14 cattle liver

Goat, fat 0.03

Goat, meat 0.02 0.01 (*)

Goat, meat byproducts 0.04 0.1 goat edible 

offal

Hog, fat 0.01

Hog, meat 0.02

Hog, meat byproducts 0.02

Horse, fat 0.03

Horse, meat 0.02

Horse, meat byproducts 0.04

Milk 0.015 0.005 cattle milk

0.005 goat milk

Poultry, meat 0.02

Poultry, meat byproducts 0.02

Sheep, fat 0.03

Sheep, meat 0.02

Sheep, meat byproducts 0.04

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.

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not been finalized by the CCPR and the CAC.

4 The MRL accommodates external animal treatment.
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Appendix C. OECD MRL Calculation Procedure Inputs/Outputs

Sweet Corn Forage (MRID 49071008)

0.0504 - 0.0795 lb ai/A, 6-7-day PHI

Residues (mg/kg) n

0.0146 1

0.0184 1

0.0242 1

0.0303 1

0.0556 1

0.062 1

0.0636 1

0.065 1

0.0673 1

0.0702 1

0.0995 1

0.102 1

Abamectin

Sweet Corn Forage

USA

0.0504-0.0795 lb ai/A, 6-7 day PHI

Total number of data (n) 12

Percentage of censored data 0%

Number of non-censored data 12

Lowest residue 0.015

Highest residue 0.102

Median residue 0.063

Mean 0.056

Standard deviation (SD) 0.029

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.102

- Mean + 4 SD 0.172

- CF x 3 Mean 0.168

Unrounded MRL 0.172

Rounded MRL 0.2
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Sweet Corn Stover (MRID 49071008)

0.0504 - 0.0795 lb ai/A, 6-7-day PHI

Residues (mg/kg) n

0.0221 1

0.0248 1

0.0273 1

0.0467 1

0.0554 1

0.0592 1

0.0707 1

0.0818 1

0.125 1

0.138 1

0.235 1

0.329 1

Abamectin

Sweet Corn Stover

USA

0.0504-0.0795 lb ai/A, 6-7 day PHI

Total number of data (n) 12

Percentage of censored data 0%

Number of non-censored data 12

Lowest residue 0.022

Highest residue 0.329

Median residue 0.065

Mean 0.101

Standard deviation (SD) 0.094

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.329

- Mean + 4 SD 0.478

- CF x 3 Mean 0.304

Unrounded MRL 0.478

Rounded MRL 0.5
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Soybean Forage (MRID 49071010)

0.0776-0.127 lb ai/A, 6-8 day PHI

Residues (mg/kg) n

0.0138 1

0.014 1

0.0172 1

0.0188 1

0.0192 1

0.0244 1

0.0247 1

0.0257 1

0.0337 1

0.0348 1

0.0391 1

0.0486 1

0.0599 1

0.0602 1

0.0965 1

0.0979 1

0.115 1

0.132 1

0.145 1

0.158 1
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Abamectin

Forage

USA

0.0776-0.127 lb ai/A, 6-8 day PHI

Total number of data (n) 20

Percentage of censored data 0%

Number of non-censored data 20

Lowest residue 0.014

Highest residue 0.158

Median residue 0.037

Mean 0.059

Standard deviation (SD) 0.047

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.158

- Mean + 4 SD 0.249

- CF x 3 Mean 0.177

Unrounded MRL 0.249

Rounded MRL 0.3
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Soybean Hay (MRID 49071010)

0.0776-0.127 lb ai/A, 6-8 day PHI

Residues (mg/kg) n

0.0448 1

0.0449 1

0.0489 1

0.062 1

0.08 1

0.11 1

0.117 1

0.122 1

0.156 1

0.185 1

0.215 1

0.226 1

0.295 1

0.332 1

0.365 1

0.366 1

0.414 1

0.453 1

0.553 1

0.607 1
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Abamectin

Soybean Hay

USA

0.0776-0.127 lb ai/A, 6-8 day PHI

Total number of data (n) 20

Percentage of censored data 0%

Number of non-censored data 20

Lowest residue 0.045

Highest residue 0.607

Median residue 0.200

Mean 0.240

Standard deviation (SD) 0.174

Correction factor for censoring (CF) 1.000

Proposed MRL estimate

- Highest residue 0.607

- Mean + 4 SD 0.938

- CF x 3 Mean 0.719

Unrounded MRL 0.938

Rounded MRL 1