NCC Submits Comments on Abamectin (Agri-Mek)

On March 15, 2018, the NCC submitted comments to EPA on the agency's draft human health and ecological risk assessments for the registration review of abamectin (Agri-Mek).

Published: March 16, 2018
Updated: March 16, 2018

March 15, 2018

Office of Pesticide Programs
Regulatory Public Docket (7502P)
U.S. Environmental Protection Agency
1200 Pennsylvania Ave., NW Washington, DC 20460

RE: Docket ID Number EPA-HQ-OPP-2013-0360

Dear Ms. Javier:

The National Cotton Council (NCC) appreciates the opportunity to comment on the Environmental Protection Agency’s (EPA) “Abamectin (Avermectin). Human Health Draft Risk Assessment in Support of Registration Review and Proposed Uses for Crack and Crevice and Spot Spray Applications” and the EPA’s “Abamectin: Preliminary Ecological Risk Assessment for Registration Review.”  The NCC urges EPA to recognize the unique mode of action (MOA) abamectin offers for resistance management scenarios.  As EPA urges producer to recognize the values of rotating chemical MOA’s for resistance management purposes, EPA must recognize rotation is not possible unless there are multiple MOA’s available.  This product especially serves critical mite resistance management objectives.

The NCC is the central organization of the United States cotton industry.  Its members include producers, ginners, cottonseed processors and merchandizers, merchants, cooperatives, warehousers and textile manufacturers.  A majority of the industry is concentrated in 17 cotton-producing states stretching from California to Virginia. U.S. cotton producers cultivate between 9 and 12 million acres of cotton with production averaging 12 to 18 million 480-lb bales annually. The downstream manufacturers of cotton apparel and home furnishings are located in virtually every state. Farms and businesses directly involved in the production, distribution and processing of cotton employ more than 125,000 workers and produce direct business revenue of more than $21 billion.  Annual cotton production is valued at more than $5.5 billion at the farm gate, the point at which the producer markets the crop.  Accounting for the ripple effect of cotton through the broader economy, direct and indirect employment surpasses 280,000 workers with economic activity of almost $100 billion. In addition to the cotton fiber, cottonseed products are used for livestock feed and cottonseed oil is used as an ingredient in food products as well as being a premium cooking oil.

First, the NCC appreciates the EPA’s thorough review of merited science that demonstrates the safety of this product with regards to human health.  The unique MOA (Group 6, Glutamate-gated chloride channel{GluCl} allosteric modulators, Insecticide Resistance Action Committee (IRAC), IRAC Mode of Action Classification Scheme, July 2017, Version 8.3), provides producers with an insect management tool that reduces risk concerns for human health and safety.

The draft Human Health Risk Assessment demonstrates no scientific evidence for carcinogenicity to humans, sufficient scientific evidence to reduce FQPA Safety factors, aggregate risk assessment of no concern, and no dietary risk of concerns.  Even with the remaining uncertainty factors, it is clearly a product of low, if any, human health concerns when used as labeled.  The NCC did note that, even though the majority of the Occupational Handler Exposure and Risk Assessments were not of concern given PPE requirements, EPA did have certain scenarios that indicated a concern.  The NCC also noted EPA’s December 12, 2017 “Abamectin. Addendum for Occupational and Residential Exposure Assessment for Proposed Use to Add Indoor and Outdoor Crack and Crevice Spray Applications and for Registration Review” included a review of a recent study which provided data to reach a conclusion of no concern.


The NCC recognizes that foliar applications of abamectin are not made annually on most U.S. cotton acreage, but abamectin is a very critical product for control of mite outbreaks.  Sporadic mite outbreaks can occur prior to square, or mid to late season.  Mites are tiny eight-legged arthropods, and there are multiple species with some geographic variation.  Mites typically overwinter as females, and begin population build-up on spring weed vegetation.  The life cycle of mites is temperature driven.  Steinkraus et. al. ( states, “At 77o F it takes about nine day for a spider mite to mature.  Females may live for four weeks and lay 100 eggs.  Because of their short life cycle, spider mite populations can increase very rapidly in hot weather.  For example, the potential progeny of one female mite in one moth increases from 20 at 60oF, to 12,000 at 70oF, to 13 million at 79oF!”  Mites typically feed on the underside of the leaf and require a 10X hand lens to see.  The mites pierce the leaf cells and remove the cell content.  Under high mite pressure, the mites can defoliate fields and cause shedding of fruit.

Mite infestations are typically monitored closely with most university threshold recommendations for treatment when 30 to 50% of the plants are infested.  Plant stage, for example seedling cotton, may trigger treatment more rapidly due to few leaves to support the plants.  Because mites feed mostly on the underside of the leaf, high spray volume enhances control.  The NCC emphasizes the threshold recommendations to demonstrate that high populations are typically present before treatment is made, and these high populations, if not effectively treated in a timely manner, can result in major losses.  Additionally, with such high numbers present (and depending on the growth stage of first treatment), multiple applications may be required but alternate MOA’s are encouraged for resistance management purposes.  While there are alternative mite products, the loss of each product increases the selection for resistance to others and reduces long term effective utility of all products.


Studies conducted by Dr. Kathy Lawrence at Auburn University (personal communication) have shown Avicta Complete (seed treatment containing Abamectin) to effectively reduce Reniform nematode populations as well as the leading alternatives.  The NCC remains concerned that as many options as possible remain for producers to alternate MOAs for effective resistance management and stewardship of the few products available.  Not all nematode treatments utilize the abamectin seed treatment, but abamectin remains a valuable rotation product that provides control of nematodes with an alternate MOA.  In 2016, experts estimated a yield loss of  672,000 cotton bales (480 lbs. lint/bale) due to nematodes (Beltwide Nematode and Seedling Disease Committee, Disease Database,, resulting in a financial loss of approximately $225 million in lint and $44 million in seed (calculations made using NASS Marketing Average Price for 2016).  These estimates demonstrate the significance of nematode populations to cotton lint and seed across the cotton belt.

Nematodes are microscopic worm-like animals that feed primarily on the root system of host plants, such as cotton plants.  The plant parasitic nematode punctures root cells with its stylet and withdraws nutrition from the host plant.  Plant parasitic nematodes can be sedentary or migratory. They complete their life cycle inside roots (endo-parasitic), outside roots (ecto-parasitic), or a combination of both (semi-endo parasitic).  They generally progress through an egg stage and four juvenile stages (J-1 to J-4) before becoming adults. Some species produce eggs by sexual reproduction, while others do not require males to reproduce. Nematode damage to cotton plants includes stunting, yellowed leaves, wilting, and plant stress. Yield loss may be dramatic.  Plant-parasitic nematodes have been identified in every state where cotton is grown. Cotton nematode species are associated with soil types and climatic areas. The major species are root-knot, reniform, lance, and sting nematodes. The root-knot nematode is found across the cotton belt. The reniform nematode is prevalent from North Carolina to Texas, and the lance and sting nematodes are concentrated in the Southeast. (

The NCC has reviewed EPA’s Ecological Risk Assessment for Registration Review of Abamectin, and urges the EPA to refine the Ecological Risk Assessment to reflect data and realistic use.  The EPA acknowledges the data show that abamectin is not toxic to terrestrial plants, but then states uncertainties due to a tiny number of case reports, several of which contained mixtures of products and none conclusively linked to abamectin.

The EPA has based much of its Ecological Risk Assessment (RA) from a Use Summary Table (UST) “2.3.a Maximum Use Patterns for Registered Uses Of Abamectin” and the “Table 3.6.1.b. seed Treatment Application Rates Modeled in T-Rex.” based on a memo from BEAD (USEPA, 2011).   As for the cotton information in this table and footnoted, the NCC has many concerns.  The NCC assumes the footnote on page 12 for cotton seed treatment was meant to be 6 rather than 5.  With that assumption, the NCC takes exception to the seeding rate of 85,000 seeds/A for cotton.  Since the 1990’s, most extension cotton specialists have considered between 30,000 and 40,000 plants per acre the optimum plant population (  Additionally, they have shown populations as low as 15,000 plants per acre compensated in growth and result in negligible yield losses.  Due to advanced technology in planting equipment, seed treatment of seeds, herbicide resistant traits, and plant incorporated protectant traits, producers cost for a bag of seed has dramatically increased.  The producer’s up-front cost for a bag of seed ensures maximum efficiency in planting rate and uniformity of planting depth.

The NCC also takes issue with the UST designation that seed treatments get 2 applications.  The NCC assumes this designation was made to reflect a scenario where a grower planted a field and had a crop failure forcing the grower to replant.  Replants are generally rare exceptions, and depending on geographic location and date the replanting may not go back to cotton.  EPA should not be making risk assessments based on rare exceptions.  The combination of doubled seeding rate and doubled application questions all risk assessment scenarios involving cotton seed treatment.

The NCC notes that in the UST, aerial/ground applications are reported to be 2 applications with a 21-day minimum between applications.  This does not seem to correspond with the input data representing cotton in “Table 3.6.1.a T-REX Calculated EECs (Upper Bound) as Food Residues for Terrestrial Animals from Flowable Abamectin Labeled Uses.”, page 37.  It appears the input for cotton provided 4 applications applied 21 days apart rather than 2.  Even though the two applications applied 21 days apart would be a rare event and not part of an IRM strategy, the data alleging 4 applications are unbelievable.

The NCC is also concerned with the EPA assessment that large amounts of the product are moved from the field through soil erosion and resides in sediment ponds.  The cotton industry has made great strides in soil preservation and continues to achieve higher goals of soil retention and health ( as illustrated in the chart below based on cotton production data collected by the Field to Market Alliance.   

35 years


Further to this point, seed treatments and herbicide tolerant crops have enabled growers to expand adoption of reduced tillage practices and in many areas, to incorporate winter cover crops ( ).

“To control weeds and diseases, traditionally producers were forced to remove all plant residues and weeds from the soil surface prior to planting, and then continue to cultivate the soil while the crop was growing to control late emerging weeds. While tilling does control some disease and weeds, it also loosens the soil. Today, thanks to seed treatment fungicides, herbicides and herbicide tolerant cotton, diseases and weeds can be controlled without tilling, allowing what is referred to as “no-till” and conservation tillage systems to be adopted.

Cotton has made great strides in reducing tillage and using winter, or cover crops. The number of acres of cotton produced with reduced-tillage systems has been increasing for the last 10 years. Today, according to a study done by Cotton Incorporated, two thirds of growers say they use some form of conservation tillage. [ Reed, J.N., E.M. Barnes and K.D. Hake. 2009. U.S. Cotton Growers Respond to Natural Resource Survey. Technical Information Section. International Cotton Advisory Committee, THE ICAC RECORDER, Vol. XXVII. No. 2, June 2009 Reed, J.N., E.M. Barnes and K.D. Hake. 2009. US Cotton Growers Respond to Natural Resource Survey. Technical Information Section. International Cotton Advisory Committee, THE ICAC RECORDER, Vol. XXVII. No. 2, June 20097] In addition to preserving the soil, reducing tillage significantly reduces fuel use and its associated cost to growers.”


The NCC urges EPA to refine the Ecological Risk Assessment with field relevant data while moving forward with this registration review.  The NCC additionally urges EPA to carefully examine the benefits of this material and the potential impact on the entire cotton industry with inadequate products for control of mites and nematodes.

Thank you for allowing the NCC to comment on EPA Human Health Draft Risk Assessment for Registration Review and Preliminary Ecological Risk Assessment for the Registration Review of abamectin.


Steve Hensley
Senior Scientist, Regulatory and Environmental Issues
National Cotton Council