NCC Submits Comments on Pyriproxyfen (Knack)

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 pyriproxyfen (Knack).

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-2011-0677

Dear Ms. Newcamp:

The National Cotton Council (NCC) appreciates the opportunity to comment on the Environmental Protection Agency’s (EPA) Human Health Draft Risk Assessment for Registration Review and Preliminary Ecological Risk Assessment for the Registration Review of Pyriproxyfen.  The NCC urges EPA to recognize the unique mode of action (MOA) pyriproxyfen offers for resistance management scenarios.  As EPA urges producers to recognize the value 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 is especially critical to whitefly resistance management strategies.

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, a hormonal juvenile insect growth regulator (IGR) that suppresses embryogenesis within the insect egg and/or pupae by inhibiting metamorphosis and adult emergence of target insects, provides producers with an insect management tool with little human health concerns.  The uniqueness of the product targeting specific hormonal processes of insects greatly reduces risk concerns for humans and many other taxa of the environment.

The draft Human Health Risk Assessment clearly demonstrates no scientific evidence for carcinogenicity to humans, no mutagenic activity for humans, sufficient scientific evidence to reduce FQPA safety factors, aggregate risk assessment of no concern, no risk of concern for dietary, residential, aggregate, and occupational exposure with one exception related to pet collars.  It is clearly a product of low, if any, human health concerns.

The preliminary ecological risk assessment identifies concerns that need refined assessments. EPA notes recent submission of some studies that should provide data to refine the ecological risk assessment.  EPA also notes “Additional data needed in order to conduct a full risk assessment for pollinators include the following studies:

            -Field Trial of Residues in Pollen and Nectar using TEP (Non-guideline)

            -Semi-field testing for pollinators using TEP (Non-guideline/OECD 75, Tier 2)

            -Field Testing for Pollinators Using TEP (OCSPP 850.3040 Tier 3)”

The NCC encourages EPA to complete the ecological risk assessment with more refined data while recognizing the low concerns to vast taxa and human health.  The NCC is concerned that some of the current assessment of aquatic taxa represents unrealistic exposure, and does not reflect the rapid degradation of the product as well as its known strong binding characteristics to organic matter.  Additionally, the NCC reiterates to EPA that cotton pollen is not highly attractive to honey bees, and urges EPA not to overestimate pollinator risk with the incorrect assumption that treated cotton pollen is the sole pollen source for the risk assessment.

The NCC recognizes that pyriproxyfen is not used annually on the majority of U.S. cotton acreage, but is a very critical product for control of whitefly outbreaks.  There are many papers discussing the challenges to the control of whitefly outbreaks and the extreme need for multiple modes of action (MOA) in rotation to avoid uncontrollable populations (Hequet et al., 2007, Sticky Cotton: Causes, Effects, and Prevention, USDA ARS Tech. Bull. No. 1915, 210pp; Nichols et. al. Management of White Fly Resistance to Key Insecticide in Arizona, ;

Whiteflies: Cotton Insect Management Guide,  Pyriproxyfen is a critical (Integrated Resistance Management (IRM) tool for managing whiteflies, and its loss would increase applications of other materials that would not provide the benefits of pyriproxyfen. Ellsworth et al. (1999, The University of Arizona, Cooperative Extension IPM Series No. 13, Sticky Cotton Sources & Solutions) reported “insecticide treatment to specifically prevent stickiness has cost Southwestern cotton growers $47 million for aphids and $154 million for whiteflies from 1994-1998.”  The development and implementation of a new integrated system of whitefly management greatly reduced costs, but optional management tools must remain available to comply with IRM recommendations.

The whitefly is more than just a pest that may reduce yield.  The whitefly, and the sugars it excretes can result in heavy deposits resulting in sticky cotton.  Sticky cotton impacts the entire cotton chain – from producer losses, slowing ginning process by up to 25 % (Ellsworth et al, 1999), lowering grade and value $0.03/lb – $0.05/lb (Ellsworth et al. 1999), to textile losses, requiring extra efforts to spin fibers, gumming of sugars in process equipment thus requiring frequent shutdown for cleaning, and potential reduction in final product due to staining and fiber grade.  The seriousness of sticky cotton can impact entire regions as mills attempt to avoid the purchase of sticky cotton.

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 whiteflies.

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 Pyriproxyfen.


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