UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

SEP 22 2011 

MEMORANDUM 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

SUBJECT: BEAD Chemical Profile for Registration Review: Pyrethrins (PC Code 069001) 

FROM: 

THRU: 

TO: 

Nikhil Mallampalli, Entomologist 

Biological Analysis Branch 

Jihad Alsadek, Economist 

Science Information and Analysis Branch 

Elizabeth Hill, Economist 

Economic Analysis Branch 

Biological and Economic An}!lis Div on (7503P) 

Arnet 

Biological 

Jones, 

Analysis 

Chief 

Branch 

~~ U 

Diann Sims, Chief I..f)~ Science Information and Analysis Branch 

~ Timothy Kiely, Chief ~ 

Economic Analysis Branch 

Biological and Economic Anal iviSiOn (7503 

Joel Wolf 

Chemical Review Manager 

Risk Management and Implementation Branch 2 

Pesticide Reevaluation Division (7508P) 

BEAD Product Review Panel date: August 24, 2011 

INTRODUCTION 

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The purpose of this document is to convey usage information and a broad overview of the pest 

management roles of pesticides that are beginning to undergo registration review. The 

anticipated audience consists of the team of EP A staff currently evaluating the registration status 

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of pyrethrins, and eventually the general public. This document builds upon the data already 

provided in the “Usage and Label Use Data Packages” that are also provided to Registration 

Review teams by BEAD. The document is based on information and data available to BEAD as 

of May 2011. 

Pyrethrins were first registered in the United States for use as insecticides in the 1950s. A 

Reregistration Eligibility Decision (RED) was issued for this “active ingredient” (actually a 

group of very similar chemicals) in 2006 (see 

http://www.epa.gov/oppsrrd1/reregistration/REDs/pyrethrins_red.pdf for details). As was done in 

the RED, the term “pyrethrins” in this paper refers to formulations containing any or all six 

isomers found in pyrethrum, extracts which are derived from the dried and ground flowers of the 

pyrethrum plant, Chrysanthemum cinerariaefolium. 

The Insecticide Resistance Action Committee (IRAC), comprised of technical personnel from 

various large agrochemical and public health companies, classifies pyrethrins as a member of the 

Mode of Action Group 3 (subgroup 3A). This group of insecticides acts as sodium channel 

modulators, thus causing disruption of nerve impulses in the target insects. All pyrethroids 

“initially stimulate nerve to produce repetitive discharges and subsequently cause paralysis” 

(Narahashi, 1976). 

Pyrethrins target a wide range of insects in many agricultural crop systems, such as lepidopterous 

caterpillars, leafhoppers, aphids, beetles, and thrips (FAO 1975), and is also used against a 

variety of urban insect pests such as cockroaches and ants. Like other compounds derived from 

the chemical structure of pyrethrum, it is most toxic to the target pest on contact, and has a quick 

“knockdown” effect (Doull 1976). Some manufacturers formulate pyrethrins with a synergist 

compound (usually piperonyl butoxide, also known as PBO, or MGK-264), as well as with other 

older pyrethroids such as tetramethrin, to extend its active life and increase its toxic effect on 

target insects (Jones 1998). Pyrethrum (as mixture of pyrethrins isomers) is also available and (if 

formulated without synergists) are approved for use in U.S. organic agriculture (Cornell 

University 2005; see also www.omri.org). 

USE SITES 

Agricultural Use Sites 

Pyrethrins are registered for hundreds of agricultural uses, including most fruit, nut, and 

vegetable crops, as well as most major acreage crops such as corn, soybean, wheat, etc. Given 

the insecticide’s short residual activity and tendency to degrade in sunlight after application, it is 

likely that use on crops grown outdoors is limited to spot treatment intended to clean up small 

infestations or knock pests off plants shortly before harvest. At least one reference located by 

BEAD specifically mentions this type of use (FAO 1975). There are also indoor (greenhouse) 

uses listed for a variety of crops (e.g., tomatoes, ornamental plants, etc.). For these crops, 

pyrethrins may be a more frequent choice of producers, since residual activity may be longer due 

to lower exposure to sunlight. 

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Non-Agricultural Use Sites

Sites listed in the LUIS report include wood products (e.g., beams, decks, and pilings), woodland 

areas, wood surfaces, and zoos (enclosures and outdoor perimeter areas). Woolen fabrics are also 

listed; it is likely these are impregnated and intended to protect wearers from biting flies and 

ticks. 

Usage data (see below) indicate that other non-agricultural use sites where pyrethrins are used to 

any degree include residential and commercial buildings, food handling establishments, 

institutional turf, nursery/greenhouse, and for mosquito abatement. 

COMMON FORMULATIONS AND APPLICATION METHODS 

Pyrethrins are formulated as granular, emulsifiable concentrate, solution ready-to-use and as 

pressurized gas and liquid. It is unclear which of these is predominantly used in agricultural 

settings. BEAD speculates that for non-agricultural settings, ready-to use and liquid formulations 

are more frequently used. For agricultural uses, any of the formulations may be used; BEAD has 

no information on extent of use of each type. 

Application methods in agricultural and non-agricultural uses (based on the RED) are diverse, 

and include: aerosol can, mist blower, metered release devices, total release aerosol, fixed wing 

aircraft, helicopter, truck-mounted ultra low volume (ULV) equipment, cold aerosol generator, 

hand held sprayers (high or low pressure handwands), thermal/cold/ULV fogging equipment, 

conventional dusting equipment (e.g., power duster, bulb duster, shaker can), outdoor misting 

systems, and irrigation systems. 

Of these, power dusting was banned by the RED due to the Agency’s inability assess risk 

scenarios; all other application methods are apparently still on the labels. However, due to human 

health risk concerns, several risk mitigation measures (e.g., limits on the number of applications 

per year or individual area treated) were imposed by the RED for three general application 

methods: broadcast dusts applied to carpets, indoor metered release devices, and outdoor 

residential misting systems. 

As far as agricultural application methods, BEAD has no specific data on extent of use of 

different types. However, given the short residual activity, BEAD speculates that ground 

application using either tractor drawn equipment or backpack sprayers are often used 

USAGE 

Usage in non-agricultural settings (lawn care, residential uses, public health pest control) is 

higher than use in agriculture as a whole. Details are provided below. 

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Agricultural use 

Based on private market pesticide usage data from 1998-2010, the annual total agricultural usage 

averaged approximately 2,000 pounds active ingredient for 123,000 acres for an overall average 

of 0.02 lbs. a.i. application rate per acre. In comparison to this rate, the average a.i. application 

rate for lettuce is 0.03 lbs. a.i. per acre, 0.05 lbs. a.i. for oranges, 0.02 lbs. a.i. for strawberries, 

and 0.01 lbs. a.i. for winter wheat. 

 

From 1998-2010, the largest markets in terms of total pounds of active ingredient applied are 

lettuce (17%), winter wheat (16%), oranges (9%), and strawberries (8%). The highest total area 

treated (TAT) are winter wheat (20%), and soybeans and lettuce (9% each). 

On average, the states with the most agricultural usage in terms of pounds a.i. applied are 

California (52%), Oklahoma (16%), and Arizona (6%) (GfKynetic, 1998-2010). 

Figure 1 provides usage trends, in terms of pounds applied, for pyrethrin’s largest agricultural 

markets. The use of pyrethrins on lettuce fluctuated while was rising on both oranges and 

strawberries. The use of pyrethrins on winter wheat spiked in 2007 but there was little use in 

other years (1998-2010). Another option to show the use of pyrethrins across all crops is in 

Figure 2. Figure 2 shows the use of pyrethrins to be fluctuating during the period 1998-2010, 

and is highest in 2007. 

Figure 1. Usage data for pyrethrins in the largest agricultural markets. 

Source: Proprietary Data, 1998-2010 

Note: “Other crops” depicted above include: alfalfa, almonds, apples, artichoke, asparagus, beans, broccoli, cabbage, 

caneberries, cantaloupes, carrots, cauliflower, celery, cherries, corn, cotton, cucumbers, dry beans, grapes, hazelnuts, 

lemons, lima beans, onions, oranges, peaches, pears, peas, pecans, peppers, pistachios, plums/prune, potatoes, 

pumpkin, sorghum, soybeans, spinach, squash, sugar beets, sugarcane, sunflowers, sweet corn, tomatoes, walnuts, 

spring wheat, and watermelons. 

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Figure 2. Usage data for pyrethrins across all crops .

Source: Proprietary Data, 1998-2010 

Non-Agricultural use 

The use of pyrethrins by consumers for indoor use appeared to be rising between 2003-2006 

(52,000 lbs. a.i. in 2003 and 113,000 lbs. a.i. in 2006); see Table 1 below. There was little use in 

food handling establishments (FHEs) and on institutional turf, less than 500 lbs. a.i. each. The 

use of pyrethrins by lawn care operators (LCOs) was declining from 3,000 lbs. a.i. in 2002 to 

less than 500 lbs. a.i. in 2006. The use for mosquito abatement was rising (2,000 lbs. a.i. in 

2003 and 12,000 lbs. a.i. in 2006). The use of pyrethrins for nurseries and greenhouses was less 

than 500 lbs. a.i. in 2002, 2004, and 2006. Pest control operators used about 9,000 lbs. a.i. of 

pyrethrins in 2003. 

 

Table 1. Non-Agricultural use of pyrethrins across recent years in various site categories. 

Site 2002(Lbs.) 2003(Lbs.) 2004(Lbs.) 2005(Lbs.) 2006(Lbs.) 2008(Lbs.) 

Consumers/Indoors - 52,000 113,000 

Food Handling 

Establishments 

(FHEs) 

- - - - - <500 

Institutional Turf - - - - <500 - 

Lawn Care 

Operators (LCOs) 

3,000 - - - <500 - 

Mosquito 

Abatement 

- 2,000 - - 12,000 - 

Nursery/Greenhouse <500 <500 - <500 - 

Pest Control 

Operators (PCOs) 

- 9,000 - - - - 

Note: - indicates that data are not available. 

Source: Kline and Company, Inc., 2002-2006. 

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BEAD cautions that since usage of pyrethrins as reported to the databases is low (and for nonagricultural uses, is limited to years prior to 2009), some usage may be under-represented and 

some usage trends may need refinement. BEAD hopes that the response from the stakeholder 

public to the questions posed in the “Data Needs” section (below) will help the Agency in more 

precisely assessing recent usage of these insecticides. 

BIOLOGICAL ASPECTS RELEVANT TO PYRETHRINS 

A search of the database on arthropods resistant to pesticides (maintained online by Michigan 

State University and accessible at www.pesticideresistance.org) indicates that many insects have 

evolved resistance to pyrethrins (formulated with and without synergists) over the many years 

that the products have been in use. The list is diverse, covers both cases within and outside the 

U.S., and includes urban pests such as German cockroaches and houseflies, as well as 

widespread agricultural and stored commodity pests such as the green peach aphid (Myzus 

persicae), Indian meal moth (Plodia interpunctella), and red flour beetle (Tribolium castaneum). 

BEAD’s initial assessment, based on a scan of the literature mentioned in the database and other 

internet accessible sources, is that such resistance has not become consistently widespread in the 

U.S.; rather, it develops repeatedly in isolated instances. 

Another interesting aspect of pyrethrins that may be acting to increase usage in some crops is 

that some formulations without synergists (e.g., ‘Pyganic”, which contains pyrethrum, an 

unrefined combination of all six pyrethrins isomers) are on the list of Organic Materials Review 

Institute (OMRI) approved “organic” insecticides (see www.omri.org). OMRI lists are often used 

by certifying agencies to validate organic products (Cornell University 2005). Since chemical 

pest control options are limited for such producers, this product may be seeing increased usage in 

recent years as the demand for some organic foods has increased in the general public. However, 

this is merely speculation on BEAD’s part at this point, as no specific data for this type of use are 

immediately available. 

HISTORY OF BEAD ASSESSMENTS FOR PYRETHRINS 

To date, BEAD has not conducted any assessments for pyrethrins. However, two Section 18 

emergency exemption requests are recorded in EPA’s Section 18 Action Database (EPA, 2011). 

Please refer to Attachment 1 for a review of these requests. 

DATA NEEDS RELEVANT TO BEAD’S FUTURE WORK ON PYRETHRINS 

Obtaining additional information on the following items would improve future BEAD 

assessments of the importance of pyrethrins and may be required as part of the registration 

review of this pesticide. 

1) Usage data such as pounds AI applied, area treated, typical use rates, and typical number 

of applications on the following sites: industrial sites, livestock, milk, and meat. 

2) Importance to users in organic farming (e.g., frequency of use per season, application 

rates and methods in specific organic crops). 

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3) Usage data for the agricultural crops that are not covered in the usage section of this 

document. 

4) Usage data (pounds AI applied and area treated) for indoor/outdoor consumer use, use in 

food handling establishments/food processing establishments, and use in and around 

commercial and institutional facilities. 

REFERENCES

Cornell University. 2005. Resource Guide for Organic Insect and Disease Management 

Available at: http://web.pppmb.cals.cornell.edu/resourceguide/index.php [Accessed 

August 2011]. 

FAO. 1975. Data Sheets on Pesticides, No.11: Pyrethrins. Available at: 

http://www.inchem.org/documents/pds/pds/pest11_e.htm [Accessed August 2011]. 

Doull, J. 1976. The Treatment of Insecticide Poisoning. Ch. 16 in: C.F. Wilkinson (ed.), 

Insecticide Biochemistry and Physiology. 753 pp. Plenum Press, New York. 

Environmental Protection Agency (EPA). 2011. Section 18 Action Database. Located at: 

 http://cfpub1.epa.gov/oppref/section18/search.cfm 

Jones, D.G (ed.). 1998. Piperonyl Butoxide: The Insecticide Synergist. 323 pp. Academic Press, 

 San Diego, CA. 

Narahashi, T. 1976. Effects of Insecticides on Nervous Conduction and Synaptic Transmission. 

Ch. 9 in: C.F. Wilkinson (ed.), Insecticide Biochemistry and Physiology. 753 pp. Plenum 

Press, New York. 

GfK Kynetec. (1998-2008). EPA Proprietary Data. 

ATTACHMENT 1 

Chemical Site Pest Applicant

Received

Date

Date

Response

Date Status

PYRETHRINS

AIRCRAFT

SURFACES,

CONTAINERS

BROWN

RECLUSE

SPIDER New York 6/24/2004 6/24/2004

CRISIS

APPROVED

PYRETHRINS AQUATIC SITES

RED SWAMP

CRAYFISH WISCONSIN 8/6/2010 8/25/2010

CRISIS

APPROVED