Document ID: EPA-HQ-OPP-2006-0579-0004
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-03-21T04:00Z

SEQ CHAPTER \h \r 1 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

  SEQ CHAPTER \h \r 1 OFFICE OF

PREVENTION, PESTICIDES AND TOXIC SUBSTANCES

MEMORANDUM

SUBJECT:	Projected Percent Crop Treated Estimates for Spinosad (PC
110003) on Dairy Cattle, Beef Cattle and Alfalfa for Use in Chronic
Dietary Risk Assessment (DP 334157)

FROM:	Alan Halvorson, Economist

		Economic Analysis Branch

		Colwell Cook, Entomologist

		Biological Analysis Branch

Biological and Economic Analysis Division (7503P) 

THRU:	Arnet Jones, Branch Chief

		Biological Analysis Branch

Biological and Economic Analysis Division (7503P) 

TO:		Sidney Jackson, Risk Manager Reviewer

Risk Integration, Minor Use and Emergency Response Branch

Registration Division (7505P)

PRP Date:  December 13, 2006

I.	SPECIFIC PROJECTED PERCENT CROP TREATED (PPCT) REQUEST

This memorandum is intended to analyze previously provided estimates for
spinosad use on dairy cattle (23% of dairy cattle), beef cattle (31% of
beef cattle) and alfalfa as forage (1% of crop area) that were used in
the chronic dietary risk assessment of this chemical.  The goal is to
verify and/or modify them as appropriate and to provide corresponding
Federal Register (FR) language. 

II.	FR LANGUAGE

EPA estimates projected percent crop treated (PPCT) for a new pesticide
use for use in chronic dietary risk assessment by assuming that the
percent crop treated (PCT) during the pesticide’s initial five years
of use on a specific use site will not exceed the average PCT of the
dominant pesticide (i.e., the one with the greatest PCT) on that site
over the three most recent pesticide usage surveys.  Comparisons are
only made among pesticides of the same pesticide types (i.e., the
dominant insecticide on the use site is selected for comparison with a
new insecticide).  The PCTs included in the average may be each for the
same pesticide or for different pesticides since the same or different
pesticides may dominate for each year selected.  Typically, EPA uses
USDA/NASS as the source for raw PCT data because it is publicly
available.  When a specific use site is not surveyed by USDA/NASS, EPA
uses other data which may include proprietary data.  

This estimated PPCT, equivalent to the average PCT of the market leader
is appropriate for use in the chronic dietary risk assessment.  This
method of estimating a PPCT for a new use of a registered pesticide
produces a high-end estimate that is unlikely, in most cases, to be
exceeded during the initial five years of actual use.   

The predominant factors that bear on whether the estimated PPCT could be
exceeded are whether the new pesticide use is more efficacious or
controls a broader spectrum of pests than the dominant pesticide(s),
whether there are concerns with pest pressures as indicated in emergency
exemption requests or other readily available information, and/or other
factors based on analysis of additional information.  All information
readily available has been considered for spinosad on dairy cattle, beef
cattle and alfalfa, and it is the opinion of BEAD that it is unlikely
that actual PCTs for spinosad on these sites will exceed the
corresponding estimated PPCTs during the next five years.  For cattle,
the estimated PPCTs likely would not be exceeded because spinosad
generally is more expensive than the leading alternative insecticides
although it has efficacy on the same order for the targeted pests.  For
alfalfa, its estimated PPCT likely also would not be exceeded because it
is considerably more expensive than the leading alternatives, and
treatments for the targeted pest armyworms have been relatively small on
average over the past eight years.   

 

III.	PROJECTIONS BASED ON MARKET LEADER APPROACH 

PPCT estimates for dairy cattle and beef cattle were previously provided
in a memorandum from BEAD to HED dated August 26, 2005 (Attachment I). 
Although spinosad was registered on cattle, projections were provided
because no usage data were available for spinosad on cattle.  Also
because of limited data availability, the PPCT estimates for dairy
cattle were based on two years of data, while those for beef cattle were
based on one year of data.  These PPCT estimates explicitly utilized the
market leader approach, and are explained in more detail in the
attachment.  The PPCT estimates for alfalfa hay and other hay were
provided in an e-mail from BEAD to HED dated August 12, 2005 (Attachment
II).  These PPCT estimates implicitly utilized the market leader
approach, finding that all alternatives treated less than 1% of acreage
with respect to the pest targeted by spinosad, and thus that spinosad
was expected to treat less than 1% of alfalfa and other hay.      

ADDITIONAL FACTORS

Cattle 

	There are numerous insect pests that plague cattle, both dairy and
beef.  Flies (horn, stable, face,cattle grubs) are major pests of
livestock throughout the United States.  The major pest of cattle in the
United States is usually the horn fly.  This insect pierces the flesh
and takes blood meals from the hosts.  The bite of the flies is painful
and disturbs the livestock, interfering with feeding (Koehler, et al.). 
Horn flies lay eggs in fresh manure and their life cycle can take as
little as 15 days under optimal temperatures.  

	Most producers employ a variety of techniques to control livestock
pests, starting with sanitation around farm buildings.  In addition, fly
control consists of insecticide-impregnated ear tags, pour-ons, spray
formulations, or dusts.  Many of these products use permethrin,
synthetic pyrethroids, organophosphates (OP), or a combination of OPs
and permethrin/pyrethroids.  There are also feed-through products
(usually ivermectin) that limit fly development in manure (Whittier,
2000).  The feed-through products are usually not enough to offer full
control since these insects can disperse long distances.  

	According to the label spinosad may be applied directly to dairy or
beef cattle, as a pour-on or spray, to control horn flies and lice, or
on agricultural animal premises to control stable flies and house flies.
 Spinosad has a novel mode of action on insects.  It excites the insect
nervous system, consistent with activation of nicotinic acetylcholine
receptors and has effects on GABA receptor function as well (Thompson,
et al. 1999).  Spinosad has demonstrated activity against the larvae of
Lepidoptera and Diptera, and some Coleopterans (Thompson, et al. 1999). 

The spray or pour-on product is targeting adult flies.  Kristensen and
Jespersen (2004) demonstrated that the toxicity of spinosad on house
flies was slow-acting, but highly toxic, though not as toxic as some
pyrethroids.  The efficacy rating for permethrin is good; the rating for
the pyrethroids: lambda-cyhalothrin and zeta-cypermethrin is excellent
(Parkman, 2005).  However, there are many permethrin products.  There
are no data specific to horn flies, or stable flies, to suggest that
spinosad usage may exceed the market leader, permethrin, for this use. 
Further, on the basis of cost, spinosad is unlikely to exceed the market
leader permethrin on dairy cattle since its cost in agriculture
generally is considerably more than that of permethrin.    Spinosad is
not a feed-through product and also should not exceed the market leader
ivermectin for that use on beef cattle.  Ivermectin, the market leader,
is dual purpose, and can be used both as a pour-on to treat external
pests and as a feed-through for internal pests.   

Alfalfa

	Section 18s:  Spinosad has been granted section 18s to control
outbreaks of armyworms in alfalfa beginning in 2003.  The market leaders
for alfalfa that target armyworms accounted for less than 1% of the
alfalfa acres treated at the national level in each of the years 1998
through 2005.  (The market leaders were lambda-cyhalothrin in 2001,
indoxacarb in 2003, and chlorpyrifos in the remaining years.)  On the
basis of cost, spinosad is unlikely to exceed the less than 1% of acres
treated by the market leaders since its cost per acre on average has
been considerably more than that of the market leaders over the past
eight years (considerably more than that of lambda-cyhalothrin and
chlorpyrifos over each of seven years and about the same as that of
indoxacarb for one year).  There are no other data to suggest that
spinosad would exceed the market leader.  

V.	CONCLUSIONS/RECOMMENDATIONS

All information currently available for the predominant factors
mentioned above or relevant to the case in question have been considered
for spinosad, and it is the opinion of BEAD that it is unlikely that
actual PCT for spinosad will exceed the estimated PPCT during the next
five years.

VI.  ReferenceS:

P. G. Koehler, J. F. Butler, and P. E. Kaufman.  Horn Flies.  University
of Florida IFAS Extension Bulletion ENY-285 (located at:   HYPERLINK
"http://edis.ifas.ufl.edu/pdffiles/IG/IG13700.pdf" 
http://edis.ifas.ufl.edu/pdffiles/IG/IG13700.pdf ).

Kristensen, M. and J. B. Jespersen.  2004.  Susceptibility of spinosad
in Musca domestica (Dipter: Muscidae) field populations.  J. Econ.
Entomol.  97(3):1042-1048.  

Parkman, J. P.  2005.  Pest Management Strategic Plan for Beef Cattle in
Tennessee and Kentucky.  USDA, available at:   HYPERLINK
"http://www.ipmcenters.org/pmsp/pdf/KY_TN_Beef_Cattle.pdf" 
http://www.ipmcenters.org/pmsp/pdf/KY_TN_Beef_Cattle.pdf .   

Gary D. Thompson, Scott H. Hutchins and Thomas C. Sparks. 1999. 
Development of spinosad and attributes of a new class of insect control
products.  In: Radcliff’s IPM World Textbook.  (located at:  
HYPERLINK "http://ipmworld.umn.edu/chapters/hutchins2.htm" 
http://ipmworld.umn.edu/chapters/hutchins2.htm ).  

Whittier, W. D. 2000.  Summer fly control on cattle.  Virginia
Cooperative Extension, Virginia Tech.  located at :   HYPERLINK
"http://www.ext.vt.edu/news/periodicals/livestock/aps-00_07/aps-0242.htm
l" 
http://www.ext.vt.edu/news/periodicals/livestock/aps-00_07/aps-0242.html
).  



ATTACHMENT I:  	 

Projected Spinosad Percent Head Treated (PHT) as Conservative Inputs for

	Dietary Risk Analysis, Based on Spinosad Not Overtaking the Dominant
Insecticide

---------------- Dominant Insecticide Data ---------------

	Spinosad

	Site	Year	Dominant Insecticide (*)	PHT(#)	Projected PHT

Dairy Cattle	1999	Permethrin	10%

Milk Cows	2001	Permethrin	36%

Dairy Cattle	Average	Permethrin	23%	23%

	Beef Cattle	 1999	Ivermectin	31%	31%

Note 1 -- No usage of spinosad on cattle was found in data sources
through 2001.  Although these 

	   sources are dated, no later sources are available.  Therefore,
estimates were projected as above.

	Note 2 --  No information is available which would allow approximation
of the percentage of cattle

	   facilities treated (with only pounds a.i. given).  However, we could
assume that these would be

	   about the same as the corresponding percentages of cattle treated.

	(*) Insecticide treating most head of cattle per year

	(#) This computation uses the average annual rate per head and annual
pounds a.i. for a given chemical

   to compute no. of head of cattle treated by that chemical.  This
computation is approximate because

   of the variability of rates.  PHTs for beef and dairy cattle include
all cattle in the beef and dairy herds 

	   (cows, bulls, calves, etc.), respectively.  The PHT for milk cows
includes only milk cows.   

Sources --

	- USDA/NASS, Agricultural Chemical Usage, 2001 Dairy Cattle and Dairy
Facilities Summary

	- USDA/NASS, Agricultural Chemical Usage, 1999 Cattle and Cattle
Facilities Summary

	- USDA/NASS, Cattle, 2/1/02

	Prepared by Alan Halvorson, Ph.D., BEAD/EAB, 8/26/05.  Footnot

	at 703-308-8070 and   HYPERLINK "mailto:halvorson.alan@epa.gov" 
halvorson.alan@epa.gov 

	Revised 12/28/06 ( (.

	



ATTACHMENT II:

  

Arthur Grube/DC/USEPA/US

08/12/2005 01:12 PM	

To

Steve Jarboe/DC/USEPA/US@EPA

cc

Jihad Alsadek/DC/USEPA/US@EPA

Subject

Re: Spinosad %CT on alfalfa/hay(1)

 

Based on past use of other insecticides to control armyworms etc.  I
project that much less than 1% of alfalfa would be treated.    Our data
on non-alfalfa hay is very limited but I would expect that percent crop
treated for non-alfalfa hay would also be below 1%..

Arthur H. Grube Ph.D.

Senior Economist

EPA Office of Pesticide Programs

1200 Pennsylvania Avenue, NW (7503C)

Washington, DC 20460

------------------------------------------------------------------------
--------

DOC #

Active Date:

Retired Date: