Document ID: EPA-HQ-OPP-2003-0237-0028
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-09-06T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

	WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, 	PESTICIDES 	AND

TOXIC 	SUBSTANCES

MEMORANDUM

SUBJECT:	BEAD Responses to Public Comments Received Regarding Methyl
Parathion’s Interim Risk Management Decision Document

FROM:		David W. Brassard, Senior Entomologist

Biological Analysis Branch

Biological and Economic Analysis Division (7503C)

THRU: 		Arnet Jones, Chief

				Biological Analysis Branch

				Biological and Economic Analysis Division (7503C)

TO:				John Pates/Laura Parsons/Susan Lewis

				Reregistration Branch I

				Special Review and Reregistration Division (7508C)

Peer Review Panel review date: January 19, 2005

The purpose of this memorandum is to respond to benefits related public
comments received regarding methyl parathion’s “Interim Risk
Management Decision Document” issued in the Federal Register on June
2, 2004.  Of the eight detailed comments received by the Office of
Pesticide Programs (OPP), three had benefits related comments.  These
comments addressed BEAD’s benefit assessments on field corn, rice, and
cotton.  BEAD did not consider any of these comments to be substantive
enough to require revising BEAD’s benefit assessments or OPP’s
“Interim Risk Management Decision Document.”  The following table
contains a summary of the individual benefits related comments and
BEAD’s response to those comments.

Table 1.  Summary of Substantive Methyl Parathion Comments

Commenter	

Comment and BEAD Response (if any)

Field Corn

Steven R Sheffield

Caroline Kennedy

Patti Bright et al.

Various environmental groups	

Comment:   “Methyl parathion was first registered in the U.S. in 1954
and has been used fairly consistently on many of the same crops and same
locations for the past 51 years. As a result, many pest species that
methyl parathion is used to protect against have evolved a genetic
resistance to methyl parathion. For example, this has been clearly
documented by Parimi et al. (2003) for the western corn rootworm
(Diabrotica virgifera virgifera) in the corn belt of the Midwestern U.S.
The time span of 51 years is more than enough time for all pest species
targeted by methyl parathion to have evolved genetic resistance to it.
Further, there is evidence suggesting that, as seen with organochlorine
insecticides, there is cross-resistance with the organophosphorus
insecticides as well, so this only compounds the resistance problem.”

BEAD Response: BEAD acknowledges that there is evidence of resistance to
methyl parathion in some western corn rootworm populations and to other
target pest species as well.  In its benefit assessment on field corn,
BEAD reviewed 8 corn rootworm efficacy studies and judged methyl
parathion to provide poor control in 3 out of the 8 comparisons
(equivalent to a 38% control failure rate).  Methyl parathion was judged
to provide good to excellent control in the other 5 comparisons.  Four
out of the five alternative foliar insecticides evaluated in these
studies experienced similar or greater control failure rates (38-100%). 
Only lambda cyhalothrin did not experience control failures in these
tests.  Similar results were observed in BEAD’s corn borer and
sunflower moth efficacy assessments in which alternative
organophosphate, carbamate, organochlorine, and pyrethroid insecticides
(except lambda cyhalothrin) were as likely to experience control
failures as methyl parathion.  BEAD’s efficacy reviews suggest that
insect pest tolerance or resistance to methyl parathion is no more
prevalent than with most of the alternatives.  BEAD is not aware of
widespread, generalized resistance problems to all pests controlled by
methyl parathion.   In general, methyl parathion resistance can be
characterized as localized and sporadic.  This is because growers have
learned various techniques of resistance management including
alternation of different chemistries and avoidance of pesticides
exhibiting habitual control failures.

Rice

Steve Hensley

USA Rice Federation

Arlington, VA 22203	

Comment: Limiting methyl parathion to 2 applications per year will
severely limit its usefulness and effectiveness in controlling stink
bugs and grasshoppers in the South.  USA Rice recommends that 4
applications per year (at 0.75 lb ai/A) be allowed.

BEAD Response: BEAD acknowledges that a small percentage of rice growers
may be affected by this limitation.  In its benefit assessment, BEAD
concluded that most rice growers formerly applied 1 to 2 applications of
methyl parathion per growing season.  Growers in Arkansas, Louisiana,
and Mississippi averaged 1.1 to 1.5 applications per year and Texas
growers averaged 2.2 applications per year.  Since about 53% of Texas
rice is treated with methyl parathion, BEAD estimates that only 5% of
Texas rice would have received more than 2 applications per season.  The
chief disadvantage of the alternative lambda-cyhalothrin, which is also
widely used by rice growers for rice stink bugs, is its long preharvest
interval (21 days).  BEAD believes that growers will respond to methyl
parathion application limitations by applying lambda-cyhalothrin earlier
in the season and relying on methyl parathion during the last 21 days of
the season.  Zeta-cypermethrin, and carbaryl are also available for rice
stink bug control.

Cotton

S. Gerret Van Duyn

National Cotton Council of America	

Comment: “Methyl [parathion] is a critical component of the cotton
industry’s insect control program for plant bugs and other sucking
insects.”  The National Cotton Council (NCC) disagrees with the
statement in the IRED that many alternative chemistries (including
organophosphates) are available for use as substitutes for methyl
parathion because the statement does not adequately assess the
alternatives situation for plant bug control and for development of
insect resistance management programs.  The NCC asserts that since
azinphos-methyl is being phased out on cotton it cannot be considered an
alternative to methyl parathion. Also because terbufos is also not
available for use by cotton growers, this reduces the number of
alternatives to acephate and dicrotophos.  NCC asks “that EPA
reconsider its assessment to show increased benefit of methyl to cotton
production.”

BEAD Response: BEAD acknowledges the historical importance of methyl
parathion to cotton growers for plant bugs and other sucking insects. 
The use of methyl parathion on cotton, however,  dropped precipitously
from 25% of cotton acreage treated in 1995 to only 2% treated in 2001. 
This drop has occurred for a variety of reasons which include the
success of the Boll Weevil Eradication Program, the widespread use of BT
cotton, development of resistance of some populations of the brown stink
bug to methyl parathion, and methyl parathion’s high toxicity to
beneficial insects.  BEAD’s benefit assessment for the use of methyl
parathion on cotton concluded that acephate and dicrotophos were the
most likely alternatives against the brown stink bug, green stink bug,
and southern green stink bug due to their efficacy, low cost, and in the
case of acephate, lower toxicity to beneficial insects.  BEAD also
concluded that some growers may employ synthetic pyrethroids and
neonicotinoids for green stink bug, and southern green stink bug control
but their use would be limited due to their higher costs.  Since BEAD
never mentioned azinphos-methyl or terbufos as potential alternatives to
methyl parathion, BEAD believes that their availability in the future is
irrelevant to this situation.  BEAD also does not believe that the
availability of methyl parathion is critical to the development of
insect resistance management (IRM) programs.  Current IRM programs
stress the importance of rotating insecticides from different chemical
classes to avoid resistance.  Since methyl parathion, acephate, and
dicrotophos are all organophosphate insecticides, the availability of
methyl parathion would be of little value in an IRM program.  BEAD
believes that growers would be better off rotating with pyrethroids or
neonicotinoids for IRM purposes.