UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
Memorandum
DATE:

SUBJECT:
BEAD
Benefits
Assessment
for
Methyl
Parathion
Use
on
Walnuts
FROM:
Donald
W.
Atwood,
Entomologist
Herbicide
and
Insecticide
Branch
Jihad
Alsadek,
Economist
Economic
Analysis
Branch
THROUGH:
Arnet
Jones,
Chief
Herbicide
and
Insecticide
Branch
David
Widawsky,
Chief
Economic
Analysis
Branch
TO:
Laura
Parsons,
Chemical
Review
Manager
Susan
Lewis,
Chief
Reregistration
Branch
2
Special
Review
and
Reregistration
Division
(
7508C)

PRP
REVIEW
DATE:
August
21,
2002
SUMMARY
BEAD
has
reviewed
available
data
related
to
methyl
parathion
use
on
walnuts.
Sufficient
alternatives
are
available
with
proven
efficacy
against
the
targeted
pest,
codling
moth.
Market
data
supports
movement
from
methyl
parathion
to
chlorpyrifos
if
methyl
parathion
was
not
available.
Chlorpyrifos
currently
is
the
product
of
choice
for
control
on
most
acres
and
is
less
expensive
than
methyl
parathion.
In
addition,
chlorpyrifos
shares
the
negative
correlation
to
azinphos
methyl
resistance
which
was
a
key
factor
in
methyl
parathion
registration
for
this
crop.
BEAD
concludes
that
there
would
be
no
biological
or
economic
impact
if
methyl
parathion
was
not
available
for
use
on
walnuts.

LIMITATIONS
AND
SCOPE
OF
ASSESSMENT
2
There
are
limits
to
this
assessment.
Commercial
walnut
production
in
the
US
is
limited
to
California.
This
assessment
is
limited
to
walnuts
in
general
and
does
not
consider
methyl
parathion
usage
variances
which
might
occur
between
different
varieties.
It
is
assumed
that
producers
will
not
shift
to
alternate
crops.
This
analysis
also
assumes
that
farm
gate
prices
are
not
affected
by
any
changes
at
the
grower
level
and
that
growers
do
not
drastically
alter
their
production
practices.
This
analysis
will
focus
solely
on
operation
costs,
ignoring
overhead
and
other
opportunity
costs,
which
can
be
difficult
to
measure
and
are
beyond
the
scope
of
this
exercise.
Thus,
net
cash
returns
overstate
actual
profits
to
the
grower.

The
scope
of
this
analysis
includes
an
examination
of
potential
grower
and
industry­
level
impacts
associated
with
methyl
parathion
being
unavailable
for
use
on
walnuts.
This
mitigation
scenario
reflects
the
health
risks
to
pesticide
mixers,
loaders,
and
applicators
as
identified
by
the
Health
Effects
Division
of
the
Office
of
Pesticide
Programs.

BEAD
estimates
of
yield
losses
associated
with
methyl
parathion
unavailabilty
are
based
on
the
best
professional
judgement
of
BEAD
analysts
when
estimates
are
not
available
from
other
sources.
BEAD
estimates
are
based
on
a
review
of
available
comparative
efficacy
data,
USDA
crop
profiles,
state
crop
production
guides,
discussions
with
university
extension
and
research
entomologists
knowledgeable
in
sweet
corn
production,
and
other
sources
listed.
Walnut
production
is
a
very
complex
system
that
can
be
influenced
by
a
variety
of
parameters
(
e.
g.,
weather).
BEAD's
ability
to
quantitatively
capture
the
wide
array
of
events
that
could
unfold
given
each
hypothetical
scenario
listed
above
is
very
limited.

PRODUCTION
OF
U.
S.
WALNUTS
California
produces
99%
of
the
walnuts
grown
in
the
United
States
and
38%
of
the
world's
production.
1
Over
40%
of
the
California
walnut
crop
is
currently
being
exported.
About
35%
of
the
crop
is
marketed
in
shell.
Production
and
crop
value
for
1999­
2001
are
provided
in
Table
1.
The
average
farm
size
is
38
acres.
2
Table
1.
Production
and
Crop
Value
for
walnut
production.
1
Year
Bearing
Acres
(
1000)
Yield
per
Acre
(
Tons)
Production
(
1000
Tons)
Price
per
Ton
(
dollars)
Crop
Value
(
1000
dollars)

1999
193
1.18
227
1050
238,350
2000
191
1.48
283
886
250,738
2001
193
1.24
239
NA
NA
Walnuts
are
ideally
suited
to
deep,
well­
drained,
fine
sandy
loam
to
clay
loam
soils,
but
will
not
3
produce
adequate
commercial
crops
without
irrigation
in
most
California
growing
areas.
3
Flood,
furrow,
and
sprinkler
irrigation
are
predominant.
Drip
and
micro­
sprinkler
irrigation
being
used
more
often
in
marginal
soils.
Irrigation
takes
place
from
mid­
April
through
October.
Orchard
soils
are
generally
not
cultivated,
but
herbicide­
treated
tree
rows
are
common.
Mechanized
winter
pruning
is
practiced.
A
smooth
orchard
floor
is
necessary
to
facilitate
harvest
of
walnuts
that
are
shaken
to
the
ground,
swept
into
a
windrow,
and
picked
up
with
pickup
machines.
All
these
harvest
activities
are
mechanized.
Some
orchards
are
disced
and
rolled
before
harvest
to
insure
a
smooth,
firm
surface
for
harvest.

The
Sacramento
and
San
Joaquin
Valleys
of
California
are
the
largest
production
areas.
Acreage
is
well
distributed
throughout
these
regions.
3
The
coastal
valleys
in
the
counties
of
Santa
Barbara,
San
Luis
Obispo,
Monterey,
and
San
Benito
also
have
significant
production.
Unique
areas
in
the
Sierra
Foothills
and
Lake
County
also
have
some
walnut
production.
Over
15
varieties
of
walnuts
are
grown
in
the
state
commercially,
with
numerous
other
cultivars
being
planted
on
a
smaller
scale.
Selected
cultivars
are
grafted
onto
rootstocks.
The
three
rootstocks
generally
used
in
California
are
Northern
California
Black,
Paradox
hybrid,
and
English
Walnut.
Both
varieties
and
rootstocks
vary
in
susceptibility
to
diseases,
nematodes,
and
insect
pests.

Activities
in
the
orchard
during
the
summer
months
include
mowing,
summer
training
young
trees,
vertebrate
pest
and
weed
control,
and
harvest.
Pruning
occurs
between
October
and
January,
and
mummy
nut
removal
takes
place
around
February.

USE
AND
USAGE
OF
METHYL
PARATHION
ON
WALNUTS
California
received
a
Special
Local
Needs
(
SLN)
label
to
use
methyl
parathion
on
walnuts
in
1997.
Table
2
shows
the
use
of
methyl
parathion
in
California
walnuts
from
1998
to
2000.
The
observed
increase
in
acres
treated
with
methyl
parathion
between
1998
and
1999
illustrates
increased
usage
to
control
codling
moth
populations
that
had
become
resistant
to
azinphos­
methyl.
Usage
is
now
stable
at
18%
of
acres
treated.
Application
is
primarily
by
ground
equipment
(
85­
95%).
4
Table
2.
Usage
of
Methyl
Parathion
on
Walnuts
in
California
from
1998­
2000.

Year
Bearing
Acreage1
(
1000
acres)
Acres
Treated4
(
1000
acres)
%
Acres
Treated
Pounds
AI
Applied4
(
1000
lbs)

2000
193
35
18%
56
1999
191
35
18%
57
1998
193
20
10%
33
TARGET
PESTS
IN
WALNUT
PRODUCTION
4
Methyl
parathion
is
used
to
control
codling
moth
in
California
walnut
production.
The
use
of
methyl
parathion
to
control
codling
moth
was
initiated
in
1997
to
control
populations
that
were
resistant
to
azinphos­
methyl.

Codling
moth
is
the
most
economically
important
pest
in
walnuts,
with
approximately
60%
of
the
acreage
susceptible
to
damage.
3
Those
acres
of
susceptible
cultivars
require
one
to
three
treatments
per
year
to
manage
this
pest.

Damage
results
from
the
codling
moth
larvae
boring
into
the
nuts
and
feeding
on
the
kernel.
The
moth
overwinters
on
the
tree
or
the
soil,
laying
eggs
in
the
spring
that
emerge
as
larvae
to
enter
nutlets.
Later
developing
larvae
also
enter
the
nuts
to
feed
on
the
kernel.
There
are
typically
three
to
(
less
common)
four
generations
per
year.
The
navel
orangeworm
uses
the
entry
site
in
the
walnut
from
the
codling
moth
larvae
to
access
the
kernel,
encouraging
populations
of
this
pest.
The
codling
moth
is
monitored
with
pheromone
traps.

ALTERNATIVE
CONTROL
Cultural
Control
No
cultural
methods
are
available
which
will
provide
control
of
the
codling
moth.

Biological
Control3
Although
over
250
biological
control
organisms
have
been
shown
to
attack
codling
moth,
none
are
capable
of
keeping
populations
below
that
which
causes
economic
damage.
Codling
Moth
Granulosis
virus
has
been
shown
to
be
somewhat
effective.
It
must
be
ingested
by
larvae
and
from
9
to
12
applications
are
needed
each
year
to
cover
the
long
generation
time.
Timing
these
treatments
is
extremely
difficult
because
irrigation
schedules
prevent
growers
from
getting
into
orchards
in
a
timely
matter.
Also,
because
walnut
trees
are
large,
it
is
not
possible
to
get
the
thorough
spray
coverage
with
this
material
necessary
for
reliable
control.

Trichogramma
platneria,
a
codling
moth
egg
parasite,
has
reduced
codling
moth
damage
by
up
to
70%
when
12
weekly
releases
of
150,000­
200,000
wasps
per
acre
per
week
are
released
in
low
to
moderate
population
situations.
This
level
of
control
is
not
adequate
to
prevent
a
buildup
over
time
and
economic
damage
in
most
walnut
orchards
in
the
state.

At
this
time
codling
moth
mating
disruption
is
not
economically
feasible
in
walnuts
because
of
large
tree
size
and
the
large
volume
of
air
which
would
have
to
be
permeated
with
pheromone.

Novel
ways
of
applying
codling
moth
pheromones
and
the
parasite
Trichograma
platneri
may
provide
some
alternative
controls
for
this
pest.
Pheromone
mating
disruption
control
programs
have
5
been
effective
in
pome
fruit
for
codling
moth
control
when
early
season
pest
populations
are
initially
at
low
to
moderate
levels.
Heavy
codling
moth
pest
pressure
is
not
adequately
controlled
by
the
pheromone
mating
disruption
programs.
However,
consultants
and
University
extension
personnel
report
that
early
season
control
of
codling
moths
with
azinphos­
methyl
works
to
prevent
buildup
of
pest
populations
and
has
facilitated
the
success
of
the
codling
moth
mating
disruption
programs.

Alternative
Insecticides
Table
3
presents
all
insecticides
which
are
currently
used
to
control
codling
moth
on
walnuts.
Insecticides
with
less
than
1%
of
acreage
treated
were
considered
ineffective
and
not
included
in
this
analysis
(
malathion,
Bt,
carbaryl,
naled,
and
pyriproxyfen).

Methyl
parathion
was
registered
as
a
SLN
insecticides
in
walnuts
due
to
development
of
codling
moth
resistance
to
azinphos­
methyl.
While
azinphos­
methyl
was
once
the
primary
insecticide
used
to
control
this
pest,
methyl
parathion
and
chlorpyrifos
are
now
more
widely
used
in
walnut
production.

Table
3.
Insecticides
used
to
control
codling
moth
in
walnuts.

Insecticide
­
In
Order
of
Importance
(
Based
on
Estimated
Usage
for
the
Control
of
Codling
Moth)
4,
5,
6
%
Share
of
Total
Insecticide
Use
(
Total
Acre
Treatments)
for
Control
of
Codling
Moth6
PHI
4
Limitations
and
advantages
4
chlorpyrifos
35.3
14
Reduced
from
8lbs
ai/
A
to
4
lbs
ai/
A.
Now
limited
to
2
applications/
year.
Effective
against
azinphos­
methyl
resistant
populations.

esfenvalerate
14.2
21
Very
disruptive
to
biological
control
of
mites.

phosmet
12.7
14
Limited
to
12
lbs
ai/
A.
Less
disruptive
to
beneficial
mites
than
some
other
OP's.
Used
where
minimal
non­
target
impact
is
essential.

methyl
parathion
11.3
14
Effective
against
azinphos­
methyl
resistant
populations
azinphos­
methyl
7.1
21
Under
4
year
phase
out.
Resistant
codling
moth
populations.

tebufenozide
5.9
30
A
high
priority
material.
Need
for
good
coverage
and
large
trees
limit
the
utility
of
this
material
Insecticide
­
In
Order
of
Importance
(
Based
on
Estimated
Usage
for
the
Control
of
Codling
Moth)
4,
5,
6
%
Share
of
Total
Insecticide
Use
(
Total
Acre
Treatments)
for
Control
of
Codling
Moth6
PHI
4
Limitations
and
advantages
4
6
permethrin
5.8
1
Disruptive
to
biological
mite
control
and
not
used
in
the
San
Joaquin
Valley
because
of
this
problem
methidathion
2.3
7
Can
provide
control.

diazinon
2.1
45
Can
provide
control.

diflubenzuron
1.2
28
A
high
priority
material.
Need
for
good
coverage
and
large
trees
limit
the
utility
of
this
material
7
BIOLOGICAL
IMPACT
OF
METHYL
PARATHION
CANCELLATION
ON
WALNUTS
Neither
changes
in
cultivation
practices
nor
use
of
biological
control
agents
can
adequately
control
codling
moth
in
walnuts
at
this
time.
There
are
alternative
insecticides
to
methyl
parathion
which
are
efficacious
and
currently
have
greater
market
share
than
methyl
parathion.
While
methyl
parathion
is
useful
in
resistance
management,
it
is
not
essential.
Chlorpyrifos
currently
has
a
greater
market
share
and
is
also
effective
against
codling
moth
populations
which
have
shown
resistance
to
azinphos­
methyl.
The
scheduled
phase­
out
of
azinphos­
methyl
in
the
next
4
years
will
reduce
the
need
for
methyl
parathion
as
a
resistance
management
alternative.
BEAD
feels
that
there
would
be
little
biological
impact
if
methyl
parathion
was
not
available
for
use
on
walnuts,
with
the
majority
of
growers
switching
to
chlorpyrifos
with
no
resulting
loss
in
production
or
quality.

ECONOMIC
IMPACT
OF
METHYL
PARATHION
CANCELLATION
ON
WALNUTS
Analysis
of
proprietary
data
on
insecticide
cost
indicates
there
would
be
no
negative
impact
if
methyl
parathion
was
not
available
for
use
on
walnuts.
6
Data
for
1998­
2000
show
insecticide
costs
of
$
26.78
and
$
20.86
per
acre
for
methyl
parathion
and
chlorpyrifos,
respectively.
Switching
to
chlorpyrifos,
the
current
market
share
leader
for
codling
moth
control,
would
result
in
a
savings
of
$
5.92/
acre.
6
CONCLUSIONS
The
absence
of
methyl
parathion
as
a
pest
management
tool
would
have
no
impact
on
walnut
production
in
the
US.
This
product
was
registered
as
a
SLN
insecticide
for
use
against
azinphosmethyl
resistant
codling
moth
populations.
Chlorpyrifos
also
has
the
same
negative
correlation
to
resistant
pest
populations
and
currently
has
the
largest
market
share
for
walnut
acres
treated.
BEAD
concludes
that
most
producers
currently
using
methyl
parathion
would
switch
to
chlorpyrifos.
As
the
price
of
chlorpyrifos
is
less
than
that
of
methyl
parathion,
it
would
also
be
to
the
producers
advantage
to
switch
to
the
efficacious
but
cheaper
alternative.

REFERENCES
1
Agricultural
Statistics.
2002.
USDA/
NASS.
http://
www.
usda.
gov/
nass/
pubs/
agr02/
acro02.
htm
2
Census
of
Agriculture.
1997.
USDA/
NASS.
http://
www.
nass.
usda.
gov/
census/

3
Crop
Profile
for
Walnuts
in
California
1998.
USDA/
NASS.
http://
pestdata.
ncsu.
edu/
cropprofiles/
docs/
cawalnuts.
html
8
4
California
Pesticide
Use.
1998­
2000.
Dept.
of
Pesticide
Regulation.
University
of
California.
http://
www.
ipm.
ucdavis.
edu/
PUSE/
puse1.
html
5
Noncitrus
Fruits
and
Nuts
2000
Preliminary
Summary.
2001.
NASS/
USDA
http://
usda.
mannlib.
cornell.
edu/
reports/
nassr/
fruit/
pnf­
bb/
ncit0701.
pdf
6
Proprietary
EPA
Data.
1999­
2001.
DOANE.
