Document ID: EPA-HQ-OAR-2003-0230-0098
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2004-06-10T04:00Z

U.
S.
A.
CUN2003/
061
­
SWEET
POTATO
­
FIELD
SWEET
POTATOES
GROWN
OUTDOORS
AFTER
BROADCAST
FUMIGATION
UNDER
POLYETHYLENE
TARPS
TABLE
OF
CONTENTS
Introduction
................................................................................................................................
2
Critical
Need
for
Methyl
Bromide...............................................................................................
2
Economic
impacts.......................................................................................................................
2
Response
to
Questions
from
MBTOC/
TEAP
..............................................................................
3
Definitions
..................................................................................................................................
8
References
..................................................................................................................................
9
LIST
OF
TABLES
Table
1.
Region,
Key
Pests,
and
Critical
Need
for
Methyl
Bromide
...........................................
2
Table
2.
Measures
of
Economic
Impact
for
Sweet
Potatoes........................................................
3
Table
3.
Nematicide
Test
on
California
Sweet
Potatoes,
1991
....................................................
5
Table
4.
Historical
Use
of
Methyl
Bromide
in
the
Sweet
Potato
Sector*.....................................
6
Table
5.
Calculation
of
the
Nominated
Amount
of
Methyl
Bromide
in
the
Sweet
Potato
Sector.
6
Page
2
INTRODUCTION
The
U.
S.
nomination
for
sweet
potato­
field
(
CUN
2003/
061)
has
only
requested
methyl
bromide
(
MB)
use
where
there
is
moderate
to
severe
root­
knot
nematode
infestation
in
California
(
see
Table
1)
and
where
the
alternative
1,3­
D
may
be
unavailable
due
to
local
township
cap
restrictions
on
its
use.
In
California,
sweet
potatoes
are
grown
in
the
Central
Valley,
predominantly
in
Merced
and
Stanislaus
Counties,
with
the
greatest
production
in
Merced
County.
Sweet
potato
growers
have
historically
used
MB
for
two
purposes:
fumigating
transplants
in
a
greenhouse­
like
setting
and
fumigating
open
fields
planted
with
sweet
potatoes.
California
sweet
potato
growers
have
transitioned
away
from
using
MB
for
open
field
pre­
plant
soil
fumigation.
In
2001
and
2002,
California
sweet
potato
producers
used
no
MB
on
their
open
fields,
using
instead
1,3­
D.
This
was
possible
because
the
township
caps
have
been
temporarily
increased
through
2004,
but
the
increase
is
not
expected
to
be
available
starting
in
2005.
There
are
no
feasible
alternatives
other
than
1,3­
D,
and
farmers
in
these
areas
face
strong
economic
losses
in
using
alternatives
(
see
Table
2).
In
addition,
the
other
alternatives
for
sweet
potatoes
fail
to
provide
necessary
pest
control
for
moderate
to
severe
nematode
infestations.

CRITICAL
NEED
FOR
METHYL
BROMIDE
TABLE
1.
REGION,
KEY
PESTS,
AND
CRITICAL
NEED
FOR
METHYL
BROMIDE.

U.
S.
State
/
Region
Key
Pests
Critical
Need
for
Methyl
Bromide
Sweet
Potato
Council
of
California
(
CUE02­
0016)
Nematodes:
root­
knot
nematodes
(
Meloidogyne
spp.)
At
moderate
to
severe
pest
pressure,
only
1,3­
D
or
MB
can
effectively
control
the
target
pest
in
California
sweet
potatoes.
However,
the
use
of
1,3­
D
may
be
limited
by
township
cap
regulatory
restrictions.
If
1,3­
D
is
not
available
because
of
township
caps,
MB
applications
are
typically
made
using
67:
33
or
50:
50
mixtures
with
chloropicrin
under
plastic
mulch.

ECONOMIC
IMPACTS
In
order
to
determine
whether
a
proposed
alternative
to
MB
is
considered
to
be
`
economically
feasible'
for
those
situations
where
technically
feasible
alternatives
exist,
the
U.
S.
took
a
`
weight
of
the
evidence'
or
`
portfolio'
approach.
Rather
than
rely
on
a
single
indicator
or
even
a
series
of
indicators,
each
with
a
`
bright
line',
the
situation
of
the
applicant
with
respect
to
five
measures
was
assessed.
The
five
measures
selected
for
consideration
were:
loss
per
hectare;
loss
per
kilogram
of
MB;
loss
as
a
percent
of
gross
revenue;
loss
as
a
percent
of
net
cash
returns;
and
change
in
profit
margins.
These
measures
were
selected
because
information
needed
to
support
their
use
was
fairly
readily
available,
because
they
describe
different
aspects
of
potential
loss
and
finally,
because
they
are
independent
of
each
other.
In
cases
where
information
was
not
available
for
one
or
more
of
the
measures,
the
remaining
measures
were
used.
In
cases
where
a
stream
of
benefits
was
derived
from
a
MB
application,
net
present
value
was
used
in
the
calculations.

When
evaluating
the
case
made
by
each
application,
expert
economic
judgment
was
used
to
determine
whether
each
loss
(
or
change
in
profit
margin)
was
significant,
not
significant,
or
Page
3
borderline
within
the
context
of
the
applicant's
market.
Once
decisions
on
individual
measures
were
reached,
an
overall
assessment
was
made
which
included
the
individual
measures
The
economic
assessment
compares
profitability
of
using
MB,
and
the
alternative
where
farmers
adopt
fallow/
crop
rotation,
such
as
growing
oat
forage,
on
a
field
for
two
years
between
sweet
potato
crops.
We
estimated
losses
for
a
hectare
that
is
planted
with
sweet
potatoes
on
one
third
of
the
land
and
oat
forage
on
the
other
two
thirds.
The
California
growers
estimate
that
yield
change
could
range
from
­
30
percent
to
+
15
percent,
but
that
a
decrease
is
the
most
likely
scenario.
Further
research
is
needed
on
how
crop
rotation
affects
sweet
potato
yields
to
narrow
this
range
of
uncertainty.
We
estimated
four
yield
loss
scenarios:
0%
yield
loss,
10%
yield
loss,
20%
yield
loss,
and
30%
yield
loss,
as
shown
in
the
following
table.
We
have
assumed
no
quality
decreases
in
sweet
potatoes
but
quality
losses
may
well
occur.
The
losses
arise
from
a
combination
of
the
lower
value
of
the
oat
crop,
the
higher
costs
of
production,
and,
in
some
scenarios,
from
the
yield
losses.
All
of
the
analysis
is
based
on
estimates
and
not
on
actual
field
trial
data.
Research
on
these
scenarios
is
ongoing
and
should
provide
data
over
the
next
few
years.

TABLE
2.
MEASURES
OF
ECONOMIC
IMPACT
FOR
SWEET
POTATOES
Percent
Yield
Loss
Scenario
0%
10%
20%
30%

Loss
per
hectare
US$
867
US$
1,301
US$
1,736
US$
2,169
Loss
per
Kg
of
MB
US$
5.15
US$
7.73
US$
10.31
US$
12.88
Loss
as
a
%
of
Gross
Revenue
7%
10%
13%
16%

Loss
as
a
%
of
Operating
Profit
38%
57%
76%
96%

Profit
Margin
(
with
MB
6%)
­
1%
­
12%
­
25%
­
41%

RESPONSE
TO
QUESTIONS
FROM
MBTOC/
TEAP
1.
MBTOC
notes
that
this
CUN
is
a
contingent
application
to
provide
an
allocation
of
MB
if
local
regulatory
caps
for
1,3­
D
are
already
taken
up
by
other
uses
and
that
MB
is
no
longer
used
now
for
sweet
potato
production
in
the
circumstances
of
this
CUN.
MBTOC
requests
that
the
Party
supply
reasons
why
the
1,3­
D
requirement
cannot
be
met
outside
of
the
local
allocation,
and
that
other
uses
that
may
have
access
to
alternatives
other
than
MB
can
then
use
them
rather
than
part
of
the
1,3­
D
cap.

Sweet
potato
growers
in
California
cannot
meet
nematode
control
needs
by
acquiring
additional
1,3­
D
through
reductions
in
1,3­
D
allocations
for
other
crops.
The
township
usage
caps
for
1,3­
D
are
imposed
by
the
State
of
California
to
reduce
air
contamination.
Where
sweet
potatoes
are
grown
in
California,
they
are
by
far
the
predominant
crop
in
the
township,
so
there
are
few,
if
any,
other
crops
from
which
1,3­
D
allocations
can
be
taken.
The
cap
is
on
the
total
amount
of
1,3­
D
that
can
be
used
in
a
township,
not
on
the
supply
of
1,3­
D
allocated
to
individual
crops
within
a
township.
The
principal
competing
crops
Page
4
are
almonds,
grapes,
nectarines
and
peaches,
which
also
require
1,3­
D
use.
The
U.
S.
submitted
MB
critical
use
nominations
for
all
of
these
other
crops
as
well.
The
U.
S.
nomination
in
these
sectors
already
assumes
that
1,3­
D
will
be
used
up
to
the
level
of
the
township
cap,
which
has
been
split
proportionally
among
the
relevant
nominating
sectors
(
thereby
reducing
the
amount
nominated
in
each
sector).
In
the
average
township
about
261
hectares,
or
about
three
percent
of
the
total
area,
can
be
fumigated
with
1,3­
D
in
any
year
according
to
California
regulations
(
assuming
a
rate
of
156.9
kg/
ha
[
140
lb/
A]
of
deep
shank
application).
The
details
of
the
reasoning
and
assumptions
used
to
calculate
the
nominated
amount
for
California
sweet
potatoes
on
a
contingent
basis
are
shown
in
Table
3
and
4.

We
understand
that
the
MBTOC
has
general
concerns
about
contingent
nominations,
but
we
would
urge
MBTOC
to
consider
the
possible
consequences
of
not
approving
the
request.
If,
during
2005,
sweet
potato
growers
cannot
get
1,3­
D
due
to
the
local
environmental
restrictions,
it
will
be
too
late
to
go
back
and
ask
MBTOC
and
the
Parties
for
assistance
in
obtaining
MB.
Further,
the
emergency
use
exemption
will
only
have
limited
value
in
addressing
the
amount
needed
by
these
growers.
As
a
consequence,
there
is
a
significant
risk
that
many
of
the
growers
would
have
to
go
out
of
business.
We
do
not
believe
that
this
result
was
intended
by
the
critical
use
decision,
or
is
desired
by
MBTOC.
We
believe
that
this
can
be
avoided
by
providing
the
U.
S.
with
an
exemption
that
explicitly
allows
MB
to
be
newly
produced/
imported
for
use
for
sweet
potato
production
only
in
the
event
and
only
to
the
extent
that
that
1,3­
D
is
not
available
due
to
the
application
of
the
township
restrictions.
Accordingly,
we
urge
MBTOC
to
approve
this
request
with
the
above
noted
restrictions
given
the
unique
circumstance
of
this
nomination.

2.
MBTOC
seeks
information
on
why
specific
nematicides
cannot
be
used
to
control
the
pests
that
apparently
may
lead
to
the
requirement
for
MB
in
2005.

The
pesticides
registered
in
California
for
root­
knot
nematode
control
are
MB,
1,3­
dichloropropene
(
Telone),
ethoprop
(
Mocap),
aldicarb
(
Temik),
metam­
sodium
(
Vapam)
and
chloropicrin.
Since
the
registrations
for
most
of
these
nematicides
have
existed
for
more
than
25
years,
the
U.
S.
EPA
has
been
unable
to
find
data
in
its
own
files
or
the
files
of
the
registrant
that
compare
the
relative
efficacy
of
nematicides
used
for
California
sweet
potatoes.
However,
usage
data
suggest
strongly
that
1,3­
D
is
the
most
cost
effective
alternative.
For
example,
use
data
from
the
California
Department
of
Pesticide
Regulation
show
that
in
2001
there
were
about
eight
times
more
acre­
treatments
of
sweet
potatoes
with
1,3­
D
than
with
ethoprop,
the
second
most
used
nematicide.
Also,
the
Sweet
Potato
Council
of
California
claims:
1)
that
the
bulk
of
the
reported
ethoprop
usage
is
for
insect
(
grub)
control,
rather
than
nematode
control;
2)
very
little
aldicarb
is
used,
most
of
which
reflects
informal
grower
evaluation
of
its
comparative
value
as
a
nematicide.
3)
Aldicarb
has
a
120­
day
pre­
harvest
interval
(
PHI)
label
restriction
which
is
too
long
for
most
varieties
because
it
increases
the
probability
of
mid­
and
late
season
nematode
damage
to
tubers
which
reduces
marketability;
and
4)
metam­
sodium
is
usually
used
in
areas
where
Telone
cannot
be
used,
however,
it
is
subject
to
a
500
foot
(
152
Page
5
meter)
buffer
zone
around
occupied
dwellings
(
personal
communication
between
B.
Weimer,
Sweet
Potato
Council
of
California
and
R.
Michell,
USEPA,
July
7
&
8,
2003).
Although
the
buffer
requirements
for
1,3­
D
have
been
reduced
on
the
federal
label,
states
are
allowed
to
have
more
stringent
requirements
and
as
yet
California
has
not
adopted
reduced
buffers.

3.
MBTOC
notes
that
trials
on
alternatives
to
MB
commenced
in
2001
and
requests
the
Party
to
supply
results
of
these
trials
as
an
aid
to
evaluation
of
the
critical
need
for
MB.

EPA
obtained
preliminary
results
from
research
trials
on
nematicides
conducted
by
the
Merced
County,
California
Cooperative
Extensive
Service
(
Stoddard,
2002).
These
data
were
generated
because
pest
control
in
sweet
potato
may
be
difficult
due
to
township
caps
on
1,3­
D.
The
initial
results
from
one
study
suggest
that
ethoprop
and
1,3­
D
had
similar
nematode
control.
The
study
author
indicated,
however,
that
this
result
might
have
been
due
to
a
block
effect
(
i.
e.,
due
to
the
location
in
the
field)
as
opposed
to
the
effect
of
the
nematicides.
Also,
the
author
noted
that
this
result
is
from
only
one
year
of
data
and
that
previous
research
showed
marginal
nematode
control
with
ethoprop
(
see
Table
3
below).
Follow­
up
studies
are
being
conducted
and
results
will
be
included
in
future
submissions.

TABLE
3.
NEMATICIDE
TEST
ON
CALIFORNIA
SWEET
POTATOES,
1991
(
C.
S.
STODDARD
PERSONAL
COMMUNICATION)

Treatment*
Rate
(
kg
ai/
ha)
Yield
(
kg/
ha)
Root
Knot
Nematode
(#/
250
ml
soil)

Control
15142
925
ns
Metam
sodium
356
23520
963
Ethoprop
9.9
14963
1350
MeBr
224
28806
375
*
Yield
per
plot,
MB
and
metham
sodium
were
significantly
better
than
the
other
two.
There
were
no
significant
differences
between
nematode
counts.
Page
6
TABLE
4.
HISTORICAL
USE
OF
METHYL
BROMIDE
IN
THE
SWEET
POTATO
SECTOR*.

Historical
Use
Average
Use
Rates
(
kg/
ha)
Total
Amount
(
kg)
Area
Treated
(
ha)

1997
156
347,470
2,226
1998
152
245,812
1,619
1999
167
202,180
1,214
2000
164
153,527
934
2001
 
 
 
*
Acres
planted
in
U.
S.:
97,900
(
39,619
ha).
Percent
of
U.
S.
Sweet
Potato
acreage
requested:
3%.
Source:
Rates,
amounts,
and
area
treated
are
from
applicants'
information.
Percent
of
U.
S.
acreage
is
from
USDA,
2001.
National
Agricultural
Statistics
Service,
Agricultural
Statistics
2001
TABLE
5.
CALCULATION
OF
THE
NOMINATED
AMOUNT
OF
METHYL
BROMIDE
IN
THE
SWEET
POTATO
SECTOR.

Calculation
of
Nominated
Amount
0016
 
Sweet
Potato
Council
of
California
Hectares
(
ha)
1,214
%
of
Regional
hectares
(
ha)(
A)
29
Applicant
Request
for
2005
Kilograms
(
kg)
of
MB
224,528
Double
Counted
hectares
(
ha)(
B)
0
Growth
/
Increasing
Production
(
ha)(
C)
1,214
Quarantine
and
Pre­
Shipment
hectares
(
ha)(
D)
0
Adjustments
to
Request
Adjusted
Hectares
Requested
(
ha)(
E)
1,214
Key
Pest
Impacts
(%)(
F)
0
Regulatory
Impacts
(%)(
G)
100
Soil
Impacts
(%)(
H)
0
Impacts
to
Adjusted
Hectares
Total
Combined
Impacts
(%)(
I)
100
Qualifying
Area
(
ha)(
J)
1,214
Use
Rate
(
kg/
ha)(
K)
185
CUE
Amount
Nominated
(
kg)(
L)
224,528
%
Reduction
from
Initial
Request
(
M)
0
Sum
of
all
CUE
Nominations
in
Sector
(
kg)(
N)
224,528
Multiplier
for
Margin
of
Error
(
O)
1.0000
Total
U.
S.
Sector
Nomination
(
kg)(
P)
224,528
Page
7
Footnotes
for
Table
5
Values
may
not
sum
exactly
due
to
rounding.

A.
Percent
of
regional
hectares
is
the
area
in
the
applicant's
request
divided
by
the
total
area
planted
in
that
crop
in
the
region
covered
by
the
request.
B.
Double
counted
hectares
is
the
area
counted
in
more
than
one
application
or
rotated
within
one
year
of
an
application
to
a
crop
that
also
uses
MB.
C.
Growth
/
increasing
production
hectares
is
the
amount
of
area
requested
by
the
applicant
that
is
greater
than
that
historically
treated
or
treated
at
a
higher
use
rate.
Values
in
parentheses
indicate
negative
values
and
are
shown
to
demonstrate
a
trend,
but
are
not
used
in
further
calculations.
This
entire
application
is
considered
growth
because
there
was
no
use
of
MB
for
this
crop,
however
it
differs
from
other
situations
in
that
the
request
is
only
in
case
the
applicant
is
not
able
to
obtain
the
(
preferred)
alternative.
D.
Quarantine
and
pre­
shipment
(
QPS)
hectares
is
the
area
in
the
applicant's
request
subject
to
QPS
treatments.
None
of
the
request
was
for
a
quarantine
or
pre­
shipment
use.
E.
Adjusted
hectares
requested
is
the
hectares
in
the
applicant's
request
minus
the
acreage
affected
by
double
counting,
growth
/
increasing
production,
and
quarantine
and
pre­
shipment.
F.
Key
pest
impacts
is
the
percent
(%)
of
the
requested
area
with
moderate
to
severe
pest
problems.
Key
pests
are
those
that
are
not
adequately
controlled
by
MB
alternatives.
Although
the
entire
acreage
is
affected
with
nematodes,
the
applicant
would
prefer
to
use
1,3­
D
unless
prohibited
by
regulatory
constraints.
G.
Regulatory
impacts
is
the
percent
(%)
of
the
requested
area
where
alternatives
cannot
be
legally
used
(
e.
g.,
township
caps).
Entire
request
is
for
area
expected
to
be
impacted
by
regulatory
cap.
At
present,
because
the
caps
have
been
temporarily
doubled,
the
township
caps
are
not
binding.
2004
is
to
be
the
last
year
of
relaxed
township
caps
for
1,3­
D.
H.
Soil
impacts
is
the
percent
(%)
of
the
requested
area
where
alternatives
cannot
be
used
due
to
soil
type
(
e.
g.,
heavy
clay
soils
may
not
show
adequate
performance).
I.
Total
combined
impacts
is
the
percent
(%)
of
the
requested
area
where
alternatives
cannot
be
used
due
to
key
pest,
regulatory,
or
soil
impacts.
In
each
case
the
total
area
impacted
is
the
area
which
is
impacted
by
one
or
more
of
the
individual
impacts.
For
each
application
the
assessment
was
made
by
biologists
familiar
with
the
specific
situation
and
able
to
make
judgments
about
the
extent
of
overlap
of
the
impacts.
For
example,
in
some
situations
the
impacts
are
mutually
exclusive
 
in
heavy
clay
soils
1,3D
will
not
be
effective
because
it
does
not
penetrate
these
soils
evenly,
but
none
of
the
heavy
soil
areas
will
be
impacted
by
township
(
regulatory)
caps
because
no
one
will
use
1,3D
in
this
situation,
so
this
soils
impact
must
be
added
to
the
township
cap
regulatory
impact
in
a
California
application.
In
other
words
there
is
no
overlap.
In
other
situations
one
area
of
impact
might
be
a
subset
of
another
impact.
In
these
cases,
the
combined
impact
is
equal
to
the
largest
individual
impact
J.
Qualifying
area
is
calculated
by
multiplying
the
adjusted
hectares
requested
by
the
total
combined
impacts.
K.
Use
rate
is
the
requested
use
rate
for
2005.
This
rate
is
typically
based
on
historical
averages.
In
some
cases,
the
use
rate
has
been
adjusted
downward
to
reflect
current
conditions.
L.
CUE
amount
nominated
is
calculated
by
multiplying
the
qualifying
area
by
the
use
rate.
M.
Percent
reduction
from
initial
request
is
the
percentage
of
the
initial
request
that
did
not
qualify
for
the
CUE
nomination.
N.
Sum
of
all
CUE
nominations
in
sector.
Self­
explanatory.
O.
Multiplier
for
margin
of
error.
This
amount
is
one
percentage
point
of
the
original
(
1991)
baseline
amount.
This
factor
is
intended
to
compensate
for
the
compounding
influence
of
using
the
low
end
of
the
range
for
all
input
parameters
in
the
calculation
of
the
US
nomination
(
i.
e.,
using
the
lowest
percent
impact
on
the
lowest
number
of
acres
at
the
lowest
dosage
is
likely
to
result
in
values
that
are
unrealistically
too
small).
The
U.
S.
nominated
this
sector
for
100%
of
the
amount
requested,
therefore
the
multiplier
is
1.0.
P.
Total
U.
S.
sector
nomination
is
calculated
by
multiplying
the
sum
of
nominations
in
a
sector
by
the
margin
of
error
multiplier.
Page
8
DEFINITIONS
THAT
MAY
BE
RELEVANT
TO
THIS
CUN
Source
of
yield
loss
estimates
Where
published
studies
of
yield
losses
under
conditions
of
moderate
to
severe
key
pest
pressure
were
not
available
(
the
situation
for
which
the
U.
S.
is
requesting
continued
use
of
methyl
bromide),
the
U.
S.
developed
such
estimates
by
contacting
university
professors
conducting
experiments
using
methyl
bromide
alternatives
in
the
appropriate
land
grant
institutions.
The
experts
were
asked
to
develop
such
an
estimate
based
on
their
experience
with
methyl
bromide
and
with
alternatives.
The
results
of
this
process
were
used
when
better
data
were
not
available.

Source
of
buffer
restriction
implications
for
methyl
bromide
use
Estimates
of
the
impact
of
buffers
required
when
using
some
methyl
bromide
alternatives
on
the
proportion
of
acreage
where
such
alternatives
could
be
used
were
developed
from
confidential
information
submitted
to
EPA
in
support
of
a
registration
application
for
a
methyl
bromide
alternative.
Because
at
the
time
of
the
analysis,
a
request
to
reduce
the
size
of
the
required
buffer
for
some
alternatives
was
under
consideration,
a
smaller
buffer
was
selected
for
the
analysis.
Since
that
time
the
size
of
the
regulatory
buffer
has
been
reduced
so
that
it
now
conforms
to
the
buffer
selected
for
the
analysis.

Source
of
area
impacted
by
key
pests
estimates
One
of
the
important
determinants
of
the
amount
of
methyl
bromide
requested
has
been
the
extent
of
area
infested
with
`
key
pests',
that
is,
pests
which
cannot
be
controlled
by
alternatives
to
methyl
bromide
when
such
pests
are
present
at
moderate
to
severe
levels.
Because
there
are
few
surveys
that
cover
substantial
portions
of
the
areas
for
which
methyl
bromide
is
requested,
we
have
relied
on
a
variety
of
sources
in
addition
to
the
surveys.
These
sources
include
websites
of
land
grant
universities;
discussions
with
researchers,
both
those
employed
by
USDA
in
the
Agricultural
Research
Service
(
ARS)
and
those
at
land
grant
universities;
discussions
with
growers
whose
operations
cover
widely
different
locations
encompassing
different
incidences
of
key
pests;
information
from
pesticide
applicators;
and,
information
taken
from
the
applications
themselves.

Source
of
area
impacted
by
regulations
estimates
There
are
two
main
sources
used
to
develop
the
estimate
of
area
impacted
by
regulations.
First,
for
the
impact
of
Township
caps
in
California
we
have
used
a
series
of
papers
by
Carpenter,
Lynch,
and
Trout,
cited
below,
supplemented
by
discussions
with
Dr.
Trout
to
ensure
that
any
recent
regulatory
changes
have
been
properly
accounted
for.
Second,
the
estimate
of
the
area
impacted
by
buffers,
is
described
above.

Source
of
area
impacted
by
soil
type
estimates
First,
for
the
area
impacted
by
karst
topography,
estimates
were
developed
and
mapped
by
he
Florida
Department
of
Environmental
Protection.
The
area
of
California
used
for
agriculture
and
which
is
made
of
clay
soils
unsuitable
for
pest
control
with
a
methyl
bromide
alternative
has
been
determined
by
discussions
with
agricultural
researchers
and
agricultural
extension
agents
in
California,
and
discussion
with
other
knowledgeable
individuals
such
as
pesticide
applicators.
The
estimates
for
California
understate
the
areas
in
which
alternatives
to
methyl
bromide
are
not
Page
9
suitable
because
no
effort
was
made
to
estimate
the
extent
of
hilly
terrain
where
currently
available
substitutes
cannot
be
applied
at
uniform
dosages.

Source
of
area
impacted
by
combined
impacts
estimate
Combined
impacts
were
determined
on
a
case
by
case
basis
for
each
specific
crop/
location
combination
after
consultation
with
individuals
knowledgeable
with
the
specific
circumstances.
The
nature
of
the
individual
impacts
is
such
that
in
some
situations
they
are
independent
of
each
other,
in
some
they
are
mutually
exclusive,
and
in
some
cover
identical
areas.
It
was
not,
therefore,
possible
to
have
a
formula
that
would
arrive
at
an
appropriate
estimate
of
combined
impacts.
A
more
complete
description
is
found
in
the
footnotes
to
the
`
calculation'
table.

REFERENCES
California
Department
of
Pesticide
Regulation.
2003.
Product
and
Use
Information.
Available
online
at
http://
www.
cdpr.
ca.
gov/
dprdatabase.
htm
Carpenter,
Janet,
Lori
Lynch
and
Tom
Trout.
2001.
Township
Limits
on
1,3­
D
will
Impact
Adjustment
to
Methyl
Bromide
Phase­
out.
California
Agriculture,
Volume
55,
Number
3.

Stoddard,
C.
S.
2002.
Research
Progress
Report:
Fumigation
and
cover
crop
trial
on
sweet
potatoes.
University
of
California
Cooperative
Extension
Service,
Merced
County.