UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
Date:
21­
December­
2005
Subject:
Terbacil
in/
on
Watermelon.
Summary
of
Residue
Chemistry
Data.

DP
Barcode:
D313911
Registration:
3E6640
PC
Code:
012701
Decision
#:
354086
MRID
No.:
46007101
40
CFR
180.209
From:
Tom
Bloem,
Chemist
Registration
Action
Branch
1,
Health
Effects
Division
(
RAB1/
HED;
7509C)

Through:
PV
Shah,
Ph.
D.,
Branch
Senior
Scientist
RAB1/
HED
(
7509C)

To:
Daniel
Rosenblatt;
RM
05
Registration
Division
(
7505C)

The
Interregional
Research
Prject
Number
4
(
IR­
4)
proposed
the
establishment
of
the
following
permanent
tolerances
for
combined
residues
of
terbacil
(
3­
tert­
butyl­
5­
chloro­
6­
methyluracil)
and
its
metabolites
3­
tert­
butyl­
5­
chloro­
6­
hydroxymethyluracil,
6­
chloro­
2,3­
dihydro­
7­
hydroxymethyl
3,3­
dimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one,
and
6­
chloro­
2,3­
dihydro­
3,3,7­
trimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one,
calculated
as
terbacil
(
see
attachment
1
for
structures):

Watermelon
.
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1
ppm
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
2
of
14
Executive
Summary
Background:
Terbacil
provides
control
of
annual
grasses
and
broadleaf
weeds
via
photosynthesis
inhibition
(
inhibition
of
photosystem
II).
Terbacil
is
readily
absorbed
by
roots
and
translocated
upward;
when
absorbed
by
leaves,
translocation
is
minimal.
Tolerances
are
currently­
established
for
the
combined
for
residues
of
terbacil
and
its
metabolites
3­
tert­
butyl­
5­
chloro­
6­
hydroxymethyluracil
(
metabolite
A),
6­
chloro­
2,3­
dihydro­
7­
hydroxymethyl
3,3­
dimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one
(
metabolite
B),
and
6­
chloro­
2,3­
dihydro­
3,3,7­
trimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one
(
metabolite
C),
calculated
as
terbacil,
in/
on
alfalfa,
apple,
asparagus,
blueberry,
caneberry,
peach,
peppermint,
spearmint,
strawberry,
and
sugarcane
ranging
from
0.1­
2.0
ppm
(
40
CFR180.209;
see
attachment
1
for
structures).
A
time
limited
tolerance
in/
on
watermelon
is
also
established
at
0.4
ppm
(
expires
30­
Jun­
2007;
Section
18
registration).

Proposed
Application
Scenarios:
The
petitioner
provided
a
supplemental
Dupont
 
Sinbar
®
Herbicide
(
wettable
powder
(
WP);
80%
terbacil
by
weight;
EPA
Reg.
No.
352­
317)
label
which
includes
instructions
for
application
to
watermelon.
Table
1
is
a
summary
of
the
proposed
application
scenario.
The
supplemental
label
indicates
that
for
seeded
watermelon,
applications
are
to
be
made
after
planting
but
before
the
crop
emerges;
however,
application
to
emerged
crops
is
also
permitted
as
the
supplemental
label
cautions
that
the
spray
solution
should
not
be
allowed
to
contact
the
crop
(
over­
the­
top
applications
are
prohibited).
No
rotational
crop
restrictions
are
included
on
the
supplemental
label.
However,
the
supplemental
label
states
that
all
applicable
directions,
restrictions,
and
precautions
on
the
main
label
must
be
followed.
The
main
label
indicates
that
no
crops
may
be
planted
within
2
years
of
application
as
injury
to
the
subsequent
crops
may
result.
The
main
label
also
indicates
that
application
through
irrigation
equipment
is
prohibited
and
that
unless
otherwise
directed,
the
product
is
to
be
applied
with
fixed­
boom
power
sprayer.
HED
concludes
that
the
proposed
application
instructions
are
adequate.

Table
1.
Summary
of
Proposed
Application
Scenario
for
Terbacil
Application
Equipment
Max.
Single
Applic.
Rate
(
lb
ai/
acre)
Max.
No.
Applic.
per
Season
PHI1
(
days)
Comments
Watermelon
ground
equipment;
fixed­
boom
power
sprayer
0.10­
0.15
1
70
lower
rate
is
for
coarse
texture
soils
lower
in
organic
matter;
20­
40
gallon/
acre
1
PHI
=
preharvest
interval
Nature
of
the
Residue
­
Plants:
The
petitioner
has
previously
submitted
and
HED
has
reviewed
alfalfa,
blueberry,
and
sugarcane
metabolism
studies.
Based
on
these
data,
HED
concluded
that
the
nature
of
the
residue
in
plants
is
adequately
understood
and
the
residues
of
concern,
for
risk
assessment
and
tolerance
enforcement,
are
terbacil
and
metabolites
A,
B,
and
C
(
Terbacil
Reregistration
Standard,
8­
Mar­
1989,
R.
Schmitt;
D222891,
D.
Miller,
5­
Dec­
1996;
HED
Reregistration
Eligibility
Document
(
RED),
D.
Miller,
18­
Dec­
1996).
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
3
of
14
Nature
of
the
Residue
­
Livestock:
The
petitioner
has
previously
submitted
and
HED
has
reviewed
acceptable
ruminant
(
D190213,
D.
Miller,
9­
Sep­
1993)
and
poultry
(
D192398,
D.
Miller,
28­
Jul­
1993)
metabolism
studies.
Based
on
these
data,
HED
concluded
that
the
nature
of
the
residues
in
livestock
is
adequately
understood
and
the
residues
of
concern,
for
risk
assessment
and
tolerance
enforcement,
are
terbacil
and
metabolites
A,
B,
and
C
(
HED
RED,
D.
Miller,
18­
Dec­
1996).

Nature/
Magnitude
of
the
Residue
in
Rotational
Crops:
A
confined
rotational
crop
study
is
not
currently
available.
The
HED
RED
(
D.
Miller,
18­
Dec­
1996)
stated
that
if
the
aerobic
soil
metabolism
study
(
MRID
42369901),
which
was
being
reviewed
by
the
Environmental
Fate
and
Effects
Division
(
EFED),
revealed
no
new
metabolites
other
than
those
regulated
in
the
primary
crops,
then
a
confined
rotational
crop
study
may
not
be
required.
The
following
information
was
gathered
from
the
EFED
RED
(
D229773,
J.
Hetrick,
26­
Jun­
1997):

Terbacil
is
persistent
under
aerobic
and
anaerobic
soil
conditions
(
t1/
2=
235
to
653
days).
Minor
nonvolatile
transformation
products
(<
10%
of
applied)
are
t­
butylurea
and
3­
t­
butyl­
6­
methyluracil.
The
major
volatile
transformation
product
is
CO2.
The
reported
laboratory
degradation
data
indicate
terbacil
is
persistent
in
terrestrial
environments.
Marginally
acceptable
field
dissipation
studies
indicate
terbacil,
at
5
lbs
ai/
acre,
is
persistent
and
mobile
under
actual
use
conditions.
Field
dissipation
half­
lives
in
Delaware,
Illinois,
and
California
ranged
from
204
to
252
days.
The
maximum
depth
of
terbacil
detection
was
45
to
50
cm.
Metabolites
A
(
maximum
concentration
(
0.14
ppm)
15
days
after
application)
and
B
(
maximum
concentration
(
0.07
ppm)
60
days
after
application)
were
detected
in
the
field
dissipation
studies.

ChemSAC
was
consulted
concerning
the
need
for
additional
confined/
field
rotational
crop
studies.
Based
on
the
demonstrated
persistence
of
terbacil
in
the
aerobic
and
anaerobic
soil
metabolism
studies
(
half­
life
=
235­
653
days;
EFED
RED,
D229773,
J.
Hetrick,
26­
Jun­
1997),
the
ChemSAC
concluded
that
a
confined
rotational
crop
study
is
not
necessary
(
see
ChemSAC
minutes
for
1­
Feb­
2006).
Therefore,
HED
concludes
that
the
residues
of
concern
in
rotational
crops
are
terbacil,
metabolite
A,
metabolite
B,
metabolite
C,
and
3­
t­
butyl­
6­
methyluracil.
Metabolites
A,
B,
and
C
were
included
as
these
are
residues
of
concern
in
the
primary
crops
and
may
form
in
rotational
crops
via
uptake
and
metabolism
of
parent.
3­
t­
butyl­
6­
methyluracil
was
included
as
it
was
identified
in
the
aerobic
soil
metabolism
study.
HED
notes
that
3­
t­
butyl­
6­
methyluracil
was
identified
at
<
10%
TRR;
however,
the
aerobic
soil
metabolism
study
was
conducted
for
only
1
year
and
the
proposed
registered
plant­
back
intervals
(
PBIs)
are
2
years
(
i.
e.
concentration
of
3­
tbutyl
6­
methyluracil
may
be
significant
after
2
years;
t­
butylurea
was
not
included
based
on
concentration
and
toxicological
considerations).
Based
on
the
watermelon
application
rate
and
the
results
of
the
currently
available
field
trial
studies
(
6.7­
33x
the
watermelon
application
rate;
terbacil
and
metabolite
A
residues
of
#
0.19
ppm),
the
ChemSAC
concluded
that
an
additional
field
rotational
crop
study
was
not
necessary
and
tolerances
in/
on
crops
resulting
from
rotation
into
watermelon
fields
which
have
been
treated
with
terbacil
were
unnecessary.
However,
the
ChemSAC
did
state
that
a
field
rotational
crop
study
may
be
required
for
future
registrations
(
see
ChemSAC
minutes
for
1­
Feb­
2006).
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
4
of
14
Magnitude
of
the
Residue
­
Plants:
The
petitioner
submitted
a
watermelon
field
trial
study
which
presented
the
magnitude
of
terbacil
(
limit
of
quantitation
(
LOQ)
=
0.50
ppm),
metabolite
A
(
LOQ
=
0.30
ppm),
metabolite
B
(
LOQ
=
0.10
ppm),
and
metabolite
C
(
LOQ
=
0.10
ppm)
residues
in/
on
watermelon
following
a
single
application
at
0.248­
0.297
lb
ai/
acre
(
1.6­
2.0x;
PHI
=
69­
94
days).
Combined
residues
of
terbacil
and
metabolites
A,
B,
and
C
in/
on
the
treated
samples
were
<
LOQ
(<
1.0
ppm).
Terbacil
residues
which
were
<
LOQ
were
found
in/
on
many
of
the
treated
samples
and
ranged
from
<
0.001­
0.091
(
n=
11)
with
one
sample
at
0.230
ppm
(
no
residues
of
metabolites
A,
B,
or
C
were
found
in/
on
any
sample).

The
high
terbacil
LOQ
was
due
to
residues
at
0.134
ppm
and
0.182
ppm
in/
on
two
of
the
control
samples
collected
from
the
field
trials.
The
study
indicated
that
these
may
be
treated
samples
mislabeled
as
untreated
samples;
however,
no
evidence
supporting
this
claim
was
provided.
Terbacil
residues
were
found
in/
on
many
of
the
remaining
control
samples
at
<
0.001­
0.074
ppm
(<
0.001
ppm
(
n=
2)
and
0.047­
0.078
ppm
(
n=
8)).
If
the
0.134
ppm
and
0.182
ppm
control
samples
are
excluded
and
based
on
the
residues
in/
on
the
remaining
control
samples,
a
terbacil
LOQ
of
at
least
0.20
ppm
would
be
established
(
assumes
LOQ
=
3x
the
background).
Assuming
a
terbacil
LOQ
of
0.20
ppm,
terbacil
residues
in/
on
the
treated
samples
would
be
<
LOQ
for
all
excluding
one,
0.230
ppm.

Based
on
the
discussion
from
the
previous
paragraph,
HED
concludes
that
the
data
submitted
in
the
watermelon
field
trial
study
are
acceptable
despite
the
exaggerated
rate
due
to
residues
less
than
or
slightly
greater
than
the
LOQ.
HED
generally
allows
for
a
25%
reduction
in
the
suggested
number
of
field
trials
when
residues
are
<
LOQ
(
Table
5,
OPPTS
860.1500).
However,
since
the
terbacil
and
metabolite
A
LOQs
are
high
and
since
the
label
indicates
that
application
after
crop
emergence
is
permitted
(
all
the
currently­
available
field
trials
were
conducted
post
planting
and
prior
to
crop
emergence),
HED
concludes
this
reduction
is
not
appropriate
and
requests
additional
watermelon
field
trials,
conducted
with
application
after
crop
emergence,
in
Regions
3
(
n=
1),
5
(
n=
1),
and
6
(
n=
1).
Provided
the
petitioner
agrees
to
submit
these
data
and
based
on
the
currently
available
data,
HED
concludes
that
a
tolerance
of
1.0
ppm
for
the
combined
residues
of
terbacil
and
metaoblites
A,
B,
and
C
in/
on
watermelon
is
appropriate.
A
revised
Section
F
is
requested.

Magnitude
of
the
Residue
­
Livestock:
As
there
are
no
feed
commodities
associated
with
watermelon,
the
magnitude
of
the
residue
in
livestock
is
not
relevant
to
the
current
petition.

Enforcement
Method
­
Watermelon:
There
are
currently
two
terbacil
enforcement
methods
in
the
Pesticide
Analytical
Manual
(
PAM;
Vol.
II).
The
HED
RED
(
D.
Miller,
18­
Dec­
1996)
concluded
that
Method
I
is
unacceptable
as
it
does
not
include
instructions
for
the
quantitation
of
metabolites
A,
B,
and
C
and
Method
II
is
unacceptable
as
it
uses
a
microcoulometric
detector.
The
HED
RED
went
on
to
say
that
an
adequate
gas
chromatograph/
nitrogen­
phosphorus
detector
(
GC/
NPD)
method,
which
is
a
modification
of
Method
II
in
PAM
(
Vol.
II),
may
be
an
appropriate
enforcement
method
and
requested
that
the
petitioner
submit
this
procedure
to
HED
for
a
petition
method
validation
(
PMV;
since
the
procedure
is
similar
to
Method
II,
an
independent
laboratory
validation
(
ILV)
was
deemed
unnecessary).
The
petitioner
did
not
submit
a
separate
study
with
the
analytical
procedure
for
this
method.
However,
the
watermelon
field
trial
study
employed
the
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
5
of
14
method
in
question
and
this
study
included
a
copy
of
the
analytical
procedure
as
an
attachment.
This
information
was
forwarded
to
the
Analytical
Chemistry
Laboratory
(
ACL)
of
the
Biological
and
Economic
Analysis
Division
(
BEAD)
for
a
PMV
(
D324601,
T.
Bloem,
21­
Dec­
2005).

Recommendations:
Provided
the
petitioner
submits
a
revised
Section
F
and
the
ACL
is
able
to
validate
the
proposed
plant
enforcement
method,
HED
concludes
that
the
residue
chemistry
database
supports
a
conditional
registration
and
establishment
of
a
1.0
ppm
tolerance
for
the
residues
fo
terbacil
and
its
metabolites
A,
B,
and
C
in/
on
watermelon.
The
residue
chemistry
database
may
support
unconditional
registration
upon
submission
of
Food
and
Drug
Administration
(
FDA)
multiresidue
testing
of
terbacil
and
its
metabolites
A,
B,
and
C
through
protocol
D
and
additional
watermelon
field
trial
data.

A
human­
health
risk
assessment
will
be
prepared
as
a
separate
document.

Summary
of
Residue
Chemistry
Deficiencies:

CRevised
Section
F
CPMV
of
the
plant
and
livestock
enforcement
methods
CFDA
multiresidue
testing
of
terbacil
and
its
metabolites
A,
B,
and
C
through
protocol
D
Cadditional
watermelon
field
trials,
conducted
with
application
after
crop
emergence,
in
Regions
3
(
n=
1),
5
(
n=
1),
and
6
(
n=
1)
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
6
of
14
N
HN
O
C(
CH3)
3
O
Cl
H3C
Detailed
Considerations
Background
Terbacil
provides
control
of
annual
grasses
and
broadleaf
weeds
via
photosynthesis
inhibition
(
inhibition
of
photosystem
II).
Terbacil
is
readily
absorbed
by
roots
and
translocated
upward;
when
absorbed
by
leaves,
translocation
is
minimal.

Table
2.
Test
Compound
Nomenclature.

Chemical
structure
Common
name
terbacil
Company
experimental
name
DPX­
D0732
IUPAC
name
3­
tert­
butyl­
5­
chloro­
6­
methyluracil
CAS
name
5­
chloro­
3­(
1,1­
dimethylethyl)­
6­
methyl­
2,4(
1H,
3H)­
pyrimidinedione
CAS
registry
number
5902­
51­
2
End­
use
product
(
EP)
Sinbar
80WP
(
wettable
powder
80%
terbacil
Table
3.
Physicochemical
Properties
of
the
Technical
Grade
Test
Compound.

Parameter
Value
Reference
Melting
point/
range
175­
177
°
C
Terbacil
Reregistration
Standard
(
8­
Mar­
1989,
R.
Schmitt)
pH
not
available
Density)
1.34
g/
cm3
(
25
/

C)

Water
solubility
(
mg/
L
(
25
°
C))
710
Solvent
solubility
(
mg/
mL
(
25
°
C))
dimethylformamide
33.7
cyclohexane
22
methyl
isobutyl
ketone
13.8
butyl
acetate
9.7
Xylene
6.5
Vapor
pressure
4.7
x
10­
7
mm
Hg
(
29.5
/

C)

Dissociation
constant,
pKa
not
available
Octanol/
water
partition
coefficient
(
KOW)
81.9
UV/
visible
absorption
spectrum
not
available
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
7
of
14
860.1200
Directions
for
Use
The
petitioner
provided
a
supplemental
Dupont
 
Sinbar
®
Herbicide
(
80%
WP)
label
which
includes
instructions
for
application
to
watermelon.
Table
1
is
a
summary
of
the
proposed
application
scenario.
The
supplemental
label
indicates
that
seeded
watermelon,
applications
are
to
be
made
after
planting
but
before
the
crop
emerges;
however,
application
to
emerged
crops
is
also
permitted
as
the
supplemental
label
cautions
that
the
spray
solution
should
not
be
allowed
to
contact
the
crop
(
over­
the­
top
applications
are
prohibited).
No
rotational
crop
restrictions
are
included
on
the
supplemental
label;
however,
the
supplemental
label
states
that
all
applicable
directions,
restrictions,
and
precautions
on
the
main
label
must
be
followed.
The
main
label
indicates
that
no
crops
may
be
planted
within
2
years
of
application
as
injury
to
the
subsequent
crops
may
result.
The
main
label
also
indicates
that
application
through
irrigation
equipment
is
prohibited
and
that
unless
otherwise
directed,
the
product
is
to
be
applied
with
fixed­
boom
power
sprayer.
HED
concludes
that
the
proposed
application
instructions
are
adequate.

860.1300
Nature
of
the
Residue
­
Plants/
Livestock
Plants:
The
petitioner
has
previously
submitted
and
HED
has
reviewed
alfalfa,
blueberry,
and
sugarcane
metabolism
studies.
Based
on
these
data,
HED
concluded
that
the
nature
of
the
residue
in
plants
is
adequately
understood
and
the
residues
of
concern,
for
risk
assessment
and
tolerance
enforcement,
are
terbacil
and
metabolites
A,
B,
and
C
(
Terbacil
Reregistration
Standard,
8­
Mar­
1989,
R.
Schmitt;
D222891,
D.
Miller,
5­
Dec­
1996;
HED
RED,
D.
Miller,
18­
Dec­
1996).

Livestock:
The
petitioner
has
previously
submitted
and
HED
has
reviewed
acceptable
ruminant
(
D190213,
D.
Miller,
9­
Sep­
1993)
and
poultry
(
D192398,
D.
Miller,
28­
Jul­
1993)
metabolism
studies.
Based
on
these
data,
HED
concluded
that
the
nature
of
the
residues
in
livestock
is
adequately
understood
and
the
residues
of
concern,
for
risk
assessment
and
tolerance
enforcement,
are
terbacil
and
metabolites
A,
B,
and
C
(
HED
RED,
D.
Miller,
18­
Dec­
1996).

860.1340
Residue
Analytical
Methods
­
Plants/
Livestock
Livestock:
As
there
are
not
feed
commodities
associated
with
watermelon,
a
discussion
concerning
an
enforcement
method
for
livestock
is
unnecessary.

Plants:
There
are
currently
two
terbacil
enforcement
methods
in
PAM
(
Vol.
II).
The
HED
RED
(
D.
Miller,
18­
Dec­
1996)
concluded
that
method
I
was
unacceptable
as
it
does
not
include
instructions
for
the
quantitation
of
metabolites
A,
B,
and
C
and
method
II
is
unacceptable
as
it
uses
a
microcoulometric
detector.
The
HED
RED
went
on
to
say
that
an
adequate
GC/
NPD
method,
which
is
a
modification
of
Method
II
in
PAM
(
Vol.
II),
may
be
an
appropriate
enforcement
method
and
requested
that
the
petitioner
submit
this
procedure
to
HED
for
PMV
(
since
the
procedure
is
similar
to
enforcement
method
II,
an
ILV
was
deemed
unnecessary).
The
petitioner
did
not
submit
a
separate
study
with
the
analytical
procedure
for
this
method.
However,
the
watermelon
field
trial
study
employed
the
method
in
question
and
this
study
included
a
copy
of
the
analytical
procedure
as
an
attachment.
This
information
was
forwarded
to
the
ACL
of
BEAD
for
a
PMV
(
D324601,
T.
Bloem,
21­
Dec­
2005).
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
8
of
14
860.1360
Multiresidue
Methods
Data
have
been
submitted
pertaining
to
the
analytical
behavior
of
terbacil
and
its
regulated
metabolites
through
FDA
Multiresidue
Protocols
and
these
data
have
been
forwarded
to
FDA
for
inclusion
in
PAM
(
Vol.
I,
Appendix
I).
The
registrant
has
submitted
the
results
of
FDA
Multiresidue
Protocol
C
to
the
Agency
(
Protocols
A,
B,
and
E
are
not
applicable)
which
demonstrates
that
terbacil
and
its
metabolites
yield
acceptable
results
when
tested
under
the
specified
GLC
conditions.
Results
from
Protocol
D,
however,
were
not
submitted,
and
the
registrant
is
required
to
use
this
method
to
test
an
appropriate
commodity
and
submit
the
results
for
terbacil
and
its
regulated
metabolites
for
inclusion
in
PAM
(
HED
RED,
D.
Miller,
18­
Dec­
1996).
These
data
have
not
been
submitted.

860.1380
Storage
Stability
46007101.
der.
wpd
The
maximum
storage
interval
from
harvest
to
analysis,
for
the
watermelon
samples
collected
as
part
of
the
field
trial
study,
was
268
days.
As
part
of
the
watermelon
field
trial
study,
the
petitioner
submitted
watermelon
storage
stability
data
which
resulted
in
acceptable
recoveries
of
terbacil
and
metabolites
A,
B,
and
C
following
279
days
of
storage.
However,
the
data
did
not
include
a
0­
day
analysis
to
confirm
the
fortification
level.
Adequate
storage
stability
data
have
been
previously
submitted
and
reviewed
for
terbacil
and
metabolites
A,
B,
and
C
in/
on
alfalfa
(
24
months),
apples
(
6
months),
blueberry
(
6
months),
mint
(
18
months),
milk
(
1
month),
and
sugarcane
(
6
months;
HED
RED,
D.
Miller,
18­
Dec­
1996).
HED
concludes
that
the
combination
of
the
watermelon
storage
stability
data
submitted
with
this
petition
and
the
previously
reviewed
storage
stability
data
are
sufficient
to
validate
the
watermelon
field
trial
study.

860.1480
Meat,
Milk,
Poultry,
and
Eggs
As
there
are
no
feed
commodities
associated
with
watermelon,
the
magnitude
of
the
residue
in
livestock
is
not
relevant
to
the
current
petition.

860.1500
Crop
Field
Trials
46007101.
der.
wpd
The
petitioner
submitted
a
watermelon
field
trial
study
which
presented
the
magnitude
of
terbacil
(
LOQ
=
0.50
ppm),
metabolite
A
(
LOQ
=
0.30
ppm),
metabolite
B
(
LOQ
=
0.10
ppm),
and
metabolite
C
(
LOQ
=
0.10
ppm)
residues
in/
on
watermelon
following
a
single
application
at
0.248­
0.297
lb
ai/
acre
(
1.6­
2.0x;
PHI
=
69­
94
days).
Combined
residues
of
terbacil
and
metabolites
A,
B,
and
C
in/
on
the
treated
samples
were
<
LOQ
(<
1.0
ppm).
Terbacil
residues
which
were
<
LOQ
were
found
in/
on
many
of
the
treated
samples
and
ranged
from
<
0.001­
0.091
(
n=
11)
with
one
sample
at
0.230
ppm
(
no
residues
of
metabolites
A,
B,
or
C
were
found
in/
on
any
sample).

The
high
terbacil
LOQ
was
due
to
residues
at
0.134
ppm
and
0.182
ppm
in/
on
two
of
the
control
samples
collected
from
the
field
trials.
The
study
indicated
that
these
may
be
treated
samples
mislabeled
as
untreated
samples;
however,
no
evidence
supporting
this
claim
was
provided.
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
9
of
14
Terbacil
residues
were
found
in/
on
many
of
the
remaining
control
samples
at
<
0.001­
0.074
ppm
(<
0.001
ppm
(
n=
2)
and
0.047­
0.078
ppm
(
n=
8)).
If
the
0.134
ppm
and
0.182
ppm
control
samples
are
excluded
and
based
on
the
residues
in/
on
the
remaining
control
samples,
a
terbacil
LOQ
of
at
least
0.20
ppm
would
be
established
(
assumes
LOQ
=
3x
the
background).
Assuming
a
terbacil
LOQ
of
0.20
ppm,
terbacil
residues
in/
on
the
treated
samples
would
be
<
LOQ
for
all
excluding
one,
0.230
ppm.

Based
on
the
discussion
from
the
previous
paragraph,
HED
concludes
that
the
data
submitted
in
the
watermelon
field
trial
study
are
acceptable
despite
the
exaggerated
rate
due
to
residues
less
than
or
slightly
greater
than
the
LOQ.
HED
generally
allows
for
a
25%
reduction
in
the
suggested
number
of
field
trials
when
residues
are
<
LOQ
(
Table
5,
OPPTS
860.1500).
However,
since
the
terbacil
and
metabolite
A
LOQs
are
high
and
since
the
label
indicates
that
application
after
crop
emergence
is
permitted
(
all
the
currently­
available
field
trials
were
conducted
post
planting
and
prior
to
crop
emergence),
HED
concludes
this
reduction
is
not
appropriate
and
requests
additional
watermelon
field
trials,
conducted
with
application
after
crop
emergence,
in
Regions
3
(
n=
1),
5
(
n=
1),
and
6
(
n=
1).
Provided
the
petitioner
agrees
to
submit
these
data
and
based
on
the
currently
available
data,
HED
concludes
that
a
tolerance
of
1.0
ppm
for
the
combined
residues
of
terbacil
and
metaoblites
A,
B,
and
C
in/
on
watermelon
is
appropriate.
A
revised
Section
F
is
requested.
The
following
paragraphs
are
a
detailed
summary
of
the
watermelon
field
trial
study.

Watermelon
Field
Trail
Study
(
46007101.
der.
wpd):
Five
watermelon
trials
were
conducted
in
Regions
2
(
n=
2),
3
(
n=
1),
6
(
n=
1),
and
10
(
n=
1).
At
each
field
trial,
the
plants
were
treated
with
a
single
broadcast
spray
application
of
a
80%
WP
terbacil
formulation
at
0.248­
0.297
lb
ai/
acre
(
23­
40
gallons/
acre
(
GPA)).
Applications
were
made
after
planting
but
prior
to
crop
emergence.
Duplicate
control
and
treated
samples
were
collected
at
maturity,
69­
94
days
after
application.

The
harvested
samples
were
analyzed
for
residues
of
terbacil
and
metabolites
A,
B,
and
C
using
the
Dupont
method
AMR­
1719­
90.
Acceptable
method
validation
and
concurrent
recovery
data
were
provided.
Based
on
the
lowest
method
validation
level
which
resulted
in
acceptable
recoveries,
the
LOQ
for
terbacil,
metabolite
B,
and
metabolite
C
is
0.10
ppm
and
the
LOQ
for
metabolite
A
is
0.30
ppm
(
unacceptable
recoveries
at
0.10
ppm).
Since
terbacil
residues
in/
on
control
samples
from
the
field
trials
ranged
from
<
0.001­
0.182
ppm
(<
0.001
ppm
(
n=
2),
0.047­
0.078
ppm
(
n=
8),
0.134
ppm,
and
0.182
ppm),
the
study
indicated
a
LOQ
of
0.50
ppm
for
terbacil.
The
study
indicated
that
it
is
possible
that
the
controls
samples
which
resulted
in
terbacil
residues
of
0.134
ppm
and
0.182
ppm
may
have
been
treated
samples
but
were
mislabeled
as
untreated;
no
evidence
to
confirm
this
suspicion
is
available.
HED
notes
that
if
the
0.134
ppm
and
0.182
ppm
control
samples
are
excluded
and
based
on
the
residues
in/
on
the
remaining
control
samples,
a
terbacil
LOQ
of
at
least
0.20
ppm
would
be
established
(
assumes
LOQ
=
3x
the
background).
The
maximum
storage
interval
from
harvest
to
analysis
was
268
days.
The
petitioner
has
submitted
adequate
storage
stability
data
to
validate
this
interval
(
see
storage
stability
section
OPPTS
860.1380).

Residues
of
terbacil,
metabolite
A,
metabolite
B,
and
metabolite
C
were
<
LOQ
in/
on
all
samples
(<
0.50
ppm,
<
0.30
ppm,
<
0.10
ppm,
and
<
0.10
ppm,
respectively).
Since
the
terbacil
LOQ
is
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
10
of
14
based
on
the
detection
of
terbacil
residues
in/
on
field
trial
control
samples
at
0.134
ppm
and
0.182
ppm
and
since
the
study
indicated
that
these
samples
may
have
been
treated
samples
mislabeled
as
untreated
samples,
terbacil
residues
which
were
<
LOQ
are
reported
(<
0.001­
0.230
ppm).
Table
4
is
a
summary
of
the
water
melon
field
trial
data.

Table
4.
Residue
Data
from
the
Watermelon
Crop
Field
Trials.

Trial
Identification
(
City,
State;
Year;
EPA
Region)
Crop;
Variety
Commodity
Total
Rate
(
lb
ai/
acre)
PHI
(
days)
Residues
(
ppm)

Terbacil1
Metabolite
A
Metabolite
B
Metabolite
C
Holtville,
CA;
1997;
Region
10
watermelon;
Calsweet
mature
fruit
1
x
0.297
94
<
0.502,
<
0.502
(
0.091,
0.046)
<
0.30,
<
0.30
<
0.10,
<
0.10
<
0.10,
<
0.10
Gainesville,
FL;
1997;
Region
3
watermelon;
Mickylee
mature
fruit
1
x
0.245
70
<
0.503,
<
0.503
(
0.028,
0.041)
<
0.30,
<
0.30
<
0.10,
<
0.10
<
0.10,
<
0.10
Tifton,
GA;
1997;
Region
2
watermelon;
Crimson
Sweet
mature
fruit
1
x
0.254
90
<
0.504,
<
0.504
(
0.039,
0.045)
<
0.30,
<
0.30
<
0.10,
<
0.10
<
0.10,
<
0.10
Salisbury,
MD;
1997;
Region
2
watermelon;
Jade
Star
mature
fruit
1
x
0.253
69
<
0.505,
<
0.505
(
0.048,
<
0.001)
<
0.30,
<
0.30
<
0.10,
<
0.10
<
0.10,
<
0.10
Weslaco,
TX;
1997;
Region
68
watermelon;
Sugar
Baby
mature
fruit
1
x
0.248­
0.251
71
<
0.506,
<
0.506
(
0.230,
0.056)
<
0.507,
<
0.507
(
0.054,
0.050)
<
0.30,
<
0.30
<
0.30,
<
0.30
<
0.10,
<
0.10
<
0.10,
<
0.10
<
0.10,
<
0.10
<
0.10,
<
0.10
1
quantified
residues
<
LOQ
are
presented
in
parenthesis
2
terbacil
residues
of
0.047
ppm
and
<
0.001
ppm
were
found
in/
on
controls
3
terbacil
residues
of
0.050
ppm
and
<
0.001
ppm
were
found
in/
on
controls
4
terbacil
residues
of
0.056
ppm
and
0.057
ppm
were
found
in/
on
controls
5
terbacil
residues
of
0.134
ppm
and
0.074
ppm
were
found
in/
on
controls;
the
study
stated
that
it
is
possible
that
the
treated
samples
were
labeled
as
untreated
and
the
untreated
samples
were
labeled
as
treated
(
there
is
no
evidence
to
confirm
this
suspicion)
6
terbacil
residues
of
0.078
ppm
and
0.074
ppm
were
found
in/
on
controls
7
terbacil
residues
of
0.182
ppm
and
0.062
ppm
were
found
in/
on
controls;
the
study
stated
that
it
is
possible
that
the
treated
samples
were
labeled
as
untreated
and
the
untreated
samples
were
labeled
as
treated
(
there
is
no
evidence
to
confirm
this
suspicion)
8
study
indicate
two
field
trials
conducted
in
Weslaco,
TX;
HED
considers
this
as
a
single
field
trial
as
they
were
conducted
on
the
same
farm
using
the
same
application
date,
equipment,
and
watermelon
variety
860.1520
Processed
Food
and
Feed
Table
1
of
OPPTS
860.1000
indicates
that
there
are
no
watermelon
processed
commodities;
therefore,
a
watermelon
processing
study
is
unnecessary.

860.1850/
860.1900
Confined
and
Field
Accumulation
in
Rotational
Crops
A
confined
rotational
crop
study
is
not
currently
available.
The
HED
RED
(
D.
Miller,
18­
Dec­
1996)
stated
that
if
the
aerobic
soil
metabolism
study
(
MRID
42369901),
which
was
being
reviewed
by
the
EFED,
revealed
no
new
metabolites
other
than
those
regulated
in
the
primary
crops,
then
a
confined
rotational
crop
study
may
not
be
required.
The
following
information
was
gathered
from
the
EFED
RED
(
D229773,
J.
Hetrick,
26­
Jun­
1997):

Terbacil
is
persistent
under
aerobic
and
anaerobic
soil
conditions
(
t1/
2=
235
to
653
days).
Minor
nonvolatile
transformation
products
(<
10%
of
applied)
are
t­
butylurea
and
3­
t­
butyl­
6­
methyluracil.
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
11
of
14
The
major
volatile
transformation
product
is
CO2.
The
reported
laboratory
degradation
data
indicate
terbacil
is
persistent
in
terrestrial
environments.
Marginally
acceptable
field
dissipation
studies
indicate
terbacil,
at
5
lbs
ai/
acre,
is
persistent
and
mobile
under
actual
use
conditions.
Field
dissipation
half­
lives
in
Delaware,
Illinois,
and
California
ranged
from
204
to
252
days.
The
maximum
depth
of
terbacil
detection
was
45
to
50
cm.
Metabolites
A
(
maximum
concentration
(
0.14
ppm)
15
days
after
application)
and
B
(
maximum
concentration
(
0.07
ppm)
60
days
after
application)
were
detected
in
the
field
dissipation
studies.

Two
field
rotational
crop
studies
and
have
been
submitted
and
reviewed
(
MRID
00011948
­
see
EFED
review,
23­
July­
1981;
MRID
43221501
­
D206093,
D.
Miller,
31­
Aug­
1994).
MRID
43221501
presented
data
concerning
the
magnitude
of
terbacil
and
metabolites
A,
B,
and
C
in/
on
beet
(
root
and
tops),
wheat,
and
lettuce
following
a
bare
soil
application
at
5.0
lb
ai/
acre
(
33x
the
watermelon
rate)
and
a
2­
year
plant­
back
interval
(
PBI).
Due
to
phytotoxicity,
neither
immature
nor
mature
wheat
and
lettuce
plants
could
be
harvested
for
residue
analysis.
Phytotoxicity
was
also
observed
for
beets
with
severe
reduction
in
harvest
yield
noted
and
only
small
samples
of
immature
and
mature
beets
harvested.
Terbacil
residues
were
0.19
ppm
in/
on
immature
beet
(
whole
plant),
0.07
ppm
in/
on
mature
beet
top,
and
<
0.05
ppm
in/
on
mature
beet
root.
Metabolites
A,
B,
and
C
were
<
0.05
ppm
in/
on
all
mature
and
immature
beet
samples.
MRID
00011948
presented
data
concerning
the
magnitude
of
terbacil
and
metabolite
A
in/
on
beet
(
root
and
tops),
sunflower
(
seed),
and
cabbage
following
ten
annual
applications
of
terbacil
at
1.0
lb
ai/
acre
(
10­
month
PBI;
silt
loam
soil;
6.7x
the
watermelon
rate)
and
three
annual
applications
of
terbacil
at
1.0­
2.0
lb
ai/
acre
(
2­
year
PBI;
muck
soil;
13.3x
the
watermelon
rate;
2.0
lb
ai/
acre
the
1st
year
and
1.0
lb
ai/
acre
for
the
2nd
and
3rd
years).
Residues
of
terbacil
and
metabolite
A
were
<
LOQ
in/
on
all
samples
excluding
cabbage
grown
in
muck
(
2­
year
PBI)
where
terbacil
residues
of
0.18
ppm
were
found.

Conclusions:
The
ChemSAC
was
consulted
concerning
the
need
for
additional
confined/
field
rotational
crop
studies.
Based
on
the
demonstrated
persistence
of
terbacil
in
the
aerobic
and
anaerobic
soil
metabolism
studies
(
half­
life
=
235­
653
days;
EFED
RED,
D229773,
J.
Hetrick,
26­
Jun­
1997),
the
ChemSAC
concluded
that
a
confined
rotational
crop
study
is
not
necessary
(
see
ChemSAC
minutes
for
1­
Feb­
2006).
Therefore,
HED
concludes
that
the
residues
of
concern
in
rotational
crops
are
terbacil,
metabolite
A,
metabolite
B,
metabolite
C,
and
3­
t­
butyl­
6­
methyluracil.
Metabolites
A,
B,
and
C
were
included
as
these
are
residues
of
concern
in
the
primary
crops
and
may
form
in
rotational
crops
via
uptake
and
metabolism
of
parent.
3­
t­
butyl­
6­
methyluracil
was
included
as
it
was
identified
in
the
aerobic
soil
metabolism
study.
HED
notes
that
3­
t­
butyl­
6­
methyluracil
was
identified
at
<
10%
TRR;
however,
the
aerobic
soil
metabolism
study
was
conducted
for
only
1
year
and
the
proposed
registered
PBIs
are
2
years
(
i.
e.
concentration
of
3­
t­
butyl­
6­
methyluracil
may
be
significant
after
2
years;
t­
butylurea
was
not
included
based
on
concentration
and
toxicological
considerations).

Based
on
the
watermelon
application
rate
and
the
results
of
the
currently
available
field
trial
studies
(
6.7­
33x
the
watermelon
application
rate;
terbacil
and
metabolite
A
residues
of
#
0.19
ppm),
the
ChemSAC
concluded
that
an
additional
field
rotational
crop
study
was
not
necessary
and
tolerances
in/
on
crops
resulting
from
rotation
into
watermelon
fields
which
have
been
treated
with
terbacil
were
unnecessary.
However,
the
ChemSAC
did
state
that
a
field
rotational
crop
study
may
be
required
for
future
registrations
(
see
ChemSAC
minutes
for
1­
Feb­
2006).
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
12
of
14
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
13
of
14
860.1550
Proposed/
Recommended
Tolerances
Table
5
is
a
summary
of
the
proposed
and
recommended
tolerances
for
residues
of
terbacil
and
its
metabolites
A
(
3­
tert­
butyl­
5­
chloro­
6­
hydroxymethyluracil),
B
(
6­
chloro­
2,3­
dihydro­
7­
hydroxymethyl
3,3­
dimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one),
and
C
(
6­
chloro­
2,3­
dihydro­
3,3,7­
trimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one),
calculated
as
terbacil.
A
revised
Section
F
should
be
submitted.
There
are
no
Codex
or
Mexican
maximum
residue
limits
(
MRLs)
in/
on
the
requested
crops.
A
revised
Section
F
is
requested.

Table
5.
Tolerance
Summary
Proposed
Recommended
Commodity
Definition
Tolerance
(
ppm)
Commodity
Definition
Tolerance
(
ppm)

Watermelon
1
watermelon
1.0
RDI:
RAB1
Chemists
(
21­
Dec­
2005)
T.
Bloem:
806R:
CM#
2:(
703)
605­
0217:
7590C
Template
Version
September
2003
Attachment
1:
Chemical
Structures
Terbacil
Summary
of
Analytical
Chemistry
and
Residue
Data
D313911
Page
14
of
14
N
HN
O
C(
CH3)
3
O
Cl
H3C
N
HN
O
C(
CH3)
3
O
Cl
HOH2C
N
N
O
Cl
HOH2C
O
H3C
CH3
N
N
O
Cl
H3C
O
H3C
CH3
N
HN
O
C(
CH3)
3
O
H
H3C
(
H3C)
C
N
NH2
H
O
Attachment
1:
Chemical
Structures
Name
Structure
terbacil
3­
tert­
butyl­
5­
chloro­
6­
methyluracil
5­
chloro­
3­(
1,1­
dimethylethyl)­
6­
methyl­
2,4(
1H,
3H)­
pyrimidinedi
one
metabolite
A
3­
tert­
butyl­
5­
chloro­
6­
hydroxymethyluracil
metabolite
B
6­
chloro­
2,3­
dihydro­
7­
hydroxymethyl­
3,3­
dimethyl­
5Hoxazolo
(
3,2­
a)
pyrimidin­
5­
one
metabolite
C
6­
chloro­
2,3­
dihydro­
3,3,7­
trimethyl­
5H­
oxazolo
(
3,2­
a)
pyrimidin­
5­
one
3­
t­
butyl­
6­
methyluracil
t­
butylurea
