369
BARRIER EF.F'ICACYof ORGANOPHOSPHATE,PYRETHROID,
PHENYLPYRAZOL, and cHLoRoNrcorINyL
FORMULATTONS
againstHETEROTERMESAUREUS ISOpTERA:
RHINOTERMITIDAE)
Paul B. Baker and Brian E. Weeks
University of Arizona, Depafiment of Entomology, Tucson, Arizona
Abstract A modified test-tubebioassaywas developed for Heterotermesaureus rsingArizona soil samples
from covered and exposed weatheredtermiticide plots. An organophosphate,a pyrethroid, a phenylpyrazol,
and a nicotinoid were evaluated at 4 hours and 12 months post-application. Termites *"r" plu""d in
bioursays and checked after 7 days for survival and soil penetration. Bioassays conducted at 12 months showed
statistical differences (P<0.05) among termiticides tested in terms of survival and penetration.
Key Words Termiticides bioassay weathered soil
INTRODUCTION
Application of liquid termiticides continuesto be a primary tool in the prevention of termite
structural invasions. Chemical stability of termiticides in soil is required for long-term protection' Evaluation of residual toxicity and termiticide degradationhas been reported f.o- Florida
to Hawaii by Su and Scheffrahn(1990),Gold et al. (1996),andGraceet al. (1993).The testingof
termiticide efficacy is on-going, becausetermiticides responddifferently in different regions, and
under different physical and environmental conditions. In Arizona the use of Aggregate Base
Course (ABC) in construction fill is increasing. This gravel and rock mixture contains low organic matter and is used to establisha solid basefor concretefoundation slabs.Termiticide
availability under theseconditions has never been reported. Therefore, candidatetermiticides need to
be continually evaluatednot only for residuals but their bioavailability to prevent termites from
penetratingtreated soil.
The U.S. Environmental Protection Agency (USEPA) has delegatedto USDA Forest
Service the responsibility to evaluate termiticide effectiveness.Evaluations are made with ground
boardor concreteslabtests,as describedby Kard et al. (1989).Basedon thesetests,a termiticide
concentrationfails when >5 of the 10 replications have been breachedby subterraneantermites
(Kard et al., 1989).The goal is 5 yearsof protectionof the pinewood exposedto
treatedsoil. If
protection is maintained for 5 years, the registration processcan move forward. However,
it has
become more apparent that a lack of termite penetration in the treated soil can not always
be
attributed to the effectivenessof the termiticide, due to the possibility that termite foraging
is
random. This characteristichas been demonstratedby Su et al. (1999) for the Formosan
subterranean termite Coptotermesformosana Shiraki, and by Delaphane and La Fage (19g9)
for the
eastern subterraneantermite Reticultermesflavipes (Kollar). The desert subterranean
termite
Heterotermesaureus (Snyder) probably has a similar foraging pattern. Bioassayswere
designed
to evaluate tunneling of this species into insecticide-treatedsoil under concrete and
exposed
ground board (Su et al.,1993; Tamashiroet a1.,1987:
Baker.2001r.
Bexnn eNn Wesrs
In this study, we selected4 classesof termiticides and applied them at labeled ratesfollowing standardpre-constructionproceduresto exposedor covered small concreteslabs.A bioassay
was used to evaluatethe barrier efficacy of the treated soils againstH. aureus.
MATERIALS
and METHODS
Insecticides
Termiticides testedwere: Premise2 (imidacloprid, 0.17o'.Bayer,KansasCity, Mo.); Talstar
T/I (bifenthrin 0.12Ta,FMC Corporation, Princeton, N.J.), Talstar T/I (bifenthrin 0.l2Vo plus
cellulose, FMC Corporation, Princeton, N.J.), Termidor 80WG (fipronil 0.125%o,Aventis Environmental Sciences,Inc., Montvale, N.J.), Termiticide DSB-I formulation (Arizona Chemical
Group, Inc., Mesa, Aiz.), and Termiticide DSB-2 formulation (Arizona Chemical Group, Inc.,
Mesa, Aiz.). Premise,Talstar,and Termidor arecommercially registeredtermiticides.Termiticide
DSB-1 and DSB-2 are currentlybeing registeredas a termiticide.TermiticideDSB-1 and DSB-2
are organophosphates,bifenthrin is a pyrethroid, fipronil is a phenyl pyrazole, and imidacloprid
is a chloronicotinyl.
Termiticide solutions were preparedfollowing label instructions and applied as previously
describeddegradationstudies(Baker, 2001). Native soil compositionwas: 71.67osand,25.8Vo
srlt,2.67oclay, I.8Vagravel, and 8.I pH. It was excavatedfrom each0.46 m by 0.46 m by 0.3 m
plot, and replaced with white construction sand. Either native soil or Aggregate Base Course
(ABC) filI wasrefilled in eachplot. The compositionof ABC ftllis:84.6Vo sand,l4.l%osilt,l.4Va
clay,27.3Vogravel, and 7.89 pH. The coursefill consistsof 79.4Vosand,15.l7o silt, 5.57ocIay,
62.4Vogravel, and 8.0 pH. In order to sample theseplots, all ABC fill was passedthrough a 1.3
cm screenbecauseit can contain upward of 35Voby volume of 2.54 cm rocks and above.Exposed
0.46 mby 0.46 m plots had pine-wood frames (2.5 cm by 10 cm by 1.25 cm) placed at ground
level. Coveredconcreteslabshad pine-woodframes(2.5 cm by 10 cm by 2.5 cm) placedon the
ground at each plot.
Insecticide applicationswere made using a stainlesssteel 18.5 I watering can. Rateswere at
industry
standardsof 1 gallon / 10 sq ft (852 ml I 0.47 m) for all native soils and 1.5 gallons /
the
10 sq ft (I.231 / 0.47 m) for the ABC fill. In all casesthey were applied as pre-treatmentto the
native soil and ABC fill. After plots were treated,concretewas applied. The plots were protected
from direct sun with cover. Covers were constructedof 1.25 cm plywood cut to 0.6 m by 0.6 m.
Approximately 20.3 cm from the corners, four hole were drilled to enable 15.2 cm bolts to be
placed through the holes and fastenedwith 0.6 cm nuts. Once the bolts were in place, 5 cm plastic
spacerswere bolted to the covers with a 1.3 cm washer and nut. To increasethe holding in the
concrete,construction wire was woven about the 4 posts in the shapeof a figure 8.
Test Site
Tucson averagesmore than 360 days per year of sun, with soil temperaturesin the summer
in excessof 60"C, and the day temperaturesexceeded37"C seventy-five times. During the 12month testing period, there was 3.9 cm of rain near the plots.
Sampling
Soil sampleswere taken at 4 and 12 months post-treatmentby using a2.54 cm by 19 cm
stainlesssteelcore samplerto a depth of approximately 5 cm. Sampleswere either directly taken
in the exposedplots or by gently tilting the covered mini-slab to one side. Attempts to maintain
the soil profile integrity failed in all the samples,primarily becausethe soil was dry; thus samples
were composite.After sampleswere taken, white construction sandwas used to fill the hole, and
coveredslabswere repositionedover the plot. Two soil sampleswere taken, composited,and split
B.q.nnisnEpncecv or FonMul.crroNs AcAINsr Htrpnornnuos eunous
37r
between residue testing and bioassay.All samples were held in their plastic sleevesor plastic
bags and frozen at 0'C until shippedfor analysis or used in the bioassay.
Bioassay
A bioassayprocedure similar to that describedby Su et al. (1993) and modified by Baker
(2001) was used to test the barrier efficacy againstH. aureus. At 24 hours prior to the bioassay
screening,soil sampleswere removed from the freezer and left to air dry. All soil sampleswere
packedinto 15 cm by 15 mm glasstubesto a depthof 5 cm. Agar plugs (0.5 cm) were sandwiched
above and below each sample.Located below and in contact with the soil samplewere 3.5 cm by
5.5 cm rolled cardboard and a sliver of wood to provide food and harboragefor the termites. A
plastic cap was forced over the bottom to prevent termites from escapingand to hold the sample
in place.
Twenty-threeundifferentiated workers and 2 soldiers were placed into the top of each glass
tube. All termites used in this study were field collected and held in complete darknessat29"C
and907oRH for less than 3 months. For the initial bioassaythere were 3 replicates,but in the 12month test, there were 3 separatebioassaysof each samplefor a total of 9 replicates,in an attempt
to evaluate the bioassay method. All test units were held vertically at 29"C and 907o RH for 7
days.Attempts were made to hold the imidacloprid samplesfor 14 daysbut survival in the checks
was low.
Data Analysis
Significant differences (P<0.05) among means in percentagesurvival and centimeters of
penetrationwere separatedby Duncan's multiple range test (SAS Institute, 2000).
RESULTSand DISCUSSION
Application
4 HoursPost'Termiticide
SoilSamples
Mean distancepenetratedin treated soils by termites and mean percent survival is summarized in Table 1. All treatments,except bifenthrin plus cellulose, had no survival or penetration.
None of the 3 soil substratehad any influence on survival or penetration at least initially.
Soil Samples L2 Months Post-Termiticide Application
One year after application all the treatments- except fipronil, bifenthrin, and bifenthrin
plus cellulose - had increasedsurvival and penetration (Table 2). Exposed plots in generalhad
greatersurvival and the most penetration due in part to exposure to environmental elements,
particularly sun and heat.
Penetrationwas nearly complete with imidacloprid and the DSB compounds 1 and2, implying significant degradation and the inability to provide protection. This is in disagreement
with USDA trials in Aizona in which most of the non-repellent termiticides had not failed to
provide protection after 12 months (Kard, 1999). Native covered plots had the lowest survival
and penetration. Fipronil and bifenthrin plus cellulose had the lowest survival and almost no
penetrationof the treated soil over all three soil types. Covered ABC fill gave mixed results with
some products, imidacloprid and DSB-I plus having greater survival than the untreated soil. In
part, this result could be attributed to the 27Vogravel in which the termiticides had no adsorption
capacity. However, bifenthrin, fipronil, and bifenthrin plus had no penetration and a small percentagesurvival.
Imidacloprid performance was best under native soils both in mortality and distance penetrated. It would appearbased on time of application; in August during our most intense rainy
period (July-September)the exposedimidacloprid plots could have leached.Felsot et al. (2000)
reported non-termiticide residues of imidacloprid 90 cm deep. The pyrethroid bifenthrin treat-
Bersn eNo Wesrs
rr'l
I T-I
a)
U)
a
e
O
C g - o O c g - i l f ,
\ o ' - - t r ) A A A
; F - C O
o
d
d
(t
Y
h
6
a
a
C)
r
I
a
^
A
A
a
^
^
>'
(t
^
6
a
A
M
A
A
A
A
A
A
-
U)
-
N
F
-
lJi
l.i
t
o
k
6 i
>ii
()+
I
|-tr
C)
,-
vl9v?c19oq
- + A r A . 6 - ^
o
o
.fr
!
U)
s
frl
U)
H =
?Et
Q
>l
.o
L
o
fr'l
lr
a
0)
ao
^/.
t
(4
s o o o
X
.c.l
r
o
ao
X
9r
O
-n q q \
+ c o c . l
()
G
I
N O O O O O O O
X
r)
u>
n q 9 9 \
(h
O ^ '
> . .
tri
o
Q
,-
>.
6e
X
a
o\o00rncocio
\O
cO
f-
F-
>t
rr'1
U)
1i
!
-
o
.0
-
v)
-
d.
o
o0
fi
()
rrl
(t
.t
q
z
p
o
g
a ' i a
! 2 !
t
(n
9 € Ea
\i
>.tr U s X
()
o
-
F-
(.)
.n
p :
E
i
>, l:
s B
a
q
r
ts\.; :',1
d
o
,!2
>'
\
t-
bo
X
4
!
. i - a
9
v
n\qncl
n O O r O * O
d
-
ro(}\-O'O-O.o,!
9
9
a - { A - i A i a
-<
a
a
C)
V
!
-.
(.)
X
9
v
dcnrnoorn\o€
-
C)
a
a
9
v
f r'l
6 >
o c.l
r ) i
a
(
J
O
cd- O o oP
U)
tH
U)
s
O
o
q n n n n q -
I
E
I\OO\r-OO\\O
*o\coco
o\*
o\Oo\or*oirci
\nci
N-
X
B
o
C)
9r
li
O
Q
H
f r'l
(h
e
a
a
6
A
^
^
a
i : a
C)
A
A
o
( ! c € ( i o o o
rrl
U)
C)
A
( ! n o 9 \ n n v ? (.)
d
C)
-:.
I
* 4 )
!2
!.1 a.
B
X
(
Frn
e ( g
( | i ^
a
E r
2
7
x . v
9l€
t 6
. a - x*
e ( J
::
rr'1 \ O c o
O
X
H
o
o
o
o
o
r--i o o o o o
s
X
N
-
ol.irn
*
*
N
h
*
rn
N
*
trts
.(.) .^
:i
c.)
-
- ! ,
-i
P €
E 8
o *
5 X
e 0 )
cd
a
C)
^>
,.Y
o
6
li
. Y O
o t r
Sl
f;rn
H
P
-
A
E
9€
, , ?- - ^
a
t
Q
A
H
H
*
r-:
A
A
d
-
rY
>x
B
( J O
rr'l
oo c..l oo 5 co O, .+
i d.i + oroo
*
n F ,(rr
va
trl N
s
X
F
t
cd
C)
*
9
C)
=t-1i90e
t
$ \ n $ O F - N Q
\orn+ro**
P
o
H
!?
lr)(\Nc.l
lr)
-1v?c.l-1-n
:ra
. 9 6
tcJ B.^
-
a
c.i'F
(
N
i = = ( h ( h 9 . ^
ti.':
o
o
X
U)
o
t*\ *
()
o.l
e d
( | r ^
\o cn
-
=
c t O
!
9cl\nn\
l r ) c o c n c o O O O
F
o
t
U)
g
o
b ;
o g l
O
4
I
o
H
@
-(.)
'E c..l
* ! )
A.
N
5
€
r ^ A ^
)
L
- a
.q
-
o
-
a
d
o
d
-
!?
-
o
B
<
. : @ c . l - k H !
d
)
H
H
-
A
A
lJ{
A
l-{
A
l-l
r'Y
i:.
I
:q ,.:.
t
i 9 6 ( h - - H .
ri
\J
O
r'Y
l<
rY
F
a
c.l
BannrEnErprclcy op FonuulerroNs AGATNST
Harrnorzxuts aunnus
3'73
ments,with and without the celluloseowere consistentacrosstreatments.Baskaranet al. (1999)
reported that bifenthrin was more stable,at least initially, than chloropyrifos. Fipronil continued
to limit survival and low penetration from the initial 4 hours. Ramesh and Balasubramanian
(1999) reported fipronil appearedmore susceptible to hydrolysis than other organophosphate
compoundssuch as chloropyrifos; however, after 12 months fipronil still has bioavailability.
In conclusion, it appearsthat some of the selectedtermiticides are breaking at year l, with
soil influencing the termiticide's ability to maintain the barrier. More information will be forthcoming in the next few years.
REFERENCES
Baker, P'B. 2001. An update on termiticide degradation in Arizona soil. Turfgrass, Landscape and Urban IpM
ResearchSummary. In: Agricultural Experiment Station Series p-126: 5-9.
Baskaran, S.R., Kookana, S., and Naidu, R. 1999. Degradation of bifenthrin, chlorpyrifos, and imidacloprid
in soil and bedding materials at termiticidal application rates. Pesticide Science 55: 1222-1228.
Delaplane, K.S', and La Fage, J.P. 1989. Foraging tenacity of Reticultermesflavipes and,Coptotermes
formosans. Sociobiology 16: 183-189.
Felsot, A.S., Evans, R.G., and Tallman, L.C. 2000. Soil distribution and plant uptake of imidacloprid under
drip and furrow irrigation. National Irrigation Symposium. Proceedingsof the 4'h Decennial Symposium,
Phoenix,Ariaona, November 14-16. Pp. 416-42j.
Go1d,R.E', Howell, H.N., Pawson,B.M., Wright, M.S., and Lutz, J.C. 1996. Persistenceand bioavailability
of termiticides to subterraneantermites (Isoptera: Rhinotermitidae) from five soil types and locations in
Texas.Sociobiology 28: 337-363.
Grace, J.K., Yates, J.R, Tamashiro, M., and Yamamoto, R.T. 1993. Persistenceof Organochlorine insecticides
for Formosan subterraneantermite (Isoptera: Rhinotermitidae) control in Hawaii. J. Econ. Ent. g6: 761'766.
Kard, B. 1999. Termiticides: The Gulfport Report. February pest control 67:42-46.
Kard, B.M., Maudlin, J.K., and Jones, S.C. 1989. Evaluation of soil termiticides for control of subterranean
termites (Isoptera). Sociobiology 15: 285-297.
Ramesh, A., and Balasubramanian,M. 1999. Kinetics and hydrolysis of fenamiphos, fipronil, and trifluralin
in aqueousbuffer solutions.J. Agric. Food Chem. 4j: 336j-33j1.
SAS Institute. 2000. SAS Version 8e for Windows. SAS Institute, Inc. Cary, N.C.
Su, N.-Y., and Scheffrahn, R.H. 1990. Comparison of 11 soil termiticides against the Formosan subrerranean
termite and eastern subterraneantermite (Isoptera: Rhinotermitidae). J. Econ. Entomol. 83: Lglg-1924.
Su, N.-Y, Scheffrahn, R.H., and Ban, P.M. 1993. Barrier efficacy of pyrethroid and organophosateformulations against subterraneantermites (Isoptera: Rhinotermidae) J. Econ. Entomol. 86:772-776.
Su, N.-Y' Ban, P.M., and Scheffrahn, R.H. 1999. Longevity and efficacy of pyrethroid and organophosate
termiticides in field degradation studies using miniature slabs. J. Econ. Entomol. 92: 890-89g.
Tamashiro, M', Yate, J.R., and Ebesu, R.H. 1987. The Formosan subterraneantermite in Hawaii: problem
and control' In: Tamashiro, M., and Su, N.-Y., eds., Biology and control of the Formosan subter.anean
termite. College of Tropical Agriculture and Human Resources,University of Hawaii, Honolulu.