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are less persistant than the cyclodienes.
To assure equivalent long-term
protection, chlorpyrifos and lindane would have to be reapplled more
frequently (two and three times as often, respectively) than the
cyclodienes (see Section A of this chapter)*
ii. Cancel
Only Aldrin and Dieldrin
Although it has been indicated that the use of aldrin for termite
control has increased recently, it currently accounts for less than 15
percent of the termiticide market (subterranean termite control).
Cancelling aldrin would eliminate a competitive alternative for chlordane
and heptachlor.
It appears that most applicators prefer chlordane and
heptachlor to aldrin.7./ However, without aldrin as a competitive
price check, further price increases of chlordane and heptachlor can be anticipated (the price of chlordane increased 60 percent in 1980 and
another 6 percent in April 1981).
Chlorpyrifos and lindane are
so much
more expensive to use than chlordane and heptachlor (see Table XXII, pg.
^?) that the price of chlordane and heptaehlor would have
to increase
significantly before these two compounds could become competitive.
Therefore, little increase in their use can be expected to result from
the cancellation of aldrin.
Cancellation of dieldrin would result in no significant impact.
Dieldrin Is no longer produced domestically and there is no recent evidence of its use.
It's
use as a termiticide was never very
significant.
^J
However, there appears to be some preference for aldrin in Hawaii
based on some evidence showing it to be more persistant than chlordane and heptachlor in alkali soils (see Section A of this
chapter).
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It Is reasonable to expect that as long
^&
as the
cyclodienes remain on
the market and are relatively inexpensive, that the outlook for new
chemicals will be bleak.
There is simply no incentive to develop new
chemicals as long as inexpensive, effective chemicals are already being
marketed and in widespread
use*
C. Economic Implications of Cancellation
i.
Cancel Only Chlordane and Heptachlor
,r.
In the event of cancellation of chlordane and .heptachlor use for
subterranean termite treatment, applicators using chlordane and
heptachlor will most likely switch to aldrin.
As
was discussed in
<^' \
A^Vf)^
.A
p/ ^
^
Section A of this chapter, aldrin is comparably priced and of equivalent
cfFl^acy.
The supply of aldrin may be limited in the short-run, since at
present there is no domestic production.
Shell Chemical Company U.S.,
has maintained its EPA registrations of aldrin but may require
substantial lead time before it can begin large scale aldrin production.
The current supplier of
^
aldrin. Shell International, may
not have the
^
-^
^
current capacity to supply the entire U.S. termiticide market.
Little or no change in the use patterns of the other registered termiticides should be expected in this scenario. Without the
competition of chlordane and heptachlor, aldrin would be given a near
monopoly position in the termiticide market.
The cost of using aldrin
would have to more than double before chlorpyrifos and lindane could become cost competitive with it (refer to Table
XXII, pg. ?^ ).
In
addition to being much more highly priced, chlorpyrifos and lindane are
/<=*/
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and triple respectively.
In addition, there would also be associated
application costs with llndane and chlorpyrlfos which would further
expand the cost differential (see the last column of Table XXII).
111.
Comparison of Tenaltlcides
As can be seen from the last two sections, the cyclodienes are
by far the most cost effective chemicals for termite control-
Llndane
or chlorpyrlfos would be used only where use of the cyclodlenes were
restricted either by the
structure's owner or government regulation.
There appears to be some disagreement with tne PCO Industry as
to which of the
eyclodlenes Is best In terms of ease of handling and
Applicators using aldrin have reported
There may also be applicator concern
applicator health effects.
problems with skin irritation.
about aldrin having a greater potentancy as a careenogen than
ehlordane.
On balance, the choice between cyclodienes seems to be one
of personal preference rather than documented advantages or
disadvantages (except for cost with respect to dieldrin).
B.
Outlook for New Chemicals
A number of chemicals, not currently used as tennltlcldes were
discussed in Section A.-i. as regard to their effectiveness against
termites. While some were effective, their persistance (length of
protection) does not compare with those chemicals currently in use.
Only tobay Chemical Company has a compound (Oftanol) under development
as a tenniticlde.
However, Insufficient testing has been done
to date
to allow evaluation of its viability as an alternative to the
cyclodlenes.
^0
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In conclusion, it is evident that chlordane is presently the most
effective termiticidal compound known.
The other cyclodienes, heptachlor,
aldrin, and dieldrin are comparable in
seems to be the most promising new
effectivness..0/
Chlorpyrifos
compound*
11.
Comparative Costs
Table XXII presents the comparative costs of the termiticides in
current use.
These are bulk user prices.
From the table, it can be seen
that the cyclodienes are virtually identical in cost-and significantly
cheaper than either chlopyrifos or llndane*
When one takes into account
the reduced persistance of llndane and chlorpyrifos, cost differences between these chemicals and the cyclodienes widen still further.
If one
assumes that chlorpyrifos persist 1/2 as long as the cyclodienes and
lindane 1/3 as long, the chemical costs for 100Z protection over a 30 year
period, double
./
Bess and Hylin (1970), and Bess et.al. (1966) present data which indicate aldrin and dieldrin are slightly superior in controlling Coptotermes formosanus in different Hawilan soils of varied pH. However, the authors clearly indicate that chlordane is the most persistant cyclodiene. One should note that their bioassay technique is a laboratory technique and not recognized in the EPA Efficacy Test Methods (Volume V, pp. 21-23). The assay measures toxicity due to exposure to soils transported to the laboratory, it does not actually measure wod protection as is done in the USDA Gulf port studies*
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Table
X33-
-Soil treatments that have been evaluated in standard stake tests established in 1946-52, in southern Mississippi but are no .longer recognized as satisfactory treatments.
Chemicals
Effective period
Years
Copper Copper Copper Copper
naphthenate
sulfamate
2
4
sulphate (dry crystals) sulphate (water)
S
1 3
Chlorinated nitrotoluene Lead arsenite (dry powder) Lead arsenite (water suspension)
Hexachloroethane Monochloronaphthalene (5% kerosene) Monochloronaphthalene (10% kerosene) Orthodichiorobenz ene
Sodium dinitro-orthocresolate Sodium meta ..arsenite (70% arsenic trioxide) Sodium meta arsenite (70% arsenic trioxide) Tetrachlorobenzene
6 3 2
\
2 3 5 1
[10% water] [16% we-ter]
14 22
8 6 8 7 7 2 -1
unrefined. refined Trichlorobenzene (oil)
Trichlorobenzene (water) Trichlorobenzene plus creosote TX still residue (petroleum by-product) Xanthone 95% pure dry
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^
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XX
Effective
Chemicals
Acetylene tetrachloride Copper ammonium fluoride
period
Years
3
Creosote (numerous formulations)
Creosote (kerosene) Pentachlorophenol (oil) Pentachlorophenol (heavy oil) RH 195/acetylene tetrachloride
Sodium arsenite Arsenite trioxide Sodium fluosilicate
2 2 3 3 4 3 5 5 3
Kerosene check
Gasoline'check
2
-1 4
Methoxychlor Toxaphene
9(.
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Smith, Beal and Johnston (1972) reported on tests of a wide range
of compounds.
Prior to undertaking stake or ground board tests,
compounds were screened for termiticidal properties in the laboratory*
Literally hundreds of compounds did not pass the initial screening.
The following two tables are adapted from the 1972 paper by Smith et
al.
Tables XX and XXI summarize test results over a number of years
and generally demonstrate a lack of long term effectiveness-
Evaluation of the chlorinated hydrocarbons showed chlordane
remained 100% effective in preventing termite attack for 23 years,
aldrin and dieldrin for 22 years and heptachlor for 19 years.
The
pesticides recorded in the two tables were registered for termite
control at the time of the publication.
Dr. Raymond Beal (1980 a and b) reported on test data obtained
^fter about 11 years of testing. Beal said "We chose insecticides for
field testing after screening chemicals in laboratory tests.
Only
those chemicals with a low mammalian toxicity, low toxicity to other
soil insects, relatively low water solubility, and a manufacturer
willing to market the material...."
met those criteria.
Nine
compounds were selected that
These were:
GS-12968, methidathion, diazinon, and
dimetilan (Ciba-Geigy Corp.); chlorpyrifos and Zytron(R)
(Dow Chemical
Corp.); camphechlor (Heyden Newport Chemical Corp.); propoxur (Chemagro
Chemical
this
Corp.); and carbaryl (Union
Carbide
Corp.).
As a result of
study, Beal concluded "dimethilan, diazinon, GS-12968,
Under
methidathion and Zytron(R) were ineffective as soil insecticides.
a concrete slab, camphechlor,
propoxur and chlorpyrifos remained 100X
rate of
fk
effective, for 11 years at the 2.0%
application.
Of these,
chlorpyrifos remains the most promising new compound to date."
is
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A number of studies are exemplary in terms of the preceding
paragraph.
Johnson, Smith and Beal (1970) note the following:
in soils in
"Numerous insecticides have been under study for many years
southern Mississippi for protection against subterranean termite attack*
Of these, aldrin, chlordane, dieldrin, and heptachlor applied
at various concentrations and rates are still effective after 17 to 21
years. "Z/
They also conducted soil residue studies.
The results
indicated that the insecticides "moved only a few Inches during
17-21
years of exposure
to the elements.**
In practice, as placed in and under
buildings, the movement, without climatic weathering, is expected to be negligible.
In 1972, Beal and Smith published the results of a long tern
study which evaluated new compounds in terms of termite control.
They
studied Baygon(R), Dimetilan(R), Dursban(R), Savin(R), Strobane(R), Diazinon(R),
Zytron(R) and the numbered compounds GS-12968 and GS-13005.
As a result
they say; "Dursban(R) is the only insecticide that is still 100X
effective after 4 years at both 1 and 22 concentrations in both tests
....**
One of their conclusions is, "We know that some of these
chemicals will give at least 4 years of protection against
termites.....This is a much shorter time than the 23 years that
chlordane has continued to control termites."
Z/
These tests are still underway and indicate the chlordane remains an effective barrier for at least 32 years, whereas heptachlor, aldrin, and dieldrin continue to be effective after 28
years (Raymond Beal, Personal Communication).
?
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q?
Comparatively speaking, primary literature reporting on formal
efficacy studies of termiticidal compounds is not copious.
An
automated (computer) search of the world-wide literature yielded only
three studies and these were of marginal value.
Nearly all of the
truly historic and current studies have been, or are being, conducted
at the USDA Southern
Forest Experiment Station
at
Gulfport,
Mississippi.
The Station has unpublished data indicating 100Z
effectiveness for 30 years using chlordane and other cyclodienes
(Dr. Lonnie Williams, personal communication).
Many compounds have
been screened for activity in controlling termites. ,Chlorpyrifos
(Dursban(R)) has recently been registered for
use as a soil treatment*
Williams (personal communication) indicated data exists demonstrating
^^
about 13 years of 1002 effective control using chlorpyrifos.
Dr.
Raymond Beat (personal communication), also of the Southern Forest
Experiment Station, informed the Agency that lindane applied at 0.4X
was effective for 11 years.
By doubling the rate to 0.8Z,
effectiveness was only increased by two additional years.
Dr. Beal
also indicated that endosulfan was tested at 0.5Z and provided about 10
years
control^./.
Increasing the rate of endosulfan to 2.OX made it
He also said that Mobay Chemical
"hold up for a few years longer."
Company is currently the only company that has a sample termite label
undergoing preparation for a new compound known as Oftanol.
-6/
Endosulfan is not registered as a termiticide for subsurface application.
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The Standard Stake Test is conducted by driving a pine, sapwood
stake into soil that has been treated with an insecticide at rates
parallel to practical applications-
The test simulates treatment of
soil in trenches around foundation walls, piers, pilings, plumbing
lines, and other ground to building connections in either crawl space
or basement type buildings.
Tests of this type have been conducted
continuously since 1944.
The Standard Ground Board Test is designed to simulate soil
treatment prior to pouring concrete slabs.
is applied to a 17 sq. in. area of soil. laid in the center of the treated area.
in use since
A known amount of pesticide A 1x6x6 inch pine board
is
Tests of this nature have been
1946.
The Modified Ground Board Test is used to more closely simulate actual conditions which would be found under a concrete slab
foundation.
In this test the soil receives a treatment similar to the
Then a trench is excavated around the
Standard Ground Board Test.
perimeter of the treated area.
A short section of plastic pipe is
Concrete is then poured over
After the concrete
placed in the center of the treated area.
the trench and treated
area, surrounding the pipe.
sets, a 2x3x4** block of pine sapwood is placed inside the pipe and the
pipe is capped.
These tests began in 1965.
termites must penetrate the treated soil barrier to
In all cases,
attack the wood.
Checks or controls consist of identical but untreated
replicas of the treated stakes or boards.
To measure the
effectiveness, the wood is periodically examined for termite attackWood rotted by microorganisms is replaced with new stakes or boards in
either test or control situations.
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IV.
THE IMPLICATIONS OF CANCELLING CERTAIN TERMITICIDES
This chapter compares the efficacy, cost and ease of handling of
the seven termltlcides being reviewed. for the appearance of new termiticides.
It also discusses the prospects
This information is used to
project the economic consequences of removing various termiticides from
the market* Where possible, the economic impact is measured; where it is
not possible to
measure, the anticipated market scenarios are described.
A.
A Comparison of Tenniticide Cost"Effectiveness
\
i.
Comparative Efficacy
Subterranean termite attacks can be controlled or prevented by
impregnating the soil adjacent to a structure with a termite toxicant.
A
primary consideration when choosing a pesticide for a particular use, is
its efficacy or effectiveness in protecting the site from the target
pest.
The effectiveness of termiticides is measured by the time over
which the toxic barrier remains effective in resisting penetration by the termites.
Currently, there are three field tests recognized as providing
reliable information about termiticides under conditions which parallel
use in practical applications.
the Ground Board
These tests are:
1) the Stake Test; 2)
These
Test; and, 3) the Modified Ground Board Test.
test methods were developed and validated by the Southern Forest
Experiment Station at Gulfport, Mississippi.
9
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resistant properties.
Carter et al. (1978), for example. Isolated the
principal compound in the common persimmon tree which causes It to be
resistant to termite attack.
Another means of rendering wood inedible is
to treat it with a material which, while not causing mortality or having
repellant properties, simply inhibits feeding.
Mauldin and Rich (1980),
in their Investigation of antibiotics, found two which had this effect on
R. flavipes, and suggested their further investigation as antifeedants. At this juncture it is unclear as to how far from commercialization
these experimental chemical control techniques are.
If they were arrayed
in a true continuum; methoprene treated bait-blocks would
appear closest
to commercial
use*
This chemical Is currently registered for use as a
control for a number of pests, including mosqultos, houseflles, cigarette
bettles and tobacco moths.
Use of the flouridated lipids are still In the
early experimental stages and consequently likely to be at the other end
of the continuum.
^0
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the presoldiers and soldiers adequately. Third, mortality can result from incomplete ecdysis from between the larval [sic] and soldier casteDestruction of the symbiotic protozoa which live in the termite gut
can.also be achieved through the use of the antibiotic chlortetracycline,
CTC, (Mauldin and Rich, 1980).
CTC meets the criteria for success as a
control agent in the bait-block method of control, as does methoprene,
namely that termites will readily feed on impregnated wood blocks and that
the product is slow-acting*
Mauldin and Rich indicate that their research
shows "that CTC has potential for use in this method and that lower
concentrates concentrates
(1% solution) are probably more effective than higher
(3X solution).
However, higher concentrations may be needed
in field exposure because of the dilution of the CTC as it is passed from
termite to termite in their normal feeding behavior."
MQW
classes of toxicants may also be employed in the bait-block
method to achieve control with the needed specificity.
Dr. Glenn
Prestwich of the State University of New York at Stony Brook (personal communications 1981) has been investigating fluoridated lipids for a candidate insecticide to be used in this method.
These compounds are
harmless until metabolized in the termite gut, whereupon they are converted to highly toxic materials"
Complete safety to humans handling compounds were developed for
the block would thus be assured if these
use.
An alternative to causing mortality
to termites is to deny them the
food source which would cause economic damage, i.e., the building.
It is
known that certain woods are more resistant to termite attack than others.
If resistant woods cannot always be used, it might be possible to render
susceptible woods resistant by treatment with chemicals lAiich confer
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and anal feeding-"
A degree of specificity of the material is achieved by
This ensures that few, if
reason of its being delivered in bait form.
any, nontarget organisms will come in contact with the pesticide.
means that far less active Ingredient is needed:
It also
in the various mirex
tests cited above, quantities of mirex were measured in grams
area*
per unit
Ostaff and Gray (1975) estimated the amount of mirex needed to
Additional
achieve control at less than one-half gram per property.
specificity as a characteristic of the insecticide is probably appropriate
as well, especially considering the accessibility of the blocks to humans
when buried to a depth of only one inch.
Among the more innovative approaches
to chemical control using
bait-blocks are the use of the juvenile hormone analog methoprene and the antibiotic chlortetracycline (CTC) as control agents.
Methoprene is an
analog of a naturally occurring insect growth regulator.
Applied as an
insecticide, it disrupts the development of the insect and the disruption
eventually results in mortality. Methoprene is currently registered for
Howard and Harverty (1978)
use against mosquitoes and certain flies.
studied the effect of methoprene on R. flavipes, the eastern subterranean
termite, and suggested at least three concentration-dependent modes of
action that can cause mortality: First, larvae [sic] can starve because their symbiotic protozoans die. Second, production of a highly abnormal
proportion of presoldiers and soldiers severely strains the capacity of the remaining larvae [sic] to feed them. In addition, because the remaining larvae [sic] are themselves partially or totally defaunated, they are unable to feed
^
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\
The principal means of delivery of new chemicals being investigated
involves the use of small wood blocks which have been partially decayed by
the brown-rot fungus G. trabeum (see
above), and then impregnated
with the
control agent.
The method consists of burying the blocks approximately
one inch below the surface at intervals of a few feet in a continuous line
so as to encircle the object being protected (e.g., a house).
Beard
(1974) used
as
a variation of this method
whereby he first established sites
foraging sites by using partially decayed blocks without insecticide,
and then substituting similarly decayed blocks impregnated with
insecticide.
In tests using mirex
as the control agent, effective termite
control was achieved where the protected objects were pine stakes
(Esenther and Beal, 1974), baited (i.e., decayed) wood blocks (Esenther
and
Beat, 1978).
wood stumps
(Beard, 1974).
and buildings
(Beard, 1974;
Ostaff and Gray, 1975).
Amburgey and Smythe (1977) have developed
standard methods for infecting wood blocks with G. trabeum, and have
identified specific strains of the fungus which are most attractive to the
eastern subterranean termite.
While mirex is no longer available as a control agent, its
effectiveness in the bait-block method has encouraged research on other
toxicants applied in this manner.
Esenther and Beal (1978) suggest that
buildings could be adequately protected with bait-blocks being replaced
every 2-3 years.
They go on to say that a slower-acting insecticide might
make the block more effective in that there would be a greater initial
uptake by the termites.
Mauldin and Rich
(1980) point
out that in order
for the method to be effective, "termites must readily feed on impregnated wood blocks.
Also, the chemical should be slow acting so that worker
termites pass the chemical on to other colony members during normal oral
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the eastern subterranean termite Reticulitermes flavipes.
These
observations occurred in the field and under experimental laboratory
conditions.
He concludes that "manipulation of ant colonies might be used
as an applied biological control measure against termites in some
situations and where the ants themselves would not be undesirable" (Beard,
1972).
The second organism cited by Beard
(1974)
is the
fungus
Entomophthora coronata, from a genus of fungi known for their
pathogenicity to insects*
Yendol and Pashke (1965) reported that E.
coronata was highly pathogenic to R. flavipes, causing
97X mortality 84
hours after infection.
If the bait-block method of control (discussed
as a means of infecting termite colonies, it is
below) were to be used
conceivable that E.
coronata might be used as an effective biological
insecticide against the eastern subterranean termite.
Whereas use of
Lasius spp. and E coronata in termite control hold some promise,
commercial exploitation of techniques using these organisms is still very
far down the pike.
iii.
Chemical Control Methods
Stimulated by concern about the environmental safety and the
continued availability of Cermitlcides currently in use, research on
alternatives has concentrated on innovative chemical controls.
These
includes new toxicants, growth regulators, antibiotics, repellants and antifeedants.
The last two types of materials would be used as a wood
treatment to prevent termite feeding.
termite
The other must be delivered to the
colony in order to cause mortality.
^Co
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found to emit certain chemical substances which serve to facilitate
communications among members of the same species*
These substances are
known as pheromones, and several of them have been synthesized and used
principally in traps to detect and monitor particular species in a highly
targeted manner.
Ebeling (1978) has briefly reviewed the literature on
Most of the work relevant to termite
the research in termite pheromones.
control has been concerned with isolation and Identification of the
trail-following pheromone (Smythe et al. 1967).
It has been found that
the brown-rot fungus Gloeophyllum trabeum (previously called Lenzites
trabea)
emits an identical' substance whose effect is to stimulate
trail-following, or foraging, behavior.
Beard (1974) has demonstrated
that the.'pheromone's effects are localized in nature, but it appears that wood blocks impregnated with the substance or simply decayed partially by
G. trabeum can be used as a device to detect the. presence of termite
colonies.
Ostaff and Gray (1975) concluded that such "bait blocks'* tend
to overestimate the extent of Infestation, so that they
probably could not
be used effectively as a quantitative monitoring device.
With regard to physical monitoring, the use of wood-moisture meters
has been advocated as a supplement to visual inspection (Amburgey, 1978).. The precise role which these meters might play in a comprehensive
monitoring program may require further research (Anonymous, 1980).
ii Nonchemical Control Methods
Beard
(1974) surveyed
the literature on natural enemies of termites
The first was his own
and found only two items of serious interest.
(Beard, 1972)
observations of ant (principally Lasius spp.) predation on
is
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C.
Future Trends and Needs for Termite IPM
In agricultural IPM programs, the availability of advisory
services, primarily In the form of Independent pest management
consultants, has been an important factor
practices by farmers.
in the adoption of IPM
In order for an IPM approach to be fully
implemented in the area of structural pest control, an upgrading of
services offered by pest control companies Is likely to be necessary
(Anonymous, 1980).
This upgrading will be an evolutionary process in
response to an identifiable market, rather than a process that can be
mandated by regulation*
Pest management specialists should be able to
market their services as consultants to designers and builders of new
structures, reviewing plans and construction practices and advising on
preventive measures so as to reduce the need for chemical appllcatlonFinally, the Increasing interest among homeowners In self-help
Indicates a market for educational and training services for pest
management specialists to offer short courses and other training
packages to the general public
D.
Technical Innovations for Termite IPM
! Monitoring
The two principal Issues involved with Integrated termite control
are
(1) detection of
termite Infestation and estimating its extent, and
invasion and
(2) detection of physical conditions that favor termite
survival.
Many Insect species have been found
to emit certain chemical
<^f
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Building codes require that foundations contain vent openings that allow movement of air under the buildings. Vines and shrubs should not be allowed to cover ventilation openings* If drainage and ventilation do not reduce soil moisture sufficiently, it is helpful to cover exposed soil with heavy roofing paper. In slab construction a "vapor barrier,*" usually consisting of a sheet of some synthetic material Impervious to water, may be placed on the ground previous to the pouring of the concrete. A gravel substrate is also helpful, providing a uniform structural base and breaking capillarity. In arid regions the advantage of low humidity is often nullified by excessive and careless irrigation of plants or lawns around the foundation. In localities of consistently high humidity, sufficient moisture may be present in various parts of the building to maintain colonies of subterranean termites that have no connection with the ground. Localized areas of excessive moisture in the superstructure may develop from leaf-filled gutters or water traps on flat roofs, leaky shower pans, plumbing leaks, or condensation from water pipes. Concrete porches, terraces, patios, or steps are often supported on an earth fill. Such earth fills frequently harbor subterranean termites, often because carpenters have disposed of wood debris in these areas. In California, most subterranean termite infestations In dwellings originate in earth-filled extensions of the foundation. The concrete cap of the porch, terrace, etc*, may break away from the foundation, allowing termites to gain access to the wod of the foundation. remedial measures involve breaking out a strip of the concrete cap adjacent to the foundation, excavating the earth fill down to the top of the footing of the foundation, refilling with chemically treated soil, and reseating the concrete cap to the
foundation,
Amburgey (1978) cites many of the same general moisture-control
tactics as the
principal means of preventing wood decay fungi in
structures.
These Include repair of plumbing leaks; caulking around
sinks, tubs, etc.;
.installing drainage tile outside the foundation or water-proofing the outside foundation walls; Installing a moisture barrier over the soil In the crawl space; altering the slope of a porch, patio or carport to drain away from the house; venting appliances such as clothes driers to the outside of the house; installing air vents or fans in attic spaces or foundation walls; or correcting faulty construction or designs that permit wood to become watted by rain.
^3
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and, if so, whether spot rather than complete treatment of the
structure
may suffice.
Information from monitoring the physical
environment will indicate whether modification of the structure
or
environs is necessary to reduce the likelihood of infestation-
ill.
Post Construction Modification
Once a structure is in place, the two strategies that can be
employed to control or prevent termite infestations are chemical
application and environmental modification.
The former has been fully
described elsewhere in this report [Chapter II].
Ebellng's (1971)
summary is worth quoting at length again in regard to correction of
environmental condi tions:
Prevention and control of subterranean termites continues after completion of construction. All cellulose-bearing debris (forms, stakes, lumber, etc.) upon which termites could develop should be removed from under and around a building. Termites commonly infest such material when it Soil moisture for subterranean rests on damp soil* termites Is optimum when the soil is continuously damp but is not saturated too long. Poor drainage and Inadequate ventilation are the principal factors contributing to excessively damp soil. Remedial measures may Involve surface or subsurface drainage, adjustment of soil grade in relation to the substructure of the building, correction of faulty guttering and downspouts, repair of leaky faucets, and repair of stopped sewers and drains. Excessive and careless irrigation of the area around a building should be avoided. Sprinklers should not be allowed to wet the side of a building or Its foundation.
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In the same article, Ebeling also indicates that soil treatment with
an insecticide is
"highly effective."
He considers pretreatment -soil
to be "of particular
treatment before and during construction
importance when concrete slab-on-ground construction is employed, because
treatment of the soil is difficult and expensive after the concrete has
been poured."
No distinction is made in this statement among sites of
more or less susceptibility to termite invasion
(e.g., wood
vs. non-wood
building sites).
Monitoring for termite management has two main aspects.
The first
is monitoring the physical environment for conditions that favor termite invasion and survival.
These conditions include design
features on existing structures that serve to hide termites from view,
provide a food source to termites, and/or trap moisture.
Physical
monitoring also includes checking for maintenance problems such as
leaks and foundation cracks
The second aspect of monitoring involves
detection of the termites themselves or evidence of their presence.
This includes sighting of shelter tubes on foundation
surfaces,
discarded wings (indicators of the presence of initiators of a new
colony), and/or adult termites.
at its earliest stages*
It also includes detection of damage
Of course, proper identification is essential
to any effective monitoring
program.
For this reason, effective
education of the hoineowner, coupled with the availability of well-trained professional help, is an important element in implementing
an
IPM approach for termites (Anonymous, 1980).
Assessing infestation and damage levels are likely to require the
services of a professional
or, at minimum, a well-trained homeowner.
The
extent of infestation may determine if chemical treatment is
necessary
Bt
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masonry surfaces to gain access to substructure wood.
Before the
foundation concrete sets, spreader sticks and grade stakes must be
removed from the construction sites, because burled wood scraps are an
Important food source source and thus encourage termite Infestation.
Door frames or jambs must not extend Into or through concrete
floors*
The level of the bottom of the basement window well should be at
least 15 cm [6"] below the nearest wood.
For wooden porches or steps,
any support, such as piers, should be separated from the building by five
centimeters to prevent hidden access for termites.
rest on a concrete base or
Wooden steps should
apron extending at least 15 cm [6"] above
\
grade
Sills should be preservative-treated with a chemical that
protects them for the life of the building, provided that cut ends are
painted or soaked with a protective solution at the time of
construction. Termites are then forced to build their tubes over the
treated sills just as they are forced to build them over the concrete
foundation.
In addition, the sill Itself is protected.
This is a vital
part of the substructure and is difficult to replace.
Some may wish to
use treated wood for other members of the substructure also.
Danger from termites is reduced further by providing proper
clearance and ventilation between ground and wood members of the substructure.
Minimum clearance between the ground and bottoms of
joists in crawl spaces should be 46 cm
between
[18**],
and the minimum clearance
Minimum
ground and beams or girders should be 30 cm [12*'].
clearance between outside finish grade and the tops of slab-on-ground
foundations or tops of foundation walls In houses with a basement,
should be 20 cm [8"] with at least 15 cm
[6"] exposed.
^0
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level of understanding among homeowners regarding ecological
principles, termite biology, and preventive
measures*
B.
An IPM Program for Termites
The design component of a termite IPM program Includes site
preparation and construction of the foundation and substructure*
Ebeling (1978) has summarized these measures as follows:
i. Site Preparation
Tree stumps, roots and wood or cellulose debris of any kind on
or in the soil should be removed when the building site is graded, so as
to remove potential sources of food or existing termite colonies*
The
ground should have sufficient slope to enable surface water to drain
away from the building and thereby avoid the damp soil that favors
termites.
Ideally, provisions should be made for connecting eave
If the building is to
gutters and downspouts to a storm sewer system.
have a basement, drainage tile around the outside is especially
important.
11. Construction of Foundation and Substructure
Much can be done at the time of construction to retard
infestation, to facilitate Inspection for termite activity and to
minimize damage and cost of control and repair.
Poured concrete
foundations or masonry unit foundations capped with reinforced concrete
serve to expose termite activity, for termites must build tubes over
"
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