Note: Descriptions are shown in the official language in which they were submitted.
~06740~
FIELD OF ~IE INVE~TION
The present invention relates to the provision o~
a bait for eradicating termites and a method of eradication
by the provision of a suitable bait at a foraging location
for the termites,
PRIOR ART
Hitherto insect eradication technlques have gen-
; erally relied upon the use of massive quantities of insectl-
cide greatly in excess of the quantity of material needed
to kill the number of insects involved. Not onl)r is this
wasteful of materialJ but more importantly potentially harm~
ful residues of unused insecticide occur and potentially
dangerous contamination of the environment can occur, The
present invention is particularly concerned with the eradic-
ation of the order of insects called ISOPTERA, commonly known
as termites or "white ants". Termites are not related to
true ants but they do have a similar social behaviour to
ants and live in colonies, the population of which ranges
between hundred and millions.
Although termites live almost exclusively on
cellulose in vegetable matter, the need for e~fective con-
trol is acute as they can cause extensive damage to other
materials in their quest for cellulose, as well as destroy~
ing growing crops, grassland, forestry (especially young
saplings),
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household goods, stored food, and cellulose based materials
such as wood, paper, cotton, fibre matter etc. 'rhe tendency
to attack each of the above materials will vary from species
to species.
S Furthermore, evidence exists of plastic containers
having been attacked by termites, the motivation behind the
attack'apparently not being nutritional but rather the
removal of an obstruction between the tsrmite and its food
source.
Termites, like other social insects, live in colonies
with a distinct social structure. In the~case of subterranean
termites, the social structure comprises a colony having a
queen or other replacement reproductives, larvae, nymphs,
workers and soldiers. Workers are responsible for basic
lS functions including obtaining and supplying food to other
termites in the colony, this food transfer being by the
well-known phenomenon of trophallaxis. In a colony of
social'insects, generally there are certain natural processes
,
which cause material to pass from one insect to another.
In the case of termites three principal natural process
occur namely trophallaxis, mutual grooming and cannibalism.
In this specification the term '~natural process" is used to
refer to these transfer operations.
One known termite control method comprises distributing'
a highly toxic material, such as an arsenic containing dust,
at a site of infestation in the hope that this will kill
directly a worthwhile number of worker termites and in
addition kill indirectly other termites in the colony which
fulfil a grooming function. However, this method relies on
pumping toxic dust into a termite tunnel and depositing
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relatively large quantities of dust. This method places -the
environment at risk, and may have only limited success.
Alternative methods rely on pumping l:Lquid or gaseous
forms of toxic material into, for example, drilled holes in
timber, but obvious disadvantages exist.
Another known method is particularly applicable to
termites in wooden building structures. This method comprises
enclosing the structure in a tent and pumping in a selected
fumigant gas, usually sulphuryl fluoride. The gas is retained
for 24 hours. This method is e*pensive and only successful
on termites which come into sufficient contact with the
fumigant, which of course is subsequently released into the
atmosphere.
Another known technique is to spray the surface of
building structures with a suitable chemical so that, although
termites within the galleries in the wood are not affected
by the chemical, the reproductives are killed as they leave
the timber. Again, however, large quantities of toxic
material must be disposed of around a structure.
U.S. patents 3,835,578 and 3,070,495 disclose a range
of insecticides as being toxic to termites but the methods
of these specifications can only be expected to Xill largely
the insects which come into direct contact with the material
which must apparently be left out in substantial quantities.
SUMMARY OF THE INVENTION
The present invention in one aspect is directed to the
provision of a bait to be placed at a foraging locating of
termites, the bait being an acceptable food to the termites
which is favoured in preference to surrounding naturally
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available foods for the termites; the bait includes a material
which has a delayed but lethal e~ect on the termite in
combination with fine cellulose particles (which preferably
are provided by selected wood flour) of a particle size
suitable for easy ingestion by the termites, the material
which has the lethal effect being in a form acceptable to
the termites.
For the purpose of enhancing the desirability of the
` bait as food, the bait includes water in either a fEee or
bound form. The water may assist providing the bait as a
cohesive mass.
The eradication technique comprises inserting the bait
into a foraging location of the termites and relying on the
bait to be ingested by some of the termites of a colony
whereby by natural process the bait is transferred to many
other termites in the colony before any substantial lethal
effect occurs so that a large number of termites can be
eradicàted.
The present invention permits eradication of termite
colonies with a high degree of convenience, economy and
effectiveness. Many of the disadvantages associated with
prior art methods are avoided and in particular the use of
very large quan~ities of potentially harmful toxic materials
is obviated.
The present invention can best be practised by selecting
a species of wood and a particle size to suit the species of
termite to be eradicated~ For example the species Mastotermes
darwiniensis Froggatt is, relatively speaking, prepared to
accept a wide range of baits but other species would be more
selective and to optimize use of the invention for a particular
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3L~67~0~
species would require simple laboratory free choice tests.
With the species Mastotermes darwiniensis Frog~att, wood
flour or sawdust of a particle size not exceeding 500 ~m is
the preferred particle size, the wood flour or sawdust
passing through a 30 mesh sieve (British standard). This
si~e of particle approximately corresponds to the size of a
single "bite" of the termite and therefore is a preferred
food relative to the surrounding timber at a foraging locating
because the termite is not put to the trouble of tearing off
the particles of wood from the timber to be consumed. The
applicant has conducted tests with the species Mastotermes
darwiniensis Froggatt and found that from a large number of
timbers available in Australia there is a preference for the
timber known as "Northern Stringybark" (Eucalyptus tetrodonta).
It has been found that it is especially advantageous to
formulate the bait as a paste-like material by using a
water-based gel such as a 1~ Agar gel. This is believed to
be particularly effective since it is thought that generally
termites are under some form of water stress and the gel
provides a readily available form of water and this contributes
to the bait being an attractive foodstuff.
A wide range of insecticides are known and a large
number are known to have a lethal effect on termites. The
present invention may be practised with any toxic material
which would have a lethal effect on termites providing the
- material is formulated into the bait according to th0 invention
so as to have the necessary delayed lethal effect. It is
preferred that the main lethal effect occurs after about
three days from the first ingestion of the bait by some
termites of the colony. This period of three days has been
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~067401
determined by experiments conducted in the Northern Territory
of Australia. A bait was prep~red but with a radioactlve
material (which would not be lethal to the termites) in
place of the toxic material for the purpos,e oE permi~ting
tracing of the distribution of the bait. The radioactive
materials chosen were scandium-46, lanthanum 140 or gold
198, these elements being in the orm of c:ompounds insoluble
in body fluid`s, so as to be confined to the gut and wholly
involved in the normal patterns of trophallaxis and excretion.
This radioactive tracing technique may be utilized in monitoring
operation of the invention by including a tracer in the bait
and subsequently scanning the colony location to detect bait
transfer as a result of trophallaxis and excretion~
The bait was in the form of a paste inserted into a
wooden dowel having a bore therein 1 cm diameter extending
about 10 cm along the dowel to receive about 4 grams of the
bait paste. The dowel had an external diameter of 1.25 cm.
A tree at a foraging location was bored with a hole of a
diameter of 1.3 cm and the dowel inserted, the bait in this
case comprising fine sawdust in 1% Agar gel and containing
scandium-46 as a finely ground oxide of specific activity 1
mCi per mg.
It was observed that the bait was removed rapidly and
completely by the termites. Tw~nty four hours after bait
insertion, a sample of termites was removèd from one of the
radioactive sites and the radioactivity assoaiated with
individual termites was determined. Further observations
were made after 48 hours and 72 hours with termite samples
extracted from other marked sites.
1t:)6740~
It was shown that the radioactivity associated with
individuals covered a wide range after 24 hours, the range
descreasing very markedly after 48 hours and still more
a~ter 72 hours.
In practising the present invention the choice of toxic
material could be from a wide range of materials. Preferably
the material is a material toxic to the syn~iotic protozoa
present in the hind gut of certain termite species. Such
toxic materials include materials selected from the following
classes: -
(a) halogenated hydrocarbons
(b~ organo-phosphorous derivatives which block specific
enzyme systems
(c) biocides selective against protozoa such as hetero-
cyclic bases.
The vast majority of possible toxic materials would,
however, not have the necessary delayed lethal effect on
termites if simply incorporated with the wood flour or
sawdust. Therefore in certain embodiments of the invention,
the toxic material is micro-encapsulated and preferably has
a micro-capsule size less than the wood particle size in the
bait so that the micro-encapsulated material is easily and
accidentally ingested by a termite foraging for wood particles.
Examples of material for the protective encapsulating coating
would be hardened gelatin, gelatin-agar, gelating-gum arabic,
cellulose derivates and hemicellulose. The choice depends
on the digestive enzymes most active within the gut of the
particular termite species to be eradicated.
Some toxic materials however, have been found surprisingly
to have an intrinsic delayed effect on termites. Examples
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~0674~
of such materials comprise certain arsenic compounds such as arsenous sulfid~
and certain cyclobuta(cd)pentalenes such as Mirex tTrade Mark), which, ~s
stated in the ~erck Index ~9th Edition), is defined as being 1,la,2,2,3,3a,
4,5,5,5a,5b,6-Dodecachlorooctahydro-1,3,4-metheno-lH-cyclobuta(cd)pen~alene.
Specific examples of toxic materials contemplated by the
applicant suitable for use in the p~esellt invention when micro-encapsulated
include aldrin and other di-methano-naphthalenes suc~h as isodrin and dieldrin,
DDT, chlordane, parathion, malathion, and heptachlor all of which are known
to be toxic to t~rmites as is disclosed in United States Patent 3,070,495.
However, this patent does not make any suggestion of micro-encapsulation
and is concerned with the use of a selected fungus as a specific attractant
with the fast acting insecticide. Furthermore, there is the prospect of
practising the present invention with pyrethroids such as bioresmethrin
which are potentially less har~ful to man.
For the purposes of exemplification only, specific
examples o the invention will now be given.
EXAMRLE 1
A termite bait was prepared for a laboratory test in
which termites of the species Coptotermes Lactus were exposed to toxic baits
and compared to a control sample subjected to a similar bait but without
the toxic material. Each insect sample comprised 2 grams of insects approxi-
mating 500 in number.
The first toxic bait co~prised 0.8 gm Eucalyptus tetro-
donta wood flour of small particle size less than about 150 ~m size mixed
with 0.04 gms arsenous sulfide powder an~ uniformly
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~1067401
dispersed in ~ gms of 1~ ~gar gel. For the purposes of
comparison a similar second toxic bait was prepared ~ubstituting
Eucalyptus regnans flour for Eucalyptus tetrodonta flour.
It was found that the termites preerred the Eucalyptus
regnans bait. After twenty-eight hours from the introduction
of the bait, 1~ of the termites were dead and in the control
sample a similar number of termites were dead.
After forty-eight hours, 50 to 60% o the termites
exposed to the toxic bait had died whereas a further 1% only
of the termites exposed to non-toxic baits had died.
This example of the invention shows that sufficient
delay occurs in the effect of the toxic material to permit a
substantial degree of transfer by natural processes within a
colony of termites.
EXAMPLE 2
Two further baits were prepared corresponding to the
toxic baits of Example 1 but subject to the difference that
only 0.02 gms of toxic material were included and in this
case the toxic material was Mirex. Again 2 gms of termites
were exposed to the two toxic baits and again the Eucalyptus
regnans bait was preferentially attacked. A control sample
of a similar quantity of termites was exposed to a non-toxic
bait.
2S Again after twenty-eight hours about 1% of the termites
were dead in both the toxic sample and the control sample.
After ninety-six hours a further measurement was taken and
it was ound that 80 to 90% of the termites exposed to the
toxic bait were dead or dying and cannibalism of the bodies
was taking place. By contrast in a control sample a mortality
rate of about 1% only was notice.
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EXAMPLE 3
An insecticidal bait was made up as follows:
Wood flour of the species Eucalyptus tetrodonta was
prepared using a handsaw to avoid any burning of the wood
S particles and sieved to produce wood flour of less than 500 ~m
size. The wood flour was soaked with 3~ acetone solution
of a slow acting halogenated insecticide, Mirex. The acetone
was removed by evaporation and vacuum treatment and 20 gms
of the wood flour was dispersed in 100 mls of 1% Agar gel.
A new forest plantation which was heavily infested with
the species Mastotermes darwiniensis Frogga~t was selected
and for eval~ation purposes a colony system was first traced
using a radioactive tracer in a non-toxic bait. Foraging
and nesting sites were flagged and two weeks later ten bait
units were inserted into the foraging sites, each of the
bait units comprising insecticidal bait as described above
located into a cavity within a wooden dowel.
One week later the site was re-examined and the locations
of foraging and nesting sectioned or excavated and sectioned.
No live termites were found in the system which extended
over an area of about l hectare and had some forty-six
nesting and foraging sites. Extension invasion was noted of
several species of ant and dead termites and fragments of
termites could be seen.
EXAMPLE_4
The present invention has also been found applicable in
an urban environment. An infestation of termites of the
species Coptoternes Aeinacififorinis was found within an
office complex at the ~ustralian Atomic Energy Commission
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Research Establishment at Lucas ~leights in Australia. The
main obvioùsly active areas for termites were within roo~
beams. By radioactive tracing the colony was mapped and
s~own to extend along roofbeams under a verandah, under a
lawn and under a concrete floor within the offices. Mirex
baits were prepared in accordance with Example 3 but the
wood flour particle size was reduced to b~ of the order of
150 ~m, Subsequent inspection showed the presence of many
dead termites. For a period of up to one year later further
baits were left out but no evidence of any further infestation
became apparent thereby leading to the conclusion that the
colony was eradicated.
EXAMPLE 5
A trial was conducted at a factory and radioactive
tracing demonstrated infestation of termites along concrete
expansion joints and underground. Toxic baits as used in
Example 4 were prepared and inserted at one expansion joint.
Five days later inspection revealed dead termites and partly
eaten carcasses but no live termites. It appeared the
colony had been completel~ eradicated.
EXhMPLE 6
A bait was prepared using micro-encapsulated samples of
Dieldrin.
50 ml of 12~% aqueous solution of gum acacia was e~ulsified
at 50C with 25 ml of peanut oil saturated with Dieldrin.
50 ml of 12~ aqueous gelatin solution was added and the pH
adjusted to 6Ø The solution was gently stirred at 50C
while 375 ml distilled water was added dropwise at a rate of
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40 to 50 drops/minute. When all the water was added the
solution was stirred ~or 30 miIlutes and then cooled quickly
at 5C on ice. The solution was than kept at 1C Eor 12
hours. The layer of encapsulated insecticide separated and
S hardened in a 10% gluteraldehyde solution for 24 hours. The
hardened micro-capsules were separated, well washed with
water and dried in a vacuum dessicator.
The micro-capsules were mixed with E regnans wood flour
and dispersed in a 1% agar gel to produce the bait embodying
the invention. This bait was tested by being offered to
approximately 500 termites of the species Coptotermes lacteus.
The termites readily consumed the bait and after 4a hours
90% had died. This compares with a natural deat rate in a
control sample of 1~.
It is preferable that the Dieldrin be relatively freshly
encapsulated since after a period of storage of the order of
ten days or more some degree of leakage of the Dieldrin from
the micro-capsules may occur and this can adversely effect
the results obtained.
Tests have been conducted with a similar bait but
without micro-encapsulation of the Dieldrin. It was found
that a substantial proportion of termites die quite quickly
although the bait shows littlé sign of being touched. This
is thought to be due to the vapour of Dieldrin having a
toxic effect and although termites in proximity to the bait
are killed quickly, Dieldrin without micro-encapsulatio,n
would not be useful for eradicating colonies.
The invention can be implemented efficiently. It has
been estlmated that a typical termite colony may comprise
106 insects at an average weight of 50 mg. ~ased on the
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assumption the insects will be killed in four days and
allowing for seven-eighths of the bait to be elimin~ted by
excretion, it has been estimated that a tot:al weight of bait
oE 125 gms only is required and when Mirex is used only 0.8
gms is required. In act due to cannibolism, the amount of
toxic material required should be less than this quantity.
In the text described above, it was estimated that the
colony comprised 7 x 106 insects and the total bait set out
amounted to l kg. On subsequent inspection it was found
that only 250 gms of bait had been removed and dissection of
the colony and foraging point dislosed a complete kill of
the colony. Thus, approximately l gm of a toxic material
such as Mirex can kill a colony of the order of 10 termites.
EXAMPLE 7
A trial was conducted using freshly encapsulated malathion,
the bait being otherwise in accordance with Example 6. A
termite colony had been located as being active in a skirting
board and wall panelling. A bait was left out and after 24
hours was found to be partly removed. After four days it
appeared that the colony had been killed. By contrast
laboratory tests with baits which had been stored for a week
or two after encapsulation of malathion or dieldrin were not
readily accepted by the insects probably due to a slow
release of-the contents of the micro-capsules.
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