GB1597293A

GB1597293A - Insect control

Info

Publication number: GB1597293A
Application number: GB973778A
Authority: GB
Original assignee: Australian Atomic Energy Commission
Current assignee: Australian Atomic Energy Commission
Priority date: 1978-03-11
Filing date: 1978-03-11
Publication date: 1981-09-03

Description

(54) INSECT CONTROL (71) We, AUSTRALIAN ATOMIC ENERGY COMMISSION a body corporate established by Statute in Australia and having as its address 45 Beach Street, Coogee New South Wales Australia, do hereby declare that the invention for which we pray that a Patent may be granted to us and a method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the control of insects, by which is meant the eradication or reduction in the number of insects at an infestation site.

To date insect eradication techniques have generally required the use of massive quantities of insecticide and the residues of a number of insecticides have been shown to be so harmful to the environment that they have been withdrawn from sale. Therefore, it is desirable to control insects in a manner which minimises environmental harm and reduces the amount of insecticide needed for a particular eradication program.

Although the general principles on which the present invention is based are applicable to "social" insects generally, the shortcomings of known methods and the application of the present invention will be exemplified by specific discussion of the order of insects, ISOPTERA, commonlv known as termites or "white ants". Termites are not related to true ants but they do have a similar social hehaviour to ants and live in colonies, the population of which ranges between hundreds and millions.

Although termites live almost exclusively on cellulose in vegetable matter, the need for effective control is acute as they can cause extensive damage to other materials in their quest for cellulose. in addition to destruction of foods such as growing crops, grassland.

forestry (especially young saplings). household goods. stored food. cellulose based materials such as wood, paper. cotton. fibre matter etc. The tendency to attack each of the above materials will vary from species to species.

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 termite 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 soidiers. Workcrs are responsible for basic functions including obtaining and supplying food to other termites in the colony. this food transfer being hy 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 processes occur namely trophallaxis, mutual grooming and cnnnibalism. In this specification the term "natural process" is interpreted to refer to such transfer operations.

One known termite control method comprises placing a highly toxic material, such as an arsenic containing dust, at a site of infestation in the hope that this will directly kill a worthwhile number of worker termites and also other termites back in the colony which fulfil a grooming function. However, this method relies on pumping toxic dust into a termite tunnel and depositing relatively large quantities of dust. This method places the environment at risk - and may be only of limited success.

Alternative methods rely on pumping liquid 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 expensive to effect 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.

The present invention is based on the concept of providing a suitable bait which would be attractive to the species of insect to be controlled. the bait including a material which has a delayed but lethal effect on the insect, whereby it is intended that the insects directly contacting and ingesting the bait will not be killed quickly but will distribute the bait within the colony by natural process such as trophallaxis thereby killing a large number of insects.

The term "delayed lethal effect" in the present specification means that no significant effect changing or interrupting the normal life stvle of a termite occurs immediately or within a short time such as a few hours after ingestion of the bait by a termite, thereby permitting the bait to be transferred through a colony of termites by natural process but after a period of time much longer than just a few hours and typically about three days, the lethal effect occurs.

According to the present invention, there is provided - a bait for killing termites comprising a paste-like mixture of a cellulose material in finely divided form so as to be acceptable as a food for the species of termite to be killed, a second, toxic material included with the cellulose material and having a delayed lethal effect on termites but no significant immediate lethal effects on the termites which ingest the bait, and a water-based binder binding the cellulose material and second material together, the bait being such that the toxic material is taken up by termites with the cellulose material and is transmitted by natural process to other termites in a colony at which time the delayed lethal effect of the toxic material occurs, the toxic material being selected from the group consisting of an arsenic compound in finely divided form. a cyclobuta (cd) pentaiene soaked into the cellulose material. a micro-encapsulated halogenated polvcyclic insecticide from the class di-methano-naphthalene (except dieldrin) and microencapsulated insecticides comprising synthetic pyrethroids, chlordane. parathion, malathion and heptachlor.

A preferred and important embodiment of the invention consists in using the cyclobuta (cd) pentalene Mirex which can simply be soaked into the cellulose material before formulation of the bait with the water-based binder. Another important class of materials for use in the present invention are microencapsulated di-methano-naphthalenes. of which very useful and important members are the group consisting of aldrin and other derivatives of aldrin (except dieldrin) effective in a similar manner to dieldrin for killing termites. The invention may also be implemented with microencapsulated synthetic pyrethroids, chlordane, parathion, malathion and heptachlor.

Use of the present invention can permit eradication of colonies of termites particularlv when a highly effective toxic material is used in an appropriate bait which is located in a foraging area and the bait is more attractive than surrounding material. The bait can be packed and located in a manner which will minimise unwanted contamination of environment or transfer to other living organisms which may be harmed. Onlv small amounts of the toxic material of the order of a few times the lethal dose related to the population are required.

Hereinafter reference to sawdust means fine wood particles which may be so fine as to be known as wood flour, and which may be produced from wood by any suitable process as well as by sawing wood.

The bait includes a water-based binder such as a 1 flj agar gel and it is thought that this has a most beneficial effect in causing the termites to prefer the bait to surrounding material as a source of food due to the fact that the termites are thought to be under a form of water stress and the binder provides a readilv available source of water. Furthermore the bait can be made a preferred food by suitable choice of the species of timber and also suitable choice of the maximum particle size. The exact species of termite to be eradicated will indicate the optimum wood flour and the optimum particle size, For example experiments with the termite species Mastoter7nes dciriviiiiejisi' Froggatt have indicated that a preferred maximum particle size is 5()() ,wm. This is provided by passing sawdust thl.OLlh a 3(1 mesh sieve (British Standard).

However. for smaller termites a finer wood flour or sawdust may be required. A tvpical wood flour has a particle size of the order of 15() Clam.

It has been found that the wood flour or sawdust should be produced without a tendencv to burn the wood particles and therefore a fast power saw should be avoided.

The choice of wood can readily be determined by laboratory tests on particular species of termites. For example Mastotermes darwiniensis appear to prefer Northern Stringybark (Eucalyptus tetrodonta).

A large number of insecticides are already known and many of them have been found to be toxic to termites. However the prior art proposals have not apparently been demonstrated to be an effective practical eradication arrangement.

In general the present invention proposes the use of toxic materials for termites in a bait as defined in the claims. It is thought that the vast majority of possible toxic materials which would be effective against termites must however be micro-encapsulated since the toxic materials would otherwise be too fast in their action to permit distribution of the toxic material through the colony.

Examples of toxic materials include chlordane, aldrin and derivatives thereof (except dieldrin), isodrin, parathion, malathion and heptachlor. Furthermore bioresmethrin might also be usable, as well as other synthetic pyrethroids.

The invention is typically implemented by a bait having a delayed lethal effect of about three days so that by natural process the bait can be distributed effectively through the colony.

This period of three days has been determined by experiments conducted in the Northern Territory of Australia. A bait was prepared but with a radioactive material (which would not be lethal to the termites) in place of the toxic material for the purpose of permitting tracing of the distribution of the bait. The radioactive materials chosen were scandium-46 lathanum 140 or gold 198, these elements being in the forum of compounds insoluble in body fluids, 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 utilised 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.

Reference will now be made to the accompanying drawing which illustrates the results of an experiment conducted in the Northern Territory of Australia and illustrating the results of the insertion of a dowel type bait into a single tree 1. The dowel type bait was formed from a piece of 1.25 cm. diameter dowelling having a 1 cm. hole drilled up its centre portion and about 4 grams of a bait paste packed into the central hole which extended to a depth of about 10 cm.

The tree was drilled with a hole of a diameter of 1.3 cm. the tree being selected as an infested tree in an infested area in which the termites of the species Mastotermes darwiniensis Froggatt had been observed.

The bait comprised a paste of sawdust in 1% agar containing scandium-46 as a finely ground oxide of specific activity 1 mcCi per mg.

It was observed that the bait was removed rapidly and completely by the termites and a survey of the area is illustrated in the drawing, showing 36 radioactive sites 2 on an area of 60 x 54 metres, which includes logs 3 and non-radioactive trees 4.

Twenty four hours after bait insertion a sample of termites was removed from one of the marked sites and the radioactivity associated with individual termites was determined.

Further observations were made after 48 hours and 72 hours with termite samples extracted from other marked sites.

It was shown that the radioactivity associated with individuals covered a wide range after 24 hours the range decreasing very markedly after 48 hours and still more after 72 hours.

The present invention also extends to a method of eradicating termites comprising inserting a quantity of a bait in any one of the forms described above into a foraging location.

The method preferably includes the preliminary step of selecting the wood flour or sawdust for the bait so as to be attractive to the termites and furthermore. preferably the method includes selecting a particle size to be graded to permit ingestion by the termite species of interest.

For the purposes of exemplification only, specific examples of the invention will now be given.

EXAMPLE 1 A termite bait was prepared for a laboratory test in which termites of the species Coptotermes Lacteus 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 approximating 500 in number.

The first toxic bait comprised 0.8 gm Eucalyptus tetr-onontn wood flour of small particle size less than about 150 ,um size mixed with 0.04 gms arsenous sulfide powder and uniformerlv dispersed in 4 gms of 1% Agar gel. For the purposes of comparison a similar second toxic bait was prepared substituting Eucalyptus regnans flour for Eucalyptus tetrodonta flour.

It was found that the termites preferred the Eucellvptus regnans bait. After twenty-eight hours from the introfuction 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% of 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.

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 found 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 noticed.

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 particles and sieved to produce wood flour of less than 500 ,am 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 Froggatt was selected and for evaluation 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 1 hectare and had some forty-six nesting and foraging sites.

Extensive 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 Coptoterines Acinaciformis was found within an office complex at the Australian Atomic Energy Commission Research Establishment at Lucas Heights in Australia. The main obviously active areas for termites were within roof beams.

By radioactive tracing the colony was mapped and shown 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 be of the order of 150 ijm. 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 S 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 completely eradicated.

EXAMPLE 6 A bait was prepared using micro-encapsulated samples of malathion.

50 ml of 121/2% aqueous solution of gum acacia was emulsified at 50"C with 25 ml of peanut oil saturated with malathion 50 ml of 12MC/o aqueous gelatin solution was added and the pH adjusted to 6.0. The solution was gently stirred at 50"C while 375 ml distilled water was added dropwise at a rate of 40 to 50 drops /minute. When all the water was added the solution was stirred for 30 minutes and then cooled quickly at 53C on ice. The solution was then kept at 10C for 12 hours. The layer of encapsulated insecticide separated and hardened in a 10% gluteraldehyde solution for 24 hours. The hardened micro-capsules were separated, well washed with water and dried in a vacuum desiccator.

The micro-capsules were mixed with E. regelans wood flour and dispersed in a lCk agar gel to produce the bait embodying the invention. This bait was tested by being offered to a termite colony 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.

The invention can be implemented efficiently. It has been estimated that a typical termite colony may comprise 106 insects at an average weight of 50 mg. Based on the assumption the insects will be killed in four days and allowing for seven-eights of the bait to be eliminated by excretion, it has been estimated that a total weight of bait of 125 gms only is required and when Mirex is used only 0.8 gms is required. In fact due to cannibalism, the amount of toxic material required should be less than this quantity.

In the test described above, it was estimated that the colony comprised 7 x 106 insects and the total bait set out amounted to 1 kg. On subsequent inspection it was found that only 250 gms of bait had been removed and dissection of the colony and foraging point disclosed a complete kill of the colony. Thus, approximately 1 gm of a toxic material such as Mirex can kill a colony of the order of 106 termites.

WHAT WE CLAIM IS: 1. A bait for killing termites comprising a paste-like mixture of a cellulose material in finely divided form so as to be acceptable as a food for the species of termite to be killed, a second, toxic material included with the cellulose material and having a delayed lethal effect on termites but no significant immediate lethal effects on the termites which ingest the bait, and a water-based binding the cellulose material and second material together, the bait being such that the toxic material is taken up by termites with the cellulose material and is transmitted by natural process to other termites in a colony at which time the delayed lethal effect of the toxic material occurs, the toxic material being selected from the group consisting of an arsenic compound in finely divided form, a cyclobuta (cd) pentalene soaked into the cellulose material, a microencapsulated halogenated polycyclic insecticide from the class di-methano-naphthalene (except dieldrin), and microencapsulated insecticides comprising synthetic pyrethroids, chlordane, parathion, malathion and heptachlor.

2. A bait as claimed in claim 1 wherein the second material is Mirex.

3. A bait as claimed in claim 1 wherein the second material is a di-methano-naphthalene selected from the group consisting of aldrin, and other derivatives of aldrin except dieldrin but having a lethal effect on termites to a similar extent as dieldrin.

4. A bait as claimed in claim 1 wherien the second material is the synthetic pyrethroid bioresmethrin.

5. A bait as claimed in any one of the preceding claims, wherein the cellulose material is fine sawdust of a selected species of timber so as to be attractive to the termites.

6. A bait as claimed in claim 5, wherein the timber is Eucalyptus tetrodonta, or Eucalyptus regnans.

7. A bait as claimed in any one of the preceding claims wherein the cellulose material has a particle size not exceeding 500 ijm.

8. A bait as claimed in claim 7 wherein the particle size of the cellulose material is approximately 150 ,uvm.

9. A bait as claimed in any one of the preceding claims wherein the cellulose material is wood flour produced by slow sawing of timber so as to avoid burning and sieving the wood flour to select fine particles.

10. A bait as claimed in any one of the preceding claims wherein the water-based binder is an agar gel comprising about 1% agar.

11. A bait as claimed in any one of the preceding claims wherein the bait is in a paste-like form and disposed in a wooden element having a cavity therein containing the bait, the wooden element being adapted to be inserted into and mounted in a foraging location for termites.

12. A bait substantially as described herein with reference to any one of the examples of the invention.

13. A method of eradicating termites comprising inserting into a foraging location a quantity of bait as claimed in any one of the preceding claims.

14. A method as claimed in claim 13, wherein the bait is as claimed in claim 3 wherein the second material was encapsulated at a time preceding insertion in the foraging location which is short compared with the period of ten days.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. termite colony 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. The invention can be implemented efficiently. It has been estimated that a typical termite colony may comprise 106 insects at an average weight of 50 mg. Based on the assumption the insects will be killed in four days and allowing for seven-eights of the bait to be eliminated by excretion, it has been estimated that a total weight of bait of 125 gms only is required and when Mirex is used only 0.8 gms is required. In fact due to cannibalism, the amount of toxic material required should be less than this quantity. In the test described above, it was estimated that the colony comprised 7 x 106 insects and the total bait set out amounted to 1 kg. On subsequent inspection it was found that only 250 gms of bait had been removed and dissection of the colony and foraging point disclosed a complete kill of the colony. Thus, approximately 1 gm of a toxic material such as Mirex can kill a colony of the order of 106 termites. WHAT WE CLAIM IS:

1. A bait for killing termites comprising a paste-like mixture of a cellulose material in finely divided form so as to be acceptable as a food for the species of termite to be killed, a second, toxic material included with the cellulose material and having a delayed lethal effect on termites but no significant immediate lethal effects on the termites which ingest the bait, and a water-based binding the cellulose material and second material together, the bait being such that the toxic material is taken up by termites with the cellulose material and is transmitted by natural process to other termites in a colony at which time the delayed lethal effect of the toxic material occurs, the toxic material being selected from the group consisting of an arsenic compound in finely divided form, a cyclobuta (cd) pentalene soaked into the cellulose material, a microencapsulated halogenated polycyclic insecticide from the class di-methano-naphthalene (except dieldrin), and microencapsulated insecticides comprising synthetic pyrethroids, chlordane, parathion, malathion and heptachlor.

2. A bait as claimed in claim 1 wherein the second material is Mirex.