GB1561901A - Control of insects - Google Patents

Description

(54) THE CONTROL OF INSECTS (71) We, AUSTRALIAN ATOMIC ENERGY COMMISSiON, a body corporate established by Statute in the Commonwealth of Australia, of 45 Beach Street, Coogee, New South Wales, Australia, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to the con- trol 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 insecticides and the residues of a number of insecticides have been shown to be so harmful to the environment that they have been withdrawn from sale.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, 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 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 sap lings), household goods, stored food, cellu- lose 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 contathiers 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 soldiers.

Workers are responsible for basic 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 processes occur namely trophallaxis, mutual grooming and cannibalism. In this specification the term "natural process" is interpreted to refer to such transfer operations.

One known termite control method comprises 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.

Alteniative 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.

This invention provides a bait for eradicating termites of a colony which comprises a paste-like product formed from a waterbased gel, a cellulose material in finely divided form so as to be acceptable as a food for the species of termite to be eradicated, and a second material having a delayed insecticidal property on the termites whereby by natural process the bait is transmitted to other termites which are killed after receiving a sufficient dose.

This invention also provides a bait as defined above, wherein the bait is located in a holder having a cavity for the bait the holder being adapted to be inserted into and mounted at a foraging location of the termites.

In a preferred embodiment, the cellulose material is fine sawdust or wood flour of a selected species of timber so as to be a preferred food for the termites.

Use of the present invention can permit eradication of colonies of termites particularly 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 ponulation are reauired.

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 gel, preferablv 1% by weight agar gel. It is thought that termites are normallv under a form of water stress and the gel provides a readily available source of water.

The particle size for the wood flour or wood sawdust and the lethal material is best selected to suit the species of termite involved. Experiments with one particular termite namely Mastotermes darwiniensis Froggatt have indicated that a fine particle size is preferred, preferably the maximum particle size is 500 ,am. This is provided by passing sawdust through a 30 mesh sieve (British Standard).

However, for smaller termites a finer wood flour or sawdust may be required.

In the case of Mastoternies darwiniensis a preferred wood has been shown to be that known as Northern Stringybank (Eucalyptus tetrodonta), but for any particular species the preferred wood can be readily selected on the basis of free choice experiments.

The lethal material is advantageously encapsulated by a protective coating, such as hardened gelatin, gelatin-agar, gelatin-gum arabic, cellulose derivatives or hemicellulose. The choice depends on the digestive enzymes most active within the gut of the particular termite species, since preferably the encapsulated material is such that approximately three days elapse from the ingestion of the material before a significant lethal effect occurs in 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 form 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 operatlon 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 Northen 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 13 cm. the tree being selected as an infested tree in an infested area in which the termites of the species Mastoter mes darniniensis Froggatt had been observed.

The bait comprised a paste or sawdust in 1% by weight agar containing scandium46 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 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.

In a preferred embodiment of the present invention, the bait includes a microencapsulated toxis material which preferably will have its main lethal effect on a termite about three days after the termite has ingested the material. It is believed that many toxic materials which can be used in embodiments of the invention have the effect of being toxic specifically to the symbiotic protozoa present in the hind gut of certain termite species and the termites in turn die when these protozoa have been killed. Such toxic materials includes (a) halogenated hydrocarbons (b) organo-phosphorous derivatives which block specific enzyme systems (c) biocides selective against protozoa such as heterocyclic bases.

Without encapsulation of the materials the termites would reject the vast majority of possible toxins which could be employed.

In order to gain maximum distribution of the toxin, the micro-capsule size should be not greater than the wood particle size in bait preparations, and preferably the microcapsules should be smaller.

EXAMPLE 1: An insecticidal bait was made up as follows: 1% agar gel-100 ml Impregnated wood flour20 g The wood flour (E. tetrodonta) was impregnated by soaking in an acetone solution (3%) of a slow-acting halogenated hydrocarbon insecticide the acetone being removed by evaporation and finally under vacuum.

Effectiveness of the bait was demonstrated by selecting a heavily infested area which was mapped out using a non-toxic radioactive bait and the insecticidal bait was then left out and after 1 week the site was examined. No live termites were found in the system extending over an area of about 1 hectare showing 46 sites. Extensive invasion by several species of ants was evident and dead termites and fragments of termites could be seen Within the main nesting areas underground, the ants had penetrated through galleries and dead termites could be found, most of which were part eaten. Some dead ants could be seen.

EXAMPLE 2: Micro encapsulated samples of Dieldrin a proprietary insecticide, were prepared in the following manner. 50 ml of 12-z% aqueous solution of gum acacia was emulsified at 500C with 25 ml of peanut oil saturated with Dieldrin. 50 ml of 12+% 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 4 > 50 drops / minute. When all the water was added the solution was stirred for 30 minutes and then cooled quickly to 5"C on ice. The solution was then kept at 1"C for 12 hours. The layer of encapsulated insecticide separated and hardened in a 10% gluteraldehyde solution for 24 hours. The hardened microcapsules 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 according to 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 48 hours 90% had died. This compares with a natural death rate in a control sample of 1%. Embodiments of the present invention may furthermore be provided with a specific attractant substance to encourage positively the termites to take the bait.

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

The method preferably includes the preliminary step of identifying the species of termite to be eradicated and selecting the cellulose material in the form of fine wood particles and of a species of timber for the bait such that the bait is at least as acceptable as a food to the termites as the matter being attacked at the foraging location.

WHAT WE CLAIM IS: 1. A bait for eradicating termites of a colony which comprises a paste-like product formed from a water-based gel, a cellulose

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

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. mes darniniensis Froggatt had been observed. The bait comprised a paste or sawdust in 1% by weight agar containing scandium46 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 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. In a preferred embodiment of the present invention, the bait includes a microencapsulated toxis material which preferably will have its main lethal effect on a termite about three days after the termite has ingested the material. It is believed that many toxic materials which can be used in embodiments of the invention have the effect of being toxic specifically to the symbiotic protozoa present in the hind gut of certain termite species and the termites in turn die when these protozoa have been killed. Such toxic materials includes (a) halogenated hydrocarbons (b) organo-phosphorous derivatives which block specific enzyme systems (c) biocides selective against protozoa such as heterocyclic bases. Without encapsulation of the materials the termites would reject the vast majority of possible toxins which could be employed. In order to gain maximum distribution of the toxin, the micro-capsule size should be not greater than the wood particle size in bait preparations, and preferably the microcapsules should be smaller. EXAMPLE 1: An insecticidal bait was made up as follows: 1% agar gel-100 ml Impregnated wood flour20 g The wood flour (E. tetrodonta) was impregnated by soaking in an acetone solution (3%) of a slow-acting halogenated hydrocarbon insecticide the acetone being removed by evaporation and finally under vacuum. Effectiveness of the bait was demonstrated by selecting a heavily infested area which was mapped out using a non-toxic radioactive bait and the insecticidal bait was then left out and after 1 week the site was examined. No live termites were found in the system extending over an area of about 1 hectare showing 46 sites. Extensive invasion by several species of ants was evident and dead termites and fragments of termites could be seen Within the main nesting areas underground, the ants had penetrated through galleries and dead termites could be found, most of which were part eaten. Some dead ants could be seen. EXAMPLE 2: Micro encapsulated samples of Dieldrin a proprietary insecticide, were prepared in the following manner. 50 ml of 12-z% aqueous solution of gum acacia was emulsified at 500C with 25 ml of peanut oil saturated with Dieldrin. 50 ml of 12+% 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 4 > 50 drops / minute. When all the water was added the solution was stirred for 30 minutes and then cooled quickly to 5"C on ice. The solution was then kept at 1"C for 12 hours. The layer of encapsulated insecticide separated and hardened in a 10% gluteraldehyde solution for 24 hours. The hardened microcapsules 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 according to 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 48 hours 90% had died. This compares with a natural death rate in a control sample of 1%. Embodiments of the present invention may furthermore be provided with a specific attractant substance to encourage positively the termites to take the bait. The present invention also extends to a method of eradicating termites comprising inserting into a foraging location a quantity of bait in any one of the forms described above. The method preferably includes the preliminary step of identifying the species of termite to be eradicated and selecting the cellulose material in the form of fine wood particles and of a species of timber for the bait such that the bait is at least as acceptable as a food to the termites as the matter being attacked at the foraging location. WHAT WE CLAIM IS:

1. A bait for eradicating termites of a colony which comprises a paste-like product formed from a water-based gel, a cellulose

material in finely divided form so as to be acceptable as a food for the species of termite to be eradicated, and a second material having a delayed insecticidal property on the termites whereby by natural process the bait is transmitted to other termites which are killed after receiving a sufficient dose.

2. A bait as claimed in Claim 1, wherein the cellulose material is fine sawdust or wood flour of a selected species of timber so as to be a preferred food for the termites.

3. A bait as claimed in Claim 2, wherein the timber is Eucalyptus rezrodoalta or Eucalyptus reg?2ans.

4. A bait as claimed in any of the preceding Claims, wherein the cellulose material has a particle size not exceeding 500 J.

5. A bait as claimed in any of the preceding Claims, wherein said water-based gel is an agar gel.

6. A bait as claimed in Claim 5, when the gel comprises about 1% agar.

7. A bait as claimed in any of the preceding Claims, wherein said second material is a slow acting insecticide which has a lethal effect on the termites within about 3 days whereby at least a substantial proportion of a termite colony can be eradicated.

8. A bait as claimed in any of Claims 1 to 6, wherein said second material is a micro-encapsulated toxic material of particle size not greater than that of the cellulose material.

9. A bait as claimed in Claim 8, wherein the toxic material is toxic to the symbiotic protozoa present in the hind gut of the termites.

10. A bait as claimed in Claim 8, wherein the toxic material is selected from halobenated hydrocarbons, organo-phosphorus derivatives for blocking specific enzyme systems of the termites, and boicides selective against protozoa.

11. A bait as claimed in any of the preceding Claims, wherein the bait is located in a holder having a cavity for the bait the holder being adapted to be inserted into and mounted at a foraging location of the termites.

12. A bait as claimed in any one of the preceding Claims, wherein the water is provided by an agar gel which has distributed therein an attractant material.

13. A bait for insecticides substantially as herein described in either of the examples of the invention.

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

15. A method as claimed in Claim 14 and further comprising the preliminary step of identifying the species of termite to be eradicated and selecting the cellulose material in the form of fine wood particles and of a species of timber for the bait such that the bait is at least as acceptable as a food -to the termites as the matter being attacked at the foraging location.