GB2174907A - Controlling insects with entomophilic nematodes - Google Patents

Abstract

A method of controlling insects, which obviates the need to use insecticides, consists in providing a supply of live entomophilic nematodes on an absorbent pad 2 that is kept moist by a continuous supply of aqueous medium 5, and applying an insect attractant, for example a pheromone, on or near the pad 2 to attract insects into contact with the nematodes. The nematodes are provided in their infective larval stage. They parasitise insects alighting on the surface 3 of the pad 2, and release pathogenic bacteria which eventually kill the insect hosts. An insect breeding medium 4 may be placed on the pad 2 to encourage insects to remain in contact with the pad for prolonged periods. <IMAGE>

Description

SPECIFICATION Method, device, and kit for controlling insects This invention relates to a method, a device, and a kit for controlling insects, especially the common housefly fMusca domestica) and related species of flying insect pests.

Since 1957, successful control of housefly infestations in the United Kingdom has been achieved using natural pyrethrins and organophosphorous insecticides. However, over the past decade there has been increasing evidence of widespread resistance to chemical insecticides in adult populations of the housefly even though different insecticides are being introduced. This has created a particular control problem where large numbers of flying insects can occur, for example in intensive animal units such as piggeries and poultry houses.

It is one object of the present invention to seek to overcome the above-mentioned problem of using insecticides by providing a method of controlling insects, especially flying insects of the type exemplified by the common housefly, which avoids or reduces the need to use insecticides.

It is known that certain species of entomophilic nematodes, particularly those belonging to the families Steinernematidae and Heterorhabditidae, produce an infective larval stage capable of parasitising insect hosts and releasing an associated pathogenic bacteria Xenorhabdus sp) which causes septacaemia in the insect. As a result, the nematode-parasitised insect host is usually killed rapidly. However, these entomophilic nematodes containing pathogenic bateria only thrive under certain conditions, and the free living infective larval form of these nematodes may be subject to desiccation.It is therefore a difficult - problem, firstly to maintain these nematodes in a viable state in their ineffective larval stage, and secondly to promote contact between these nematodes and potential insect hosts, in order to exploit the nematodes as an effective alternative to chemical insecticides.

It is a further object of the present invention to seek to overcome or at least mitigate the above-mentioned problems associated with the use of nematodes.

According to the present invention in a first aspect, there is provided a method of controlling insects which comprises providing, in an area where insects are present, a source of live entomophilic nematodes in their infective larval stage disposed on an absorbent nematode support means that is kept continuously moist to prevent the nematodes from desiccating, and further providing an insect attractant disposed on, within, or adjacent the support means such that insects in the vicinity of the nematode support means are attracted onto the support means and are thereby parasitised by the nematodes, said nematodes being of a species which contains pathogenic bacteria capable of killing the insects.

According to a second aspect of the present invention there is provided a device for use in the method of the first aspect, which comprises a source of live entomophilic nematodes in their infective larval stage disposed on an absorbent nematode support means that is kept continuously moist to prevent the nematodes from desiccating, the nematodes being of a species which contains pathogenic bacteria capable of killing insects, and an insect attractant disposed on, within, or adjacent the nematode support means for attracting insects into contact with the nematodes.

In use, the absorbent nematode support means must be kept moist to maintain the viability of the nematodes and to prevent them from desiccating. The support means may be kept moist using water or other aqueous media. The support means may preferably be kept moist using an aqueous medium containing a nematode nutrient. Examples of suitable nematode nutrients are fluid nutrient agars, sugars, glycerol, and nutrient broths.

The nematode support means may compromise an absorbent material which can be provided before use with all the necessary supply of liquid to keep it moist in use. Alternatively, it may compromise an absorbent material which needs to be continuously or intermittently supplied with liquid during use to prevent it from drying out. A suitable nematode support means, which is preferably in the form of an absorbent pad, can be made from cotton wool, cellulose fibres, synthetic fibres, glass fibres, polyethylene foam, vermiculite, purlite, potting compost, wheatfeed (bran), or capilliary matting.

The insect attractant may comprise a phermone, such as the fly sex pheromone z-9-tricosene, an insect attracting amine, a yeast or a yeast extract. The attractant may be in pure form, in aqueous solution, or in a chemical composition. The nematode support means may be impregnated with the attractant orthe attractant may be supplied at its site of use in a suitable form, such as in an aqueous solution. The attractant may also be applied in other ways, for example impregnated onto various substrates such as polyethylene or rubber and fixed to the nematode support means.

An insect arrestant may also be provided in contact with or adjacent the nematode support means in order to encourage the insects to remain close to the nematodes for prolonged periods once they have been attracted by the insect attractant. This increases the probability that insects will become parasitised by the nematodes. The arrestant may comprise an insect food, such as a carbohydrate, a protein or a fat, or an insect breeding medium, such as a fly breeding medium containing one or more of wheat feed, grassmeal, dried milk and live yeast.

The nematodes are preferably disposed on the nematode support means at a concentration of from 102 to 106, most preferably from 103 to 1 05, nematodes per cm3 of absorbent.

The nematode support means may be kept moist by a continuous or intermittent supply of liquid provided from a remote source, for example tap water from the mains. Alternatively, a reservoir of liquid may be provided to supply liquid to the nematode support, in which case the reservoir will form part of the device of the present invention.

The reservoir may be positioned separate from the nematode support means, for example above or below it. The device will therefore include a liquid supply means, for example a tube or duct, connecting between the resevoir and the nematode support means. The resevoi may be mounted above the nematode support means, in which case liquid from the resevoir may be supplied to the nematode support under gravity, either directly or through a syphon arrangement. Alternatively, the resevoir may be mounted below the nematode support means, in which case the device will include a pump means for pumping liquid from the resevoir via the liquid supply means to the nematode support means.A preferred liquid supply means where the resevoir is mounted below the nematode support, comprises a drivable continuous band of absorbent material one portion of which is submerged in the resevoir and a further portion of which makes slideable contact with the nematode support means. The band may be driven by a pump means comprising one or more powered rollers operated in contact with at least one surface of the band. In use, the driven band picks up liquid from the resevoir and continuously transfers a portion of this liquid to the nematode support means as it slides against it thereby keeping the support means moist, and then returns to the resevoir. The rate of liquid transfer to the nematode support means may be controlled by suitably adjusting the speed of the one or more rollers.

In an alternative and preferred embodiment of the device according to the present invention, the nematode support means is partly submerged within the resevoir of liquid such that the absorbent material of the support means draws liquid up into that portion of the support means which is exposed to the atmosphere. The advantage of this simpler, preferred embodiment of the present device is that it does not require a separate liquid supply means nor a means of controlling the flow of liquid through the supply means. Where the nematode support means is in the form of an absorbent pad, the pad is preferably inclined from the horizontal such that only the lower portions of the pad are in contact with the liquid in the resevoir.

The pad is preferably mounted on a rigid support.

According to the present invention in a third aspect, there is provided a kit for use in the method according to the first aspect, which comprises (i) a supply of live entomophilic nematodes in their inffective larval stage, the nematodes being of a species that contains a pathogenic bacteria capable of killing insects, (ii) an absorbent nematode support means, (iii) optionally, a liquid medium for preventing the nematodes from desiccating in use, (iv) an insect attractant supplied separately, in contact with the nematode support means, or optionally in the liquid medium where the liquid medium is provided in the kit, and, optionally, (v) a set of instructions for applying the nematodes onto the nematode support means.

The entomophilic nematodes employed in the present invention preferably belong to the families Heterorhabditidae of which the species H.heliothidis is an example, and Sternernematidae, of which the species S.bibionis and S. feltiae are examples. These nematodes occur in nature in many soil types and climatic regions and can be cultured by, for example, the methods described by R.A. Bedding (Nematologica 1981 27109-114, and Annals of Applied Biology 1984104,117-120). Suitable nematodes are available from the Glasshouse Crops Research Institute, Littlehampton, West Sussex, England.

The present invention is primarily intended to be used for controlling M.domestica (the common housefly). It may also be used to control certain terrestial insect pests such as cockroaches, other adult flying insect pests such as Calliphora vicina (bluebottle), Lucilia sericata (green bottle) Stomoxys calcitrans (stable fly), Pollenia rudis (cluster fly), Fannia canicularis (lesser housefly) and Delia brassicae (cabbage root fly), and any other insect susceptible to attack by entomophilic namatodes in the infective stage. One important application of the invention is in the eradication or control of insect pests in intensive animal units such as piggeries or poultry houses. The invention may also be useful in domestic and food processing locations.

Method and devices in accordance with the present invention will now be described by way of Example only with particular reference to the accompanying drawings in which Figure 1 is a sectioned elevation of a third insect controlling device in accordance with the invention, Figure 2 is a plan view of a fourth insect controlling device in accordance with the invention, Figure 3 is a sectioned elevation along line A-A' of the fourth insect controlling device illustrated in Figure 2, Figure 4 is a sectioned elevation of a fifth insect controlling device in accordance with the invention, and Figure 5 is a sectioned elevation of a sixth insect controlling device in accordance with the invention.

Example 1 Materials Two species of entomophilic nematode were used Heterorhabditis heliothidis (NZ strain) and Steinernema feltiae (Agriotos strain), and these were cultured in vivo in the larvae of Galleria mellonella. Infective nematodes were extracted from G. mellonella by the Baermann funnel technique, and were counted using a Fenwick multichamber counting slide (Doncaster, Edwards & Shepherd 1967). Adults of a strain of M,domestica with multiple insecticide-resistance (G strain) were used as hosts. This strain has been in laboratory culture since 1980.

Method Adult flies were tested in plastic plant-propagating units (approx 6.5 litres volume), each contained drinking water and a bait area. In the bait area was placed a first insect-controlling device according to this Example, consisting of a 10 cm diameter black pad of Lantor capillary matting (as used in plant nurseries) supported horizontally on three entomological pins embedded in corks. Each bait disc was sprayed for 1 second with a water based spray containing the fly sex phermone z-9-tricosene (0.5%). A 3 cm outside diameter,2.5 inside diameter annulus of fly breeding medium containing wheat-feed, grassmeal, Stortex (BNM Chemicals Ltd), dried milk and live yeast in the ratio by weight of 34:17:1 :1 :1 was then placed on the centre of the disc.Nematodes were added in 4 ml of tap water; 3 ml around the outside of the annulus and 1 ml in the centre, within but not in contact with the breeding medium. Approximately fifty adult flies (mixed sex) were introduced into each unit.

The following treatments were carried out at 25"C.

(a) HHeliothidis: three replicates eacy of 2 x 106 nematodes and three 1 x 106 (b) Sfeltiae: two replicates of 1 x 106 nematodes (c) Three replicates without nematodes were used as controls.

After 24 h the number of flies "knocked-down" were assessed (flies were considered "knocked-down" if they were unable to co-ordinate their locomotory movements), and after 48 h mortality was recorded.

Parasitism and septicaemia were also assessed after 48 h by dissecting a random sample of 20 dead flies from each replicate of treatment and control.

Results Following 24 h exposure to the baits containing 1 x 106 nematodes/4 ml water, 90.3% of adult flies were knocked down by H. Heliothidis and 88.9% by S feltiae; control mortality was low at 9.4% (Table 1). After 48 h, control mortality was high due to starvation, the flies being fed only water during the experiment, but all the treated flies were parasitised by S feltiae and 93.3% by HHeliothidis. There was no evidence of parasitism or bacterial infection in the untreated flies.

Dissection of the treated flies showed that most Hhellothidis were confined to the head cavity (R = 30 per fly), and thorax (2 = 25 per fly). A few nematodes were also recovered from the abdomen and proboscis.

There was little differences between the two doses of llhellothidis in the numer of flies showing septicaemia. Decay was evident in 60% of the flies, particularly in the head and thorax and to a lesser degree in the abdomen. In a few flies the wing muscles had decayed. Very larger numbers of S feltiae ( > 200/fly) were found in 60% of the parasitised flies, occuring mostly in the head cavity or the thorax and abdomen, a few nematodes were also recovered from the proboscis and gut. All parasitised flies showed evidence of septicaemia as described above.

TABLE 1 The percentage of M. domestica adults parasitised and knocked down after 48 h exposure to each of two species of nematodes Nematode Species Dose per Knockdown Parasitism Mortality 4 ml water (%) (%) (%) 24h 48h 48h Hheliothidis 2 x 106 54.9 93.3 100 Hheliothidis 1 x 106 90.3 93.3 100 Sfeltiae 1 x 106 88.9 100 100 Control 0 9.4 0 92.6 Example 2 Materials A third species of entomophilic nematode, Steinernema bibionis were cultured and extracted using the same methods described in Example 1 above. An insecticide susceptible strain (Cooper) of adult houseflies were used as hosts.

Method Adult flies were tested in 30 x 30 cm aluminium cages having two open sides covered with transparent polythene. A second insect-controlling device according to this Example was placed centrally on the floor of each treatment cage, and next to each device was placed a 4.5 cm diameter plastic pot containing cotton wool soaked in milk to provide the flies with a source of moisture and protein.

The insect-controlling device according to this Example consisted ofthree 0.3 cm thick, 9 cm diameter discs of Lantor capillary matting vertically stacked together and supported horizontally from below in the base of a 9 cm diameter plastic petri dish. The lower two discs were thoroughly soaked in tap water, the excess allowed to run off before being placed in the dish. The third disc was then dampened with the tap water, and a 9 cm outside diameter, cm inside diameter annulus of they breeding medium used in Example 1 was placed centrally on the disc. The third disc and annulus were then placed on top of the other two lower discs already in the petri dish. The top disc was then sprayed for 1 second with a water based spray containing the fly sex pheromone z-9-tricosene (0.05%).Nematodes were then added in 5 ml of tap water to the top disc within the annulus of fly food, and the assembled device then placed centrally on the floor of each cage. Approximately 100 (50 males and 50 females) flies were then introduced into each unit.

The following treatments ((a), (b), and (c)) were carried out separately at 250C.

(a) Bait pads each containing the following nematode concentrations:- nil (control), 1 x 106,500,000 and 250,000. (b) Bait pads were treated with 500,000 nematodes and sprayed for 1 second with the fly sex pheromone z-9-tricosene (muscamone) ! and compared with unsprayed treated pads. Controls without nematodes were similarly sprayed. The relative humidity for experiments (a) and (b) was 74% - 85% (c) Bait Pads were treated with 1 x 106, 500,000 or 250,000 nematodes, and these treatments and controls were sprayed with muscamone. This experiment was carried out at approximately 90% rh (rh = relative humidity).

Assessment of mortality was made at intervals of 24,48 and 72h, at which intervals dead flies were removed from each cage, sexed and stored individually prior to dissection in 7.5 x 2.5 cm glass tubes containing a 5% formaldehyde solution. All experiments were terminated after 72h, surviving flies were anaesthetised with CO2, sexed, and similarly stored in formaldehyde. A random sample of approximately 25 dead or surviving flies from each replicate were dissected and the number of nematodes found in the head, thorax or abdomen were recorded. If less than 25 flies were killed or survived, all were dissected; 25 untreated controls were similarly dissected. The bait pads were dismantled and placed in 1 litre of tap water for 3h to extract the nematodes, the proportion of dead and alive nematodes was then assessed.

*Muscamone is a registered Trade Mark TABLE 2 Results of Treatment (a) Nematode mortality (%) % Dead flies % nematode Dose/S ml after72h Showing septiciaemia survival on bait water after 72h pads after 72h M F M F 1 x 106 53.0ab 83.0a 50.5 95.5 33.0 500,000 54.0b 93.0b 56.0 100 28.0 250,000 38.0a 97.0b 37.5 88.0 44.0 Control 6.sic S.0 0 0 (nil) M = maie F = female Figures within each sex only followed by the same letter (a, b, or c) are not significantly different at P c 0.05, where P is probability level.

The results oftreatment a) are presented in Table 2 above, and show S.bibionis to be an effective parasite of adult M. domestica, with 83% females killed at all doses used. However, significantly fewer males than females were killed at each dose. There was no dose-mortality reiationship for S.bibionis, although significantly higher mortality of females was achieved at the two lowest doses of 500,000 and 250,000 nematodes.

Dissection of the treated flies showed that most S.bibionis were confined to the abdomen or thorax with a few recovered from the head, ovipositor and proboscis. There was no difference between male and female flies in the distribution of the namatodes in the body cavity, but larger numbers of nematodes were recorded from female flies. Flies which died during the first 24h contained the largest number of nematodes, while flies which died between 48-72h contained the least. The developing stages of N.bibionis were found in a few flies. Nematodes were also observed in 9.0% of the survivors from all the treatments. The majority of dead female showed symptoms of septicaemia, but bacterial infection was significantly less evident in the males.

There was no evidence of infection in the untreated control flies.

Because of the variability of the results in experiments b) and c) no valid comparisions of fly mortality were made between treatments, but in treatment b) significantly more female flies were killed after exposure to muscamone sprayed bait pads compared with the numbers killed after exposure to unsprayed pads.

In treatments a) and b), carried out &commat; 74-85% rh, the survival of nematodes on the bait pads after 72h exposure was low (R = 35%), but in treatment c) maintained &commat; 90% rh nematodes survival was almost doubled (x = 67.4%).

Example 3 (Reference Figure 1J A third insect controlling device according to this Example is illustrated in section in Figure 1, and consists of an open shallow circular dish 1 containing a dampened pad 2 of absorbent material whose top surface 3 has been sprayed with a solution of a pheromone insect attractant. An annulus 4 of the fly breeding medium of Example 1 is positioned on top of the pad 2. A supply of entomophilic nematodes in their infective larval stage is applied in a liquid medium onto the pad 2, though not in contact with the annulus 4.

The pad 2 is kept continuously moist by a supply of liquid (eg water) dripped onto the pad from a resevoir 5 of liquid within a conical flask 6 positioned above the pad on a support 7. Liquid is fed from the flask 6 through a wick 8 of hessian-type material which in its position illustrated in Figure 1 acts as a slow liquid syphon. The wick 8 is enclosed within a flexible tube 9 (eg of plastic) which is open at both ends. The tube prevents the wick from drying out. An adjustable clamp (clamp mechanism not shown) allows for control of liquid flow through the wick 8 by closing the jaws 10 of the clamp onto the tube 9.

In use, the device is placed in an area affected by insects, and the insects are drawn onto the top surface 3 of the pad 2 by the combined action of the pheromone and the fly breeding medium, and are thereby infected by the nematodes on and within the pad. Liquid drips from the end 11 of the wick 8 to keep the pad 2 continuously moist and so maintain the viability of the nematodes on the pad.

Example 4 (Reference Figures 2 and 3) Afourth insect controlling device according to this Example is illustrated in Figures 2 and 3, and consists of a hollow cone 20 of rigid material (eg glass or plastic) whose base is submerged in a resevoir 21 od liquid (eg water) within an open shallow circular dish 22. The dish 22 provides support for the base of the cone 20. The outside surface of the cone is coated with a layer 23 of capilliary-type absorbent material which is treated with a pheromone insect attracted and infective entomophilic nematodes.

In use, the capilliary action of the absorbent material 23 draws liquid from the resevoir 21 up the outside surface of the cone 20 towards its apex as moisture is lost from the material due to evapouration. The material 23 is thereby kept continuously moist, so maintaing the viability of the nematodes which will infect insects alighting on the material.

Example 5 (Reference Figure 4) Afifth controlling device according to this Example is illustrated in Figure 4, and is of similar construction to that illustrated in Figures 2 and 3, except that instead of a rigid cone 20 there is provided a solid upright cylinder 30 which is coated with a layer 31 of capiliary-type absorbent material treated with a pheromone insect attractant and infective entomophilic nematodes. As before, the capilliary action of the absorbent material 31 draws liquid from the resevoir 21 in the dish 22 up the outside surface of the cylinder 30 as moisture is lost from the material due to evapouration, thereby keeping the layer 31 containing the nematodes continuously moist.

Example 6 (Reference Figure 5) A sixth insect controlling device according to this Example is illustrated in Figure 5, and consists of a continuous band 40 of absorbent material connecting between a pad 41 of absorbent material held within an open shallow circular dish 42, and a resevoir 43 of liquid within an open tank 44 positioned directly below the dish 42. Support brackets 45,50 having lips 52 are provided to prevent movement of the dish 42 and tank 44. A semi-cylindrical recess 46 which extends through the support brackets 45 and bottom of the dish 42 and into the pad 41 receives a revolvable upper roller 47 over which the band 40 fits. The axis of the roller 47 is horizontal.The roller 47 is positioned within the recess 46 on mountings (not shown) to allow the band 40 to make slideable contact with the curved surface of the pad 41 within the recess when the roller is revolved about its axis.

The band 40 is also fitted over a revolvable lower roller 48 mounted parallel to and directly below the upper roller 47 within the tank 44. The shaft 40 of the upper roller 47 is connected to a motor (not shown) which provides the power to drive the band 40 continuously or intermittently through the resevoir 43 and across the underside of the pad 41.

As in earlier Examples, the pad 41 is provided with a source of live antomophilic nematodes in their infective larval stage, and is sprayed with a solution of a pheromone insect attractant. In use, the motor (not shown) is switched on and the absorbent band 40 picks up liquid as it passes through the resevoir 43. A portion of the liquid (eg water) is transfered to the pad 41 as the liquid-laden belt 40 rubs passed the underside of the pad within the recess 46. By making suitable adjustment to the speed of the motor, the rate of liquid transfer can be matched to the loss of liquid from the open dish 42 by evapouration, thereby ensuring that the moisture content of the pad 41 containing the nematodes remains fairly constant. Once the band 40 has passed the recess 46 it returns to the resevoir 43 to pick up more liquid.

Claims (58)

1. A method of controlling insects which comprises providing, in an area where insects are present, a source of live entomophilic nematodes in their infective larval stage disposed on an absorbent nematode support means that is kept continuously moist to prevent the nematodes from desiccating, and further providing an insect attractant disposed on, within, or adjacent the support means such that insects in the vicinity of the nematodes support means are attracted onto the support means and are thereby parasitised by the nematodes, said nematodes being of a species which contains pathogenic bacteria capable of killing the insects.

2. A method according to claim 1 wherein the nematode support means is kept continuously moist with an aqueous medium.

3. A method according to claim 2 wherein the aqueous medium contains a nematode nutrient.

4. A method according to claim 3 wherein the nematode nutrient comprises a fluid nutrient agar, a sugar, glycerol, or a nutrient broth.

5. A method according to any one of the preceding claims wherein the absorbent nematode support means comprises cotton wool, cellulose fibres, synthetic fibres, glass fibres, polyethylene foam, vermiculite, purlite, potting compost, wheatfeed or capilliary matting.

6. A method according to any one of the preceding claims wherein the absorbent nematode support means is in the form of an absorbent pad.

7. A method according to any one of the preceding claims wherein the insect attractant comprises a pheromone, an insect-attracting amine, yeast or a yeast extract.

8. A method according to claim 7 wherein the insect attractant comprises z-9-tricosene.

9. A method according to any one of the preceding claims wherein an insect arrestant is further provided in contact with or adjacent the nematode support means.

10. A method according to claim 9 wherein the insect arrestant comprises an insect food or an insect breeding medium.

11. A method according to claim 10 wherein the insect food comprises a carbohydrate, a protein or a fat and the insect breeding medium comprises one or more of wheat feed, grassmeal, dried milk and live yeast.

12. A method according to any one of the preceding claims wherein the nematodes are disposed on the nematodes support means at a concentration of from 102 to 106 nematodes per cm3 of absorbent.

13. A method according to claim 12 wherein the nematodes are disposed on the nematode support means at a concentration of from 103 to 105 nematodes per cm3 of absorbent.

14. A method according to any one of the preceding claims wherein the pathogenic bacteria are of the species Xenorhabdus sp.

15. A method according to claim 14 wherein the nematodes belong to the families Steinernematidae or Heterorhabditidae.

16. A method according to claim 15 wherein the nematodes belong to the species H.heliothidis, S.bibionis and S feltiae.

17. A device for use in the method according to claim 1, which comprises a source of live entomophilic nematodes in their infective larval stage disposed on an absorbent nematode support means that is kept continuously moist to prevent the nematodes from desiccating, the nematodes being of a species which contains pathogenic bacteria capable of killing insects, and an insect attractant disposed on, within, or adjacent the nematode support means for attracting insects into contact with the nematodes.

18. A device according to claim 17 wherein the nematode support means is kept continuously moist with an aqueous medium.

19. A device according to claim 18 wherein the aqueous medium contains a nematode nutrient.

20. A device according to claim 19 wherein the nematode nutrient comprises a fluid nutrient agar, a sugar, glycerol, or a nutrient broth.

21. A device according to any one of the preceding claims 17 to 20 wherein the absorbent nematode support means comprises cotton wool, cellulose fibres, synthetic fibres, glass fibres, polyethylene foam, vermiculite, purlite, potting compost, wheatfeed or capilliary matting.

22. A device according to any one of the preceding claims 17 to 21 wherein the absorbant nematode support means is in the form of an absorbent pad.

23. A device according to any one of the preceding claims 17 to 22 wherein the insect attractant comprises a phermone, an insect-attracting amine, yeast or a yeast extract.

24. A device according to claim 23 wherein the insect attractant comprises z-9-tricosene.

25. A device according to any one of the preceding claims 17 to 24 wherein an insect arrestant is further provided in contact with or adjacent the nematode support means.

26. A device according to claim 25 wherein the insect arrestant comprises an insect food or an insect breeding medium.

27. A device according to claim 26 wherein the insect food comprises a carbohydrate, a protein or a fat and the insect breeding medium comprises one or more of wheat feed, grassmeal, dried milk and live yeast.

28. A device according to any one of the preceding claims 17 to 27 wherein the nematodes are disposed on the nematode support means at a concentration from 102 to 106 nematodes per cm3 of absorbent.

29. A device according to claim 28 wherein the nematodes are disposed on the nematode support means art a concentration of from 103 to 10 nematodes per cm3 of absorbent.

30. A device according to any one of the preceding claims 17 to 29 wherein the pathogenic bacteria are of the species Xenorhabdus sp.

31. A device according to claim 30 wherein the nematodes belong to the families Steinernematidae or Heterorhabditidae.

32. A device according to claim 31 wherein the nematodes belong to the species H.heliothidis, S.bibionis and S. feltiae.

33. A device according to any one of the preceding claims 17 to 32 wherein the device further includes a resevoir of liquid.

34. A device according to claim 33 wherein the resevoir and nematode support means are separate from one another and are connected by a liquid supply means.

35. A device according to claim 34 wherein the resevoir is mounted below the nematode support means and the liquid supply means includes a pump means for pumping liquid from the resevoir to the support means.

36. A device according to claim 35 wherein the liquid supply means comprises a drivable continuous band of absorbent material one portion of which is submerged in the resevoir and a further portion of which makes slideable contact with the nematode support means.

37. A device according to claim 36 wherein the band is connected to a pump means comprising one or more powered rollers in contact with at least one surface of the band.

38. A device according to claim 37 wherein the speed of the one or more rollers is controllable.

39. A device according to claim 33 wherein the absorbent nematode support means is partially submerged within the reservoir of liquid.

40. A device according to claim 39 wherein the nematode support means comprises an absorbent pad and the pad is inclined from the horizontal such that only the lower portions of the pad are in contact with liquid in the resevoir.

41. A device according to claim 39 or claim 40, wherein the nematode support means is supported on a rigid support.

42. A device for controlling insects substantially as hereinbefore described with particular references to the drawings and any one of the Examples.

43. A kit for use in the method according to claim 1, which comprises (i) a supply of live entomophilic nematodes in their infective larval stage, the nematodes being of a species that contains a pathogenic bacteria capable of killing insects, (ii) an absorbent nematode support means, (iii) optionally, a liquid medium for preventing the nematodes from desiccating in use, (iv) an insect attractant supplied separately, in contact with the nematode support means, or optionally in the liquid medium where the liquid medium is provided in the kit, and, optionally, (v) a set of instructions for applying the nematodes onto the nematode support means.

44. A kit according to claim 43 wherein the liquid medium is an aqueous medium.

45. A kit according to claim 44 wherein the aqueous medium contains a nematode nutrient.

46. A kit according to claim 45 wherein the nematode nutrient comprises a fluid nutrient agar, a sugar, glycerol, ora nutrient broth.

47. A kit according to any one of the preceding claims 43 to 46 wherein the absorbent nematode support means comprises cotton wool, cellulose fibres, synthetic fibres, glass fibres, polyethylene foam, vermiculite, purlite, potting compost, wheatfeed or capilliary matting.

48. A kit according to any one of the preceding claims 43 to 47 wherein the absorbent nematode support means is in the form of an absorbent pad.

49. A kit according to any one of the preceding claims 43 to 48 wherein the insect attractant comprises a pheromone, an insect-attracting amine, yeast or a yeast extract.

50. A kit according to claim 49 wherein the insect attractant comprises z-9-tricosene.

51. A kit according to any one of the preceding claims 43 to 50 further including an insect arrestant.

52. A kit according to claim 51 wherein the insect arrestant comprises an insect food or an insect breeding medium.

53. A kit according to claim 52 wherein the insect food comprises a carbohydrate, a protein or a fat and the insect breeding medium comprises one or more of wheat feed, grassmeal, dried milk and live yeast.

54. A kit according to any one of the preceding claims 43 to 53 wherein the number of nematodes in the kit is sufficient to provide a concentration of nematodes on the absorbent nematode support means of from 102 to 106 nematodes per cm3 of absorbent.

55. A kit according to claim 54 wherein the number of nematodes in the kit is sufficient to provide a concentration of nematodes on the absorbent nematode support means of from 103 to 105 nematodes per cm3 of absorbent.

56. A kit according to any one of the preceding claims 43 to 55 wherein the pathogenic bacteria are of the species Xenorhabdus sp.

57. A kit according to claim 56 wherein the nematodes belong to the families Steinernematidae or Heterorhabditidae.

58. A kit according to claim 57 wherein the nematodes belong to the species H.heliothidis, S.bibionis and S. feltiae.