PEST CONTROL

Abstract: A method of controlling a population of pest insects in an area of vegetation is described in which a number of fixed release sites (13, 21) for control insects is defined throughout the area to be protected, and a predetermined number of pre-adult control insects is placed at each release site (13, 21) at intervals by dispensing a measured volume of pre-adult control insects from a bulk supply using a dispenser (1). A dispenser (1) for use in the method is also disclosed, and a multi-cell release site (13) is described wherein each delivery of control insects is maintained separate from previous deliveries.

Description: The present invention relates to pest control in horticulture, and is primarily concerned with a distribution system for biological control agents in glasshouses. Currently, biological control agents such as parasitic wasp larvae, or pupae of prey insects parasitised by such wasps, are used in glasshouses to control pest insects. Distribution of such agents in the glasshouse is currently achieved by the supplier providing a carrier or sealed container holding a predetermined number of control insects either as larvae or pupae of parasitised pest insects sufficient for a single site, the container or carrier being first opened and then placed at the appropriate location within the glasshouse. In time, the control insects reach a mature stage whereupon they emerge as adult control insects and leave the container in search of pest insects upon which to prey. Generally, containers are supplied on a weekly basis, since the insects emerge from their pupae in a few days. This system has serious disadvantages both in terms of transportation of containerised control insects and in terms of distribution in the glasshouse. Firstly, the container must provide ample free space for the control insects to emerge from their pre-adult stage, and thus the volume of the container is necessarily many times that of the control insects being transported. A major disadvantage of this transportation system is that, due to the relatively small volume of control insects in relation to the packaging volume, thermal insulation of the insects is difficult and temperature fluctuations inside the package can permit premature emergence of the insects if too high a temperature is reached, or death of the insects if the temperature is too low, with obvious disadvantage to the end user. Secondly, and more importantly with regard to the efficacy of the control operation, the location at which the container is deployed in the glasshouse depends largely on the assiduity of the glasshouse operator in following the site plan determined for the pest control operation. It has been found that operators will deploy opened containers only in areas easily accessible from walkways in the glasshouse, leaving remoter regions unprotected. A method according to the preamble of claim 1 is known, see in particular GB-A-2052261. The present invention seeks to provide a distribution system for control insects, mites or other arthropods which avoids the problems inherent in the prior art. Pest control in an area of vegetation is achieved by defining a number of fixed release sites in and about the area, and placing at each site a predetermined number of pre-adult control insects at intervals, the control insects being placed at the sites by delivering a fixed volume of pre-adult control insects from a dispenser. According to the invention as claimed in claim 1, a method of controlling a population of insect pests in an area of vegetation comprises the steps of defining a number of fixed release sites in and about the area, and placing a predetermined number of pre-adult control insects at each release site at predetermined intervals to provide a continuing supply of emerging control insects at each release site, the control insects being placed at the release sites by delivering a predetermined volume of pre-adult insects from a bulk supply using a dispenser, and is characterised by the use of a dispenser comprising a container whose interior is divided to define a storage volume and a measuring volume connected via a transfer opening, the storage volume being so configured that with the dispenser in a first orientation the pre-adult insects in the storage volume are guided towards the transfer opening so as to flow therethrough until the measuring volume is filled, the measuring volume having an outlet passage positioned so as to be inaccessible to the pre-adult insects when the dispenser is in its first orientation, movement of the dispenser to a second orientation causing pre-adult insects remaining in the storage volume to fall away from the transfer opening, and causing the pre-adult insects in the measuring volume to be discharged through the outlet passage. Preferably the movement required is an inversion of the container. However, rotation of the container about a horizontal axis and through an angle of less than 180° may be sufficient to dispense the material. In a preferred dispenser for use in the method, there is provided a body of cylindrical shape having an open upper end and its lower end tapered downwardly to a point, a lid closing the open upper end and having a dispensing tube extending axially to contact the lower end wall of the container along a line encircling its point, the tube being provided at its one end with one or more cutouts to afford access between the lumen of the tube and the interior of the container. In such a dispenser, control insects or a mixture of control insects and other granular material such as nutrient, which will hereinafter be referred to as 'pupae' are placed in the container, and the cap and dispenser tube applied. Inverting the container allows one 'dose' of pupae to exit via the dispensing tube, the remainder being retained in the container. Righting the dispenser recharges the dispensing tube with the required volume of pupae for the next 'dose'. Preferably the dispenser tube is formed with a pair of diametrically opposite cutouts at its one end contacting the conical lower end wall of the container. In such an arrangement, it is preferable to invert the container about an axis passing through both cutouts. This minimises the amount of material which falls back through the cutouts during inversion. Clearly, when only one such cutout is provided the preferred inversion movement is one which keeps the cutout facing upwardly, to minimise loss of material from the dispensing volume through the cutout. Preferably the control insects are delivered to the release sites once a week, but more or less frequent delivery is possible. Control insects may be delivered daily, or monthly, or at any interval therebetween. For weekly delivery, about 100 insects are placed at each site during each delivery. Release sites are preferably spaced evenly throughout the infested area, ideally one release site being provided per 100 square metres of area to be covered. In cold weather the release sites may be positioned adjacent heat sources to promote the emergence of the control insects. In the embodiment of the invention to be described later, pre-adult stages of encarsia are used as the control insects to regulate populations of whitefly in glasshouse crops. Other, alternative, control insects are usable with the method, depending on the pest insect species to be controlled. Examples of suitable control insects are mites, wasps or arthropods. Mites are most easily used in adult or pre-adult stages, wasps are most suitable when in pre-adult stages, and arthropods can be used at any stage of their development. An embodiment of the invention will now be described with reference to the accompanying drawing, which is a longitudinal sectional view of a dispenser for granular material. Referring now to Figure 1, there is seen a cylindrical container 1 having a downwardly tapered conical base wall 2. A cap 3 closes the upper end of the container 1, and a dispensing tube 5 extends axially down from the cap 3 to contact the base wall 2. Two diametrically opposed cutouts 6 at the one lower end of the dispensing tube 5 allow access from the interior of container 1 to the lumen of the dispensing tube 5 and constitute a transfer opening, the axial extend of the cutouts 6 being important as will be discussed below. The dispensing tube 5 extends upwardly out of the cap 3, the other upper exit end 4 of the tube 5 being bevelled to form a chute. A closure 7 is arranged to block the dispensing tube 5, preferably extending down the dispenser tube to close it at the upper ends of the cutouts 6. Operation of the dispenser is simple; pupae are loaded into the container 1 by removing screw threaded cap 3 and filling the container to the required level. Indicia 8 may be provided on the container, calibrated to show the approximate number of pupae required to fill the container to a predetermined level. Alternatively, a label bearing graduations may be applied to the container. When the pupae are in place, the cap 3 and dispensing tube 5 are replaced. To dispense a single 'dose' of pupae, the closure 7 is removed and the container is simply inverted, whereupon the pupae are discharged by gravity from the tube 5. Preferably the container is inverted about an axis passing through the two cutouts 6, so that the number of pupae falling out of the tube 5 through the cutouts 6 is minimised. The outer end of the tube 5 may be shaped to indicate the correct orientation for dispensing, such as by bevelling the end 4 of the tube 5 to form a 'chute', or by bending the tube adjacent its end about a transverse axis. This will encourage the operator to invert the dispenser correctly, since the end of the dispenser tube will have a perceived preferred orientation. On righting the container, the conical base wall 2 acts to guide pupae down towards the cutouts 6, whereupon the lower end of the dispenser tube 5 is filled to a predetermined height depending on the axial extent of the cutouts 6. Clearly the volume of the filled part of the tube 5, together with the apex of the conical base wall 2, defines the volume of the dose of pupae to be dispensed. It is understood that inversion of the container with the closure 7 in place will not dispense pupae, but more importantly the blocking of the dispenser tube at the level of the cutouts not only prevents the escape of prematurely emergent insects, but also prevents a build-up of pupae in the dispenser tube if the container is repeatedly inverted in transit. The conical form of base wall 2 guides the pupae towards the cutouts 6 and ensures that the dispensing tube will be adequately filled even when only a few pupae remain in the container - the entire contents of the container may thus be utilised in regulated doses without wastage. An advantage of using the dispenser is that the pupae may be shipped in bulk from the producer to the distributor, thus saving transportation cost since the volume of the bulk package is considerably less than is the case when the pupae are pre-packaged in individual release site packs. The pupae may even be refrigerated for longer journeys, for example by using insulated containers, to delay emergence of the insects. When the bulk pupae reach the distributor, he can then prepare a dispenser containing the appropriate number of pupae for each of his customers, and deliver these to the glasshouse operators preferably in well-insulated containers. Alternatively, the pupae for a single treatment of a number of release sites may be sent direct to the glasshouse operator in a sealed container, the pupae being transferred on arrival to a dispenser for use in the glasshouse.

Claims: A method of controlling a population of insect pests in an area of vegetation, comprising the steps of defining a number of fixed release sites in and about the area, and placing a predetermined number of pre-adult control insects at each release site at predetermined intervals to provide a continuing supply of emerging control insects at each release site, the control insects being placed at the release sites by delivering a predetermined volume of pre-adult insects from a bulk supply using a dispenser, characterised by the use of a dispenser comprising a container whose interior is divided to define a storage volume (1, 2) and a measuring volume (5, 6) connected via a transfer opening (6), the storage volume (1, 2) being so configured that with the dispenser in a first orientation the pre-adult insects in the storage volume are guided towards the transfer opening so as to flow therethrough until the measuring volume (5, 6) is filled, the measuring volume having an outlet passage positioned so as to be inaccessible to the pre-adult insects when the dispenser is in its first orientation, movement of the dispenser to a second orientation causing pre-adult insects remaining in the storage volume to fall away from the transfer opening (6), and causing the pre-adult insects in the measuring volume to be discharged through the outlet passage. A method according to Claim 1 comprising the use of a dispenser, wherein the storage volume (1, 2) is generally cylindrical and has a conical end wall (2) tapering to a point at one end, and the measuring volume is defined by a dispensing tube (5) extending substantially axially of the storage volume, one end of the tube contacting the conical end wall (2) along a line surrounding the point, and the other, exit, end of the tube extending out of the storage volume, the transfer opening (6) being formed in the wall (5) of the tube at its one end contacting the conical end wall (2) of the storage volume to provide access from the storage volume to the lumen of the tube. A method according to Claim 2 comprising the use of a dispenser, wherein the transfer opening (6) comprises a cutout (6) in the one end of the dispensing tube (5). A method according to Claim 3 comprising the use of a dispenser, wherein the transfer opening (6) comprises two diametrically opposed cutouts (6). A method according to Claim 4 comprising the use of a dispenser, wherein the exit end of the dispensing tube (5) remote from the conical end wall (2) of the storage volume terminates in a plane inclined to the longitudinal axis of the storage volume and parallel to the axis passing through the opposed cutouts (6). A method according to Claim 5 comprising the use of a dispenser, wherein the exit end of the dispensing tube (5) is bevelled. A method according to Claim 5 comprising the use of a dispenser, wherein the exit end of the dispensing tube (5) is inclined relative to the axis of the storage volume (1).

Inventors: DALE, JOHN, DR.
Applicants: BIOLOGICAL CROP PROTECTION LIMITED
Application year: 1990
Main classification: A01K67
IPC codes: A01K67