Abstract:
A method and delivery system for an area-specific precision control of biting insects, including flying and non-flying, biting arthropods, is described. CO 2  is metered through a tubing fence and dispensed into the center of traps that serve as visual targets for flying or walking biting arthropods. The outside membrane of a trap can be treated with mineral oil to capture and kill small arthropods such as sand flies of the genus Culicoides, or black flies of the genus Simulium. In addition, the membrane can be treated with insecticide formulations of Permethrin, Resmethrin, or Deltamethrin, to kill larger biting arthropods, such as ticks, mosquitoes, deer flies, horse flies, or stable flies. This method for biting arthropod control is an ecological-friendly alternative to the widespread broadcast application of organophosphate insecticides such as Derspan, Diprom, and Malthion.

Description:
This application is a continuation, of application Ser. No. 08/816,437, filed Mar. 14, 1997, now U.S. Pat. No. 5,943,815. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and apparatus for dispensing an insect attractant such as carbon dioxide along a pipeline. The invention further relates to a method and apparatus for releasing carbon dioxide gas into insect traps for purposes of capturing and/or exterminating insects. 
     BACKGROUND OF THE INVENTION 
     Flying and biting insects are presently controlled by the application of insecticides directed either at immature stages (larvicides) or adults (adulticides). These compounds are generally applied as a broadcast spray from either the air or the ground. This broadcast application generally results in two levels of failure. First, large areas of land and water are treated where there are no insects. Second, non-target, beneficial organisms are oftentimes affected and sometimes killed by the broadcast treatment. 
     Solid CO 2  (dry ice) has been used as an attractant for flying and biting insects insects to gather data about this insect population density. This data has been used to aid in determining when broadcast application of insecticides is needed, and in what amounts. While dry ice has been effective as bait for insects because it sublimates CO 2  gas into the atmosphere, there have been no effective methods of metering the amounts of CO 2  gas released from a source of CO 2  for attracting insects. 
     SUMMARY OF THE INVENTION 
     In light of the foregoing, a need exists for a way of more accurately targeting insects for extermination or capturing without adversely affecting the surrounding environment. 
     A need also exists for a way of more accurately targeting insects for capture extermination and/or capture without exterminating/capturing unintended organisms. 
     According to one aspect of the present invention, a system for attracting an insect population comprises a source of chemical attractant for insects, a distribution feed tube in fluid communication with the source, a controller for controlling the flow of attractant from the source through the distribution feed tube, and at least one target in fluid communication with the distribution feed tube, the target including means for effecting, when an insect comes into contact with the target, capture of the insect and extermination of the insect. 
     According to another aspect of the present invention, a target for trapping and/or exterminating insects comprises a support structure, a surrounding element mounted on the support structure for defining an interior space within the surrounding element, means provided on the surrounding element for effecting at least one of capture of an insect that comes into contact with the surrounding structure and extermination of an insect that comes into contact with the surrounding structure, and a tube extending into the interior space of the surrounding structure for introducing CO 2  containing gas into the interior space to attract insects into coming into contact with the surrounding structure. 
     According to yet another aspect of the present invention, a process for attracting an insect population to a target comprises the steps of providing a system for capturing or exterminating and/or capturing insects, flowing primary chemical insect attractant from said source through said distribution feed tube to said at least one target, controlling the flow of said primary chemical insect attractant with said controller, and contacting insects with said means for either capturing or exterminating. 
     According to yet another aspect of the present invention, a controller for controlling the mixture and distribution of a primary chemical insect attractant comprises means for conducting a flow of said primary chemical insect attractant, switch means for determining whether the flow rate of said primary chemical insect attractant through said conducting means has exceeded a predetermined limit value, said switch means comprising timer means for evaluating the time elapsed while there is flow in said conducting means, said switch means generating a limit control signal, valve means, in control signal communication with said switch means and responsive to said limit control signal, for allowing flow of said primary chemical insect attractant through said conducting means when open and substantially stopping flow of said primary chemical insect attractant through said conducting means when closed, said switch means controlling said valve means with said limit control signal to close when either said timer means indicates that a predetermined time has elapsed or flow in said conducting means exceeds a predetermined level. 
     Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description considered with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention of the present application will now be described in more detail with reference to preferred embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view, partially in phantom, of a target according to the present invention; 
     FIG. 2 is a schematic illustration of a CO 2  fence according to the present invention; 
     FIG. 3 is a schematic illustration of a control system flow diagram for a CO 2  fence according to the present invention; and 
     FIG. 4 is a graph illustrating CO 2  flow versus manifold pressure for different sized orifices according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Ambient levels of CO 2  in the environment are typically on the order of 0.03% or less. Insects such as biting arthropods are attracted to CO 2  at concentrations greater than 0.03%. Increases in concentration of CO 2  as small as 0.1 ppm (parts per million) above the ambient level often indicate to the insect the presence of a vertebrate host (e.g., human) that can serve as a source of blood. Additionally, CO 2  released at rates of 200 to 1,000 millimeters per minute can be used to attract flying and biting insects to localized killing stations. The addition of other compounds, such as acetone or octenol, produces a synergistic affect, greatly increasing the number of individual arthropods attracted to killing stations. 
     Flying and biting insects are attracted to mammals based upon the mammal&#39;s output of CO 2  through, e.g., expiration. For example, an average human releases approximately 750 millimeters per minute of CO 2 , while an average horse releases approximately 2 liters per minute of CO 2 . 
     CO 2  is available as a liquified gas under its own vapor pressure of 5.7 MPa at 20° C. in standard high-pressure vessels containing 9 to 23 kg of gas. Liquid CO 2  is also available from low-pressure, insulated bulk tanks where the pressure is kept low by maintaining the temperature of the tank at a suitable low level with a mechanical refrigeration unit. Low pressure vessels are available in capacities of 2,720 kilograms, 3,630 kilograms, 5,440 kilograms, 11,800 kilograms, 21,800 kilograms, and 28,100 kilograms. 
     According to the present invention, a chemical attractant for arthropods, e.g. carbon dioxide (CO 2 ) from bulk storage tanks, optionally CO 2  mixed with a secondary attractant such as octenol, can be metered into a PVC pipeline, hereinafter referred to as a CO 2  fence. The gas, or gas mixture, is then fed into insect or arthropod traps spaced at roughly equal intervals. Arthropods attracted to the traps are captured in thin mineral oil coatings, and possibly also poisoned, when they make contact with the treated outer membranes on the surface of the trap. Arthropods, the abatement of which is the subject of the present invention, include, but are not limited to, sand flies of the genus Culicoides, black flies of the genus Simulium, ticks, mosquitoes, deer flies, horse flies, and stable flies. 
     Systems and processes according to the present invention are environmentally friendly alternatives to broadcast applications of insecticides. The CO 2  fence can be used to control insects in any environment. The technique is quite desirable in that it is insect-specific and does not adversely affect non-target organisms. The system is further advantageous in that it can be adapted to control biting arthropods within clearly defined areas. 
     The release rate of CO 2  from a target according to the present invention can be predetermined by the type of mammal that it is desired that the target mimic. For example, if it is desired that the target mimic a human, the release rate of CO 2  into the atmosphere through the target may be controlled to be approximately that of an average human, i.e., 750 millimeters per minute. 
     FIG. 1 illustrates a target  100  according to the present invention. As illustrated in FIG. 1, target  100  includes a top plate  102  which may be made of PVC, nylon, ABS, or any other material which is preferably easy to handle, easy to manufacture and has a low cost, as would be readily apparent to one of ordinary skill in the art. Target  100  also includes a support structure including a top support ring  104  and a bottom support ring  106 . 
     Both the top support ring  104  and the bottom support ring  106  are attached to generally cylindrical bodies  108 ,  110 , respectively. Each cylindrical body  108 ,  110  includes a center bore (shown in phantom in FIG.  1 ). Top cylindrical body  108  and bottom cylindrical body  110  both further include slots  112  into which are inserted support legs  114 . Support legs  114  are inserted into slots  112  and affixed in place. Any number of support legs  114  may be used; three support legs for each of the top support ring  104  and bottom support ring  106  are shown in the embodiment illustrated in FIG.  1 . The bore in top cylindrical body  108  (shown in phantom) is drilled approximately half-way into the top cylindrical body  108 . The bore (shown in phantom) in bottom cylinder body  110  is drilled through the entire length thereof. 
     A CO 2  feed tube  116  is inserted through bottom cylindrical body  110  and into top cylindrical body  112  through their respective bores. CO 2  feed tube  116  forms a loose seal with top cylindrical body  108 . CO 2  feed tube  116  includes feed holes  118  along the length of CO 2  feed tube  116  between top support ring  104  and bottom support ring  106 . Feed holes  118  fluidly communicate the outside of CO 2  feed tube  112  with an inside bore (not shown) thereof. 
     Top support ring  104  and bottom support ring  106  are wrapped in a surrounding structure which includes a fabric covering  120 . The fabric covering  120  is impregnated with a thin mineral oil coating and/or an insecticide which is chosen for its ability to exterminate a specific insect or insects. Preferably, the insecticide is chosen for its ability to exterminate arthropods. Suitable insecticides include, but are not limited to, Permethrin, Resmethrin, and Deltamethrin. Other insecticides may be used without departing form the spirit and scope of the invention, as would be readily apparent to one of ordinary skill in the art. The fabric covering  120  may be impregnated on the inside and/or the outside thereof. 
     Fabric covering  120  is preferably a dark, and more preferably black, cloth-like material, e.g., non-woven, perforated polyethylene cloth, that has been impregnated with either a contact insecticide for purposes of killing insects, or mineral oil, for purposes of simply capturing insects. Fabric covering  120  allows CO 2  introduced into the interior of target  100  to dissipate out into surrounding environments to attract insects. Fabric covering  120  is preferably constructed of a supple fabric which mimics, to an insect, the small movements of a mammal. By providing such visual queues through the use of a supple fabric, the insect population of interest is therefore additionally attracted to target  100 . 
     Feed holes  118  have a diameter large enough such that when taken together, there is no substantial pressure drop between the inside and outside of CO 2  feed tube  116 , but small enough such that substantially no insects may enter into CO 2  feed tube  116 . It has been found that a diameter for feed holes  118  of less than 1 millimeter is preferable. By constructing feed holes  118  of a diameter less than 1 millimeter, it has been found that the common sand fly, or sand flea, is not able to enter into CO 2  feed tube  112 , because the common sand fly, or sand flea, is most typically 1 to 3 millimeters in size. 
     Top plate  102 , as illustrated in the embodiment of FIG. 1, is preferably wider than top support ring  104  and bottom support ring  106 , in order to shelter fabric covering  120  from rain. Top plate  102  is attached to upper cylindrical body  108  with a bolt, screw, rivet, or the like (not shown). 
     Top plate  102  may be attached such that top plate  102  and top support ring  104  meet on the upper surface of top support ring  104 . Alternatively, top plate  102  may be attached to top cylindrical body  108  such that an opening or gap is presented between top plate  102  and top support ring  104 . The purpose for such a gap (not shown) would be to allow insects to enter into the inside of target  100 . 
     Bottom support ring  106  is preferably open to the atmosphere, allowing insects to freely enter target  100  from below. In an alternative embodiment, bottom support ring  106  may further include a plate (not shown), similar to top plate  102 , which closes off the interior of target  100  from the exterior thereof. 
     Fabric covering  120  is wrapped around top support ring  104  and bottom support ring  106  and is attached thereto. Fabric covering  120  may be permanently affixed to either or both of the top support ring  104  and bottom support ring  106 . Alternatively, fabric covering  120  may be releasibly attached to top support ring  104  and/or bottom support ring  106  by using snap-fit couplings or the like (not shown) on the mating surfaces of top support ring  104 , bottom support ring  106 , and fabric covering  120 . By constructing fabric covering  120  to be removable and/or replaceable, the life of target  100  may be effectively increased by allowing the oil and/or insecticide on fabric covering  120  to be replenished. Furthermore, target  100  may be periodically cleaned by removal of fabric covering  120  when fabric covering  120  is provided with snap-fit couplings or the like. 
     CO 2  feed tube  116  is connected at its bottom end to CO 2  orifice plate  122 . CO 2  orifice plate  122  includes a straight bore orifice (not shown) which governs the release rate of gas through target  100  based upon the gas pressure in the system. CO 2  orifice plate  122  is, at its lower end, fluidly coupled to distribution feed tube  124 , which supplies an insect attractant to target  100 . The metering of CO 2  or a CO 2  mixture is accomplished by using the CO 2  orifice plate  122  and maintaining a known pressure differential across CO 2  orifice plate  122 . CO 2  orifice plate  122  is held between two mated, threaded fittings at both its upper and lower ends (not shown) for connection to CO 2  feed tube  114  and the distribution feed tube  124 . 
     In an alternative embodiment, CO 2  orifice plate  122  may be replaced with a controllable valve with or without an indicator, e.g., a rotometer. Such a controllable valve would allow the adjustment of the attractant flow rate to target  100  from distribution feed tube  124 . 
     FIG. 2 illustrates a CO 2  fence system  200  according to the present invention. CO 2  source  202  supplies bulk CO 2  to CO 2  fence  200 . CO 2  from CO 2  source  202  is serially fed to shut off valve  204 , control system  206 , and shut off valve  208 . Control system  206  is illustrated in greater detail with reference to FIG. 3, below. Control system  206  controls the flow of CO 2  to CO 2  fence  200  with or without an adjunct attractant. CO 2  then is distributed through distribution piping  210  to targets  100  (see FIG.  1 ). Although FIG. 2 illustrated the CO 2  fence  200  including five targets  100 , any suitable number of targets  100  may be fluidly attached to distribution piping  210 , as would be readily apparent to one of ordinary skill in the art. The CO 2  fence  200  according to the present invention guarantees that the pressure differential across all the orifice plates  122  are the same, thus ensuring that flow rates are equivalent for the same sized orifices. 
     FIG. 3 illustrates a CO 2  control system flow diagram  300  which is usable in conjunction with CO 2  fence  200 , e.g., as control system  206  (see also FIG.  2 ). As illustrated in FIG. 3, CO 2  is fed from CO 2  bulk feed  202  to inlet CO 2  pressure regulator  302 . Inlet CO 2  pressure regulator  302  regulates the pressure at which CO 2  is allowed to enter into system  300 . Pressure regulated CO 2  then flows to flow limit switch  304  and further to solenoid valve  306 . A 7-day timer  308  is in control signal communication with flow limit switch  304 . Flow limit switch  304  is in control signal communication with solenoid valve  306 . 
     Flow limit switch  304  provides at least one functions; in the event that there is an abnormal flow characteristic in system  300 , flow limit switch  304  can be operated to send a disable control signal, e.g. “close”, to solenoid valve  306 . The 7-day timer  308  also can provide a control signal through control limit switch  304 , indicating when a chosen release period has been initiated thus activating the flow of CO 2 , and shutting off the flow of bulk CO 2  to system  300  at the end of the period. 
     When solenoid valve  306  is operated to an open position, CO 2  flows to CO 2  flow meter  310 , which indicates the rate of flow of CO 2  out of system  300 . CO 2  then flow from CO 2  flow meter  310  to outlet pressure regulator  312  which regulates the pressure of CO 2  exiting system  300 . Carbon dioxide is then allowed to flow to distribution piping  210  (see FIG.  2 ). 
     Preferably, a flow rate of CO 2 , or CO 2  mixture, from about 0.01 to about 7 SLM, (Standard Liters per Minute) more preferably about 0.1 to about 5 SLM, and even more preferably about 0.1 to about 3 SLM is maintained through the CO 2  fence according to the present invention. 
     Alternatively, a secondary insect attractant may be added to the CO 2  in system  300 . To accommodate a second or adjunct insect attractant, secondary attractant flow control  314  is placed in a parallel flow path with CO 2  flow meter  310 , as illustrated in FIG.  3 . Secondary attractant flow control  314  includes a source of secondary attractant (not shown) contained in secondary attractant saturator  316 . A metered quantity of CO 2  flows into into secondary attractant saturator  316 , wherein CO 2  is saturated with the secondary attractant. The mixture of CO 2  and secondary attractant then flows to gas mixer  318  where it is mixed with CO 2  from outlet pressure regulator  312 . The mixture of CO 2  and second attractant then flows from gas mixer  318  to distribution piping  210 . 
     CO 2  and the secondary attractant can be premixed or, alternatively, mixed via the alternative saturator system of control system  300 . The temperature of secondary attractant saturator  316  can be controlled such that the exact quantity of secondary attractant can be added. Typically, the quantity of secondary attractant added is between about 0 milligrams and about 20 milligrams per liter of released CO 2 , and preferably between about 0 milligrams and about 8 milligrams per liter of CO 2  released. Control system  300  can be configured to operate on either 3 to 220 VAC or 1.5 to 48 VDC, thus allowing battery operation. 
     FIG. 4 is a diagram showing the results of varying the gage pressure across CO 2  orifice plate  122  for different sized orifices. The upper line in FIG. 4 represents the flow-pressure characteristics for a number  79  orifice; the lower line represents the flow-pressure characteristics for a number  80  orifice. As can be readily appreciated from the data of FIG. 4, the flow of gas through orifice plate  122  is easily controlled and/or regulated by varying the gauge pressure of the gas on the upstream side of orifice plate  122 . The predictability shown in FIG. 4 of the pressure flow characteristics of orifice plate  122  allows a CO 2  fence  200  according to the present invention to be readily customized for particular uses. 
     The components of the target  100  and the CO 2  fence  200  may be made of PVC, nylon, ABS, or any other material which is preferably easy to handle, easy to manufacture and has a low cost, as would be readily apparent to one of ordinary skill in the art. 
     While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention.