Note: Descriptions are shown in the official language in which they were submitted.
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INSECT BAIT
BACKGROUND OF THE INVENTION
Field of the Invention
The invention is generally related to insect bait
materials and, more particularly, to an insect bait which has
constituents specifically chosen and proportioned to enhance the
foraging activity of carpenter ants.
Description of the Prior Art
The carpenter ant, Camponotus pennsylvanicus, is a wood
infesting insect and common household pest. They are usually
considered a nuisance pest, but can cause serious damage to
structural wood and timber. Once established in a house, carpenter
ants are very difficult to control. Homeowners frequently
undertake control efforts themselves by spraying a variety of
commercially available insecticides in areas where foragers are
observed. Professional pest control operators may also be
contacted and the typical treatment procedure used by these
professionals involves the application of insecticidal dusts or
sprays to a nest in situ, if it can be located. Effective control
is hindered by difficulties in nest location, and by the fact that
mature carpenter ant colonies often have multiple nests, utilizing
both indoor and outdoor sites. When inspections fail to locate
nests, insecticides are usually applied to a number of different
areas in and around a house. However, this type of practice is
inefficient and is rarely effective.
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A better and safer alternative to eradicating carpenter
ants and other insects in the home involves the use of insecticidal
baits. In order to be effective, a bait must be targeted to the
feeding preferences of the insect to be eradicated. Baits have the
advantage that they can be placed in areas where workers forage so
that they can be consumed and transported back to the nest, thus
eliminating the need for nest location. Currently, no baits
specific for carpenter ants are commercially available due to a
lack of knowledge of basic biology, feeding behaviour, and food
preferences that is required to develop an effective carpenter ant
bait material.
U.S. Patent 3,220,921 to Greenbaum at al. discloses the
use of an insecticide identified as hexachlorocyclopentadiene for
use in ant baits. The Greenbaum et al. reference does not provide
any indication as to what kinds of constituents and proportions of
those constituents would be attractive to carpenter ants. Rather,
Greenbaum et al. merely lists a number of different attractant
materials. Many of the materials identified in Greenbaum et al.
are not attractive to carpenter ants. In order for a trap to be
effective, it must first have a bait that attracts the insects to
be eradicated.
U.S. Patent 3,962,461 to Brown, Jr. et al. discloses a
honey bait which included a mirex insecticide. The bait in Brown
is a liquid. Thus, special procedures are required for the
incorporation of the non-water soluble insecticide into the bait.
Liquid baits have many drawbacks. For example, a liquid bait must
be positioned out of traffic areas since it is subject to spillage
and may cause discoloration of floors, rugs, etc. In addition,
liquid baits evaporate over time, and the evaporation process
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causes the dissolved materials to become more concentrated over
time. The physical change in the bait which occurs via evaporation
is likely to alter the attractive performance of the bait.
U.S. Patent 4,921,696 to Vander Meer et al. discloses a
bait material for eradicating fire ants which relies on edible oils
as the attractant.
U.S. Patent 4,823,506 to Demarest et al. discloses an
insect bait which includes an insect pheromone.
U.S. Patent 4,988,510 to Brenner et al. discloses an
insect bait for cockroaches which utilizes an insect bait for
cockroaches which utilizes a gel matrix material. The attractant
used is corn distiller's dried grains with solubles (C-DDGS). A
humectant is used to keep the gel matrix fresh until use.
U. S. Patent 5, 096, 710 to Minagawa et al . discloses a bait
which includes chemicals designed to restrict the proper
development of certain insects (e. g., chitin synthesis inhibitors,
etc.). The Minagawa et al. bait is provided in tablet form. The
Minagawa et al. bait also includes a plant oil as an essential
ingredient.
U.S. Patent 5,177,107 to Meer et al. discloses the use
of certain flurocarbon compounds as toxicants for ants.
U.S. Patent 4,988,511 to Demetre discloses an
insecticidal paste including powdered boric acid that is designed
to harden onto a surface. The paste includes sugars, milk solids,
and butter fat.
U.S. Patent 4,996, 053 to Hatcher discloses a bait for
controlling darkling beetles, hide beetles, and lesser metal worms.
The bait includes edible oils including corn and soy oils.
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U.S. Patent 4,874,611 to Wilson et al. discloses a
microencapsulated ant bait which includes a soybean extract core,
an insecticide, and a gelatin shell which includes soy protein as
the attractant.
U.S. Patent 4,245,420 to Carr discloses a bait designed
for attracting fish. The Carr bait includes a gelatin matrix
material which slowly releases the attractant to the water
environment.
British Patent GB 2,018,593 to Hurt discloses insect
control systems that utilize polymeric carriers such as
polyvinylchloride (PVC), polyurethanes, and the like.
None of the prior art references provide a bait
formulation which considers the biology, feeding behaviour, and
food preferences of carpenter ants. In order to successfully
eradicate any particular insect, the bait must include materials
that will be attractive for the~'species to be eradicated.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an insect
bait material which is specifically designed to attract and
eradicate carpenter ants.
It is another object of this invention to provide an
insect bait material which utilizes specific sugar constituents in
combination with alkali and alkaline earth salts such as NaCl, KC1,
CaClz, and MgCl2.
It is another object of this invention to provide an
insect bait which is devoid of saturated and unsaturated fats and
oils.
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It is another object of this invention to provide an
insect bait which utilizes specific sugar constituents in
combination with urea.
It is another object of this invention to provide an
insect bait which utilizes specific sugars in combination with
proteins and certain amino acids.
It is another object of this invention to provide an
insect bait which utilizes agar as a matrix material.
According to the invention, the biology, feeding
behaviour and food preferences of carpenter ants have been
investigated and bait materials specific for attracting carpenter
ants have been developed. It has been observed that carpenter ants
prefer sucrose and fructose to other sugars, and that sucrose and
fructose are effective separately or together at low concentrations
ranging from 5-40%, and most preferably 10-30%. The consumption
rate of a bait material by carpenter ants can also be enhanced
significantly by combining either urea or alkali and alkaline earth
salts, such a NaCl, KC1, MgCl2 and CaCl2, in the bait material with
sucrose and/or fructose sugars. In addition, selection of agar as
the matrix material can also enhance the attractiveness of the bait
material. Proteins and amino acids are preferred as nutrient
source by carpenter ants, and saturated and unsaturated fats and
oils are not preferred. Subsequent studies have suggested that the
insect bait may be useful as an attractant for several other insect
species.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages
will be better understood from the following detailed description
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of the preferred embodiments of the invention with reference to the
drawings, in which:
Figure 1 is a graph showing the consumption rate of
different sugars at different concentrations by carpenter ants;
Figure 2 is a graph showing the relative rate of
consumption of a 10% sucrose solution and a 10~ sucrose solution
plus 10% NaCl; and
Figure 3 is a graph showing the relative rate of
consumption of a 10% sucrose solution and a 10% sucrose solution
plus 10% urea.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS OF THE INVENTION
Figure 1 shows the results of a comparative test where
the rate of consumption of different sugars offered to a nest of
carpenter ants was monitored. In the tests, solutions of a
specified sugar were positioned outside a carpenter ant nest and
the time for the carpenter ants to remove 0.5 mls of the solution
was determined. The concentration of the sugar in the solutions
ranged from 1% to 40%, and, for each specific sugar constituent,
the consumption rate for 1%, 5%, 10%, 20%, and 40% sugar solutions
was determined. Figure 1 shows that more concentrated sugar
solutions were generally depleted faster than less concentrated
solutions for all the sugars tested; however, it should be
understood that sugars are phagostimulants and will have a
deterrent effect at too high a concentration.
Most notably, Figure 1 shows that the rate of consumption
of sucrose and fructose was considerably faster than for trehalose,
glucose, maltose and galactose, at all concentration levels between
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5% and 40% by weight. In addition, Figure 1 shows that sucrose and
fructose occurs were able to provide an attraction to carpenter
ants at low concentrations. Specifically, 5% solutions of each
sugar were able to provide a significant attraction to carpenter
ants as demonstrated by the rate of consumption data. Although not
indicated on Figure 1, it has been determined that the perception
threshold for sucrose by carpenter ants is very low ( less than 2 . 5%
w/w). The rate of consumption for sucrose and fructose begins to
level off for solutions having between 20% and 40% concentration.
Thus, having higher concentrations than 40% of sucrose or fructose
in a bait will not provide much attraction and consumption benefit
to the bait, if any, and may present a deterrent because of factors
such as receptor adaptation to the sugars. Hence, an ideal bait
for carpenter ants should preferably include 5-40% by weight of
sucrose and/or fructose, and most preferably 5-20% or 5-30% by
weight of sucrose and/or fructose. Sucrose and fructose can be
used in combination in a bait for carpenter ants and will provide
a suitable attraction. As discussed above, the effects on
attraction and consumption for a combination of sucrose and
fructose will begin to level off at a total concentration between
20% and 40%. Thus, suitable baits may include, for example, 1-39%
of each of sucrose, fructose, or combinations thereof.
Figure 2 shows results for a similar consumption rate
test as that described above in conjunction with Figure 1.
Specifically, the consumption rate of a 10% sucrose solution
control and a 10% sucrose solution with small quantities of NaCl
was determined. The overall rates of consumption differ from those
in Figure 1, but these differences were due, at least in part, to
differences in colony condition (different test colonies) and
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different temperatures at the time the tests were run. The
addition of salt increased the consumption rates of sucrose
solutions from 20% to almost 50%. The highest consumption rates
were observed at a salt concentration of 0.5%. Consumption rates
for sucrose did not change significantly during the test period,
although a decrease in consumption of both solutions was noted at
the highest salt concentration (1.0%). This decrease reflects a
drop in forager numbers and forager recruitment. Figure 2 shows
that including 0.05% to 0.5% NaCl significantly improves the rate
of consumption of the sugar solution. Some similar tests also have
been run with potassium chloride and increased consumption rates
were observed with this salt, although the phagostimulant effects
were not as strong as with NaCl. Other alkali and alkaline earth
salts such as calcium chloride and magnesium chloride can be
expected to have similar results.
In view of the above, including a salt in the carpenter
ant bait material should provide for enhanced attraction of the
bait, and, preferably, the salt will constitute 0.1%-1% by weight
of the bait. The results in Figure 2 suggest a decrease in feeding
as the salt concentration approaches 1% by weight.
Figure 3 shows results for a similar consumption rate
test as that described above in conjunction with Figure 1.
Specifically, the consumption rate of a 10% sucrose solution
control and a 10% sucrose solution with varying concentrations of
urea ranging from 0.5% to 6% were determined. Figure 3 shows the
addition of urea also increased the consumption rate of a standard
10% sucrose solution. Significant effects were noted with a urea
concentration as low as 0.5%, wherein the consumption rate was
increased by approximately 30%. The increase in consumption rates
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for the sugar controls was due to increased recruitment with the
presentation of the two food sources. Forager numbers increased
at both test solutions, but collection of urea occurred at higher
rates. Urea concentrations above 3% did not appear to lead to
continued increases in consumption.
In view of Figure 3 showing that including urea in
combination with the sucrose improves the rate of consumption of
the solution, urea would be a preferable component of an insect
bait. Preferably, in a bait material, the urea would constitute
0.5%-4.0% by weight of the bait.
Consumption tests similar to that described in
conjunction with Figure 1 were conducted with solutions containing
amino acids and proteins. It was determined that proteins, and
particularly protein hydrolysates such as Hy-Case (an acid digest
of casein available from Sigma Chemical), Biosate (a
bacteriological peptone that is composed of plant and animal
protein hydrolysates--yeast autolysate and pancreatic casein
digest, available from the Baltimore Biological Laboratory), and
Gelysate (a pancreatic hydrolysate of gelatin available from the
Baltimore Biological Laboratory), all of which are water soluble
protein mixtures, were attractive to carpenter ants at
concentrations as low as 1% wt/wt. The rate of consumption of the
hydrolysate solution levelled off between 10-40%; therefore,
including higher concentrations of a water soluble protein
hydrolysate than 40% in a bait material is not beneficial.
Preferably, a bait will include 1-20% of a water soluble protein
hydrolysate. It was also determined that certain, water soluble,
amino acids, and particularly leucine, valine, and proline were
attractive to carpenter ants at concentrations as low as 0.5%
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wt/wt. In contrast, solutions containing aspartic acid and
glutaric acid did not demonstrate any attractive effect on
carpenter ants. Preferably, a bait material will include 0.5-20~
of amino acids, and particularly leucine, valine, and proline. In
addition, amino acids may be used in a bait in combination with
proteins.
In a series of "choice" tests, carpenter ant nests were
simultaneously offered baits with sugars and carbohydrates, baits
with fats and oils, and baits with proteins, where all of the baits
were placed side-by-side. The baits included a gelatin matrix
material with the proteins, fats and oils, or sugars and
carbohydrates dispersed within the matrix. The carpenter ants
routinely selected the baits with proteins and the baits with
sugars and carbohydrates. Baits with fats and oils, including both
saturated and unsaturated fats and oils from both animal and plant
sources, were never accepted by carpenter ants during choice tests.
Therefore, carpenter ant baits preferably should not include any
fats and oils and, if included, the amount should be minimized so
that the bait will not present a deterrent to the carpenter ants.
Thus, for example, if flour is to be included in the bait material,
it would be preferable to use de-fatted flour. An interesting
result from the "choice" tests was that carpenter ants routinely
removed more nutrient from the protein baits than from the sugar
baits.
In order to facilitate long term usage, baits should
generally be solid rather than liquid. However, carpenter ants
typically only ingest liquids. Thus, it has been determined that
providing the bait with a matrix that is gelatinous in character
is preferred for carpenter ants to meet both the shelf-life and
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other requirements of a bait material product, and the "liquid-
food" requirements of the carpenter ant. The preferred matrix
material is agar; however, other useful matrices include gelatin,
carrageenan, starch, acacia, guar gum, pectin, starch, proteins,
collagen, and synthetic polymers such as polyvinylpyrrolidone, and
these constituents can be used alone or in combination to make the
matrix material. Preferably, the matrix material comprises 0.5%
to 4.0% by weight of the bait material.
Consumption tests similar to those described in
conjunction with Figure 1 have shown that agar is more attractive
to carpenter ants than gelatin. When the agar baits and gelatin
baits were offered to the same carpenter ant nests, the carpenter
ants consumed the agar baits, on average, at a greater rate than
the gelatin baits. Therefore, it is preferable to formulate
carpenter ant baits with an agar matrix material.
The ideal insecticide for use in the bait would be one
that can be picked up by the forager and carried back to the nest
to be passed around to other carpenter ants. Contact insecticides
would not generally be suitable since the bait material would then
only be useful for killing foragers. Sulfimide, hydramethylnon,
and abamectin are examples of suitable insecticides. Preferably,
the insecticide constitutes 0.01-10% by weight of the bait.
While the above studies have been conducted with
carpenter ants (Camponotus species), it has been noted that the
baits are effective attractants for a wide variety of other
insects, particularly insects with chewing mouth parts and those
with sponging and lapping mouth parts. The insect baits of this
invention are especially effective for the control of ants, Family
Formicidae, and may be used for the control of ants such as the
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southern fire ant, Solenopsis xyloni, leaf cutting ants, Acromyrmex
versicolor, Argentine ants, Iridomyrmex humilis, cornfield ants,
Lasius alienus, pavement ants, Tetramorium caespitum, larager
yellow ants, Acanothomyops interjectus, thief ants, Solenopsis
molesta, and the red and black imported fire ants, Solenopsis
invicta and Solenopsis saevissma richteri, respectively. These
ants are serious economic pests which have been known to attack
human beings, livestock, and agronomic crops; therefore, it is
highly desirable to control them. Other ants that can be
controlled are nuisance pests such as Pharaoh ants, Monomorium
pharaohnis; oderous house ants, Tapinoma sessile; and acrobat ants,
Crematogaster cerasi.
A simple procedure for formulating an agar based bait,
provided herein for exemplary purposes only, would be to add 6
grams of agar to 500 ml of distilled water, bringing the agar/water
mixture to boil, adding the attractant material to the agar/water
mixture when it is fluidized (e. g., sucrose and/or fructose and/or
proteins and/or amino acids and/or alkali or alkaline earth salts
and/or urea and/or carbohydrates and/or insecticide), and then
cooling the mixture. The mixture may be molded to form a desired
bait shape. It should be understood that the amounts of
constituents added to the agar/water mixture can be varied
considerably within the practice of this invention, and that the
amounts of agar and water employed will vary depending on the bait
being formulated.
While the invention has been described in terms of its
preferred embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the appended claims.
