Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INSECT REARING TRAY
FIELD OF THE INVENTION
The present invention relates to insect rearing trays, and more
particularly to trays for use in leafcutter bee incubation.
BACKGROUND OF THE INVENTION
Leafcutter bees are employed in the pollination of alfalfa crops. Alfalfa
seed can be economically produced wherever environmental conditions are
sufficient
for alfalfa pollination and growth. The deep-.rooted, long-lived perennial
habit of alfalfa
allows it to produce good forage and/or seed yields from subsoil moisture even
when
surface precipitation is low. Production of alfalfa seed during the
establishment year
is sometimes possible in western Canada, but the normal practice is to take
one
season to establish a healthy stand and then pollinate and harvest a seed crop
the
second and following years.
Since the alfalfa leafcutter bee was introduced in the early 1960s, alfalfa
seed production in western Canada has been steadily expanding_ Honeybees are
an
effective pollinator in areas like California, but they do not effectively
pollinate alfalfa in
western Canada. Across the prairies, alfalfa seed production requires
leafcutter bees
to pollinate the crop, as this species is the only one that can be relied upon
to
efficiently and effectively do so. Bumblebees and other native bees will also
pollinate
alfalfa, but their fluctuating populations make them unreliable for use in
alfalfa seed
production.
t_eafcutter bees are necessary for optimum seed set of alfalfa and many
seed producers keep their own bees. The loose-cell system of leafcutter bee
management is widespread across the western Canadian production area. Canadian
leafcutter beekeeping was developed around the principle of loose-cell
management,
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as individual cocoons rather than in nest tunnels. Although this management
system
requires a large financial investment in equipment and demands intensive
handling of
bees, it is favoured for control of diseases, moulds and parasites since it
allows
sterilization of nesting material and treatment of cocoons. The system places
the
optimum number of bees onto the crop at the appropriate time to obtain a high
seed
yield and an adequate return of viable bees for the following year. This
creates a
second enterprise in years when a surplus of leafcutter bee larvae is
produced;
producers can generate profits from the sate of excess bees that are sometimes
equal
to the sale of the seed. There is a demand for Canadian leafcutter bee larvae
in the
United States, since alfalfa seed producers there have difficulty maintaining
their bee
populations due to disease.
Leafcutter bee cells containing pupae are generally over wintered in
temperature controlled cold rooms. In spring, the bee cells are incubated in
wood,
plastic or cardboard trays until pupation is complete and emergence occurs.
The
process of spring incubation of bee cells must be well timed with alfalfa
bloom and
closely monitored. Males begin emerging first and die soon after mating,
followed by
the females, which can live for about 60 days. Once female emergence has
started,
incubation trays are taken to the field and placed into bee shelters
containing nests.
Typically, trays are transported during the early morning or late evening when
temperatures are lower; care must be taken to prevent prolonged exposure of
the
newly emerged bees to high temperatures during transport of the trays to the
fields.
This can be difficult for producers using existing trays that when stacked
directly on
top of one another provide no ventilation.
The female finds the tunnel-like nesting site and begins stacking in nest
~s cells until the tunnel is full. Each cell is constructed of about fifteen
leaf pieces and
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capped with two or three larger leafi pieces. When the tunnel is full, the bee
caps the
tunnel with a solid plug of leaf pieces. The female will continue until she
has
produced twelve to fifteen cells. The eggs hatch and pupate within a few
weeks. To
finish the season, nest material is collected and cells are pushed out,
tumbled to
remove debris and wintered at constant temperature in clear plastic bags.
Following
winter storage, cells are placed into trays to a depth of 1.5 to 2.0 inches
for spring
incubation.
Existing trays are made of wood, plastic or cardboard, the latter
inexpensive but useless after two or three seasons. Wood trays are the most
common and are usually homemade and reused from season to season; however,
the costs of manufacturing and maintaining wood trays can be significant, so
plastic
trays have been gaining in popularity among producers. Plastic trays are easy
to
maintain and disinfect, and they can be manufactured of strong, durable
material.
One significant disadvantage of existing trays, whether wood or plastic, is
the use of
aluminium mesh screen on the top surface to provide ventilation and
observation
means, as the incorporation of such screens increases the production cost
white
being susceptible to tearing.
Some mould species rnay cause considerable damage to leafcutter bee
populations and may also be harmful to the health of alfalfa seed producers.
Producers working in close proximity to bees and cocoons on a regular basis
can be
exposed to high levels of spores from bee-related fungi. Some of these moulds
have
been implicated in allergic reactions and bronco-pulmonary disease and are
considered major fungal allergens. A number of moulds, yeasts and bacteria are
commonly associated with the bees and grow on nest material. on cocoon
surfaces
2s (leaf debrisl. pollen balls, adult bees and dead larvae. Methods for
controlling moulds
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heat treatment of nest material, and Para formaldehyde fumigation of nest
material.
Chalkbrood disease of leafcutter bees was first identified in American
bee populations in the early 1970s and is a major problem in western Canada.
Chalkbrood is now found at economically damaging levels in all major American
alfalfa seed-growing areas where leafcutter bees are used for pollination. The
disease kills leafcutter bee larvae after they ingest spores ofi the fungus
while feeding
on pollen. When an adult female feafcutter bee emerges from her cell, she may
become dusted with spores, which stick to her body hairs. These spores then
become mixed into the pollen balls, which she prepares for the larva before
laying her
eggs. The young larva eats the pollen ball and ingests chatkbrood spores.
Death
generally occurs in the final larval instar before pupation, so dead larvae
are usually
full-sized. This is a significant problem for producers buying used leafcutter
bee nests
or other equipment.
Research to develop new technology for controlling moulds, yeasts and
bacteria on the surface of alfalfa leafcutter bee cells has led to the
discovery of Para
formaldehyde as a fumigant, which is highly efficacious in decontaminating the
cells.
Fumigation of bee cells for control of chalkbrood and other moulds should
occur just
prior to their incubation. Cells are placed in incubation trays in a well-
sealed
fumigation chamber. The trays are placed in racks that will permit air
movement
between trays and fumigation is carried out. Adult bees will emerge from
incubation
trays carrying fewer spores. Adequate ventilation in the fumigation chamber
and in
the incubator is required following fumigation since the bee cells and
incubation trays
may absorb the fumigant gas and release it during the incubation process to
follow.
Ventilation is usually continued during the first five to seven days of
incubation to
~S ensure there is no build-up of formaldehyde gas residue. Adequate fresh air
intake
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also be surface sterilized by dipping in a 3% bleach solution for three
minutes just
prior to incubation. After dipping, the cocoons should be well drained and
spread out
to dry in a ventilated area away from direck sunlight. Once they are
completely dry, the
cocoons may be incubated.
The wasp parasite, Pteromalus venustus, is the most common parasite
associated with populations of the alfalfa leafcutter bee in western Canada.
For
control of these parasites during spring incubation of bee cells, producers
may use
the insecticide dichlorvos in the resin strip formulation known as Vapona~.
Early
treatment with dichlorvos is not recommended and can cause significant bee
mortality. Treatment is recommended during days seven to fourteen of the
incubation
cycle when the parasites typically emerge. Current incubation tray lids have
aluminium mesh screens that can restrict parasites from leaving the tray when
the lids
are not taken off. During the first two weeks, some producers remove the lids
from
the incubation trays to allow parasite escape and capture them using black
lights and
water traps at the floor level of the incubation chamber. Use of dichlorvos
during
incubation can result in higher mortality in developing bee pupae when rates
and
treatment times are increased. During this process, mortality of bees can also
be
higher in the top layer of cells in the incubation tray due to increased
exposure to the
insecticide. Use of dichlorvos in the incubator should be followed by an
extended
period of ventilation lasting 48-72 hours.
The Canadian forage seed industry holds significant economic value.
The value of forage seed exports averaged $56 million during the years
19901995.
The main exports are timothy, creeping red fescue, alfalfa, clover and
Ieafcutter bees.
Trading mainly to the United States, sales are also made regularly to Europe
and
occasionally to Russia and China. Of all forage seed produced in this $100
million
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element of maintaining and increasing the strength of alfalfa and teafcutter
bee export.
However, as pointed out above, there are numerous problems with
existing leafcutter bee management tools. Existing trays incorporate aluminium
mesh
screens on their upper surface to enable ventilation and observation, but such
screen
is weak and may discourage parasitoid egress from the tray when lids are left
on_
The removal of the tray lid during initial incubation and parasitoid emergence
is an
option, however some producers choose to leave lids in place, thus risking
higher
mortality due to parasitoids. Also, the use of screen on the upper surtace
does not
address the need for air circulation due to heat build-up during transport, as
stacking
of trays directly on top of each other effectively eliminates any air
circulation.
While artificial nests are known in the art, for example United States
patents 3,936,894 to Barber and 4,365,372 to Norman, none effectively address
the
problems canvassed above. Improved ventilation is addressed in the field of
observation or mating chambers, far example United States patents 5,158,497 to
Rossignol et al. and 5,628,671 to Stevens, but the teaching is inapplicable to
the
unique requirements of incubation trays.
SUMMARY OF THE INVENTION
The present invention seeks to provide an insect rearing tray that
provides ventilation while stacked, structural strength, and parasite egress
encouragement.
According to one aspect of the present invention there is provided an
insect rearing tray comprising:
a base member for containing insects, the base memb~r having an open
top;
a cover member for covering the open top of the base member and
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lower surface and a peripheral wall; and
vent openings in the peripheral wall sized to retain the insects within the
container.
In exemplary embodiments of the present invention, the upper surface
also has vent openings sized to retain the insects within the container.
Preferably, the
base member and the cover member have corresponding mating means for mating
the base member to the cover member, and these mating means are preferably
designed to enable the cover member to be mated to another cover member rather
than the base member, ifi so desired. The base member and cover member of the
present invention are preferably made of injection-moulded plastic, the
plastic being
one selected from the group consisting of ABS, poiystyrene and polypropylene.
As the peripheral wall incorporates vent openings, the need for
ventilation and air circulation is met even while trays are stacked. Also,
producers
can leave the cover member in place during initial incubation and parasitoid
emergence, as the structure is such that parasites are not discouraged from
exiting
the tray. if producers choose to leave the cover member on the incubation
tray, the
vent openings along the peripheral wall should allow air to pass closer to the
surface
of the bee cells inside. The incorporation of vent openings in the upper
surface of the
container enables observation of the insects with the cover member in place,
especially important when determining sex and quantifying emergence of the
bees.
Finally, removing the need for aluminium mesh screens increases the structural
strength, and the ability to solely employ injection-.moulding manufacture in
providing
a ventilated container decreases manufacturing costs.
A detailed description of an exemplary embodiment of the present
invention is given in the following. It is to be understood, however, that the
invention
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BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary
embodiment of the present invention:
Figure 1 is a perspective view of the present invention with the base
member mated to the cover member;
Figure 2 is a side elevational view;
Figure 3 is an end elevational view;
Figure 4 is a detailed cross.-sectional view of the mating means along
line 4-4 of Figure 1; and
Figure 5 is a top plan view showing a preferred amsngement of vent
openings in the upper surface.
DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT
Referring now in detail to the accompanying drawings, there is
illustrated an exemplary embodiment of the insect rearing tray of the present
invention
generally referred to by the numeral 10. As can best be seen in Figures 7, 2
and 3
(not in scale to each other), the insect rearing tray 10 is comprised of a
base member
12 for containing insects (not shown), the base member 12 having an open top
(not
shown), a cover member 16 for cowering the open top of the base member 12 and
engageable with the base member 12, and vent openings 24. When mated together,
the base member 12 and cover member 16 provide a container having an upper
surtace 18, a lower surface 20 and a peripheral wall 22. The vent openings 24
in the
exemplary embodiment are located on the peripheral wall 22 and upper surface
18.
The insect rearing tray 10 also comprises mating means 2fi, an
exemplary embodiment best seen in Figures 1, 4 and 5, for mating the base and
cover members 12, 16. Figure 4 provides a detailed cross-sectional view of the
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the centre line of the insect rearing tray 10 can be seen as an inverse mirror
image
an-angement. With this arrangement, the cover member 16 can be mated with the
base member 12 even when in a reversed position. Also, this arrangement
enables
the mating of two base members 12 or two cover members 16, if desired.
The utility of the present invention becomes clear in the following
situation_ Once the over wintering of the bee cells (not shown) is complete
and spring
arrives, the bee cells can be emptied into a base member 12. A cover member 16
is
then placed on the base member 12 and mated using mating means 26 to provide a
container within which the bees can incubate. The cover member 1 fi can be
left in
place during the entire incubation process if so desired, which commonly lasts
a
period of 24 days. The use of vent openings 24 in the upper surface 18 and
peripheral wall 22 enables observation of the bees for sexing and quantifying
emergence. Once female emergence has reached approximately 75%, which
commonly occurs around day 23 or 24 of the incubation cycle, the insect
rearing tray
10 is then transported to the field for adult bee release. This transport need
not be
limited to times of day when the temperature is at its lowest, as the vent
openings 24
in the peripheral wall 22 allow for increased air cooling of the bees.
While a particular embodiment of the present invention has been
described in the foregoing, it is to be understood that other embodiments are
possible
within the scope of the invention and are intended to be included herein. It
will be
clear to any person skilled in the art that modifications of and adjustments
to this
invention, not shown, are possible without departing from the spirit of the
invention as
demonstrated through the exemplary embodiment. For exampl~, the insect rearing
tray 10 could be designed so as to open to the side rather than the top, and
various
forms of mating means 26 could be used to achieve the same result. The
invention is
