FACTORS TO BE CONSIDERED WHEN USING THE “TRICKLE OXALIC ACID TREATMENT”
The final
treatment of the colonies in autumn or early winter is a component of many
anti-Varroa treatment regimes. The aim is to reduce the Varroa infestation
level to an absolute minimum, so that in the following season there is no
problem with Varroa before the late summer. This procedure has proved itself to
be effective in beekeeping practice. It is one method of anti Varroa treatment
which does not cause residues in the hive products, oxalic acid is an organic
substance. The treatment is carried out after the colony has ceased to rear
brood. In this brood free condition one treatment is sufficient to achieve an
effectiveness of over 90%.
Many strong
colonies with older queens cease to rear brood in October. In nucleus colonies
with young queens this is seldom the case. This might possibly be due to their
development phase only ending in late summer, while the older stronger colonies
have already reached their peak of development by June. Brood rearing in autumn
is influenced by apiary location, but more so by the weather. The first night
frosts cause the queen to stop egg laying. Three weeks later the colony is
brood free. At this time the oxalic acid trickle method is at it’s most effectiveness.
The removal of the hive roof and crown board to facilitate the treatment has no
detrimental effect on the bees.
PRIOR TO
TREATMENT - CHECK THE NATURAL MITE FALL
Not every
colony requires to be treated in the late autumn. A prior check on the natural
mite fall carried out in November is worth while. To facilitate this insert is
placed on the floorboard. The natural mite fall check is carried out a week or
two later. If the fallen mites are light coloured there is still infected
emerging brood in the colony! If the natural mite fall is more than 1 mite per
day a further treatment is recommended, more than 5 mites per day needs
immediate treatment. If untreated colonies indicate an average of 1 mite per
day in November, this indicates that there are still some hundreds of mites in
the colony.
The over
wintering capability of such a colony is not in danger, however by the
following summer the colony could be very heavily infested. Therefore treatment
is recommended. If this is not done then in early summer, drone brood
sacrificial combs must be utilised.
DESCRIPTION
OF THE TRICKLE METHOD
The treatment
is carried out using a warm sugar syrup solution at an oxalic acid
concentration of 3.5% applied using a syringe or some other suitable device.
The procedure should be carried out in such a manner that it can be
administered in a droplet form.
Oxalic acid
may be purchased in the local chemist; The cost is £4.70 per 500 gram. At 2004
prices. Warm tap water may be used to make up the solution.
The solution
should be stored for immediate use only, in a bottle with a secure top and
clearly marked as to the contents. Any calcium in the water will combine with
the oxalic acid and precipitates as insoluble calciumoxalate crystals. The
effect on concentration of the solution will be negligible. The addition of
sugar to the solution will merely result in a more rapid mite fall; it has no
effect on the efficiency or bee tolerance and does no harm. During the
treatment the weather must be cold, a few degrees above freezing is ideal.
Smoke should be used only sparingly, if at all as the colonies are clustered
tightly due to low temperature.
The colonies
cluster under a deep crown of stores in November/ December. The treatment of
colonies on single brood chambers is relatively easy since the cluster position
can be seen. In the case of double brood chambers it is often more difficult,
especially if the bees are clustered in the lower box. The use of a torch may
expose the position of the cluster or the top box may be tipped up. In this way
the treatment can be trickled into and not onto the cluster. It is best to take
a little care and time when treating. It is better to do two passes over each
frame space. The more bees which are in contact with the solution the better
the treatment will be tolerated and the solution will be more readily
distributed around the colony. It is a good idea to note the number of seams of
bees as soon as the hive is opened and the bees are tight clustered. As
treatment proceeds the cluster tends to break up, and you have more seams of
bees than was first noticed. Treat for the number of seams first noticed, but
spread the acid over as many bees as possible.
According to
the size of the colony the dose varies between 30-50 milli litres. 30 milli
litres if the colony is tightly clustered in temperatures under or at 0ºC and
only covering 4-5 frames, 50 milli litres when the cluster is on 6-7 frames.
The treatment must only be administered once.
Repeated
applications are not tolerated well by the bees. Large numbers of bees will
become over acidified and fly prematurely and not show as mortality on the hive
floor. In colonies free of brood a second treatment would be superfluous
anyway.
The mite fall
resulting from the late treatment should be noted and compared with the result
of the initial findings for natural mite fall. The mite drop continues to
increase over a 4-5 week period, even when most of the poisoned mites (80%)
drop during the first week after treatment
The trickle method at a glance
1. A 3.5%
solution of oxalic acid and sugar. (200 g sugar 35g oxalic acid “accurate
measurements please “dissolved in 3/4 litre of warm water, then more warm water
added to the solution to make a 1 litre total quantity).
2. 100 mIll
syringe.
3. Acid proof
gloves (important!)
4. Each
colony is dosed with 30 to 50 ml. of solution at a dosage of
5. Treatment
is in November or December at just above 0°C. Try to administer when there is
some weather coming up that will enable them to fly and relieve themselves
Administer treatment in as many droplets of solution as possible and drip onto
as many bees as possible. (Do not shake solution onto bees!)
6. Mite fall
continues for 4-5 weeks.
7. Good
efficiency only in brood free colonies.
8. Two
applications is one too many.