Agriculture Reference
In-Depth Information
'Organic' controls
Thymol, formic acid, lactic acid, oxalic acid and other essential oils are 'soft' chemicals
that are reliable to varying degrees but, for good effect, they must be employed at
the right time and in the right circumstances. Some, however, are very temperature
dependent. I found, for example, that those based on thymol could cause the bees to
abandon the hive and abscond if employed when the temperature was too hot. This is
particularly the case with homemade thymol treatments. Commercial treatments are,
however, available based on some of these substances - such as Apilife Var (various oils
and thymol; see Figure 27), Apicure (formic acid) and Apiguard (thymol).
The biggest problem with essential oils compared with such chemical treatments as
fluvalinate (used in Apistan) is the small difference between the amount of the substance
that will kill the mites and the amount that will kill the bees. Fluvalinate, for example,
is 800-1000 times more toxic to varroa than to bees, whereas the best essential oils are
only two to four times more toxic. This doesn't apply to all oils, however. Thymol is not
toxic to bees, for example. Unless you know what you are doing, therefore, it is not wise
to make your own treatments using various oils because you may well be assisting the
varroa mites in finishing off your colony. Further, oils may well contaminate the wax
and the honey in the hive and may well be dangerous to humans. Be careful, therefore,
using these treatments.
Devices for the efficient use of oxalic and lactic acids are also commercially available.
One of these is simply a heated spoon that contains crystals of oxalic acid. The spoon is
plugged into a car battery, inserted into the hive's entrance and turned on. The crystals
then vaporize in the hive. This process takes about two minutes.
Biotechnical controls (manipulations)
If carried out correctly and at the right time, drone-brood trapping can dramatically
reduce the number of varroa and will not affect the colony as much as worker-brood
trapping (see below). This method is based on the fact that, as mentioned earlier, varroa
mites are more attracted to drone brood than worker brood.
The frames of drone brood (in which the varroa mites prefer to live when starting their
reproductive cycle) are removed from the hive and destroyed. This method may hence
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