BusyKnight of Texas questioned the reports claiming Varroa mite
resistance to fluvalinate (Apistan R). For verification of these
claims, and unfortunately they are no longer rumours or anecdotal
observations, you may refer to Apidologie 26(1) where Lodesani et al.
confirm the 'ineffectiveness' of Apistan in Italy's Lombardy region.
It has been claimed that this is the result of the inappropriate use
of the product by applying the (cheaper) liquid formulation in various
forms (eg. dipping cardboard strips and suspending them in the hive).
However, inappropriate use also consitutes the placement of Apistan
strips for prolonged periods, far exceeding the recommended treatment
period as stated on the label.
Here in Western Canada, there has been a rapid increase in the use of
Apistan as Varroa has entered new areas. But what has been happening
is that many producers have adopted a management of convenience by
installing strips during fall preparation and leaving them in until
early spring. Surely, an ideal environment towards the rapid
development of 'Apistan-resistant' mites. Also, the extended
exposure may cause fat-soluble fluvalinate to migrate into the comb,
potentially affecting bee brood development after successive years.
What this means is that the threat of Apistan resistant mites may be
much nearer than many of us think. The repercussions of losing
Apistan as a Varroa mite control agent will be serious. Not only will
producers resort to all kinds of "snake-oil" recipes but in the
process, may end up contaminating their bees, equipment or honey.
Indeed, in Europe several other products are registered for use
including Bayverol (flumetrin). The problem with flumethrin is that
it also belongs to the family of synthetic pyrethroids, as fluvalinate
does. As has been observed in other mite pests, most notably the
two-spotted spider mites, the build-up of resistance to one
pyrethroid has often led to the simultaneous resistance to other
closely related pyrethroids. It would not be surprising if the
Apistan-resistant mites of Lombardy display comparable levels of
tolerance (resistance?) to flumethrin.
While there is a genuine danger for the beekeeping industry to lose
Apistan as a valuable tool of control, there appears no imminent
arrival of other effective controls. The only alternative available
in Canada is formic acid which under favorable conditions may offer
good control. But formic acid, as cheap as it is, has to be handled
with care and may not always be good to the bees. It is therefore in
everyone's interest to retain Apistan's effectiveness as long as
possible:
. Use Apistan only when needed,
. Do not use alternate Apistan application methods,
. Always remove strips upon treatment completion,
. Do not re-use Apistan strips (I know it's tempting),
. Alternate with other (registered) products (eg. formic
acid).
Paul van Westendorp [log in to unmask]
Provincial Apiarist
British Columbia
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