Amitraz Resistance Update
September 25, 2024
In our last apiculture newsletter, we described the development of new assays to detect two mutations (DNA changes) in the one gene associated with resistance. The two mutations were in different parts of the gene (beta-2 octopamine receptor). This is in contrast to resistance to pyrethroids where there are 3 mutations that lead to Bayvarol/Apistan resistance – but all 3 mutations are tightly clustered.
Since the reporting of the new tests, more literature has emerged suggesting that one of the (N87S) is *not* associated with resistance as they authors found varroa with the mutations that were sensitive to amitraz as well as resistance bees that also carried the mutation.
However since the two mutations were quite distinct on the gene, the concern was that other mutations could become apparent that weren’t covered by the two tests we developed. In other words, the two tests would show no evidence of the known resistance markers and yet amitraz would not kill varroa.
And indeed they have. . .’they’ meaning yes, more than one.
Two new mutations have been described in separate reports in the last month (Aug/Sept 2024) – one named Y337F in Turkish varroa populations (Inak et. al., 2024) and the other as F290L in Spanish populations (Hernández-Rodríguez et al., 2024). The latter authors described the earlier reports of the two mutations discovered in the same gene. It is likely that others will arise as the ability to rotate chemicals becomes more difficult overseas.
In short, keep any varroa from alcohol/CO2 washes or sugar shakes, where amitraz resistance may be suspected. While we can test for known mutations, screening methods for multiple or unknown mutations in this particular gene will need to be developed as well.
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