Rothamsted scientists have identified the specific mutation in the voltage-gated sodium channel (the target site for pyrethroids like tau-fluvalinate [Apistan] and flumethrin) that confers resistance in mites. Interestingly the mutation appears to be lost in the absence of pyrethroid application, suggesting it may be deleterious unless pyrethroids are present. This implies that areas historically associated with pyrethroid resistance – of which there are many – may be able to use these chemicals again to control the mite.
Identification of the mutation may enable genetic screening for resistance to be undertaken. In addition, now the mutation is identified it should be possible to determine how quickly it is acquired during Apistan treatment (which can of course also be tested for phenotypically), and how long it takes to be lost after treatment terminates. This may enable some sort of rational pyrethroid treatment regime to be developed, with alternating pyrethroid and non-pyrethroid applications.