Pyrethroid resistance discovered in a major agricultural pest in southern Australia: the redlegged earth mite Halotydeus destructor (Acari: Penthaleidae).

BACKGROUND

The redlegged earth mite (Halotydeus destructor Tucker) is an important pest of field crops and pastures. Control of this pest relies heavily on chemicals, with few genuine alternatives presently available. Pesticide responses of H. destructor from the field with reported chemical control failures were compared with mites from susceptible 'control' populations. Toxicology bioassays were conducted on adult mites across multiple generations.

RESULTS

Very high levels of resistance to two synthetic pyrethroids, bifenthrin and alpha-cypermethrin, were detected in this species for the first time. For bifenthrin, LC(50) estimates showed a difference in resistance of greater than 240 000-fold. Resistance to alpha-cypermethrin was almost 60 000-fold. This resistance was shown to be heritable, persisting after several generations of culturing. There was no evidence that resistance to organophosphorus chemicals had evolved, which is likely to be a direct consequence of the history of chemical applications these mites have experienced.

CONCLUSION

These results highlight the need for more judicious management decisions in order to control pest species in a sustainable manner. The implications of these findings in regard to the management and future research of the redlegged earth mite are discussed.