EFFECT OF ALPHACYPERMETHRIN AND BIFENTHRIN ON THE SURVIVAL OF 5 ACARINE PREDATORS OF HALOTYDEUS DESTRUCTOR (ACARI, PENTHALEIDAE)

The synthetic pyrethroids, alphacypermethrin and bifenthrin, were eval uated in the laboratory and field for their impact on the survival of five acarine predators of the pasture pest, Halotydeus destructor (Tuc ker). In laboratory bioassays, alphacypermethrin at the proposed field rate (5 g a.i. ha(-1)) for H. destructor and the scarab beetle pest, Aphodius tasmaniae Hope caused medium-high mortality to Walzia austral ica Womersley (Anystidae), Bdellodes affinis Atyeo (Bdellidae), Balaus tium murorum (Hermann) (Erythraeidae) and Parasitus fimetorum (Berlese ) (Parasitidae) but was not toxic to Cyta latirostris (Hermann) (Bdell idae). In the held populations of W. australica and B. affinis treated with this rate were significantly reduced but recovered after 8 weeks . Bifenthrin at 5 g a.i. ha(-1) killed 96-100% of W. australica, B. af finis, B. murorum and P. fimetorum in laboratory bioassays and signifi cantly reduced field populations of W. australica and B. affinis for 1 7 weeks. In bioassays both products at 2.5 g a.i. ha(-1) permitted 10- 30% survival of B. affinis and B. murorum and alphacypermethrin permit ted 59% survival of W. australica. A 2.5 g a.i. ha(-1) rate of alphacy permethrin is recommended for control of H. destructor in pasture when A, tasmaniae is not present, thus minimizing the impact of chemical c ontrol on the survival of some predatory mite species.