CHEMICAL RESISTANCE IN POPULATIONS OF TETRANYCHUS URTICAE (KOCH) (ACARINA: TETRANYCHIDAE) FROM APPLE ORCHARDS IN NEW SOUTH WALES, AUSTRALIA

Abstract

The response of eleven Tetranychus urticae populations from the Orange district of New South Wales to seven commercial acaricides has been determined in laboratory tests. The frequency of resistance to these compounds and the probable source of such resistance are discussed. Widespread resistance at the 50% mortality level to methidathion (up to 108‐fold) and tetradifon (6.4‐fold), and less frequent resistance to dicofol (17.5‐fold) have been established in the sample populations. A rapid bioassay method involving direct excision of mite‐infested leaf dises, adjustment of the test population by a vacuum needle apparatus, and spray tower application, are described. Copyright © 1973, Wiley Blackwell. All rights reserved