SEASONAL ABUNDANCE AND CONTROL OF SPIDER MITES (TETRANYCHIDAE) INFESTING COMMERCIAL STRAWBERRIES IN COASTAL NEW SOUTH WALES

The seasonal abundance of the spider mites Tetranychus urticae Koch and T. ludeni Zacher was studied on commercial strawberry farms near Sydney, New South Wales between 1978–1981. T. urticae was the dominant species with T. ludeni assuming a minor role. T. urticae usually first appeared each year in May‐June, with populations developing through winter and increasing to, and sometimes exceeding, the economic threshold level in spring‐summer. In early January, populations were low or absent. In winter, temperature was not an impediment to pest population increase and adult females remained in a non‐diapausing phase. Miticide sprays gave variable control of T. urticae outbreaks, probably due to the difficulties of applying the spray to the underside of leaves and widespread resistance within pest populations. The predator Phytoseiulus persimilis Athias‐Henriot, where it occurred, survived under most conditions and was an important factor in controlling T. urticae infestations. Another predator, Amblyseius womersleyi Schicha, occurred infrequently and at low numbers and contributed little to control.