SYSTEMATIC PRESENCE-ABSENCE SAMPLING METHOD APPLIED TO 2-SPOTTED SPIDER-MITE (ACARI, TETRANYCHIDAE) ON STRAWBERRIES IN VICTORIA, AUSTRALIA

An empirical relationship between the mean density of twospotted spider mite, Tetranychus urticae Koch, on strawberries, Fragaria x ananassa Duchesne, and the proportion of mite-free leaflets was established from the results of 170 samples taken during two seasons. Confidence intervals for the mean density predicted from a presence-absence sample were derived, and an adjustment was made to account for the sample not being truly random. A sampling plan is proposed that could be adopted readily by growers wishing to provide integrated control of twospotted spider mite on strawberries. Following a systematic sample of 100 leaflets, it is recommended that the predator Phytoseiulus persimilis Athias-Henriot be released if the proportion of mite-free leaflets falls to 75% and that spraying with a miticide be undertaken when it drops to 5%.