A POTTER SPRAY TOWER BIOASSAY OF 2 PETROLEUM SPRAY OILS AGAINST ADULTFEMALE PANONYCHUS-ULMI (KOCH) AND TETRANYCHUS-URTICAE KOCH (ACARI, TETRANYCHIDAE)

A Potter spray tower was used to determine the susceptibility of adult female European red mites (Panonychus ulmi (Koch)) and two-spotted sp ider mites (Tetranychus urticae Koch) to suffocation by petroleum spra y oils (PSOs). The LC95 values calculated for P. ulmi against C23 Ampo l D-C-Tron NR and C21 Caltex Lovis were 104 and 165 mu g cm(-2), respe ctively. For T. urticae the values were 169 and 207 mu g cm-2, respect ively. The results are consistent with established relationships betwe en PSO efficacy and increasing PSO molecular weight. The results are d iscussed in relation to previously reported bioassays on spider mites and to concurrent evaluations of PSOs for use in pome fruit integrated pest management programmes in Australia. Exp Appl Acarol 22: 553-558 (C) 1998 Kluwer Academic Publishers.