Main content area

Baseline bioassays with hexythiazox and clofentezine of three mite species (Acari: Tetranychidae) occurring on Washington and Oregon tree fruits

Rathman, R.J., Beers, E.H., Flexner, J.L., Riedl, H., Hoyt, S.C., Westigard, P.H., Knight, A.L.
Journal of economic entomology 1990 v.83 no.5 pp. 1711-1714
Panonychus ulmi, ova, Pyrus, hexythiazox, bioassays, clofentezine, Tetranychus mcdanieli, Malus domestica, Tetranychus urticae, insecticide resistance, Oregon
Eggs from Panonychus ulmi (Koch), Tetranychus urticae Koch, and T. mcdanieli McGregor collected from apple and pear orchards in Oregon and Washington were tested with the acaricides hexythiazox and clofentezine to establish baseline responses before the compounds were registered and were widely used in the field. Within mite species, few significant differences were detected among LC50's for populations tested with either compound; differences at this response level ranged from 2- to5-fold. LC50's were significantly different between species; they werehigher for P. ulmi than for either T. urticae or T. mcdanieli. Although not significantly different, LC50's for both compounds were generally higher for T. mcdanieli than for T. urticae. LC50's for P. ulmi were three times higher for clofentezine than hexythiazox. For T. urticae, LC50's for bothchemicals were similar, but the LC50 for clofentezine with T. mcdanieli was somewhat lower than the LC50 for hexythiazox. LC50's for hexythiazox for populations of T. urticae collected from apple versus pear and populations collected from Medford, Oreg., versus morenorthern fruit-producing regions in Oregon and Washington were not significantly different.LC50's for clofentezine were not significantly different for populations of T. urticaecollected from apple and pear.