Toxicity of Tebufenpyrad to Tetranychus urticae (Acari: Tetranychidae) and Amblyseius womersleyi (Acari: Phytoseiidae) Under Laboratory and Field Conditions

The toxicity of the pyrazole acaricide tebufenpyrad to the twospotted spider mite, Tetranychus urticae Koch, and the predatory mite Amblyseius womersleyi Schicha was evaluated in laboratory and field studies. In a laboratory study with the susceptible T. urticae, tebufenpyrad was highly effective against eggs, immatures (larvae and protonymphs), and adults at 25 ppm (100% mortality). Moderate levels of resistance to tebufenpyrad were observed in dicofol-resistant DR-20 (resistance ratio, 15-fold), fenpyroximate-resistant FR-20 (24-fold), and pyridaben-resistant PR-20 strains (33-fold), indicating a careful use of this acaricide on apple orchards. Additionally, tebufenpyrad had no repellent activity against either adults or immatures of the susceptible and resistant T. urticae. In 1995 and 1996 field studies of a population of T. urticae, efficacy of tebefenpyrad, expressed as a protective value at 15 or 20 d in each treated plot relative to an untreated plot, was similar to that of the commonly used azocyclotin and fenazaquin. In the laboratory and field studies with A. womersleyi, tebufenpyrad exhibited adverse effects, but this predatory mite species was more tolerant than T. urticae: 2.8, 82.2, and 46.6% mortalities against eggs, immatures, and adults at 25 ppm, respectively. No phytotoxicity was observed with this acaricide in 17-yr-old ‘Fuji’ and 11-yr-old ‘Tsugaru’ apple trees. Based on laboratory and field data, tebufenpyrad may be used to prevent damage by T. urticae and in alteration with the earlier types of acaricides in a resistance management program if a properly timed tebufenpyrad treatment is done.