Nineteen EOs were pre-screened for their acaricidal effects with a
0.1% concentration using the dipping method. Each experimental unit
consisted of a kidney bean leaf disk (diameter 30 mm) onto which 30
female T. urticae adults were inoculated on wet cotton pads soaked in
distilled water in a plastic Petri dish (diameter 60 × 15 mm). The
female adults were inoculated on the lower surface of a bean leaf disk
with a fine brush. The bean leaf disk with adult mites was dipped in
the test solution for 5 s, then, placed upside down, so that the lower surface
of the leaf was facing up, on the cotton pad in the Petri-dish,which
was then maintained at 24 ± 2 °C, 40–80% relative humidity, and
16:8 h light:dark in the laboratory. The total number of live and dead
adult mites was checked 24 h after dipping. The T. urticae adults were
considered dead if no movement was apparent by probing with the
tip of a fine brush. The number of eggs oviposited by the female mites
treated with EOs was counted under a dissecting microscope (Stemi
2000, Carl Zeiss, Jena, Germany). These experiments were replicated
three times. Using the result of this experiment, five EOs were preselected
as more effective than the others. These oils were re-tested
for their acaricidal effects using higher concentrations, 0.5% (5 ml/l)
and 1% (10 ml/l).