Susceptibility of Panonychus ulmi Koch populations collected from apple orchards in Isparta province was studied against etoxazole, spirodiclofen and hexythiazox, and their detoxification enzyme (esterase, glutathione-S-transferase (GST), monooxygenaz cytochrome P450 (P450) and acetylcholinesterase (AChE)) levels were determined. For this purpose, 13 P. ulmi populations were collected from Isparta province and its districts during summer periods of 2012-2013. Acaricides were applied to mites by spray tower-leaf bioassay method. The data were analyzed by the program POLO PC and LC50 values were calculated. The resistance ratios are calculated by comparing LC50 values of field populations with LC50 values of the susceptible population. The resistance ratios in P. ulmi populations ranged from <1 to 1.95-fold for spirodiclofen, <1 to 2.36-fold for hexythiazox, and <1-7.30-fold for etoxazole. In all population, detoxification enzymes levels were examined biochemically with different substrates. The levels of detoxification enzymes are changed according to populations.