MO-bioassay. Mean times (± S.D.) tick nymphs stayed attached to the filter paper. The filter paper on the attachment site of the rotating drum was treated either with 10% DDA (n = 28) or with one of the 10% DDA-based formulations (Trial 1: batch no. 030138, n = 23; batch no. 030142, n = 20). The control run (blank test, n = 27) was performed without repellent but under otherwise identical conditions. Differences between the control and each of the test substances are statistically significant (ANOVA, P < 0.001).