Possible risk factors on Queensland dairy farms for acaricide resistance in cattle tick (Boophilus microplus)

A case control study was carried out within a cross-sectional survey design ed to investigate the management by Queensland dairy farmers of the cattle tick Boophilus microplus. Although 199 farmers were surveyed, data on acari cide resistance were only obtained from 66 farms. Multiple models were used to predict the probability of acaricide resistance associated with 30 puta tive risk factors. The region of the state in which the farm was located an d the frequency of acaricide application were consistently associated with acaricide resistance. The risk of resistance to all synthetic pyrethroids ( Parkhurst strain) was highest in Central Queensland and increased when more than five applications of acaricide were made in the previous year, when s pray races were used and when buffalo fly treatments with a synthetic pyret hroid were applied frequently. The probability of resistance to amitraz (Ul am strain) was highest in Central Queensland, increased when more than five applications of acaricide were made in the previous year, and decreased on farms when a hand-spray apparatus was used to apply acaricides to cattle. The probability of resistance to flumethrin (Lamington strain) was highest in the Wide Bay-Burnett region. (C)2000 Elsevier Science B.V. All rights re served.