Acaricide Resistance Development in Rhipicephalus (Boophilus) Microplus (Acari: Ixodidae) Populations against Amitraz and Deltamethrin on Communal Farms of the King Sabata Dalindyebo Municipality, South Africa

Abstract

Chemical acaricides are widely used to control ticks and tick borne pathogens on cattle. However, prolonged and indiscriminate use of these chemicals inevitably leads to selection of resistant ticks. In-vitro bioassays (adult and larval immersion tests) were conducted to assess amitraz and del-tamethrin resistance in Rhipicephalus (Boophilus) microplus populations from communal farms of the King Sabata Dalindyebo municipality of South Africa. Data generated on percentage inhibi-tion of oviposition (% IO) revealed that all the tick populations assessed showed resistance (% IO≤ 95%) to at least one of the acaricides. All six tick populations assessed for efficacy (% IO≥ 95% at the DD) with deltamethrin were resistant (% IO≤ 95%) and only one of six tick populations as-sessed for efficacy with amitraz was susceptible. Based on resistance ratios, the adult immersion test detected amitraz and deltamethrin resistance in three and five of the six tick populations re-spectively. With the larval immersion test, deltamethrin and amitraz resistance (Larval mortality < 90 % at the DD) was detected in all four, and three of four R. (B.) microplus populations assessed respectively. This data is critical for the design of an effective and sustainable tick control strategy on the communal farms.