2514 © The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. Short Communication Spray and Pour-On Acaricides Killed Tennessee (United States) Field-Collected Haemaphysalis longicornis Nymphs (Acari: Ixodidae) in Laboratory Bioassays R. A. Butler, 1,3, J. G. Chandler, 1 K. M. Vail, 1, C. J. Holderman, 2, and R. T. Trout Fryxell 1, 1 Department of Entomology and Plant Pathology, The University of Tennessee, Knoxville, TN, USA, 2 Central Life Sciences, Dallas, TX, USA, and 3 Corresponding author, e-mail: rbutle25@vols.utk.edu Disclaimer: The content of this publication is solely the responsibility of the authors and does not necessarily represent the offcial views of the Foundation for Food and Agriculture Research. Subject Editor: Timothy Lysyk Received 18 April 2021; Editorial decision 1 June 2021 Abstract Haemaphysalis longicornis Neumann (Asian longhorned tick) is an exotic and invasive tick species presenting a health and economic threat to the United States (U.S.) cattle industry due to its ability to transmit pathogens and infest hosts in large numbers. The objective of this study was to evaluate available products at causing H. longicornis mortality in a laboratory bioassay. The effcacy of products was evaluated at label rates using H. longicornis nymphs collected from a cattle farm in eastern Tennessee in two different bioassays (spray or dip) against untreated controls. After exposure, ticks were transferred to clean petri dishes and checked for mor- tality at 0, 1, 2, 3, 4, 21, 24, and 48 h post exposure. No mortality occurred in the untreated controls, whereas all treated ticks were dead within 24 h of exposure (P < 0.0001). These fndings support the hypothesis that currently available spray and pour-on products are effective at causing H. longicornis mortality. We conclude that these acaricides can be used as a component to prevent H. longicornis dispersal and for control in the U.S. Key words: acaricide, management, bioassay, Haemaphysalis longicornis Haemaphysalis longicornis Neumann (Asian longhorned tick) (Acari: Ixodidae) is an exotic and invasive pest recently discovered in the United States (U.S.), with populations now established in several eastern states (Egizi et al. 2020). This species feeds on a variety of wildlife, companion animal, livestock, and human hosts (Schappach et al. 2020; USDA-APHIS, 2020). Recently, this economically im- portant tick species has been found with Theileria orientalis gen- otype Ikeda which is associated with diseased cattle (Oakes et al. 2019; Thompson et al. 2020) and newly invasive populations of this tick can transmit this pathogen (Dinkel et al. 2021). Knowing the U.S. strain of H. longicornis has a parthenogenetic reproduc- tive strategy (Hoogstraal et al. 1968; Qiu et al. 2020), it is specu- lated that the strategy can increase the ticks invasive potential and cause signifcant blood loss causing death from anemia (Rainey et al. 2018; Oda et al. 2019; Egizi et al. 2020). Current H. longicornis management strategies are adopted from the ticks’ native range or include those used for North American tick species (Schappach et al. 2020). In the United States, there are no established or evaluated H. longicornis management programs and there are limited data on acaricide effcacy (Schappach et al. 2020). Previous studies in other countries evaluated systemic and top- ical products for H. longicornis control. Otaki et al. (2018) found lotilaner (Credelio, Elanco, Greenfeld, IN), a veterinary drug com- monly used to treat companion animal ectoparasites, effectively killed H. longicornis adults when administered to dogs as a chewable tablet. Similarly, afoxolaner (Nexgard, Merial, Duluth, GA) canine chewable tablets killed 100% of H. longicornis 48 h after frst expo- sure (Kondo et al. 2014). Amitraz, commonly formulated as a spray and cattle pour-on (PO), signifcantly reduced the number of female H. longicornis on calves (Heath et al. 1980). Topical imidacloprid and permethrin were 100% effective at killing female H. longicornis ticks within 4 d after feeding for 3 h on treated dogs (Hagimori et al. 2005). Journal of Medical Entomology, 58(6), 2021, 2514–2518 doi: 10.1093/jme/tjab115 Advance Access Publication Date: 1 July 2021 Short Communication Downloaded from https://academic.oup.com/jme/article/58/6/2514/6312693 by guest on 30 April 2023