{"doi":"10.1093/amt/tsae016","title":"Repellent assays to assess efficacy of botanical compounds against <i>Amblyomma americanum</i> and <i>Haemaphysalis longicornis</i> nymphal ticks","abstract":"The invasive tick Haemaphysalis longicornis was introduced to the United States in 2010 or earlier, posing a potential new challenge to vector control efforts. Amblyomma americanum, a vector of ehrlichiosis and other pathogens of human importance, is experiencing range expansion and population growth in northern regions of the United States. Here, we investigate the repellent efficacy of botanical compounds, including carvacrol, eugenol, nerolidol, eucalyptol, and thymol, against A. americanum and H. longicornis nymphs. AIs including carvacrol, eucalyptol, eugenol, nerolidol, and thymol were obtained from Sigma–Aldrich (St. Louis, Missouri) and tested for repellency against A. americanum or H. longicornis nymphal ticks. Compounds were diluted in acetone to create a range of concentrations between 0.5% and 10%. A commercial 25% DEET product (OFF Deep Woods, Johnson & Johnson, New Brunswick, New Jersey) diluted in acetone was prepared and included in all assays as a standard treatment. Amblyomma americanum and H. longicornis nymphs were obtained from BEI Resources Repository (https://www.beiresources.org). Nymphs were stored at 22 °C and RH ≥ 75%. Only actively questing nymphs were used in the assays. Temperature and humidity of the room were recorded hourly for each assay mentioned below and ranged from 22 to 23 °C and 35%–40% RH. Preliminary experiments were conducted with different assay designs before selecting the 2 most effective assays described below. In addition, range-finding assays and comparisons of drying time were conducted to determine optimal conditions for testing. General methods for horizontal tick repellencies were followed as previously described by Bissinger et al. (2009) (doi: 10.1007/s10493-008-9235-x) with minor modifications. Briefly, after dilution of each compound and control in acetone to obtain a range of concentrations, 300 µl of solution was applied to one half of a circular 9-cm-diameter Whatman no. 1 filter paper (Whatman, Marlborough, Massachusetts). Another half of the filter paper was saturated in 300 µl of acetone alone to serve as a negative control. Filter papers were treated 30 min before the start of the experiment. Petri dish lids were lined with one treated and one control filter paper half using double-sided tape. Five A. americanum or H. longicornis nymphs were introduced to each petri dish arena using a small paintbrush, and dishes were secured with a rubber O-ring (Grainger, Lake Forest, Illinois) sandwiched between the petri dish top and bottom. Tick position on the treated or untreated filter paper half was observed and recorded at 5, 10, 15, 20, 25, 30, 45, 60, 120, and 180 min. Petri dishes were oriented on the work surface such that the line dividing the treated and untreated sides was perpendicular to and equidistant from the observer to reduce the influence of observer cues on tick movement. Mean percent repelled over the course of the assay was calculated as follows: Assays were conducted following the methods of Carroll et al. (2004) (doi: 10.1603/0022-2585-41.2.249) with modifications. Briefly, filter papers were cut into 4 × 8 cm rectangles. On each rectangle, a pencil was used to draw horizontal lines 2 cm from the top and bottom edges dividing the paper into 3 zones. Each compound or control was diluted as described above, and then 150 µl of each concentration was applied to the middle 4 × 4 cm zone of a filter paper rectangle. One filter paper rectangle was treated with 150 µl of acetone only to serve as a negative control. Filter papers were treated 30 min before the start of the experiment. Two ring stands were placed 50 cm apart, with ring heights adjusted to 16 cm above the work surface and a wooden dowel suspended between them. Five 8-cm-long wire hangers were attached to the dowel using binder clips, and another binder clip was secured at the bottom of the wire. The top edge of one treated filter paper rectangle was secured to each hanging clip. Below each hangi","journal":"Arthropod management tests","year":2024,"id":479769,"datarank":0.10397207708399181,"base_score":0.6931471805599453,"endowment":0.6931471805599453,"self_citation_contribution":0.10397207708399181,"citation_network_contribution":0.0,"self_endowment_contribution":0.10397207708399181,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":1,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9629,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":306865,"name":"Laura C. Harrington","orcid":"0000-0002-2143-2051","position":1,"is_corresponding":false},{"id":1319164,"name":"Elisabeth Martin","orcid":null,"position":0,"is_corresponding":true}],"reference_count":0,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T02:06:54.284166Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}