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Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/3/2017 Publication Date: 1/14/2018 Citation: Showler, A., Harlien, J.L. 2018. Botanical compound p-anisaldehyde repels larval lone star tick, Amblyomma americanum (L.) (Acari: Ixodidae), and halts reproduction by gravid adults. Journal of Medical Entomology. 55:200-209. https://doi.org/10.1093/jme/tjx158. DOI: https://doi.org/10.1093/jme/tjx158 Interpretive Summary: The lone star tick is widely distributed across large regions of the United States and Mexico. The pest feeds on blood by attaching to three hosts during its larval, nymphal, and adult stages. White-tailed deer and wild turkey are common hosts, and there are many other hosts. The lone star tick is the most frequently reported tick species to bite humans in the southeastern and southcentral United States, and it can transmit infectious diseases caused by microbes. As lone star tick resistance to conventional insecticides becomes more common, alternative control tactics are being investigated. The series of bioassays we developed was effective for assessing a range of tick responses to chemicals. Contact exposure resulted in an LD50 of 0.162% and an LD90 of 0.311% p-anisaldehyde. Although volatiles were not lethal to larval lone start ticks, p-anisaldehyde was strongly repellent. The compound at a relatively low concentration applied to gravid adults reduces egg laying and the few eggs that were produced did not hatch. Technical Abstract: The lone star tick, Amblyomma americanum (L.), widely distributed across eastern, southeastern, and midwestern regions of the United States and south into Mexico, is an obligate blood feeder that attaches to three hosts during the larval, nymphal, and adult stages. White-tailed deer and wild turkey are common hosts, as well as a wide variety of other avian and mammalian hosts. Amblyomma americanum is the most frequently reported tick species to bite humans in the southeastern and southcentral United States, and it can transmit infectious diseases caused by microbes. As A. americanum resistance to conventional insecticides becomes more common, alternative control tactics, such as application of bioactive botanical natural products are being investigated. p-Anisaldehyde has been found in many plant species and it has shown effects that include mortality, attractancy, and interference with host seeking. The series of bioassays we developed was effective for assessing a range of ixodid tick responses to chemicals. Contact exposure resulted in an LD50 of 0.162% and an LD90 of 0.311% p-anisaldehyde. Although volatiles were not lethal to larval A. americanum, p-anisaldehyde was strongly repellent against them in several bioassays that indicate aspects of the repellency such as counteracting the negative geotropic orientation on a vertical surface, the ability to trap larvae between and inside treatment barriers on different substrates and to divert upward larval movement from one surface to another, and the extent to which larvae fall from a treated surface. The compound at a relatively low concentration applied to gravid adults strongly reduces egg laying and the few eggs that were produced did not hatch. Aside from repelling larval A. americanum and halting reproduction, p-anisaldehyde has a variety of effects on other arthropods including attraction. Research on this compound as a potentially multifaceted pest management tool has been sparse. This study, for example, is the first to demonstrate p-anisaldehyde’s repellent properties against an arthropod pest. p-Anisaldehyde might also act as a strong repellent against other tick species. |
