USDA-ARS, Knipling-Bushland U.S. Livestock Insects Research Laboratory, 2700 Fredericksburg Road, Kerrville, TX.
Department of Life Science, Schreiner University, 2100 Memorial Boulevard, Kerrville, TX.
J Med Entomol. 2020 Jul 4;57(4):1184-1192. doi: 10.1093/jme/tjaa037.
Ixodids are blood-feeding ectoparasitic vectors of many disease agents that infect humans, livestock, and wild animals. As ixodid resistance to conventional synthetic acaricides becomes increasingly problematic, natural products are receiving greater attention as possible alternative control tactics. Formic acid, produced by ants, is a commercially available product for fumigating varroa mites, Varroa destructor Anderson & Trueman, infesting honey bee, Apis mellifera L., hives, and it has been reported to repel ixodids. Lone star tick, Amblyomma americanum (L.), larvae and nymphs were used as a model ixodid to investigate deterrent, repellent, and lethal effects of formic acid as a fumigant and contact toxin in vitro in the laboratory. Although formic acid failed to deter or repel A. americanum, it was highly toxic as a fumigant to larvae at a 1% concentration even when exposure was limited to 5 min. Contact by crawling on wet, moist, and dry treated substrates under ventilated conditions causes >90% mortality to larvae in 5% formic acid concentration treatments within 30-120 min, and temporary immersion killed ≈60% of the larvae by 24 h after they were removed from the 5% formic acid treatment solution. Substantial nymphal mortality occurred after 1-1.5 h following exposure to substrate treated with the 10% concentration and immersion killed ≈45% of the nymphs. It appears that formic acid volatiles are more lethal to A. americanum immatures than direct contact with the external integument.
硬蜱是许多感染人类、家畜和野生动物的病原体的血食外寄生虫媒介。随着硬蜱对传统合成杀螨剂的抗性越来越成问题，天然产物作为可能的替代控制策略受到了更多关注。蚁酸是由蚂蚁产生的，是一种可商购的用于熏杀寄生在蜜蜂 Apis mellifera L. 蜂巢中的瓦螨 Varroa destructor Anderson & Trueman 的产品，据报道它能驱赶硬蜱。孤星蜱 Amblyomma americanum (L.) 的幼虫和若虫被用作模型硬蜱，以研究蚁酸作为熏剂和接触毒素在实验室中的驱避、驱避和致死作用。尽管蚁酸未能阻止或驱赶 A. americanum，但作为熏剂，即使暴露时间限制在 5 分钟，1%浓度的蚁酸对幼虫也具有很高的毒性。在通风条件下，幼虫在湿、潮和干处理过的基质上爬行接触，在 5%蚁酸浓度处理下，30-120 分钟内导致 >90%的幼虫死亡，24 小时后，将幼虫从 5%蚁酸处理溶液中取出后，临时浸泡可杀死 ≈60%的幼虫。暴露于 10%浓度处理过的基质 1-1.5 小时后，大量的若虫死亡，浸泡可杀死 ≈45%的若虫。似乎蚁酸挥发物对 A. americanum 若虫的致死作用大于与外部表皮的直接接触。
