Lethal effects of a silica gel + thyme oil (EcoVia) dusts and aqueous suspensions on Amblyomma americanum (Ixodida: Ixodidae) larvae and nymphs

Authors: Showler, Allan; DORSEY, BAILEE - Schreiner University; CAESAR, RYAN - Schreiner University

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2020
Publication Date: 3/24/2020
Citation: Showler, A., Dorsey, B.N., Caesar, R.M. 2020. Lethal effects of a silica gel + thyme oil (EcoVia) dusts and aqueous suspensions on Amblyomma americanum (Ixodida: Ixodidae) larvae and nymphs. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjaa054.
DOI: https://doi.org/10.1093/jme/tjaa054

Interpretive Summary: Hard ticks suck blood from host animals and transmit pathogens that cause important medical and veterinary diseases. As synthetic conventional acaricide resistance becomes increasingly common, alternative tactics are likely to enhance control efforts. Laboratory bioassays assessed the lethality of CimeXa, a commercial silica gel desiccant dust, and EcoVia, a commercial product containing silica gel + thyme oil, against lone star tick larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and EcoVia achieved total larval mortality within 1 h when they were initially immersed in the dusts and when they crawled across treated substrate. Larvae were killed faster than nymphs. Temporary immersion of larvae and nymphs in aqueous suspensions of the dusts were less effective than exposure to the dusts applied dry. Larval and nymphal mortality associated with crawling on dried aqueous suspensions of the products was also not as strong as when the immature life stages crawled across substrate treated with dry dusts, and EcoVia was not more efficient than CimeXa. CimeXa and EcoVia can likely be used to protect cattle in a prophylactic context because silica gel does not degrade, and EcoVia might be effective at eliminating ticks that are feeding on cattle as well. The two dust products are likely to be effective against other ixodid species, such as the southern cattle fever tick, which transmits the causal agents of babesiosis to cattle.

Technical Abstract: Ixodids suck blood from host animals and transmit pathogens that cause important medical and veterinary diseases. As synthetic conventional acaricide resistance becomes increasingly common, alternative tactics are likely to enhance control efforts. Laboratory bioassays assessed the lethality of CimeXa, a commercial silica gel desiccant dust, and EcoVia, a commercial product containing silica gel + thyme oil, against lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and EcoVia achieved total larval mortality within 1 h when they were initially immersed in the dusts and when they crawled across treated substrate. Larvae were killed faster than nymphs. Temporary immersion of A. americanum larvae and nymphs in aqueous suspensions of the dusts were less effective than exposure to the dusts applied dry. Larval and nymphal mortality associated with crawling on dried aqueous suspensions of the products was also not as strong as when the immature life stages crawled across substrate treated with dry dusts, and EcoVia was not more efficient than CimeXa. CimeXa and EcoVia can likely be used to protect cattle in a prophylactic context because silica gel does not degrade, and EcoVia might be effective at eliminating ticks that are feeding on cattle as well. The two dust products are likely to be effective against other ixodid species, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which transmits the causal agents of babesiosis to cattle.