Lethal effects of a commercial diatomaceous earth dust product on Amblyomma americanum (Ixodida: Ixodidae) larvae and nymphs

Authors: Showler, Allan; FLORES, NICOLE - Schreiner University; CAESAR, RYAN - Schreiner University; MITCHELL, ROBERT - Environmental Protection Agency (EPA); Perez De Leon, Adalberto - Beto

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2020
Publication Date: 4/25/2020
Citation: Showler, A., Flores, N., Caesar, R.M., Mitchell, R.D., Perez De Leon, A.A. 2020. Lethal effects of a commercial diatomaceous earth dust product on Amblyomma americanum (Ixodida: Ixodidae) larvae and nymphs. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjaa082.
DOI: https://doi.org/10.1093/jme/tjaa082

Interpretive Summary: With increasing development of resistance to conventional synthetic acaricides in economically and medically important ticks, interest in finding alternative control tactics has intensified. Laboratory bioassays were conducted, using the lone star tick as a model species, to assess the efficacy of a diatomaceous earth-based product, Deadzone, in comparison with a silica gel-based product, CimeXa. CimeXa is already known to be highly lethal against ixodid larvae and nymphs. The two dust treatments were 100% effective against larvae and nymphs within 24 h after contact occurred by immersion in dry dusts and after crawling across a surface treated with the dry dusts. Contact by crawling on a dried aqueous film of the dusts, even at a concentration of 10%, was not as effective as exposure to the dusts in dry powder form. As has been demonstrated with CimeXa, it is likely that Deadzone will be capable of providing prophylactic protection of cattle from economically important one-host ixodids, such as the southern cattle fever tick, which vectors the causal agents of babesiosis. Diatomaceous earth can be stored indefinitely, will remain efficacious for as long as sufficient quantities remain on the substrate, it is a natural (organic) substance, and it might be amenable for limited use in environmentally protected habitats.

Technical Abstract: With increasing development of resistance to conventional synthetic acaricides in economically and medically important ixodid species, interest in finding alternative control tactics has intensified. Laboratory bioassays were conducted, using the lone star tick, Amblyomma americanum (L.), as a model species, to assess the efficacy of a diatomaceous earth-based product, Deadzone, in comparison with a silica gel-based product, CimeXa. CimeXa is already known to be highly lethal against A. americanum larvae and nymphs. The two dust treatments were 100% effective against larvae and nymphs within 24 h after contact occurred by immersion in dry dusts and after crawling across a surface treated with the dry dusts. Contact by crawling on a dried aqueous film of the dusts, even at a concentration of 10%, was not as effective as exposure to the dusts in dry powder form. As has been demonstrated with CimeXa, it is likely that Deadzone will be capable of providing prophylactic protection of cattle from economically important one-host ixodids, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini), which vectors the causal agents of babesiosis. Diatomaceous earth can be stored indefinitely, will remain efficacious for as long as sufficient quantities remain on the substrate, it is a natural (organic) substance, and it might be amenable for limited use in environmentally protected habitats.