Lethal effects of silica-based CimeXa and kaolin-based Surround dusts against ixodid tick (Acari: Ixodidae) eggs, larvae, and nymphs

Authors: Showler, Allan; OSBRINK, WESTE; MUNIZ, EDUARDO - SCHREINER UNIVERSITY; CAESAR, RYAN - SCHREINER UNIVERSITY; ABRIGO, VERONICA - CONSULTANT

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2018
Publication Date: 9/10/2018
Citation: Showler, A., Osbrink, W.L., Muniz, E., Caesar, R., Abrigo, V. 2018. Lethal effects of silica-based CimeXa and kaolin-based Surround dusts against ixodid tick (Acari: Ixodidae) eggs, larvae, and nymphs. Journal of Medical Entomology. 56:215-221. https://doi.org/10.1093/jme/tjy152.
DOI: https://doi.org/10.1093/jme/tjy152

Interpretive Summary: Lone star and the Gulf coast ticks are widely distributed across the United States and Mexico where they are obligate blood feeders during the larval, nymphal, and adult stages. White-tailed deer, wild turkey, and small mammals are common hosts, and the two tick species can transmit diseases of veterinary and medical importance. As tick resistance to conventional acaricides increases, alternative control tactics are being investigated. The insecticidal dust formulations CimeXa and Surround, based on silica gel and kaolin, respectively, were assessed for their acaricidal effects against lone star tick eggs, larvae, and nymphs in the laboratory. Aqueous concentrations of the two dusts did not have adverse effects against egg mass hatching, but coverage by the dry dusts, particularly CimeXa, were strongly lethal to larvae and to a lesser extent against nymphs. Similarly, 93.3% mortality of larvae was observed 24 h after crawling across a thin layer of CimeXa and 88.3% mortality was observed 48 h after crawling across Surround dust. Substantial numbers of nymphs (83.6%) were killed within 48 h after crawling across a thin layer of CimeXa dust, but Surround was less lethal (53.9% mortality). Larval mortality after crawling on dried aqueous suspensions of the two dusts for 30 min increased to 79.2% at 0.1 mg Surround/10 ml water by 48 h post treatment, and <68% in the other treatments at 0.1 mg dust/ml and 1 mg dust/ml. Nymphal mortality in the treatments involving dried aqueous suspensions was negligible. Applied under natural conditions to plants that were infested with Gulf coast tick larvae and nymphs, CimeXa reduced numbers retrieved by flagging by >95% at 24 and 48 h post-treatment. In addition to their efficacy, the dusts are relatively nontoxic to vertebrates, they can persist indefinitely unless washed or rubbed off treated surfaces, and buildup of resistance in the target pest is unlikely, hence, the dusts offer a potent and practical alternative to synthetic acaricides. CimeXa and Surround might also be useful for control of other important tick species, such as the southern cattle fever tick.

Technical Abstract: The lone star, Amblyomma americanum (L.) and the Gulf coast ticks, A. maculatum Koch, are widely distributed across eastern, southeastern, and midwestern regions of the United States and south into Mexico, and they are obligate blood feeders that attach to three hosts during the larval, nymphal, and adult stages. White-tailed deer, wild turkey, and small mammals are common hosts. Amblyomma americanum is the most frequently reported species of tick to bite humans in the southeastern and southcentral United States, and, together, the two species can transmit diseases of veterinary and medical importance. As tick resistance to conventional acaricides becomes more common, alternative control tactics, such as application of bioactive botanical natural products are being investigated. The insecticidal dust formulations CimeXa and Surround, based on silica gel and kaolin, respectively, were assessed for their acaricidal effects against A. americanum eggs, larvae, and nymphs in the laboratory. Aqueous concentrations of the two dusts did not have adverse effects against egg mass hatching, but coverage by the dry dusts, particularly CimeXa, were strongly lethal to larvae and to a lesser extent against nymphs. Similarly, 93.3% mortality of larvae was observed 24 h after crawling across a thin layer of CimeXa and 88.3% mortality was observed 48 h after crawling across Surround dust. Substantial numbers of nymphs (83.6%) were killed within 48 h after crawling across a thin layer of CimeXa dust, but Surround was less lethal (53.9% mortality). Larval mortality after crawling on dried aqueous suspensions of the two dusts for 30 min increased to 79.2% at 0.1 mg Surround/10 ml water by 48 h post treatment, and <68% in the other treatments at 0.1 mg dust/ml and 1 mg dust/ml. Larval mortality after remaining on dried aqueous suspension for 48 h was <42%. Nymphal mortality in the treatments involving dried aqueous suspensions was negligible. Applied under natural conditions to Gulf cordgrass plants that were infested with A. maculatum larvae and nymphs, CimeXa reduced numbers retrieved by flagging by >95% at 24 and 48 h post-treatment. CimeXa applied as a dry dust, in particular, is an effective dust-based acaricide against larvae, and CimeXa and Surround occlude mobility of larvae and nymphs. In addition to their efficacy, the dusts are relatively nontoxic to vertebrates, they can persist indefinitely unless washed or rubbed off treated surfaces, and buildup of resistance in the target pest is unlikely, hence, the dusts offer a potent and practical alternative to synthetic acaricides. CimeXa and Surround might also be useful for control of other important tick species, such as the southern cattle fever tick, Rhipicephalus microplus (Canestrini).