Lethal Effects of Silica Gel-Based CimeXa and Kaolin-Based Surround Dusts Against Ixodid (Acari: Ixodidae) Eggs, Larvae, and Nymphs

: As tick resistance to conventional acaricides becomes more common, alternative control tactics are gaining attention. Insecticidal dusts CimeXa and Surround, based on silica gel and kaolin, respectively, were assessed against Amblyomma americanum (L.) (Ixodida: Ixodidae) eggs, larvae, and nymphs in the laboratory. Coverage by the dry dusts, particularly CimeXa, was strongly lethal to larvae and to a lesser extent to nymphs. Larval mortality was also high when larvae crawled across thin layers of CimeXa and, to a lesser extent, Surround dusts. CimeXa was more lethal to nymphs that crawled across a thin layer than Surround. Larval mortality after crawling on dried aqueous suspensions of the dusts for 30 min and for 48 h caused moderate mortality (<80%) regardless of a 10-fold difference in concentration; nymphal mortality was negligible. In a field experiment, CimeXa dust strongly reduced numbers of Gulf coast tick, Amblyomma maculatum (Koch) (Ixodida: Ixodidae), larvae and nymphs by 24 h. Possible application of CimeXa to control other species of ixodid ticks is discussed as well as advantages and disadvantages of using dusts for tick control under field conditions.