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

Abstract

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.

Integrative Alternative Tactics for Ixodid Control

“…For reducing ixodid populations, Thompson et al [ 200 ] suggested that M. minutiflora and A. gayanus should be planted in infested areas. Fernandez-Ruvalcaba et al [ 201 ], using A. gayanus and M. minutiflora plots, reported that questing R. microplus larvae were 52.1% and 73.3% less abundant than on nonrepellent and nonacaricdial grass species (as determined by flag sampling [ 28 ]). All R. appendiculatus instars avoid climbing on M. minutiflora but not on kikuyu grass, Pennisetum clandestinum Hochst.…”

“…Kaolin is a porous, fine-grained aluminosilicate white mineral clay that causes a variety of detrimental effects to arthropods [ 28 ]. Kaolin particles adhere to the arthropod integument, occluding the normal range of motion of appendages, strongly obstructing mobility, and they can also abrade the integumentary cuticle, leading to desiccation [ 491 , 492 ].…”

“…Kaolin particles adhere to the arthropod integument, occluding the normal range of motion of appendages, strongly obstructing mobility, and they can also abrade the integumentary cuticle, leading to desiccation [ 491 , 492 ]. A commercial kaolin-based product, Surround WP (Engelhard, Iselin, NJ), with surfactants, disrupts the larval ixodid cuticle, resulting in relatively rapid desiccation (compared to nymphs) because the small larval body size is associated with a high evaporative surface area: volume ratio [ 28 , 493 ].…”

“…Surround WP was moderately lethal to A. americanum larvae and nymphs, but to a lesser extent than silica- and diatomaceous earth-based dusts [ 28 , 30 ]. On the other hand, larval and nymphal A. americanum exposed to aqueous suspensions dried on a surface resulted in higher larval (not nymphal) mortality than a dried aqueous suspension of a silica gel-based product (CimeXa) [ 28 ]. The greatest mortality, ≈90%, occurred when larvae crawled across dry Surround WP treated substrate, and nymphal mortality was as high as 70% [ 28 ].…”

“…Miller et al [ 27 ] suggested that organophosphate resistance in R. microplus required high-sode treatments to overcome resistance. Research into naturally derived compounds such as desiccant dusts [ 28 , 29 , 30 , 31 , 32 ] have been showing promise as alternatives to overcome the weaknesses inherent to synthetic acaricides.…”