Field evaluation of novel experimental nootkatone-based products for control of Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae).

Abstract

A total of eight nature-based products were tested against nymphal blacklegged ticks Ixodes scapularis Say or lone star ticks, Amblyomma americanum (L.) during the summers of 2023 and 2024. Field trials were performed using a micro-plot arena system in a natural field setting. The arena system has previously been used to successfully evaluate products against blacklegged nymphs and was modified for use with lone star nymphs. One of the eight products evaluated in the study, the commercially available BugArmor Zero-Bite, did not exhibit any significant tick-killing activity. The other seven products were nootkatone-based (NootkaSHIELD™) experimental formulations provided by the Swiss company Evolva and still in the product-development process. Of those samples, Evo A (10% nootkatone) and Evo C (10% nootkatone) provided over 94% knockdown control (efficacy within the first two weeks of application) of blacklegged ticks, and 81.2% and 91.0% knockdown control of lone star ticks, respectively. Both formulations also displayed significant residual control (efficacy after 2 weeks post treatment) but results for Evo A (10% nootkatone) varied greatly between 2023 and 2024. Evo B (10% nootkatone) also demonstrated high levels of efficacy, with 78.5% knockdown control and 80.8% residual control. Treatments using the three NootkaSHIELD™ formulations containing 3% nootkatone all resulted in knockdown efficacies below 45%. The results of this study suggest that NootkaSHIELD™ products containing 10% nootkatone are promising candidates for future commercial availability to control ticks.