ABSTRACT

There is a critical need to develop effective, high-quality, fungal-based biopesticides for use against ticks. Dermacentor albipictus, the winter tick, is a one-host species that can cause mortality in large ungulates, particularly moose (Alces alces). The larval stage of this species aggregates on the ground in a prolonged, quiescent state during the summer and then quests for hosts in autumn. This behaviour offers an opportunity to treat a vulnerable life stage with entomopathogenic fungi in an environment where both are acclimated. We produced granular formulations of Metarhizium brunneum (Petch) and Metarhizium anisopliae (Metschn.) Sorokin, and tested their efficacy against winter tick larvae under semi-natural conditions within the laboratory. When granules were applied at rates of 5.0 × 10⁵ and 1.5 × 10⁷ conidia/cm², mortality ranged from 53–91% and 58–98% after nine weeks, respectively. Overall, the granular formulations had a similar ability to cause mortality to winter tick larvae regardless of application rate. Fungal granules persisted for nine weeks post application at concentrations of 9 × 10⁴–6 × 10⁵ CFU/g. These results demonstrate the potential of granular formulations of Metarhizium to persist and kill a one-host tick whose larvae have a prolonged off-host stage.

摘要

迫切需要开发有效的、高质量的、基于真菌的生物农药来对抗蜱虫。Dermacentor albipictus，即冬季蜱，是一种单宿主物种，可导致大型有蹄类动物，尤其是驼鹿 ( Alces alces )死亡。该物种的幼虫阶段在夏季长时间聚集在地面上，处于静止状态，然后在秋季寻找寄主。这种行为提供了一个机会，可以在两者都适应的环境中用昆虫病原真菌治疗脆弱的生命阶段。我们生产了绿僵菌(Petch) 和绿僵菌的颗粒制剂(Metschn.) Sorokin，并在实验室内的半自然条件下测试了它们对冬季蜱幼虫的功效。当颗粒以 5.0 × 10 ⁵和 1.5 × 10 ⁷分生孢子/cm ^{2 的}比例施用时，九周后死亡率分别为 53-91% 和 58-98%。总体而言，无论施用率如何，颗粒制剂都具有导致冬季蜱幼虫死亡的相似能力。真菌颗粒在施用后以 9 × 10 ⁴ –6 × 10 ⁵ CFU/g 的浓度持续存在 9 周。这些结果表明绿僵菌的颗粒制剂具有持久和杀死单宿主蜱的潜力，该蜱的幼虫具有较长的脱离宿主阶段。