Department of Animal Parasitology, Veterinary Institute, Federal Rural University of Rio de Janeiro, Seropédica, Rio de Janeiro, 23897-000, Brazil.
Laboratory of Environmental Microbiology, Brazilian Agricultural Research Corporation, Embrapa Environment, Jaguariúna, São Paulo, 13918-110, Brazil.
Sci Rep. 2021 Mar 2;11(1):4972. doi: 10.1038/s41598-021-84142-8.
The tick Rhipicephalus microplus poses a serious threat to the cattle industry, resulting in economic losses aggravated by tick resistance to chemical acaricides. Strains of Metarhizium spp., a well-known group of entomopathogenic fungi, can contribute to managing this ectoparasite. We explored two novel granular, microsclerotia- or blastospores-based formulations of Metarhizium robertsii for R. microplus control under semi-field conditions. Fungal persistence in soil was also observed for 336 days. The experiment used pots of Urochloa decumbens cv. Basilisk grass, treated with 0.25 or 0.5 mg of granular formulation/cm (25 or 50 kg/ha) applied to the soil surface prior to transferring engorged tick females onto the treated soil. The fungal granules yielded more conidia with subsequent sporulation under controlled indoor conditions than in the outdoor environment, where the levels of fungus rapidly declined over time. Metarhizium-root colonization ranged from 25 to 66.7% depending on the propagule and rate. Fungal formulations significantly reduced the number of tick larvae during the humid season, reaching at least 64.8% relative efficacy. Microsclerotia or blastospores-granular formulations of M. robertsii can reduce the impact of R. microplus, and thus prove to be a promising tool in the control of ticks.
微小牛蜱对养牛业构成严重威胁，由于 ticks 对化学杀螨剂的抗药性，其造成的经济损失加剧。节肢动物病原真菌中的金龟子绿僵菌菌株可以帮助管理这种外寄生虫。我们探索了两种新型的颗粒状、微菌核或芽生孢子基体制剂，用于半田间条件下控制微小牛蜱。还观察了真菌在土壤中的持久性，时间长达 336 天。该实验使用 Basilisk grass 的 Urochloa decumbens cv. 盆栽，在将饱血的 tick 雌性转移到处理过的土壤之前，在土壤表面施用 0.25 或 0.5mg 颗粒制剂/cm（25 或 50kg/ha）。在受控室内条件下，真菌颗粒产生了更多的分生孢子，随后进行了孢子形成，而在户外环境中，真菌水平随时间迅速下降。根据繁殖体和速率的不同，金龟子绿僵菌的根定殖范围从 25%到 66.7%不等。真菌制剂在潮湿季节显著减少了 tick 幼虫的数量，相对功效至少达到 64.8%。金龟子绿僵菌的微菌核或芽生孢子颗粒制剂可以减少微小牛蜱的影响，因此被证明是 tick 控制的一种有前途的工具。
