Use of Metarhizum aniopliae s.l. to control soil-dwelling longhorned tick, Haemaphysalis longicornis

The longhorned tick (bush tick), Haemaphysalis longicornis (Ixodida: Ixodidae), is a serious pest; it transmits the severe fever with thrombocytopenia syndrome (SFTS) virus to humans and has a wide distribution. The use of chemical control is not favored for environmental and health reasons, so more environmentally sound management methods need to be developed. Herein, we describe the use of an entomopathogenic fungal library to develop a fungus-mediated tick management system. Field-collected nymphs were assayed for their susceptibility to entomopathogenic fungi belonging to genera Beauveria, Metarhizium, Cordyceps, and Akanthomyces. Three M. anisopliae s.l. isolates, JEF-214, -279, and -290 showed high virulence in a dose-dependent manner. One Cordyceps isolate was pathogenic but virulence was much lower than the M. anisopliae isolates. Beauveria isolates were not pathogenic to the tick. Because the longhorned tick dwells on the soil surface except for blood-feeding periods, the soil surface was sprayed with conidial suspensions of the isolates after the release of longhorned ticks. The treatments resulted in 60–90% mortality after 30 days. M. anisopliae s.l. isolates were highly virulent against longhorned tick, and the application of fungus-based biopesticides on the soil surface could be an effective control strategy to reduce the tick population for long-term tick management.