03074naa a2200349 a 450000100080000000500110000800800410001902200140006002400520007410000250012624501290015126000090028052020110028965000300230065000270233065000160235765000160237365000100238965000140239965000350241365300170244865300260246565300210249170000170251270000210252970000180255070000120256870000190258070000200259970000250261977300800264421563862023-09-04       2023    bl uuuu     u00u1 u    #d  a0175-75987 ahttps://doi.org/10.1007/s00253-023-12467-72DOI1 aPAIXÃO, F. R. S. da  aMicrosclerotial pellets of Metarhizium spp.bthermotolerance and bioefficacy against the cattle tick.h[electronic resource]  c2023  aAbstract: The cattle tick, Rhipicephalus microplus (Acari: Ixodidae), is a multi-billion dollar ectoparasite of global importance affecting beef and milk production. Submerged cultures of cosmopolitan entomopathogenic fungal species of the genus Metarhizium typically produce microsclerotia that provide both long-term survival and environmental resistance. Microsclerotia hold great potential as an unconventional active propagule to control this tick under laboratory and semi-field conditions. However, heat stress caused especially by elevated temperatures poses a critical environmental constraint for the successful development and efficacy of microsclerotia under tropical conditions. First, we screened six strains of Metarhizium anisopliae, Metarhizium robertsii and Metarhizium humberi for their ability to produce microsclerotia by submerged liquid cultivation. In addition, we assessed the biological fitness and bioefficacy of dried microsclerotial pellets under amenable (27 °C) and heat-stressed (32 °C) incubation against engorged adult females of R. microplus. Microsclerotia in pelletized formulation prepared with carriers based on diatomaceous earth and microcrystalline cellulose exhibited conidial production at different extents according to the fungal strain and the incubation temperature, but most strains displayed reduced sporogenesis when exposed to 32 °C. Engorged tick females exposed to sporulated microsclerotia from pelletized M. anisopliae CG47 or IP 119 had fewer number of hatching larvae in comparison to the control group, irrespective of the incubation temperature tested. The minimum dosage of microsclerotial pellets that effectively reduced hatchability of tick larvae was estimated to be 2 mg per plate (equivalent to 6.0 kg per hectare). Metarhizium microsclerotial pellets exhibited significant tolerance to 32 °C and pronounced acaricidal activity against this economically important ectoparasite of cattle, even under simulated environmental heat stress.  aBiological control agents  aEntomopathogenic fungi  aHeat stress  aMetarhizium  aCalor  aCarrapato  aFungo Para Controle Biológico  aEctoparasite  aFungal entomopathogen  aFungal propagule1 aMUNIZ, E. R.1 aCATÃO, A. M. L.1 aSANTOS, T. R.1 aLUZ, C.1 aMARRETO, R. N.1 aMASCARIN, G. M.1 aFERNANDES, É. K. K.  tApplied Microbiology and Biotechnologygv. 107, n. 7-8, p. 2263-2275, 2023.