Efficacy of Metarhizium anisopliae conidia in oil-in-water emulsion against the tick Rhipicephalus microplus under heat and dry conditions

PAIXÃO, FLÁVIA R. S.; ARRUDA, WALQUÍRIA; MUNIZ, ELEN R.; LUZ, CHRISTIAN; FERNANDES, ÉVERTON K. K.; BARRETO, LUCAS P.; ANGELO, ISABELE C.

BIOCONTROL (DORDRECHT)

SPRINGER

Año: 2020

1386-6141

Environmental stress conditions compromise the effectiveness of microorganisms for use in biological control. We investigated the thermotolerance of seven Metarhizium isolates from Central Brazil to 32 °C, and the thermotolerance of conidia of Metarhizium anisopliae s.str. IP 119 (Metchnikoff) (Hypocreales: Clavicipitaceae) and M. robertsii formulated in oil-in-water emulsion to 45 °C. We also evaluated the efficacy of oil-formulated conidia of M. anisopliaes.str. IP 119 against the tick Rhipicephalus microplus (Canestrini) (Acari: Ixodidae) under stress conditions (32 °C; 75% RH). The conidial germination on tick?s cuticle was assessed by Scanning Electron Microscopy. Conidia of M. anisopliaes.str. IP 119 formulated in oil-in-water emulsion caused significant control (59.4%) of R. microplus, even when treated ticks were incubated under stress (32 °C; 75% RH). Metarhizium spp. incubated at 32 °C had both decreased radial growth and conidial production. Conidia of IP 119 formulated in oil-in-water emulsion were more tolerant to 45 °C than conidia suspended in water. An oil-in-water emulsion protected M. anisopliaes.str. conidia against heat and dry conditions and may enhance its efficacy to control ticks by improving the tolerance of fungi against adverse environmental factors.