In vitro efficacy of two commercial products of Metarhizium anisopliae s.l. for controlling the cattle tick Rhipicephalus microplus

Michel Ruan Dos Santos Nogueira,Wendell Marcelo De Souza Perinotto,Fillipe Araújo De Sá,Vânia Rita Elias Pinheiro Bittencourt,Simone Quinelato,Allan Felipe Marciano,Mariana Guedes Camargo,Caio Junior Balduino Coutinho Rodrigues,Maria Clemente De Freitas,Jéssica Fiorotti

doi:10.1590/s1984-29612020035

Abstract

The effects of two different products - Metarril® SP Organic (dry conidia) and Metarril® SC Organic (emulsifiable concentrated conidia in vegetable oil) - on eggs, larvae and Rhipicephalus microplus engorged females were here explored. Three concentrations (108, 107, and 106 conidia mL-1) for both products were prepared in water + 0.1% Tween® 80 (v/v); afterward, bioassays were carried out for all R. microplus stages by immersion in suspensions (Metarril® SP) or formulations (Metarril® SC). Metarril® SP suspensions showed low efficacy and did not affect biological parameters of treated engorged females; for eggs and larvae, only slight decreases in hatchability and larvae population were observed. Despite a delay in germination, Metarril® SC presented better results; for females, reductions in Egg Mass Weight (EMW) and Egg Production Index (EPI) were reported. On eggs, 108 conidia mL-1 increased Incubation Period (IP), shortened Hatching Period (HP) and decreased hatchability by up to 61%; for larvae, 107 and 108 conidia mL-1 reached 99.6 and 100% larval mortality respectively, 10 days after fungal exposure. Thus, further studies involving the use of oil-based formulations for ticks such as Metarril® SC need to be performed, especially to control the most susceptible stages (eggs and larvae).

Highlights

Affecting livestock production, Rhipicephalus microplus (Canestrini 1888) (Acari: Ixodidae) infestations lead to huge economic losses in Brazil (Grisi et al, 2014)
This paper reports the in vitro efficacy in controlling R. microplus by testing two products from Koppert Biological Systems based on M. anisopliae s.l. primarily indicated to agricultural pests
Conidial germination was assessed from 10 μL aliquots of each aqueous suspension or oil formulation (106 conidia mL-1) dripped on Potato Dextrose Agar (PDA) + 0.05% chloramphenicol (CAP) (Kasvi )

Summary

Introduction

Rhipicephalus microplus (Canestrini 1888) (Acari: Ixodidae) infestations lead to huge economic losses in Brazil (Grisi et al, 2014). Metarhizium spp. are applied in the field to control some arthropods (Aw & Hue, 2017); it is known about its low non-target impacts and high safety for mammals, birds, aquatic animals and plants (Zimmermann, 2007) This fungus affects all R. microplus stages (Fernandes et al, 2012; Quinelato et al, 2012; Mascarin et al, 2019) and its good performance is totally dependent on the environmental conditions (Jackson et al, 2010; Camargo et al, 2016; Ment et al, 2017; Tomer et al, 2018). Oil-based formulations improve efficacy and promote protection against environmental challenges (Samish et al, 2014)

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Results

Conclusion