Ovicidal efficacy of metarhizium anisopliae (Hypocreales: Clavicipitaceae) towards rhipicephalus sanguineus (acari: Ixodidae) eggs

Abstract

Rhipicephalus sanguineus, commonly known as brown dog tick is a widespread species with considerable public health and economic importance. Tremendous efforts were performed to control the tick populations with the concern of resistance build-up and environmental issues. Alternative towards microbial control thus emerged as one option to reduce tick populations. In this study, the ovicidal efficacy of a native isolate entomopathogenic hyphomycetes fungi, Metarhizium anisopliae strain HSAH5 was evaluated against eggs of R. sanguineus. Spray applications with three different conidial concentrations of 105, 106 and 107 conidia mL-1; 40 ppm of Flumethrin and a negative control. The M. anisopliae strain was found highly virulent to R. sanguineus eggs by reducing the hatching percentages to ≈30% compared with 8.9% in Flumethrin eggs. The result showed a significantly higher mortality in M. anisopliae group than those of the control groups (F = 42.08, df = 32, P < 0.001) at 30 days post-infection. However, there are no significant differences within the M. anisopliae group, in which the mortality between different conidial concentrations is almost the same. The estimated LC50 of M. anisopliae against eggs of R. sanguineus is 1.36 × 103 conidia ml-1. Thus, these results suggest M. anisopliae strain HSAH5 could be a potential biocontrol agent of R. sanguineus in the integrated approach to managing ticks in the residential landscape by targeting on the eggs.