Biocontrol of pigeon tick Argas reflexus (Acari: Argasidae) by entomopathogenic fungus Metarhizium Anisopliae (Ascomycota: Hypocreales)

Abstract

The pigeon tick Argas reflexus is a pathogen-transmitting soft tick that typically feeds on pigeons, but can also attack humans causing local and systemic reactions. Chemical control is made difficult due to environmental contamination and resistance development. As a result, there is much interest in increasing the role of other strategies like biological control. In this study, the efficacy of three strains (V245, 685 and 715C) of entomopathogenic fungus Metarhizium anisopliae for biological control of three life stages of pigeon tick A. reflexus including eggs, larvae, engorged and unfed adults was investigated under laboratory conditions. Five concentrations of different strains of M. anisopliae ranging from 10(3) to 10(7) conidia/ml were used. All fungal strains significantly decreased hatchability of A. reflexus eggs. Strain V245 was the most effective strain on the mortality of larval stage with nearly 100% mortality at the lowest concentration (10(3) conidia/ml) at 10 days post-inoculation. The mortality rate of both engorged and unfed adult ticks were also increased significantly exposed to different conidial concentrations compared to the control groups (P < 0.05) making this fungus a potential biological control agent of pigeon tick reducing the use of chemical acaricides.

Keywords: Argas reflexus; Metarhizium anisopliae; biological control; entomopathogenic fungus; pigeon tick.

Figure 1

Hatchability of A. reflexus eggs exposed to conidial concentration of 10³ conidia/ml of M. anisopliae strains.

Figure 2

Mortality of A. reflexus larvae exposed to two conidia concentrations (A: 10³ conidia/ml and B: 10⁴ conidia/ml) of M. anisopliae strains.

Figure 3

Mortality of A. reflexus engorged adult females exposed to three conidia concentrations (A: 10⁵ conidia/ml, B: 10⁶ conidia/ml and C: 10⁷ conidia/ml) of M. anisopliae strains.

Figure 4

Mortality of A. reflexus unfed adult females exposed to different conidia concentrations (A: 10⁵ conidia/ml, B: 10⁶ conidia/ml and C: 10⁷ conidia/ml) of M. anisopliae strains.