Biological control of Rhipicephalus (Boophilus) annulatus by different strains of Metarhizium anisopliae, Beauveria bassiana and Lecanicillium psalliotae fungi.

Virulence of 11 native strains of entomopathogenic fungi; Metarhizium anisopliae (three strains), Beauveria bassiana (six strains) and Lecanicillium psalliotae (two strains) collected from different parts of Iran, were studied against different developmental stages of Rhipicephalus (Boophilus) annulatus. After the exposure of ticks to the fungal strains in different concentrations (i.e. 10(3), 10(5), 10(7) conidia/ml), various parameters such as mortality rate and reproductive efficiency of engorged females, mortality of unfed tick larvae and eclosion percentage of infected eggs were evaluated to determine the fungal virulence. Based on the obtained results, five strains including M. anisopliae (IRAN 437 C and DEMI 001), B. bassiana (IRAN 403 C) and L. psalliotae (IRAN 468 C and IRAN 518 C) were found to be virulent to various stages of tick developmental cycle. Mortality rate of engorged females was found to be dose-dependent with regard to the conidial concentration used. Total mortality rates of 90-100%, 70% and 56.6% were observed for M. anisopliae (IRAN 437 C and DEMI 001), B. bassiana (IRAN 403 C) and L. psalliotae (IRAN 468 C), 6-11 days post inoculation (PI) with 10(7) conidia/ml, respectively. Most strains were able to inhibit egg laying by females in the range of 0-26% in different conidial concentrations. The results indicated that the mean egg laying of treated engorged tick females exposed to M. anisopliae (IRAN 437 C) was less than the mean values of those treated with other fungal strains. Results revealed 89.1%, 35.5% and 56.3% decrease in egg hatchability and 88.69%, 78.15% and 59.74% reduction in reproductive efficiency of the ticks using 10(7) conidia/ml of M. anisopliae (IRAN 437 C), B. bassiana (IRAN 403 C) and L. psalliotae (IRAN 468 C), respectively. In general, the entomopathogenic effects of native M. anisopliae and B. bassiana against various developmental stages of R. (B.) annulatus were confirmed in the present work. Likewise, although L. psalliotae, which was introduced for the first time as an entomopathogenic fungus against tick had not more than 13.3% mortality effect against adult females, but its effect on egg hatchability and reproductive efficiency was remarkable.