Pathogenicity Of The Entomopathogenic Fungus Metarhizium Anisopliae To Ticks And The Protection Of Conidia From Ultra-Violet Radiation Damage

Abstract

The potential of the entomopathogenic fungus, Metarhizium anisopliae to serve as a

bio-control agent of ticks has been studied and promising results reported. In this

study, efficacy of M. anisopliae conidia formulated in either oil or water, in inducing

mortalities to various developmental stages of ticks was evaluated. A fungal

concentration of 108 conidia/ml induced in Rhipicephalus evertsi evertsi mortalities

of: 87% in eggs, 100% in unfed larvae, 72% in engorged nymphs, 91% in unfed

adults, and 97% in fed adults when formulated in oil, and 77% in eggs, 95% in unfed

larvae, 64% in engorged nymphs, 83% in unfed adults, and 90% in fed adults when

formulated in water. Various stages of Amblyomma hebraeum, Amblyomma

variegatum, Rhipicephalus appendiculatus and R. e. evertsi were also found to be

highly susceptible to M. anisopliae in water and oil formulation. Furthermore in this

study, conidia were protected with 3% chemical sunscreens, Everysun and E45,

respectively, and exposed to UV radiation for 1, 2, 3, 4, and 5 hours. Survival of

conidia after 5 hrs of exposure to UV in oil formulation was: 4% in control, 29% in

conidia protected with Everysun, and 40% in conidia protected with E45. In

comparison, survival of conidia formulated in water was: 0% in control, 13% in

conidia protected with Everysun, and 24% in conidia protected with E45.

Furthermore, effects of the 2 sunscreens on viability and on pathogenicity of conidia

to in various stages of R. e. evertsi were evaluated. The 2 sunscreens were found to

confer protection to conidia against damage by UV radiation without interfering with

their pathogenicity to ticks. This study has therefore indicated that M. anisopliae has

a potential as a myco pesticide to control different developmental stages and species

of tick populations. Results of this study have also shown that oil and chemical

sunscreens can protect conidia from UV radiation damage, and they do not reduce

the ability of M. anisopliae conidia to germinate, or infect ticks and induce

mortalities in different stages of R. e. evertsi.

Keywords: Metarhizium anisopliae, Ultra-violet radiation, Sunscreens, Amblyomma

hebraeum, Amblyomma variegatum, Rhipicephalus appendiculatus, Rhipicephalus

evertsi evertsi, Ticks, Germination, Infection, Mortality, Formulation.