Protection of Metarhizium anisopliae conidia from ultra-violet radiation and their pathogenicity to Rhipicephalus evertsi evertsi ticks

Abstract

Metarhizium anisopliae conidia were formulated in water or in olive oil containing 3% commercial sunscreens (Everysun or E45 Sun Block 50) and exposed to an artificial UV source for up to 5 hours. Survival of conidia after 5 h of exposure to UV in oil formulation was 29% when protected with Everysun, 40% when protected with E45, and 4% in control. In comparison, survival of conidia formulated in water was 13% when protected with Everysun, 24% when protected with E45, and 0% in control. Furthermore, the influence of sunscreens on conidia viability and virulence to Rhipicephalus evertsi evertsi larvae and unfed adult ticks was evaluated. Adding these compounds to the conidial formulations did not reduce the viability of the conidia. Larval mortality was 95 and 100%, while unfed adult mortality was 90 and 97% after being exposed to unprotected conidia formulated in water or in oil, respectively. Conidia protected by Everysun or E45 formulated in water, induced 88 and 83% mortality in larvae, and 92 and 90% mortality in unfed adults, respectively. Conidia suspended in oil and protected by Everysun or E45 induced 94 and 91% mortality in larvae, and 83 and 81% in unfed adults, respectively. These observations indicate that olive oil and the two sunscreens confer protection to conidia against damages by UV radiation without interfering with their pathogenicity to ticks.