The Effects of Selective Strains of the Fungi Metarhizium anisopliae and Beauveria bassiana on Blacklegged Ticks and Non-target Organisms

Blacklegged ticks (Ixodes scapularis) are important vectors of pathogens transmitted to humans and wildlife. One potential method for reducing the incidence of tick-borne diseases is to develop new approaches to reduce tick abundance. Chemical pesticides reduce tick abundance but they can also have significant negative effects on the environment and on non-target organisms, including beneficial insects. Biological control agents such as natural predators and parasites of ticks may be a safer option. Recent studies have identified two fungi - Metarhizium anisopliae and Beauveria bassiana - as potential biological agents for controlling tick abundance. Naturally occurring strains of the fungi kill ticks but also affect non-target organisms. Recent work has suggested that a specific strain of Metarhizium anisopliae F52 (Met52®) has high specificity for killing blacklegged ticks and can efficiently control the target blacklegged ticks, but these studies were carried out by the manufacturing company of the F52 strain. In this study, I tested the specificity of two formulations of Metarhizium anisopliae Met52 strain, one a granular form and the other a liquid formulation in a petroleum distillate. I compared the effectiveness of these products to that of Beauveria bassiana GHA strain on the survival of blacklegged ticks, wax worms (Achroia grisella) and ladybeetles (Hippodamia convergens). The granular formulation of Met52 strain (Met52 G) appears to be the most pathogenic to blacklegged ticks and has the fewest non-target effects. At a concentration of 1.8*10^8 CFU/g of Met52 G spores, 83% reduction in blacklegged ticks was observed at day three post-treatment. This formulation shows a potential as a safe and effective biological agent for controlling tick abundance and tick-borne diseases. However, controlled field studies using a wider range of non-target organisms should be conducted