As vectors of a large number of pathogens, ticks pose a considerable problem not only in Germany, but also in most parts of the world. Most bites in Germany are caused by Ixodes ricinus for which there is no specific scientifically proven control agent available. An extensive application of synthetic chemical acaricides has lethal effects on non-target organisms and can further cause resistances in the target organism. However, repellents reduce the contact probability between host and tick, but do not regulate the further distribution of diseases. Although biological control options like entomopathogenic fungi are known to have high potential, there is a considerable lack of studies on formulation and applicability. The disadvantages, such as a low persistence as well as a not consistent efficacy of entomopathogenic fungi (EPF) in the field, still predominate over explicit advantages of biological control agents like a high target specificity, resulting in less toxicity for non-target organisms and a decreased probability of causing resistances in targets. Encapsulation of biological control agents in a biodegradable polymer matrix with supplemented nutrients can improve their stability, virulence as well as applicability for the above ground control of pests, such as ticks. Therefore, the overall aim of this work was to develop a biological tick control agent for the application in the field. To reduce the required dosage of a control agent, a biological attractant was encapsulated. S. cerevisiae releases CO2, attractive to ticks, by metabolizing supplemented nutrients. A co-encapsulated kill component, such as EPF biomass, germinates inside the bead and produces aerial conidia, the infection unit of EPF, on the bead surface. The attraction due to the attractant enables direct contact of the tick to the kill component, ideally resulting in high mortality rates.

This PhD examination procedure was realized in cooperation between the Bielefeld University of Applied Sciences and the Bielefeld University.