In short, the main aim of my project is to determine the congeneric risks of a mass-release of a biological control agent into an agricultural system. I work with Trichogramma, a tiny parasitoid wasp that exploits (mainly) Lepidopteran eggs as their host. Until my first field season I have been getting to know these little wasps (ca. 0.5mm in size), and how to work with them. Before I can begin to look into more detail on the congeneric risks of a mass-release of these insects, it is important to know what is already present in agricultural systems naturally. Therefore, during the summer of 2016, I travelled around different areas of Germany sampling organic cabbage fields for Trichogramma and other egg parasitoids, as well as larval and pupal parasitoids. This was done by means of sticky traps, traps containing factitious hosts, as well as manual collection. Being my first field season, I learnt quickly how to optimise my trapping technique, and built good relationships with the different farmers. I successfully trapped several populations of Trichogramma, which I am now working on identifying using molecular DNA barcoding techniques, carried out during a secondment at Wageningen UR in the Netherlands. Over the next two years, I will repeat trapping in order to compile a thorough distribution map of the species present in organic cabbage fields.
When releasing an organism as a biological control agent, it will present itself as an additional competitor for other insects with the same host or prey. Thus, intraguild competition is an important consideration in any release risk assessment. I have begun experiments on the competitive nature of different Trichogramma species, and strains thereof, including strains that are currently sold commercially for biological control purposes. The results so far are interesting, displaying differences even to strain level in the different species competitive abilities. In the coming two years, these experiments will be broadened to include more species, including those trapped in the field, different scales, and a more complex environment. This should provide a snapshot for potential interactions after a release.
I’d like to mention a thanks to Eddie Griese and Nolan Rappa for their contributions to the fieldwork, as well as Renate Kienzle for her work with the competition experiments.