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Come rain and come shine: Collecting Trichogramma populations from the field
An important part of my project comprises fieldwork. In this aspect of my PhD I am interested to find out which Trichogramma species can be found to be naturally occurring in agricultural systems in Germany, with the aim of comparing the populations on a genetic level during secondments to Wageningen University & Research.
ESR update - During the summer of my first year, with my brand-new driving licence and youthful optimism, I headed off around Germany on a 3000km trip to sample organic cabbage fields for the tiny egg parasitoid wasps, Trichogramma. This preliminary trip, despite its relatively low success in terms of collected Trichogramma populations (frustrating but expected from any first field season), provided invaluable experience, both in terms of personal development (severe hill-start training in Northern Bavaria – something that I hadn’t had much experience with having learned to drive only weeks before in the very flat city of Bremen, and developing my understanding of agricultural-based discussion in the diverse accents of spoken German), but of course also in terms of scientific method.
With my newfound experience, I approached my 2017 field season very differently, and not only with a more waterproof pair of walking boots. Firstly, due to the natural cycle of the insect communities, as well as factors including, but not limited to, weather conditions, age of crop, and any interactions between these factors, it is very difficult to estimate exact dates on which to sample in order to guarantee successful collection of (parasitised) Lepidopteran eggs, especially when not being continuously personally present in each area. For these reasons, I wanted to sample every site every week for as long a period as possible over the summer of 2017. In order to do this, I hired four field assistants who weekly sampled farms in their respective areas from July to October. Together, we sampled a total of 18 fields, belonging to 15 farms, in six distinct areas on a North–South cline down Germany. Collection of Leptidopteran eggs was the main aim of each field visit, as Trichogramma, being egg-parasitoids, may emerge from egg clutches and can then be reared in the lab to be used for behavioural experiments, and to be used for genetic analyses. Any Lepidopteran larvae and pupae, as well as other parasitoid pupae were also collected, in order that a food-web approach may be applied to the data. Sampling was carried out in a structured way that will allow us to map where insects and egg parasitism were located in each individual field. For a sneak preview, I can tell you that I found Trichogramma in all five areas, on 14 of the 18 fields sampled, but for more information, please watch this space…
I would like to thank my field assistants Eddie Griese, Janine Köthe, Johannes Lux, and Uwe Schmidt for their invaluable assistance, as well as the farmers for their cooperation and allowing me access to their crops.