So what's the problem?
The broad-leaved dock, Rumex obtusifolius, is considered a weed of permanent pastures, meadows and arable crops throughout its native range in Europe. In Switzerland, it causes particular problems in organic and integrated farming systems. The only feasible control measure currently available for organic production in Europe is cutting the root at a depth of 10cm below the soil surface. This is an extremely laborious method, and alternative solutions, such as biological control, would therefore be highly welcome. However, all potential biological control agents investigated so far have turned out to be inefficient. After studying the potential of inundative biological control with a native root-boring sesiid moth, Pyropteron chrysidiformis, we proposed a ne approach. A similar approach has been implemented successfully in Australia.
What is this project doing?
In 2008, we started this project by establishing a rearing colony of P. chrysidiformis from larvae collected in southern France. We also set up an impact experiment, in which we transferred various egg densities of this sesiid moth onto potted broad-leaved dock plants. Half of the plants were dissected in October and above and below-ground biomass was recorded. Although infested roots were heavily damaged, no significant impact of larval feeding on plant growth was observed at that stage. However, we expect to see an effect in spring 2009, when the remaining plants inoculated during summer 2008 will be dissected and analysed. In addition, we set up a preliminary host-specificity test with a few related plant species to assess the likelihood of non-target effects from this native biological control candidate.
To improve our understanding of the population dynamics of broad leaved dock and to help us develop a tool to model potential impact of this new biological control agent, we started monitoring the population composition and survival of the different life stages of broad-leaved dock in the Swiss Jura. We selected three different grassland types prone to severe infestations of R. obtusifolius, including old natural pastures, young grazed grasslands and young mown grasslands. In July 2008, we set up permanent 2 × 2 m plots on three sites for each grassland type and recorded all the R. obtusifolius plants we found in one of six different phenostage categories.
Results so far
In 2009, we revisted the permanent plots to record plants lifestage again. In addition, we will take soil samples to study the soil seed bank. We aim to increase our rearing colony of P. chrysidiformis, to produce a life table and to develop a mass-rearing technique. We will also consider setting up another impact experiment using higher numbers of eggs.
Address: Bakeham Lane, Egham, Surrey, TW209TY, United Kingdom
Tel: +44 (0)1491 829037
Address: Rue des Grillons 1, CH-2800 Delemont, Switzerland
Tel: +41 (0)32 4214877
Tel: +41 (0)32 4214879
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