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Vincent Lesieur
Email: vincent.lesieur(at)
Position: postdoc, Montpellier Supagro
Topic: Biological control of the Common Sowthistle, Sonchus oleraceus
CBGP supervisors: M.S. Tixier & J.F. Martin
Dates : March 6th, 2017 – March 5th, 2020

Vincent is back for at least three years as a postdoc in a collaborative project between Montpellier SupAgro and CSIRO.

Plants that have become weeds in Australia are rarely troublesome in their native range. This is often because populations in the native range are regulated by a variety of natural enemies such as insects and pathogens that attack the seeds, leaves, stems and roots of the plant. If plants are introduced to a new country without these natural enemies, their populations can grow unchecked to the point where they become so widespread that they are regarded as weeds.

Biological control aims to reunite the weeds with their natural enemies in order to suppress their populations and curtail spread. With this context in mind, the key research question that this project aims to address is which of the many natural enemies that attack the target weeds in their native range are the most appropriate candidate biocontrol agents. The key knowledge required to best answer this question is:

  1. the taxonomy of the weed to ensure that surveys target the right species (the weed reproductive biology, level of morphological variation and utility of existing taxonomic treatment of the plant genus will determine whether or not this phase of the research is straightforward or complicated);
  2. the weed’s genetic make-up to help pinpoint the geographical source of plants that invaded the new range (to better target field surveys in the native range in order to find agents highly adapted to the weed genotypes found in the invaded range;
  3. the areas of the native range that match climatically those where the weed occurs in the invaded range (to collect candidate agents in the native range that are more likely to be adapted to the climate of the proposed destination);
  4. the type and severity of damage that the candidate agents can inflict on the weed (to identify those agents that are most likely to be effective once released in the field);
  5. the specificity of the candidate agents (to demonstrate that the candidate agents do not pose an unacceptable risk to non-target plant species).