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Encouraging the research on an alternative to pesticides

press release of December 6, 2003

Sven Bacher, 'Privatdocent' at the Zoological Institute of the University of Berne and member of the National Centre of Competence in Research (NCCR) Plant Survival located at the University of Neuchâtel, received on Saturday, December 6th the Bernese Prize for Environmental Research.

Accompanied by CHF 15,000, this award is handed out every two years by the University of Berne with a contribution from the Federation of Commerce and Industry (Handels- und Industrieverein) of the Canton Berne and Bernese SMEs. This year the award recognised work dealing with the struggle against harmful organisms by using methods that do not rely on synthetic pesticides. The research concerns, in particular, creeping thistle, Cirsium arvense, considered as one of the world's most invasive weeds. In Switzerland, this species is menacing the ecological compensation areas, which are strips that the farmers establish in order to develop a certain biodiversity in rural areas.

The laureate's research carried out within the framework of NCCR Plant Survival has produced two methods capable of halting the proliferation of the weed. The first method calls upon the shield beetle, Cassida rubiginosa, which adores thistle leaves. Thanks to this biologist's studies, we now know the optimal population densities of the beetle that, along with the seeding of judiciously chosen wildflowers, are necessary to efficiently counter the invasive weed.

Moreover, a continuous remote video surveillance system in the field enabled the identification of Cassida rubiginosa's enemies. It seems that in 99.4% of the cases the death of the beetle can be attributed to the paper wasp, Polistes dominulus. Hence, the so-called generalist predators (ants, nabid bugs, lacewing larvae etc.) are not responsible, as previously assumed, for the weak presence of the beetle.

The second control method against Cirsium arvense involves the stem-boring weevil, Apion onopordi, that promotes infections of the rust fungus, Puccinia punctiformis, on thistle. This discovery reveals the existence of a mutualistic interaction between the insect and the fungus, announcing a first in the area of population ecology. "It is the first documented mutualistic interaction between a plant pathogen and an insect herbivore, states Sven Bacher. Usually these groups have an antagonistic relationship. This discovery enables us for the first time to consider the rust fungus as a specific weed control agent."

Finally, the threat from harmful species arriving from other continents is also at the centre of the laureate's preoccupations. For example, his studies on the horse chestnut leaf miner, Cameraria ohridella, that has attacked the white flowering horse chestnut, Aesculus hippocastanum, since the middle of 1980's, have brought about two important arguments. They have proven that removal of leaf litter is an effective control measure to limit the spread of the pest. They have also shown that the infection leads to reduced seed weight, which explains the impaired growth and survival of the next generation. Therefore the pest may threaten the survival of the last endemic horse chestnut forests in the Balkans. These researches are part of the 5th European Framework Programme.

for more information

www.ikaoe.unibe.ch/forschung/ufp/

To contact the laureate:

Sven Bacher, PD Dr.
Zoologisches Institut
Universität Bern

Tel. +41 (0) 31 631 45 39 / 11
Fax: +41 (0) 31 631 48 88

sven.bacher(at)zos.unibe.ch
www.zoology.unibe.ch/ecol/bacher/

Release Editor: Igor Chlebny