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Conventional crop protection products are – and should be – killers: Their purpose is to control pests as efficiently as possible and optimise crop yields. However, they also endanger bees and other useful insects. Biodiversity is at stake in the long term. A team from the Technical University of Munich (TUM) has now developed an alternative to the toxic substances: A biodegradable active ingredient keeps pests away without poisoning them.

“It’s not just about bees,” says Professor Thomas Brück, holder of the Werner Siemens Chair of Synthetic Biotechnology at the Technical University of Munich (TUM). “Without bees pollinating a large number of plants, not only would our supermarket shelves be quite empty, but within a short time the supply of food to the world’s population would no longer be guaranteed.

The alternative to synthetically produced insecticides now presented by Brück and his team is therefore pursuing a different strategy: when sprayed on plants, the substance has a similar effect to mosquito spray, spreading an odor that keeps unwanted insects out. It drives them away instead of killing them. The repellent is biodegradable and ecologically harmless.

“Our approach enables a fundamental change in crop protection,” says Brück. “Instead of spraying poison, which always endangers useful species, we deliberately deter only the pests.”

The Munich researchers were inspired by the tobacco plant. This produces cembratrienol, CBT-ol for short, in its leaves. This molecule protects the plant from pests.

Professor Brück and his team isolated those sections of the tobacco plant genome that are responsible for the formation of CBT-ol molecules. They then incorporated these into the genetic material of coli bacteria. Lined with wheat bran, a by-product of grain mills, the genetically modified bacteria now produce the desired active ingredient.

“The greatest challenge in production was to separate the active ingredients from the nutrient solution at the end of the process,” explains Mirjana Minceva, Professor of Biothermodynamics at the Weihenstephan TUM Campus.

The solution was a special centrifuge process that also works on an industrial scale but has never before been used for the separation of products from fermentation processes.

Initial studies have shown that the CBT spray is non-toxic to insects and still provides effective protection against aphids. In addition, the bioactivity tests showed that cembratrienol has an antibacterial effect. It could therefore also be used as a disinfection spray.

Caption Main photo: Bioreactor of the TUM Research Centre for White Biotechnology in which the CBT-ol was produced. (Picture: A. Battenberg / TUM)


Untreated wheat seedlings are quickly colonised by aphids. (Image: W. Mischko / TUM)


Wheat seedlings treated with CBT-ol avoid aphids. (Image: W. Mischko / TUM)