Protecting Plants by Deterrents Instead of Killing Insects

©. Courtesy of W. Mischko / TUM
"It's not just about the bees, it's about the survival of humanity. Without the bees that pollinate a wide variety of plants, not only would our supermarket shelves be quite bare, but within a short time, it would no longer be possible to supply the world's population with food."

The words of Professor Thomas Brück, who holds the Werner Siemens Chair of Synthetic Biotechnology at the Technical University of Munich, explain why he and his team are trying to find functional alternatives to the widespread use of chemicals intended to improve crop yields.

In short, pesticides are designed to kill. No wonder they have unintended toxic effects, such as threatening bees or getting into our drinking water with potential side effects on humans. A new approach is needed.

Brück's team has turned to the same technique we humans have long used against mosquitoes: deterrence. The bug spray or bug-proof clothing we buy does not kill the annoying pests; it merely annoys them back - so much so that they don't hang around for a meal of your fresh blood.

In the image here, you can see the same effect at work. Wheat seedlings left untreated have a red haze of aphids feeding on them. But the red insects avoid seedlings treated with cembratrienol (CBTol if you prefer acronyms), a chemical tobacco plants naturally use to discourage predators.

Tests also indicate the CBTol has antibacterial effects, which could lead to a good substitute for the current antibiotics that accumulate in the environment, creating so-called "superbugs."

The research team at TUM developed a process to produce the desired chemical as well, by genetically modifying bacteria and applying an efficient and scalable centrifugal separation chromatography process to isolate the CBTol from the nutrient-bacteria mixture. If you ardently oppose genetic engineering, this may not seem like a good idea. But using GMOs in a contained industrial process sure beats genetically modifying plants and growing them widely across the lands simply because the genetically modified plants can tolerate even higher doses of poisons.

The use of biomimicry - using the techniques plants themselves have developed to deter insects - yields a biodegradable plant protection product, which further reduces the potential for the chemicals to build up and lead to harm.

The full research report can be accessed behind the paywall in the journal Green Chemistry: Biomanufacturing for a Sustainable Production of Terpenoid-based Insect Deterrents, May 14, 2018 – DOI: 10.1039/C8GC00434J