Science Agriculture Star Wars on Weeds: Could Lasers Replace Herbicides? By Christine Lepisto Writer St. Olaf College University of Minnesota Christine Lepisto is a chemist and writer from Berlin. A former Treehugger staff writer, she now runs a chemical safety consulting business. our editorial process Christine Lepisto Updated October 11, 2018 CC BY 2.0. will668 Share Twitter Pinterest Email Science Space Natural Science Technology Agriculture Energy will668/CC BY 2.0 Weed killers, herbicides in techno-speak, must be toxic enough to kill the weeds they target. Thus, toxicity concerns -- ranging from protecting the workers using the chemicals to groundwater contamination -- confront any user of herbicides. Researchers at the Leibniz University in Hannover, Germany, may have an answer: weed-killing lasers. Farming with Laser Death Rays Sounds like a great idea? It is not so easy though. If the lasers used have too little energy, weeds like it. Laser lights of the wrong intensity make the unwanted plants grow like weeds, only more so. The Leibniz team has worked to determine the optimum laser intensity to kill the weeds rather than encourage growth. The second major obstacle is recognizing which plants to target with the laser death rays. The researchers have developed a system of cameras that film the field, and software that measures the contures of every plant. Algorithms have been developed for recognizing many different types of weeds. The system currently can treat about a square meter of growth in a greenhouse, where the apparatus can be mounted on rails for pin-point control. The scale-up for larger greenhouse applications or orderly plantations where equipment can run on rails up and down rows of vegetation can be easily conceived. Large farms present greater challenges. The researchers are currently considering whether robots or drones can bring the equipment into position precisely enough over large areas to effectively recognize and blast the weeds with the laser death ray while leaving the desired cash crop unharmed.