Investigating the treatment point of plants for laser weeding

The increasing demand for alternatives to herbicides in weed management requires innovative approaches to integrated weed management, particularly due to the EU Soil Strategy which aims to reduce the use of pesticides in agriculture by 50% by 2030. Laser-based weed control provides an alternative to chemical methods allowing precise single plant weeding in the direct vicinity of crop plants. However, laser weeding must become more efficient and effective to compete with conventional methods. Optimizing the use of laser entails a wide array of parameters to analyze, such as laser wavelength, beam diameter, angle of irradiation and treatment point. Each parameter needs to be analyzed individually to gain knowledge of its effect on the laser weeding process. In this article, we show plant experiments to determine if the treatment point of the plant has an effect on the laser weeding process and which treatment point yields the highest success rate in damaging the plant. In a first set of experiments, we evaluated two potential treatment points of the plant: the meristem and the stem of the plant. We irradiated test plants with a 1940nm laser system, as this laser wavelength is well absorbed by the water within the plant, promising a high damage potential. We irradiated plants at a young growth stadium of up to four leaves and assessed each plant individually based on their damage level after a period of three weeks. To further improve our understanding of the laser weeding process, we recorded some experiments with a thermal imaging camera to visualize the heat distribution within the plant, as laser weeding is a thermal process, where heat is generated where the laser beam hits the plant.