Laser weeding of common weed species

The massive use of herbicides since the 1950s has resulted in increasingproblems with herbicideresistant weeds and pollution of the environment,including food, feed, and water. These side effects have resulted in politicalpressures to reduce herbicide application. The European Commission aims toreduce the use and risk of chemicals and more hazardous pesticides in the EU.Therefore, new weed control methods are in demand. Laser weeding might bean alternative to replace or supplement herbicides and other weed controlmethods in an Integrated Weed Management (IPM) strategy. This work aimedto investigate how increasing laser energy affected common weeds when theapical meristem was exposed to irradiation at the early stages of development. A50 W thulium-doped fibre laser with a diameter of 2 mm and a wavelength of 2μm was used. The highest efficacy of laser irradiation was achieved when thegrass weed (Alopecurus myosuroides) had one leaf and the dicot species were atthe cotyledon stage. There was a large difference between the species’susceptibility to irradiation probably caused by differences in morphology andgrowth habit. At the 4-leaf stage, most of the species regrew after irradiation.Laser weeding may be a solution to replace or supplement other weed controlmethods in some crops, but in general the weeds must be irradiated when theyare at the cotyledon to 2-leaf stage to avoid regrowth.