Abstract
Horticultural weed control strategies based on chemical and thermal methods are environmentally and energetically questionable. A promising alternative appears to be the use of laser technology. This study evaluates the influence of CO 2 laser radiation (10,600 nm) taking into account three laser spot diameters , three laser spot positions and six laser intensities on three growth stages of two weed species (monocotyledonous: Echinochloa crus-galli , dicotyledonous: Amaranthus retroflexus ). The lethal impact of irradiation was characterised by a decrease of the weed fresh mass of 90% compared to untreated plants two weeks after irradiation. Weed-specific laser damage models were developed and validated, mapping the probabilities of success ( p success ) of the laser application. Selective lethal laser doses with p success = 0.95 were determined. The results showed that lethality was greatest if treatment was performed at early growth stages with high intensity. Monocotyledonous 2-leaf-plants were damaged at high energy levels, whilst 4-leaf-plants were difficult to kill. Dicotyledonous 2-leaf-plants were already damaged at moderate intensities. Thus, the damage of monocots required higher minimum laser doses than the damage of dicots . The influence of the spot position was important, as the unfocused treatment resulted in a decrease in lethality. In combination with robotics and image processing , the damage models developed here can be used to develop laser-based weed control. A model simulation of two driving concepts for the laser system showed that accurate aiming at the meristem as well as specific parameter adjustment is required for an efficient weed control. ► Weed damage caused by selective laser radiation was modelled. ► Influence of laser and plant parameters on the treatments success was examined. ► The prediction rate of lethal damage increased with increasing laser power. ► At least 54 J has to be applied to each weed plant for effective weed control. ► Two driving concept simulations show the advantages of a stop and go application.
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