With challenges posed by chemical and mechanical weed control, there are now
several research and commercial projects underway to develop autonomous
vehicles equipped with lasers to control weeds in field crops. Recognition
systems based on artificial intelligence have been developed to locate and
identify small weed seedlings, and mirrors can direct a laser beam towards the
target to kill the weed with heat. Unlike chemical and mechanical weed control,
laser weeding only exposes a small area of the field for the treatment. Laser
weeding leaves no chemicals in the field after the treatment or does not move
the soil which may harm crop roots and non-target organisms. Yet, it is well-
known that laser beams can harm living organisms; the effect on the
environment and fauna should be studied before laser weeding becomes a
common practice. This project aimed to study the effect of laser on some living
non-target organisms. We investigated the effect of laser treatment on the
mortality of two species of earthworms (Enchytraeus albidus and Enchytraeus
crypticus), larvae, pupas, and beetles of yellow mealworm beetles (Tenebrio
molitor) and the two-spotted lady beetle (Adalia bipunctata) for increasing
dosages of laser energy. In all earthworms experiments except one, the
mortality rates of the worms living in the uppermost soil layer of clay, sandy,
and organic soil exposed to laser heating were not significantly different from the
controls even with laser dosages up to 236 J mm -2
. Laser doses sufficient to kill
plants were lethal to the insects, and lower doses that did not kill plants, killed or
harmed the insects across all life stages tested. The larger beetles survived higher
doses than smaller. Laser weeding is a relatively new technology and not yet
widely practiced or commercialized. Therefore, we do not discuss and compare
the costs of the different weeding methods at this early stage of the development
of the technology.