Kill weeds with lasers

Lasers have been used in the agricultural industry but only for positioning of crops and such, but there's a larger posibility here for higher powered lasers in the fields! Imagine a small robot (like a pakbot or something) that goes around each row, stopping every few feet and analyzing its surroundings. Once software determines which plants are crops and which are weeds, it aims its laser at the stalks of the weeds, killing them before they even have a chance. Not a lot of power is needed to kill the weeds, only enough to disrupt the cell structure along the stem. In an upgraded version, imaging would allow the recognition of certain bugs such as beetles and slugs. They would be lasered too, hopefully bring this organic method full circle.