As one understands from the passage, when the ultimate version of the weedkilling robot comes into use, ----.

Robots make unlikely green warriors, but they could
soon be doing their bit for the environment. Trials of
a Danish robot that maps the position of weeds
growing among crops suggest that herbicide use
could be reduced by 70 per cent if farmers used it to
adopt more selective spraying techniques. Actually,
the robot drives across fields scanning the ground for
any weeds and noting their positions. A later version
will be able to kill the weeds too by applying a few
drops of herbicide. But the longer-term goal is to
avoid herbicides altogether by having the robot pluck
the weeds out of the ground rather than poisoning
them. Although weedkilling robots have already been
put to work in the United States, they cannot be used
for agricultural purposes because they do not
distinguish between plant species and tend to treat
anything green as a weed. Instead, they are used to
clear unwanted plants from railways and airport
runways.