In message , Roy Bailey
writes
In article , Ophelia
writes
[snipped]

Crops (75% worldwide) have been modified so that these herbicides can be
sprayed directly onto the plants without killing them. This, of course, so
that the weeds will die, but the plant will not.
How does the glyphosate know which are weeds and which are plants?

Roy.

Cultivated strains of some plants (canola, cotton, soya) have been
genetically modified to be resistant to glyphosate. See "Roundup Ready".

Some weeds have evolved glyphosate resistance.
--
Stewart Robert Hinsley