In response to a question from a farm adviser about a customer who'd sprayed for plantain control, and now wanted to drill new seed.

Broad leaf plantain is normally taken out successfully at the normal rates at which glyphosate is used to spray out paddocks for cropping or for new pasture.

That is between 3L/Ha and 5L/Ha when using G360 liquid, or the Granny equivalent is 1.35kg/Ha to 2.25kg/Ha.
 
The 3L/Ha (1.35kg/Ha) rate is suitable for 'clean' pasture with not much weed content, while the higher 5L/Ha (2.25kg/Ha) rate is for pasture with a heavy weed content.
 
Our customer used a rate of 1.8kg/Ha of Granny, which is right in the middle of the above rate range, equivalent to 4L/Ha of G360 liquid.  And he's seeing yellowing off of the plantain after 9 days, which is a good sign!
 
I don't know what rate Massey is actually referring to when they say that broad-leaved plantain shows "some tolerance to low rates of glyphosate".  Pity they don't mention any actual rate to define "low" for us, even if it's just approximately.  However, I don't think that our customer's 1.8kg/Ha would reasonably be called a "low" rate … it's well into the "normal" rate range.  Also, I can't recall any customer having used 4L/Ha or 1.8kg/Ha to spray out, and then telling us that their broad-leaved plantain had survived.  So I think Massey's "low" is going to mean lower than the normal rate range.
 

So my view is that our customer shouldn't need to spray again.  But if he decides to be cautious and spray again just in case, he might be as well to go for the very top rate of 2.25kg/Ha, because the effect of glyphosate is not cumulative: he can't take into account what he's already applied, and simply "top up".  Also, give it 2-3 days after application before drilling the crop.