Posted: 12/05/2013 at 17:33
You cant get agricultural roundup without a licence. I have some, and I reckon it is the same as the retail version with an added wetting agent. You cash get a more concentrated version in stump killer, but I don't think you need it for bindweed.
The thing to rremember is that bindweed roots can go down several metres (no kidding) and glyphosate (roundup) only travels down a short distance before it is used up. So the root system below has enough energy left to send up more shoots. If these get to the surface and get enough sunlight the bindweed will get going again. So with this weed you have to ensure you keep on top of it till the root system is exhausted.
Glyphosate takes 7 days or more before its effect is clearly evident, and meantime some shots from unconnected bindweed plants can appear. This is more likely if you have been digging it out, as every bit of root left in the ground forms a new plant that will need to be treated separately.
Glyphosate will work, I can assure you, if you are persistent.