Well, given I can't see any bindweed on the canes then, yes you are going to have to wait for it to twine up.

I question whether its bindweed at all; by this time of year, it should be anything up to six feet long or more, so unless you've previously pulled it out, it might not be bindweed at all. Unfortunately, I can't see the plants at the bottom of the canes clearly in that photograph to say one way or the other.

The small green plants on the front three canes are definately bind weed but I havent let them grow very high as before as there were plants growing amongst them. Will put clearer pictures on tmrow.

I'd certainly let them get taller before spraying

It looks like bindweed to me. The more leaves it has the better absorption of weedkiller there'll be so don't do it yet..

Yep definitely bindweed. Trouble is, its growth rate starts to slow at this time of year, it's most rapid between April and mid June, but yea, wait till its a bit taller and obviously growing strongly.

Thanks. Will wait a while then.