To temporarily disable Web Spreaders you have to damage them, but I am able to reduce them to 0% hp as a Mistweaver Monk using Crackling Jade Lightning and the web still persists.
I can run through it and summon nerubians and punch it once with an auto attack, and the webs will disappear though.
Update: It seems to have been fixed some time ago. I did the same scenario in the delve with the spreaders and CJL was able to shrink them away.