Worms in Arundo Donax
I have two arundo donax currently in pots on my porch, awaiting planting. Both have recently attracted the attention of small green worms. The worms have done some damage to the stalks, some small brown chewed areas, and seem to congregate down in the tubes formed in the center of the stalks, where water collects. I suspect it is the water they are after, as it's been over 100 here for the last week. They resemble cabbage worms in appearance. Any ideas what they could be and how to treat?