Good luck with this one - they are horrid creatures, which I just hand-pick. It's a nasty job, but otherwise, they'd eat me out of plant foliage!

Due to their nocturnal behavior, it is best to time control measures for early evening when caterpillars are present on the surface of the turf, shrubs or trees and are controlled with Permethrin and/or good cultural habits (hand picking the caterpillars from the shrub). BT (Bacillus Thuringiensis) is a material that kills caterpillars and is often used in vegetable or flower gardens. The plus side of using BT is that it only effects caterpillars and will not harm desirable butterflies or helpful insects such as lady bugs.
I suggest hand picking & using a BT spray, and save using the Permethrin as an absolute last resort effort.

Bayer's Tree and Shrub with the new white label will kill caterpillars.

What are they eating? If the caterpillars are on Passionvines, they are probably not Oleandar but rather Gulf Frits. They look similiar except the Oleander 's hairs are intufts rather than single spoikes. Of course, if they are on Oleanders or Mandavilla's then you are correct. Just hate to see the butterfly cats destroyed.

Even the oleander caterpillar makes a pretty, colorful moth that looks like a wasp. :o)

Yes, spray the plants every week with Bt. At least it's not a deadly chemical that'll harm most other beneficial insects -- that is, as long as you don't spray the foliage on plants that butterfly caterpillars are feeding.

That's the beauty of a systemic product.
It only targets the insects eating the plants.

I like to watch the bright red cardinal, eat the fat green caterpillars.

Here I think they are Daphnis nerii.

I've seen them eating them for 2 years now.

I go out in the evening and pick them off the leaves.

I keep a pump sprayer handy and spray with Triazicide frequently, this get's rid of them instantly. If you do not they can eat up the entire plant in a few days.

Try trimming it back, as good air circulation is key!

If all else fails replace it with one of the new varieties. They grow quickly and are less appetizing to the little guys.