Looks like the oleander moth - lays the eggs, caterpillars hatch out and completely denude the oleander bush of it's leaves. They also love desert roses.

Well that explains my devoured oleander -- up until this year I'd managed to keep the cats under control -- usually I only have to treat the oleanders once and they're good this year I did my once but before I could blink those little orange pests were back and my 5 year old tree looks dead --- think I might just cut it down this time -- its too close to the house anyway

What do you treat with? BT works well and doesn't harm beneficial insects. But you will need to spray it more than once.

This link clarifies this beautiful pest.

Here is a link that might be useful: Oleander caterpillar, Syntomeida epilais Walker