I would assume that any newly purchased Passiflora (or any non-food plant) is covered with pesticide.

I had bought this particular passion vine about 2 months ago. I had hosed it off plus we have had many hard rains which should have rinsed any sprays off. The caterpillars (about 30 zebra broad wings ) just died about 4 days ago, So I have to assume something is wrong with that particular kind of passion vine.

In that case one would suspect a systemic insecticide had been applied. It will not wash off.

Here is a link that might be useful: Example of a systemic insecticide that kills for up to 12 months

I'm thinking like Mark is. It had to be a systemic. Some of them last for a year. Sorry to hear about your loss of zebra
(long?)wings. I have fresh p. suberosa seeds if you want to grow from scratch, they are still in the little fruits. Zebras love them, and they emerge within a month from fresh seed.

There are also some passionvines that are indeed poisonous to caterpillars. I believe Red Passionvine, P. vitifolia, is one of the ones that are not recommended for Florida because, while the butterflies will lay their eggs on the vine, the caterpillars can not eat them.