Caterpillars on citrus

Giant Swallowtail caterpillar. Let them be. Those types don't cause infestations and they aren't really destructive.

Well, compared to large silkworms like cecropia and polyphemus, or smaller tent caterpillars such as webworms or walnut caterpillars, they don't do much damage. Giant Swallowtails usually only lay a couple eggs per tree. Relatively speaking, as long as your tree isn't small, it won't do much harm. If you find more than one I would get rid of a few, but I wouldn't wipe them out completely, and I sure as hell wouldn't use pesticides and take the chance of wiping out all of your pollinators. That's just me though.

Also, a couple rookie questions.

1. I’ve got a 3” raised ring around the plants about twice as big as the container it was in. I’ve seen both ways. Mulch or no mulch? I’m using pine needles by the way.
2. My trees are quite a ways from the house. Can I use the 5 gallon bucket trick to water them by putting a piece of pvc in the ground out of the bottom of the bucket? Will this keep the citrus roots too wet? If I can use this method how often should I fill assuming no rain?
Thanks for the advice.