Hi, That sounds like a tomato hornworm. They are large, scary looking green caterpillars that are easy to kill. They don't generally infest your garden in large numbers so spraying is not necessary. Just knock them into a jar of water or onto the ground and squish them. FYI, these caterpillars often play host to a wasp that lays it's eggs on the caterpillar, which eventually kills the caterpillar. My guess is that those white tubes are actually the eggs of the parasitic wasp. So, if this is the only caterpillar you see, I might leave it alone so the parasitic wasps hatch and prosper.