I grow a patio garden on my second floor deck. I bought potting soil and planted later than I normally do not until mid June. A week ago I found my tomato plants infested with full grown hornworms. I'm trying to figure out how they got there. I didn't grow them in the ground. They weren't put on my deck until June 12th. I've grown patio gardens many times and this is the first hornworm issue I've had. The plants weren't around in the spring for the moth to lay eggs and all the potting soil was new. Thank!!
Here is an article that will help you with this infestation.