BT preparations (
Bacillus thurnigensis), sprayed on the leaves at weekly intervals will kill the hornworm (Hawk moth) larvae. There are a number of commercial products containing the bacterium. It's harmless to insects (not in larval form) and birds and mammals. It cost money and time, but is "easy".
Plan B, which is my plan (I grow 100-200 plants per season), is to walk the tobacco daily, inspecting every leaf. I search for pinholes, then look at the underside. A 1st instar hornworm larva is bright green, and smaller than a grain of rice. I squish them. Any larger ones I remove from the leaf, and squish on the ground.
You can also sometimes see the hornworm eggs before they hatch. They are individual, usually, but not always, on the underside of the leaf. They are a bright, iridescent green, and are the size of Lincoln's chin on a US penny. You have to carefully pluck them off, and apply very firm pressure on them, between the tip of your thumb and index finger, to pop them. They're not particularly messy.
Here in southwest Virginia, hornworms begin to appear in mid to late June, peak over about 5 days, then wane. Each summer I experience 3 waves of hornworms, usually at intervals of about 3 weeks. This summer, I saw a fairly abortive 4th wave in late August.
Bob