Answer: Garden lime would not be recommended for pest control.
Tomato hornworms can be controlled by hand picking as you are doing, or with Bt used according to the label instructions. (This will kill all kinds of caterpillars.) The caterpillar is also naturally attacked by a wasp that lays its eggs on it. If you find a hornworm covered with what look like grains of rice, try to relocate it and allow it to live so the eggs may hatch -- this will nurture its own natural enemy.
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