Answer: Those green worms are tomato hornworms. They are quite a shock to see on your tomato plant because they get so large and I swear you can hear them chewing the leaves if you're really quiet. Those white eggs on their backs are eggs of braconid wasps.This native wasp lays eggs on the caterpillars, and the hatchlings burrow within the pest to feed. If and when you see this phenomenon again, leave the caterpillar where it is, and the wasp larvae will take care of it for you.
The next best control of these hornworms is hand picking if you only have a few. For larger numbers, spray the organic pesticide Bt on the plants. This bacteria kills the hornworms, but will not harm the birds, bees, animals and other insects in the garden. It is very safe. Check local garden centers for Bt. It's widely available.
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