Answer: The best thing to do is figure out what is eating the plants, then decide how to control it. If the damage is minor, you may not need to do anything. If it is an insect you may be able to control it by handpicking, that is the safest control. (For example, a tomato hornworm caterpillar is easy to find and remove, and just one can do a lot of damage.) If a chemical control is needed, you would use different products depending on what insect specifically is attacking your plants. For example, insecticidal soap would be effective against aphids but would not control caterpillars.
If it is an animal such as a woodchuck or deer you could fence it out or repel it with a spray on repellent labeled for that particular animal.
I hope this helps you start to troubleshoot.
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