Deterringparsleyworms is a bit more difficult. If you find the caterpillars truly objectionable, you might try row covers. Covering your tender crops may aid in deterringparsleyworms. Worm Control On Parsley: Information On DeterringParsleyWorms. If you happen to notice worms on your parsley, dill, and occasional carrot, chances are they are parsleyworms. To deterparsleyworms from damaging your plants without exterminating the caterpillars, consider implementing a distraction garden by planting extra dill, carrots, and parsley away from... Parsley can deter beetles from asparagus patches. It can also help tomatoes by deterring insects and improving the flavor. Is parsley an annual or perennial? Another way might be to use row covers, which will deter more than just caterpillars. Parsleyworms are also very susceptible to other predators in the garden. When the parsleyworm caterpillars hatch from the egg they are tiny. They eat and gradually grow bigger over time. When they are small, the damage is not as noticeable. Management Methods. Parsleyworm Photo of Black Swallowtail Papilio polyxenes (c)2009 Derek Ramsey via Wikimedia Commons, GNU Free Documentation License, Version 1.2. How do you keep worms out of parsley? If you find the caterpillars truly objectionable, you might try row covers. Covering your tender crops may aid in deterringparsleyworms. Learn how to control parsleyworms using natural, organic pest controls. Keep parsleyworms from attacking the crops in your vegetable garden.