All gardeners need to be aware of common “pests” and how to deal with them. Eric Carle was right – caterpillars are hungry! And they can do some serious damage to your crops.
A common pest of plants in the cabbage family (the Brassicas) is the Cabbageworm. You’ve probably seen their adult form, the Cabbage White butterfly, flitting around in your garden — they are those ubiquitous little white butterflies that emerge in the spring. We don’t endorse using chemicals so this post will focus on non-toxic ways to manage these critters. One of the best lines of defense is vigilance. Check for eggs on the undersides of the leaves often. At that stage you can just gently squish them with your fingers. The caterpillars are excellent at hiding and sometimes the first sign that you have them are leaves with holes. They have excellent camouflage and tend to hide down near the stem. I have found that little kids with eagle eyes are great at spotting these once you teach them what to look for. You can manually remove them from the plants. You can also use beneficial insects to keep pests at bay.
This, on the other hand, is a caterpillar you might find growing on your school’s parsley or dill.
The Black Swallowtail butterfly larvae eat fennel, dill, and parsley as their host plants. These can be removed from the plants (take the whole stem that it’s on) and raised in classrooms as part of life-cycle studies. At Bradford we grow fennel just to attract them to our gardens! Kids love watching the eggs hatch, and the caterpillars go through their various instars. They make an interesting chrysalis, and can even be overwintered to emerge in the spring. Of course, left on the plant they will do just as much crop damage as any other “pest”. In farming parlance they are known as “Parsley Worms”.
I suppose one could also raise cabbage worms to become Cabbage White Butterflies, but since they are an introduced species (accidentally in the 1800’s), and considered a true agricultural pest I probably wouldn’t, but it could raise an interesting discussion with your students on why we covet some species yet shun others.
Check out this close-up video of a Swallowtail caterpillar exploring a stem of fennel: swallowtailmovie