Funny word when you say it enough times, which is easy to do when they are defoliating large swaths of the Eastern forest. Tips for defending your own trees follow, as soon as I get the rest of the callas in and the tomatoes mulched. But first, a word about defending your dill, which can also be defoliated by a caterpillar.
Unlike the ones that are eating the forest, which grow up to be small, drab moths of no special aesthetic distinction, the caterpillars that eat dill, parsley, and fennel become black swallowtail butterflies (Papilio polyxenes).
Fortunately, there’s no need to kill them to preserve your herbs – they like Queen Anne’s lace just as much as they like other umbellifers, so you can just gently pick them up and move them to wilder pastures. There are 3 generations a year, but unless you have acres and acres to tend, it doesn’t take long to relocate all threats to the tabbouli.