The parsleyworm (AKA carrotworm or celeryworm) is a major pest of the members of the parsley family such as parsley, dill, celery, caraway, carrots, and parsnips. The adult is the Black Swallowtail, a butterfly with a three inch wingspan. This pretty black creature is found nationwide and has two rows of yellow spots near the edges of the wings, plus a row of blue spots on the hind wings. The female lays single white eggs on the host plants.

Larvae: The larvae can be easily handpicked, or can be excluded by use of agricultural fleece. Natural predators include predatory flies, parasitic wasps, lacewing larvae, and assassin bugs. They are also prey for many kinds of birds, as well as toads, snakes, and lizards. Bacillus thuringiensis can be used early on; start spraying every 7 to 10 days when you see the adults. Older populations of the larvae can be controlled with Pyrethrum or Rotenone.

Adult: These eggs hatch into the destructive stage, the larvae. These two inch long caterpillars are pale green or white with yellow/orange-spotted black bands on each segment. If startled, the larvae can expose yellow or orange osmateria (or "horns") from behind its head, and emit a strong, sweet, defensive odor. The larvae feed voraciously on the foliage of its host plants until pupation. There may be three or more generations per year, and the insect overwinters as pupae or even as adults in very warm areas.