The parsleyworm is a very large, two-inch long, green caterpillar with yellow-dotted black bands across each body segment. It has a pair of orange horns that it can project to scare off enemies.
The beautiful black-and-yellow swallowtail butterfly is the adult form of the parsleyworm.
The parsleyworm eats the leaves and stems of carrot-family plants but does little damage. The swallowtail butterfly drinks nectar from flowers.
Many gardeners prefer to attract swallowtail butterflies to their garden and do nothing to control the parsleyworm caterpillar.
In cold-winter regions, this insect overwinters as a pupa and in warm climates as an adult butterfly. Adults emerge from pupa in spring and lay single round, pale green or cream-colored eggs the size of pinheads on the tips of host plant leaves. Eggs hatch in four to nine days, then caterpillars feed for 10 to 30 days before entering the pupal stage—a chrysalis–for about 18 days.
There are two to four generations of parsleyworms each year.
The parsleyworm is found throughout the United States.
Target Plants: Parsleyworms chew the stems and leaves of plants in the carrot-family: carrots, celery, parsnip, fennel, dill, and anise as well as Queen Anne’s lace and yarrow. Adults feed on the nectar of flowers.
Feeding Habits and Damage: Parsleyworms chew the stems and leaves of carrot-family plants. Unless there is large infestation, the damage to plants is commonly minor.
Organic Controls: Handpick parsleyworms and move them to expendable host plants from the carrot family; plants specifically planted to feed the parsleyworm and host the swallowtail and other butterflies.
Serious parsleyworm infestations can be controlled by Bacillus thuringiensis dust; dust all parts of the leaves, especially the undersides or apply BT in liquid form; reapply every 10 to 14 days until the infestation is controlled.
Attracting Swallowtail Butterflies: To attract swallowtail butterflies provide water and plant nectar plants such as parsley, dill, fennel, butterfly bush or lantana.
Natural Predators: The parsleyworm’s insect predators include: assassin bugs, lacewing larvae, parasitic wasps, and predatory lies. Animal predators includes Baltimore orioles, barn swallows, bluebirds, chickadees, flycatchers, and kinglets, also snakes and toads.
Birds will eat parsleyworms but they may not eat caterpillars that have fed on licorice-flavored anise. Licorice is a flavor most birds do not like.