What are Parsley Worms?
Striking caterpillars, parsley worms turn into even more striking black swallowtail butterflies. They are easily identifiable as green worms with a brilliant, yellow dotted black band across each body segment. When the caterpillar is disturbed, it protrudes a pair of fleshy “horns,” the better to scare predators away. This larval stage of the gorgeous black swallowtail can grow up to 2 inches long.
Parsley Worm Life Cycle
Female black swallowtail butterflies are slightly larger than males and as is usual in nature a bit duller in color than their male counterparts. The wingspan may be up to 76 mm (3 in.). Both are velvety black in color with tailed hind wings marked with peacock-like eyes. The females lay spherical, 1 mm (0.03 in.) across eggs that change in color from pale yellow to reddish brown. Four to nine days later, the eggs hatch and young larvae (instars) emerge and begin feeding.
The yellowish-green parsley worm is the butterfly’s larval stage and its body is transverse with black bands and yellow or orange spots. The “horns” mentioned above are actually scent organs. The young larvae look similar but may have spines. The pupa or chrysalis appears dull gray and mottled with black and brown and is around 32 mm (1.25 in.). long. These pupae overwinter attached to stems or fallen leaves and emerge as butterflies in April-May.
How to Control Parsley Worms
Worm control on parsley is fairly simple, if you really desire their eradication. They are easy to spot and hand pick. They are also naturally attacked by parasites, or if you must, insecticides such as Sevin or Bacillus thuringiensis will kill off the caterpillars.
Although parsley worms are voracious eaters, the benefit of attracting a future pollinator (and a stunning one at that) may outweigh worm control practices on parsley. Me, I would just plant a few more parsley, dill or whatever the insects are feeding on. Healthy plants will usually recover from the foliage loss and parsley worms will not sting or bite humans.
Deterring parsley worms is a bit more difficult. If you find the caterpillars truly objectionable, you might try row covers. Covering your tender crops may aid in deterring parsley worms.