Spot Them Early
As with most pest insect problems, the sooner you spot a pest caterpillar problem the easier it will be to bring under control. The parsleyworm is so brightly colored, you’d think they would be easy to spot. However, they seem to blend in perfectly with the parsley leaves and usually you will see the damage before you will see the parsleyworm.
Control by Hand
Handpicking makes a sizable dent in most populations of Parsleyworm and can keep them from getting out of hand if you catch the infestation right away. Drop them into a can of water with insecticidal soap in it.