Garden pest
Parsleyworm
A striking striped caterpillar — and a future swallowtail butterfly.
Parsleyworm is in its active season now — scout your plants this week.
How to identify parsleyworm
A smooth green caterpillar banded with black and dotted yellow-orange, up to two inches long, on carrot-family foliage. Poke it and it everts a harmless orange 'horn' (the osmeterium) that smells odd — a bluff, not a sting.
This one is worth knowing before you squash it: it becomes a black swallowtail butterfly. On a big planting the damage is trivial and many gardeners simply let it be.
Attacks: Parsley, Dill, Carrots, Fennel, Cilantro
Life cycle: Swallowtail butterflies lay pale eggs on dill, parsley, carrot, and fennel; caterpillars feed for a couple of weeks, then form a chrysalis to emerge as the next butterfly.
Signs of parsleyworm
What you actually see on the plant — usually before you spot the pest itself.
- Bare, chewed stems on parsley, dill, carrot tops, or fennel
- One or a few large, obvious caterpillars (rarely a heavy infestation)
Organic control, least-toxic first
Start at the top and only move down if you need to. Physical and cultural fixes come before any spray.
- Relocate, don't kill
On most home plantings the best move is to move the caterpillar to a sacrificial dill or parsley plant and let it grow into a butterfly. Grow a little extra herb specifically to share.
- Hand-pick if numbers climb
If a small planting is being stripped, pick the caterpillars off and move them elsewhere.
- Spot-spray Bt only if truly overrun
Bt works but kills the swallowtails too, so reserve it for a genuine infestation, per the label.
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One rule for any product you spray: follow the label. The label is the law, and it is the tested, safe rate for your plants — homemade mixes and dish-soap sprays are not, and can scorch foliage.
Prevent it next season
- Plant extra dill, parsley, or fennel as a decoy crop to share with the butterflies
- Row cover carrots if you want zero feeding (it also blocks carrot rust fly)
Questions about parsleyworm
Should I kill the striped caterpillar on my parsley?+
Usually no. It becomes a black swallowtail butterfly and rarely does serious damage. Move it to a spare herb plant instead of killing it.
What is the orange horn it sticks out?+
A harmless scent gland called an osmeterium that the caterpillar everts to startle predators. It can't sting or hurt you.
Plan a garden that fights back
Healthy, well-spaced plants shrug off pests that flatten a crowded bed. PlotToTable sizes your beds, spaces every crop, and flags the pests that hit what you grow.