Pest identification
What's eating my fennel?
Black swallowtail caterpillar (Papilio polyxenes) — US
Signs: Large, vividly striped caterpillars consume foliage rapidly; a single plant can be stripped by a group of larvae.
Control: Hand-pick and relocate to wild fennel or dill if plants are young; consider planting extra fennel specifically for them.
Aphids (Aphis frangulae and others)
Signs: Dense colonies on flower umbels and new growth; sticky honeydew attracts ants and sooty mold.
Control: Spray with insecticidal soap or a strong water jet; attract natural predators by growing companion flowers nearby.
Slugs and snails
Signs: Chew seedlings and young stems at soil level in cool, damp conditions.
Control: Use iron phosphate bait around seedlings; water in the morning; hand-pick at night.
Keep fennel pest-free
Healthy plants resist pests best. Get the basics right:
Fennel pests — FAQ
What is eating my fennel?
Fennel is a host plant for swallowtail butterfly caterpillars, which are bold feeders that can strip plants fast. Aphids colonize flower umbels, and slugs attack seedlings. Because fennel repels or disrupts many plants, it is often grown alone. Tolerate swallowtail larvae if you can — they are spectacular and beneficial as pollinators when adult.
How do I get rid of black swallowtail caterpillar (papilio polyxenes) — us on fennel?
Large, vividly striped caterpillars consume foliage rapidly; a single plant can be stripped by a group of larvae. Hand-pick and relocate to wild fennel or dill if plants are young; consider planting extra fennel specifically for them.
How do I get rid of aphids (aphis frangulae and others) on fennel?
Dense colonies on flower umbels and new growth; sticky honeydew attracts ants and sooty mold. Spray with insecticidal soap or a strong water jet; attract natural predators by growing companion flowers nearby.
How do I get rid of slugs and snails on fennel?
Chew seedlings and young stems at soil level in cool, damp conditions. Use iron phosphate bait around seedlings; water in the morning; hand-pick at night.