Pest identification
What's eating my bronze fennel?
Black swallowtail caterpillar (Papilio polyxenes)
Signs: Bold green, black, and yellow caterpillars consume fronds rapidly; heavy infestations can completely defoliate a plant within days.
Control: Hand-pick and relocate to wild fennel if possible — these are valuable pollinators. Apply Bt only if defoliation threatens the plant's survival.
Willow-carrot aphid (Cavariella aegopodii)
Signs: Green colonies cluster on umbels and new fronds, causing sticky honeydew, sooty mould, and stunted growth.
Control: Blast off with water. Ladybirds and lacewings typically suppress populations naturally. Insecticidal soap if needed.
Slugs
Signs: Seedlings and young plants are rasped at the base; young emerging fronds are eaten at soil level in spring.
Control: Protect seedlings with ferrous phosphate pellets or copper barriers. Established plants are rarely significantly damaged.
Keep bronze fennel pest-free
Healthy plants resist pests best. Get the basics right:
Bronze Fennel pests — FAQ
What is eating my bronze fennel?
Bronze fennel is a magnet for black swallowtail butterfly caterpillars, which can strip foliage fast. Aphids — particularly the willow-carrot aphid — colonise new growth in spring. Many gardeners deliberately plant fennel for swallowtails and tolerate caterpillar feeding. Aphids are the more reliably damaging pest from a harvest standpoint.
How do I get rid of black swallowtail caterpillar (papilio polyxenes) on bronze fennel?
Bold green, black, and yellow caterpillars consume fronds rapidly; heavy infestations can completely defoliate a plant within days. Hand-pick and relocate to wild fennel if possible — these are valuable pollinators. Apply Bt only if defoliation threatens the plant's survival.
How do I get rid of willow-carrot aphid (cavariella aegopodii) on bronze fennel?
Green colonies cluster on umbels and new fronds, causing sticky honeydew, sooty mould, and stunted growth. Blast off with water. Ladybirds and lacewings typically suppress populations naturally. Insecticidal soap if needed.
How do I get rid of slugs on bronze fennel?
Seedlings and young plants are rasped at the base; young emerging fronds are eaten at soil level in spring. Protect seedlings with ferrous phosphate pellets or copper barriers. Established plants are rarely significantly damaged.