Pest identification
What's eating my costmary?
Aphids
Signs: Colonies on fresh spring growth and flower stems; leaves curl and yellow; honeydew drips onto lower foliage causing sooty mould.
Control: Squash by hand or apply a strong water jet; insecticidal soap spray; plant companion flowers to attract hoverflies and parasitic wasps.
Chrysanthemum leaf miner (Chromatomyia syngenesiae)
Signs: Pale, winding or blotchy tunnels visible through the leaf surface as larvae mine inside; leaves dry out around the damaged areas.
Control: Remove and bin affected leaves promptly; do not compost; yellow sticky traps catch adult flies; parasitic wasps (Dacnusa sibirica) for biological control.
Slugs and snails
Signs: Irregular holes and scalloped margins on young spring leaves; silvery slime trails on the soil and lower stems after wet nights.
Control: Ferric phosphate pellets; grit or wood ash mulch around crowns; nocturnal hand-picking during warm, damp spells.
Keep costmary pest-free
Healthy plants resist pests best. Get the basics right:
Costmary pests — FAQ
What is eating my costmary?
Costmary (Tanacetum balsamita) is a tough, spreading perennial herb that is strongly aromatic and naturally repels many pests. Aphids may colonise new growth in spring. Chrysanthemum leaf miner can tunnel into foliage. Slugs target young leaves in spring. Deer and rabbits tend to leave it alone due to its pungent, camphor-like scent.
How do I get rid of aphids on costmary?
Colonies on fresh spring growth and flower stems; leaves curl and yellow; honeydew drips onto lower foliage causing sooty mould. Squash by hand or apply a strong water jet; insecticidal soap spray; plant companion flowers to attract hoverflies and parasitic wasps.
How do I get rid of chrysanthemum leaf miner (chromatomyia syngenesiae) on costmary?
Pale, winding or blotchy tunnels visible through the leaf surface as larvae mine inside; leaves dry out around the damaged areas. Remove and bin affected leaves promptly; do not compost; yellow sticky traps catch adult flies; parasitic wasps (Dacnusa sibirica) for biological control.
How do I get rid of slugs and snails on costmary?
Irregular holes and scalloped margins on young spring leaves; silvery slime trails on the soil and lower stems after wet nights. Ferric phosphate pellets; grit or wood ash mulch around crowns; nocturnal hand-picking during warm, damp spells.