What's eating my achillea millefolium 'cerise queen'?

Achillea millefolium 'Cerise Queen' is a tough, aromatic perennial that most pests avoid. Aphids occasionally colonise soft stems, and slugs may nibble young spring foliage. Its aromatic leaves make it actively repellent to deer and rabbits, and it actually supports populations of predatory insects that control other garden pests.

Soft colonies on new shoot tips and flower stems in spring and early summer; sticky honeydew residue and mild distortion of growing points. Blast off with water. Yarrow flowers attract hoverflies, parasitic wasps and ladybirds which provide excellent biological control — avoid pesticides that harm these beneficials.

Holes and ragged edges in emerging spring foliage near soil level; slime trails present. Mature aromatic foliage is much less attractive and largely left alone. Ferric phosphate pellets in spring. Remove garden debris. Once the plant is established and growing vigorously, slug damage is rarely significant.

Blobs of white frothy 'cuckoo spit' on stems in early summer, surrounding a sap-feeding nymph; minor wilting or distortion of the affected shoot tip. Wipe or wash off the foam and the nymph inside with a damp cloth or water jet. No pesticide treatment is necessary — damage is always cosmetic.