What's Eating Your Rosemary?

Specks barely larger than a pinhead, in tan, red, or pale yellow, clustered on the underside of rosemary's narrow needles. Fine webbing between needle whorls is the giveaway. A magnifier or a sheet of white paper held under a tapped stem reveals them.

Needles fade to a dull silvery-yellow then turn brown and drop from the bottom of the plant upward. Indoor rosemary in dry winter air can lose half its foliage in 2 to 3 weeks. The oil glands on the needles release a thin dusty bloom where mites have been feeding.

Soft pear-shaped insects 2 to 3 mm long, in green, black, or grey, packed on the soft new shoot tips and flower spikes. They cluster on the youngest growth where rosemary's oils have not yet hardened the tissue.

New tips curl and twist, often with a sticky honeydew coating that draws sooty black mold. Heavy infestations stunt the season's growth and reduce the oil content of the leaves, leaving cooking sprigs flavorless.

Tiny white moth-like insects, 1 to 2 mm long, that lift in a small cloud when you shake the plant. Nymphs are flat translucent scales pasted to the underside of leaves. Both stages cluster on lower foliage, deeper inside the woody framework.

Lower needles yellow and drop, and a sticky honeydew coats the stems below the infestation. On potted rosemary brought indoors for winter, populations explode in a heated room and weaken the plant by spring.

Small soft insects covered in a white waxy fluff that looks like cotton or lint. They tuck deep into the leaf-stem joints and along the woody framework where rosemary's branches fork. Slow-moving and easy to miss until colonies are dense.

Stems weaken and snap easily, and the surrounding needles yellow and brown. Sticky honeydew coats the lower foliage and draws sooty mold. Indoor potted rosemary is the most vulnerable, especially plants overwintered in heated rooms.

An eye-catching 7 to 8 mm beetle striped in metallic green and purple. Larvae are grey grubs about the same length, with a darker head. Both stages feed openly on rosemary, lavender, sage, and thyme. Most common in southern England, the European mainland, and increasingly in zones 8 to 9 in North America.

Adults and larvae chew shallow notches in the needles and strip flower spikes, leaving bare stems and a thinner canopy. Damage peaks from late summer through autumn when adults are most active. Plants recover the next spring but lose that season's bloom and culinary harvest.