What's Eating Your Common Holly?

Small black flies, 2 to 3 mm long, lay eggs in spring on the underside of new holly leaves. The cream-colored larvae feed inside the leaf tissue between the upper and lower surfaces, creating distinctive winding or blotchy trails. Phytomyza ilicis on European holly is the dominant species in most of the US.

Pale yellow squiggly trails or irregular blotches appear inside the holly's glossy leaves and persist for the life of each leaf, which can be 3 years on common holly. Heavily mined hedges look mottled and yellowed even from a distance. Damaged leaves drop earlier than healthy ones, thinning the canopy over time.

Tiny 2 to 4 mm armored or soft-bodied insects that look like small brown, tan, or grey bumps glued to the stems, along the leaf veins on the underside, and on the spiny leaf margins. They don't move once settled and are often mistaken for natural plant growths or bird droppings.

Heavy infestations yellow the foliage and cause premature leaf drop, thinning the holly's evergreen canopy over a season or two. Soft scale species produce sticky honeydew that coats lower branches and draws sooty black mold. Stems with heavy scale dieback at the tips, and entire branches can decline without treatment.

Reddish-brown specks barely larger than a pinhead, found on the underside of holly's glossy evergreen leaves. Southern red mite is a holly specialist active in cool spring weather and again in autumn, unlike most spider mites which peak in summer heat. Fine webbing is rare and damage often appears before mites are noticed.

Leaves develop a fine pale stippling along the veins, then take on a dull bronze cast that is most visible from the side rather than head-on. Damage is heaviest on the southern and eastern faces of a hedge where sun catches the leaves. Heavy populations cause leaf drop on lower branches.

Soft pear-shaped aphids covered in a fluffy white waxy coating that looks like cotton or wool, clustered on the soft new shoots and along the leaf-petiole joints of spring growth. Adults are 2 to 4 mm long under the fluff.

New shoots distort and curl, and a sticky honeydew coats the leaves below, drawing sooty black mold that masks the glossy holly surface. Heavy spring infestations stunt the season's new growth and reduce the next year's berry crop on female trees.

Unmistakable up close. A 3 to 4 foot tall brown mammal. Most active at dawn and dusk. Deer avoid mature spiny holly leaves but readily browse young plants and the softer leaves on new growth, especially in late winter when other forage is scarce.

Whole branches stripped of leaves to about 5 feet up, with ragged torn ends rather than the clean cuts a rabbit would leave. Damage is heaviest from January through March on young holly hedges and recently planted specimens. Established mature hedges over 6 feet rarely suffer significant damage.