Foliage Damaged in Winter
Wind Burn - Severe windburn may damage Holly foliage during the winter, but affected trees usually regenerate themselves in the spring. A protective material such as burlap or agricultural fleece wrapped loosely around the Holly tree will protect it somewhat. If the Holly is not too large, you can spray the tree with Antitranspirant Spray before winter weather arrives. You may need to spray again during a warm spell in January or February. If this is a chronic problem, move the Holly to a more protected location.
Berries Fail to Appear
Lack of Pollination - Berries may fail to appear for several reasons: the plant is male, the plant is too young, the plant is female but there is no male nearby, flowers were injured by late spring frosts or cold, or rainy weather curtailed pollen spread by honeybees. All Hollies need pollination except Chinese Holly (Ilex cornuta).
Leaves Turn Yellow or White
Mineral Deficiency - Leaves of an underfed Holly turn yellow or white in the spring when new growth starts, and again in the late summer after berries have formed. Feed the shrub as described above. Maintain soil acidity by adding powdered sulfur, used coffee grounds or peat moss to the soil.
Leaves Turn Brown
Holly Bud Moth - Adult Holly bud moths are grayish mottled with brown, and have a 1/2-inch wingspread. They lay eggs in July and August on Holly leaves and twigs. The larvae, which hatch in the spring, are yellowish to greenish gray worms 1/2 inch long. They attack new leaves in mid-May, tying them together into unsightly brown or black masses. The moths are severe Holly pests in the Pacific Northwest. Handpick any infested leaves and clean up plant debris, where the pests spend their pupal stage.
Leaves Mined and Rolled
Leaf miner - This most important insect pest of Holly is a small yellowish white maggot, 1/6 inch long. The adult is a small black fly that emerges about May 1 and makes slits in the lower leaf surfaces, where it deposits eggs. Although the maggots begin feeding in June, leaf injury isn't obvious until mid-August, when small, irregular, serpentine ridges appear on leaf surfaces. By mid-September these mines, or tunnels, increase in size. If infested severely, the entire upper surfaces of the leaves may be blistered by this Holly leaf miner. Remove and burn all affected leaves. If necessary, prune back branches until healthy growth remains. Remove severely damaged bushes. For more details see the file Controlling Leafminer
Leaves Discolored and Deformed
Mites - Southern red mites can be serious pests of Holly in the spring and the fall. They're about 1/50 inch long, barely visible to the unaided eye. They have 4 pairs of legs, piercing-sucking mouthparts, and very compact bodies. Inspect your Holly tree. If it has mites, the tops of its lower leaves will be stippled with tiny yellow dots or red spots. Leaves, stalks, and adjacent stems may be distorted or swathed in fine webbing. For more details see the file Controlling Mites
Leaves and Branches Encrusted With Small Bumps
Scale Insects - Holly scale usually congregates on leaf undersides to suck plant sap. The scale insect's covering is a small oval shell, light brown to tan in color. The insect itself and its eggs are lemon yellow. This scale over winters in a partially grown condition. It starts feeding in late March or early April, and lays eggs in June and July. There is usually only one generation a year. The symptoms of Holly scale include reduced vigor, yellow spotting of the leaves, brownish bumps on leaves and twigs, and sooty mold growing on sticky honeydew secreted by the pests. For more details see the file Controlling Scale
Sunken Spots on Leaves
Anthracnose - This fungus disease causes distinct lesions on Holly leaves, appearing as moist, sunken spots with fruiting bodies in the center. Leaf spots may run together, resembling a blotch or blight. Sometimes terminal shoots blight down to several inches below the buds. Pustules containing pinkish spores appear. Dieback and defoliation may occur in severe cases. For more information see the file on Controlling Fungal Disease
Leaves Covered With White Powder
Powdery Mildew - Powdery mildew is caused by fungus that attack Holly leaves, sometimes covering them entirely with a thin white powdery coating. For more information see the file on Controlling Fungal Disease