Photinia: Root weevils categories: Ornamentals Photinia Photinia Insects Shrubs revision date: 2023-04-04 12:00 Adult root weevil damagePhoto by: E.P. Breakey Biology Root weevil larvae feed on the roots and bark of plants. Feeding typically occurs near the crown region. The white grubs are found in the soil around the roots. Heavy feeding by root weevil […]
Lilac: Bacterial blight categories: Lilac Lilac Diseases Ornamentals Shrubs revision date: 2023-02-09 12:00 Lilac bacterial blight (1)Photo by: J.R. Glass Biology Bacterial blight starts as brown spots on leaves and stems in the early spring. These spots become black with age and cause death of leaves and young shoots, which may bend over at the […]
Lilac: Powdery mildew categories: Lilac Lilac Diseases Ornamentals Shrubs revision date: 2023-02-09 12:00 Powdery mildew on lilacPhoto by: C.R. Foss Biology Powdery mildew is a fungal disease of the leaves. On lilac, it shows typical powdery gray-white growth on the upper leaf surface. Powdery mildew usually occurs fairly late in the season, and does relatively […]
Lilac: Lilac borer categories: Lilac Lilac Insects Ornamentals Shrubs revision date: 2022-12-03 12:00 ash borer pupal ‘skeleton’Photo by: A.L. Antonelli Biology The lilac borer, also known as the ash borer, is a member of the clearwing moth family. The adults of many clearwing moths mimic yellowjackets or paper wasps. The larvae of this moth cause […]
Lilac: Lilac leafminer categories: Lilac Lilac Insects Ornamentals Shrubs revision date: 2022-12-03 12:00 Lilac leafminer damagePhoto by: R.S. Byther Biology Leafminers feed by removing green tissue from between the upper and lower surfaces of the leaves. Symptoms of feeding by the green larvae include large brown blotches which may distort the leaves. The adult lilac […]
Lilac: Oystershell scale categories: Lilac Lilac Insects Ornamentals Shrubs revision date: 2022-12-03 12:00 Severe oystershell scale infestation on twigPhoto by: Unknown Biology Oystershell scale insects are usually found on trunks, branches, and twigs. They occur less frequently on the leaves and other plant parts. The mature scale is approximately 1/8″ long, striped with grayish and […]
Kinnikinnick: Leaf gall categories: Kinnikinnick Kinnikinnick Diseases Ornamentals Shrubs revision date: 2022-12-03 12:00 Kinnikinnick leafgallPhoto by: R.S. Byther Biology Leaf gall of kinnikinnick is caused by the same fungus which causes leaf and flower gall of azalea. Initially, infected plant parts show a thickening and then gradually become fleshy in appearance. Infected leaves and flowers […]
Kinnikinnick: Leaf spot categories: Kinnikinnick Kinnikinnick Diseases Ornamentals Shrubs revision date: 2022-12-03 12:00 Kinnikinnick leaf spotPhoto by: R.S. Byther Biology Leaf spot is a fungal disease. Symptoms include development of brown, necrotic spots on leaves. The fungus most likely overwinters on infected leaves and possibly on twigs. The disease is favored by cool, wet conditions […]
Kinnikinnick: Rust categories: Kinnikinnick Kinnikinnick Diseases Ornamentals Shrubs revision date: 2022-12-03 12:00 Rust pustules on underside of serviceberry leaf and on petiolePhoto by: R.S. Byther Biology Kinnikinnick rust is a fungal disease of the leaves which requires an alternate host (spruce) to complete its life cycle. Symptoms of rust on kinnikinnick are seen in late […]
Kinnikinnick: Aphid (Manzanita leafgall aphid) categories: Kinnikinnick Kinnikinnick Insects Ornamentals Shrubs revision date: 2023-04-04 12:00 Kinnikinnick leafgall aphidPhoto by: R.S. Byther Biology The manzanita leafgall aphid feeds on the leaves of kinnikinnick and other manzanita species (Arctostaphylos spp.). The aphids are grayish or greenish in color and prefer new growth. Aphid feeding causes the leaves […]
Hypericum: Rust categories: Hypericum Hypericum Diseases Ornamentals Shrubs revision date: 2022-12-03 12:00 Hypericum rust: upper leaf surfacePhoto by: R.S. Byther Biology Hypericum rust in Washington is caused by a rust fungus that does not have an alternate host. Yellow, red, or brown spots are observed on leaf surfaces. In spring and early summer, powdery orange […]
Hydrangea: Failure to bloom categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Biology Improper pruning is the most common reason hydrangeas fail to bloom. Both bigleaf (Hydrangea macrophylla) and oakleaf (H. quercifolia) hydrangeas produce their flowers on the previous year’s growth. If these stems are removed, new growth may fail to produce flowers […]
Hydrangea: Fungal leaf spots categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Mycosphaerella leaf spot, www.forestryimages.orgPhoto by: B.J. Jacobsen, NCSU Biology Several fungal diseases cause spotting of leaves on hydrangeas. Symptoms may include brown, black, or gray spots or angular blotches. These may be surrounded by a reddish or purple halo. Spotting may […]
Hydrangea: Hail damage categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Hail damage to hydrangea leafPhoto by: J. Glass Biology Damage to plants depends on size of the hailstones and intensity of the storm. Minor damage may not show immediately, but may appear days or weeks later as small whitish scars or spots […]
Hydrangea: Herbicide damage categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Biology Symptoms of herbicide damage may be confused with damage from insects, disease, or cultural problems. Specific injury symptoms vary depending on degree of exposure, product used, and plant species. Damage may not appear immediately, and plants may exhibit symptoms for more […]
Hydrangea: Leaf scorch categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Leaf scorch on hydrangeaPhoto by: J. Glass Biology Leaf scorch on hydrangea is a common physiological problem. Typical symptoms include yellowing leaves, or irregular dry, brown blotches. Leaf tips and margins may turn brown, as well. Severely damaged leaves may drop from […]
Hydrangea: Marginal leaf necrosis categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 drought damage to H. macrophyllaPhoto by: R. Maleike Biology Browning and dieback of leaf margins and tips can be a symptom of several problems that restrict water flow to the leaves. Drought, excess heat, excess sunlight, overfertilization, and herbicide injury are […]
Hydrangea: Powdery mildew categories: Hydrangea Hydrangea Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Powdery mildew on hydrangeaPhoto by: Dept. of Plant Pathology, NCSU Biology Powdery mildew is a fungal disease affecting leaves, young shoots, and flowers. White to grayish, powdery fungal growth develops on the top of the leaf and may also appear on tender […]
Holly: Boron deficiency categories: Holly Holly Diseases Ornamentals Shrubs revision date: 2022-12-02 12:00 Necrotic spotting on leaves from boron deficiency Photo by: R.S. Byther Biology Boron deficiency in holly is characterized by the appearance of spots on the leaves. The spots initially are red to purple and irregularly shaped on the upper surface. They appear […]
Holly: Green algae categories: Holly Holly Diseases Ornamentals Shrubs revision date: 2022-12-05 12:00 Green algae on hollyPhoto by: B.M. Johnson Biology Green algae grows on the surface only of leaves, twigs, and trunks. Wet, humid weather favors development of these microscopic, moisture-loving, primitive plants. The colonized holly is not harmed unless sufficient algal growth develops […]