WSU CAHNRS and WSU Extension

Hortsense

Search plant problems by plant name

? Help on search

A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  R  S  T  V  W  Y 

Problem
(factsheet)
Plant NameTypeDescription 
Bacterial blight (Leaf spot)ViburnumDiseaseBacterial blight of viburnum primarily affects leaves and occasionally stems. Spots on leaves first appear as brown, watersoaked areas which may be round, irregular, or angular in outline. Developing leaves may become deformed if heavily infected. Spots on stems may be more elongate and less noticeable than the leaf lesions and may also become sunken. Lesions on both stems and leaves may give off a bacterial ooze or exudate near the margins. Severe infections may also result in shoot dieback. Bacterial blight is favored by cool, moist conditions. The bacteria can infect through wounds and are easily spread by splashing water and pruning tools.
Leaf spotViburnumDiseaseVarious fungi cause leaf spot symptoms on viburnum. The spots are typically necrotic brown spots of varying sizes. At least one bacterial leaf spot is also common.
Powdery mildewViburnumDiseasePowdery mildew of viburnum is a fungal disease which primarily affects young leaves and shoots. Affected plant tissues develop a powdery white growth of fungal mycelia. The fungus can be found on either leaf surface. The disease typically appears in the summer and reaches its peak in late summer, when tiny black specks may be observed among the white mycelia. Developing leaves may be somewhat deformed by severe infections. Powdery mildew is worst on plants in the shade. It is favored by a combination of warm days, cool nights, and humid conditions, but is inhibited by rain.
Ramorum leaf and shoot blight (Sudden oak death)ViburnumDiseaseRamorum leaf blight is caused by Phytophthora ramorum, the same organism that causes sudden oak death (SOD). In Washington, most cases have been found in nurseries on rhododendrons and camellias, which are highly susceptible to this disease. Some oak species, kalmia, and Pieris are also considered highly susceptible, along with native plants such as salal and evergreen huckleberry. On viburnum, leaf damage consists of water-soaked, irregular, discolored lesions with diffuse margins. Infected leaves wilt and die. Lesions can progress from the leaf into the branch and cause cankers, while affected shoots die back. Cankers may also develop on the stem near the soil line. If the branch is girdled, the remaining leaves wilt and turn brown; they may drop or remain attached to the stem. Occasionally, bleeding is seen on infected stems. Similar symptoms may be caused by a wide range of problems on viburnum, including sunscald, frost injury, or a variety of fungal infections. Also, P. ramorum has a wide and varied host range, so if ONLY viburnum is affected, the problem is likely NOT P. ramorum. IT IS NOT POSSIBLE TO CONCLUSIVELY DIAGNOSE THIS PROBLEM BASED ON VISIBLE SYMPTOMS ONLY. In Washington, Ramorum leaf blight has so far been found only in association with infected nursery plants and water runoff from infected nursery sites. While this disease has the potential to become a serious and economically significant problem, it is not yet considered to be widespread in Washington in either cultivated or native landscapes. P. ramorum infection is NOT LIKELY in the landscape UNLESS the plant (1) is a highly susceptible species AND (2) was purchased since 2002 AND (3) is showing symptoms associated with P. ramorum infection (or is located near another plant that meets all these criteria). Currently, the only way to confirm a SOD diagnosis is with laboratory tests.
Shoot blight (Gray mold)ViburnumDiseaseShoot blight of viburnum is caused by Botrytis cinerea, a fungus commonly found on ornamentals, greenhouse plants and flowers, vegetables, and small fruits. Viburnums develop gray to brown spots along the leaf margins. The spots spread to involve the entire leaf. Flowers are blighted and shoots may be killed back. The fungus may be seen on affected plant parts as a sparse, fuzzy, gray-brown growth. The fungus may also develop dark structures on blighted tissues. This disease is favored by wet weather.
Bean aphidsViburnumInsectBean aphids are soft-bodied dark green to black insects commonly found on the undersides of leaves and on new growth. They often occur in dense colonies. Heavy aphid feeding may distort shoot tips and leaves, and leaves may turn yellow, wilt, or show other signs of stress. Bean aphids typically produce large amounts of honeydew, a sweet, sticky material. It can attract honeydew-feeding ants, which protect aphid colonies from predators. Honeydew may also become covered with a dark, unsightly growth of sooty mold. Viburnum is a winter host for the aphids, which may be found on various vegetables in the summer, including beans, lettuce, and squash.
Root weevilsViburnumInsectRoot weevil larvae feed on the roots and bark of plants near the crown. The white grubs are found in the soil around the roots. Heavy feeding by root weevil larvae can cause girdling of roots or crown, resulting in decline or death of the plant. Adults may feed on leaves, causing minor to severe notching of leaf margins. Adult root weevils range in size from 1/4" to 1/2" long. They are brownish to black, flightless beetles which climb into the foliage to feed at night.
Viburnum leaf beetleViburnumInsectViburnum leaf beetles overwinter as eggs on the previous year's new stems. Larvae hatch in spring and begin to feed on the new viburnum leaves. Larvae are pale yellow to pale green with black dots and are about 1/4 inch long when mature. Larvae crawl down the stems of the bushes to pupate in the soil in June. Adults emerge in July and feed again on the foliage. Adults are bronze colored beetles about 1/4 inch long. Both the larvae and adults eat holes in leaves, leaving only the leaf veins. High populations can defoliate bushes twice in one year. Multiple years of feeding can kill some bushes.