Shadbush, Serviceberry (Amelanchier)
Plant Health Problems
Diseases caused by Fungi:
Rusts, Gymnosporangium spp.
Serviceberry is susceptible to several types of rust diseases. Symptoms appear as brightly colored yellow-orange lesions on the leaves. When infection is heavy, some defoliation can occur.
Management can be achieved by maintaining plant vigor using sound cultural practices. Chemical control is usually not necessary. However, fungicide sprays can be applied when new growth appears in spring. Several applications may be necessary during periods of extended wet weather. Among the compounds registered for use in Connecticut are ferbam and mancozeb. Consult the label for dosage rates and safety precautions.
Powdery mildew, Erysiphe, Phyllactinia, Podosphaera.
White powdery spots or patches develop on the leaves, usually during mid- to late summer. Leaves are usually not obviously curled or deformed and, although some defoliation can occur, this disease is not considered a serious problem.
Disease can be minimized by carefully picking off affected leaves as soon as symptoms are evident and by raking and removing fallen leaves to reduce the amount of overwintering inoculum. This disease is generally not serious enough to warrant chemical control although fungicide sprays can be applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut are myclobutanil, triadimefon, thiophanate methyl, and sulfur. Consult the label for dosage rates and safety precautions.
Diseases caused by Bacteria:
Fire blight, Erwinia amylovora.
Although only an occasional problem, this can be a very serious disease. Infected flowers, shoots, and leaves appear as blackened, shriveled, and water-soaked. This condition gives symptomatic tissues a "burned" appearance, hence the name fire blight. Symptoms can often develop in a short period of time and infected tissues often remain attached to the twigs.
Control of this disease is achieved by pruning and removing all symptomatic tissues as soon as they appear. Cuts need to be made at least 8-10" below external symptoms. It is also very important to disinfest all pruning tools between cuts with 10% bleach or 70% alcohol since this bacterium is highly contagious and easily spread by tools. Following good cultural practices to ensure plant vigor is also helpful.
Fall webworm, Hyphantria cunea.
This insect feeds on serviceberry. Webworms damage the leaves by both feeding and web-building. They overwinter within cocoons located in protected places, such as crevices in bark or under debris and fences. Adult moths emerge in summer. They have a wingspan of about 1 1/4", and vary from pure satiny white to white thickly spotted with small dark brown dots. Females lay white masses of 400-500 eggs on the undersides of the leaves. The caterpillars hatch in 10 days, and all from the same egg mass live together as a colony. They spin webs that enclose the leaves, usually at the end of a branch, to feed upon them. After they have defoliated a branch, they extend their nest to include additional foliage. When caterpillars are mature, they leave the nest to seek a place to spin gray cocoons. The mature caterpillars are about 1 1/4" long with a broad dark brown stripe along the back, and yellowish sides thickly peppered with small blackish dots. Each segment is crossed by a row of tubercles with long light brown hairs. In Connecticut, there is 1 complete generation and a partial second one. In light infestations, prune out the nests and destroy them. In larger infestations, caterpillars can be controlled with foliar sprays of Bacillus thuringiensis var kurstaki, spinosad, or carbaryl, which are among the compounds registered for use against this pest in Connecticut. Consult the labels for dosage rates and safety precautions.
Gypsy moth, Lymantria dispar.
Gypsy moth caterpillars feed on serviceberry. Oak is a preferred host of the gypsy moth, and solid stands of oak are subject to periodic defoliation. When fully grown, the caterpillars are between 2 and 3" long, dark gray or brown with prominent light brown hairs. Some have a light narrow stripe along the back and all have two rows of tubercles bearing hairs. From the head, the first five pairs are blue, and the remaining six pairs are brick red. They feed during May and June, and do most of their feeding at night.
Caterpillars pupate in cracks or crevices spinning a very small amount of silk. The moths emerge in about 2 weeks. The female is buff with narrow zigzag lines across the forewings. The wingspread is about 2", and the body is so heavy that the female cannot fly. The male is reddish-brown with variable light gray and dark brown markings and a wingspread of 1 to 1 1/2". The males fly freely.
Eggs are laid on the bark of trees, on stones, or lumber. They are laid in masses of about 400 eggs and covered with buff hairs from the body of the females. Individual shade trees may be sprayed.
A fungus, Entomophaga maimaiga, discovered by Station scientists in 1989, is giving natural control of larvae. Larvae killed by the fungus characteristically remain on the tree with their head hanging down. As these are the source of fungal spores needed to infect future populations of gypsy moth caterpillars, do not destroy them. The fungus originated in Japan and was introduced to the Boston area via infected gypsy moth larvae in 1910. The fungus was never recovered, despite attempts in subsequent years, and so it was thought not to have established. This fungus grows best in warm, humid weather.
Should chemical controls become necessary, sprays can be applied when caterpillars are young, about 1/4" long. Carbaryl, malathion, methoxychlor, spinosad and Bacillus thuringiensis var. kurstaki, which are among the compounds registered for control of this pest in Connecticut, are all effective treatments. Consult the label for dosage rates and safety precautions.
Roundheaded appletree borer.
This borer tunnels in the trunk of serviceberry. See Apple.
Serviceberry gall mite, Eriophyes amelanchieri.
This mite forms small globular galls on the upper leaf surface, about 1/12" in diameter, usually reddish above and light greenish yellow below. Spraying when the buds are opening in the spring with malathion or horticultural oil, which are among the compounds registered for control of this pest in Connecticut, may be helpful. Consult the label for dosage rates and safety precautions.