Cherry (Prunus)

Plant Health Problems

Diseases caused by Fungi:

Brown rot, Monilinia fructicola.
This is the same disease that occurs on peach and is the most common and destructive disease on cherry in Connecticut. The disease is especially severe in wet, humid weather. Brown rot causes blossom and twig blights, twig cankers, and fruit rots. The symptoms of the disease are very similar to those described on peach. See Peach for a more detailed discussion of this disease.

As is the case of peach, sanitation is essential for controlling brown rot. Mummified fruit that remains on the tree should be removed and destroyed, and all dead and cankered twigs should be pruned and removed from the vicinity of the tree. For more information, see the fact sheet on Disease Control for the Home Cherry Orchard.

Leaf spot, Blumeriella jaapii.
Leaf spot occurs on both sweet and sour cherries. It appears as reddish-purple spots on the leaves, these spots later turning brown. The centers of the spot may or may not fall out giving a "shot-hole" effect. The fungus causes a yellowing and dropping of the foliage. Trees that are defoliated year after year tend to have poor vigor and to be susceptible to winter injury. Although infections generally occur only on the leaves, they can occur on fruit, stems and petioles when the disease is severe. In wet springs, infection may occur early in the season, but with dry spring weather the spotting may be delayed until after fruit harvest. The disease is most common on sour cherry, although sweet cherry is quite susceptible. The disease overwinters on diseased leaves on the ground.

Therefore, control measures should begin with the removal of the overwintering leaves from beneath the tree and in the surrounding area before budbreak. Control can also be achieved with the use of fungicide sprays. Among the compounds registered for use in Connecticut are captan, thiophanate-methyl, chlorothalonil, and sulfur. Consult the label for dosage rates and safety precautions. Adequate control can usually be achieved with a general purpose tree fruit spray containing captan. For more information, see the fact sheet on Disease Control for the Home Cherry Orchard.

Black knot, Apiosporina morbosa.
This disease is a serious problem on both plum and cherry. On cherry, it is generally more prevalent on sour cherries than on sweet cherries. The disease gets its name from the conspicuous black elongated galls on the twigs and branches. Spores from these galls are washed onto the new twig growth early in the season, causing new infections that may not be apparent until the following year. The disease is not harmful to the tree until the gall completely encircles the branch, with consequent girdling and death of the branch beyond the gall.

The first line of defense is pruning out the affected wood, which should be accomplished before budbreak. See Plum for a more detailed discussion of this disease.

Powdery mildew.
This disease is generally not prevalent on cherry in Connecticut and would rarely if ever warrant control. See Apple for a more detailed discussion of this disease.
Insect Problems:

Black cherry aphid, Myzus cerasi.
These aphids can injure cherry trees, particularly young sweet cherry trees by causing leaf curling and growth abnormalities. Severe infestations can stunt tree growth and reduce fruit set in the year following an infestation. Also, sooty mold grows on the aphid honeydew when it drops onto fruit and leaves. When the cherry buds begin to open in spring, nymphs hatch from the shiny black eggs that have overwintered on the bark. The nymphs enter the buds and puncture the tissue to drink fluids. The nymphs, like the adults, are black and shiny. The aphid colonies are concentrated on the youngest leaves on terminal shoots. Black cherry aphids develop through 2-3 generations on cherry, with a few winged adults produced by each generation. By June, most aphids have migrated to summer hosts, mainly plants in the mustard family. In autumn, the winged adults return to cherry. After mating, the females lay their small eggs on bark. These aphids may be controlled by spraying with malathion, diazinon, or insecticidal soap, which are among the compounds registered for use against this pest in Connecticut, applied after the eggs have hatched and before the leaves have curled. Consult the labels for dosage rates and safety precautions. Dormant oil can also suffocate overwintering eggs.

Cankerworms, Alsophila pometaria and Paleacrita vernata.
The measuring worms or inch-worms of these moths eat cherry foliage during the spring. When the caterpillars are abundant, they may defoliate the trees. In early spring, caterpillars hatch from the eggs laid on the trees in late fall or early spring. Older caterpillars are black or greenish with stripes. The male moths are gray with a wingspread of 1"; the female moths are wingless. Each species has only one generation a year. The abundance of cankerworms varies in cycles. The caterpillars can be controlled with one or more springtime applications of phosmet or azadirachtin, which are among the compounds registered for control of this pest in Connecticut. Consult the labels for dosage rates and safety precautions.

Cherry maggots or fruit flies, Rhagoletis cingulata and R. fausta.
These flies, in addition to the plum curculio, may cause "wormy" cherries. The life cycles of both flies are similar although the eastern cherry maggot, R. cingulata, attacks both sweet and tart cherries, and the black cherry fruit fly, R. fausta, attacks mainly tart cherries. Adults emerge from pupae in the soil between late May and July. They resemble adults of the apple maggot by having banded wings. Their bodies are mostly black, with yellowish heads and legs. The adult females feed on substances on leaf surfaces for about 10 days before they begin to insert eggs into developing cherries with their needle-like ovipositor. After they hatch, the maggots feed for about 2 weeks while they tunnel through the fruit. Infested cherries do not fall but hang on the tree, and the areas that have or had maggots appear as sunken spots. After feeding, maggots drop to the soil where they form pupae in the upper 2 inches. They remain in the ground until their emergence the following spring. Cherry maggots can be controlled by applying carbaryl or phosmet, which are among the compounds registered for use against this pest in Connecticut, during the emergence period of adults. Consult the labels for dosage rates and safety precautions. The flies can be detected by hanging baited yellow sticky traps in trees.

Eastern tent caterpillar, Malacosoma americanum.
The damage of these caterpillars varies from almost none to complete defoliation of trees. In early spring, caterpillars hatch from the eggs that have overwintered. The hairy caterpillars build silken tents in which they hide except when they are feeding on leaves. By late June, the caterpillars mature, and soon the medium-sized moths are on the wing. Females lay eggs in masses attached to twigs. Eastern tent caterpillars have definite cycles of abundance, with a severe outbreaks every 7 or 8 years. Foliar sprays of carbaryl, phosmet, or azadirachtin, which are among the compounds registered for use against this pest in Connecticut, effectively control caterpillars. Consult the labels for dosage rates and safety precautions. Carbaryl, however, should not be used before or during bloom because it is highly toxic to honey bees.

Fall webworm, Hyphantria cunea.
Webworms cause minor foliar damage on cherry trees. Caterpillars build a loosely constructed tent on the ends of infested branches. Tents, which usually are most abundant in the northeastern part of the state, are visible in late summer. Summer foliar sprays, such as carbaryl or phosmet, which are among the compounds registered for control of this pest in Connecticut, control this minor pest. Consult the labels for dosage rates and safety precautions. See Pear for additional details of the life history.

Pear sawfly or pear slug, Caliroa cerasi.
Sawflies damage the leaves especially on young trees. The adults, who are small black, shiny, four-winged sawflies, emerge from their cocoons in May. Females insert eggs into blisters in the leaves. The green slug-like larvae eat the upper surfaces of leaves, often skeletonizing them. After feeding, the larvae enter the ground to form pupae. Adults emerge again in July and August, and the females lay the eggs of a second generation. Pupae of the second generation overwinter in cocoons. The slugs can be killed with foliar applications of rotenone, which is among the compounds registered for control of this pest in Connecticut. Consult the labels for dosage rates and safety precautions.

Plum curculio, Conotrachelus nenuphar.
The adult plum curculio scars the fruit when they lay eggs, and the feeding larvae often cause cherries to drop from the tree. Adult curculios overwinter in debris in orchards and nearby forests. The adults are dark brown snout beetles that are about 1/4" long. They have distinctive humps on the wing covers. In spring, they become active about the time that the trees blossom. Females feed on blossoms and young fruit. They start to lay eggs soon after the shuck split and may continue this activity for 2 months. They insert eggs in crescent-shaped areas on the skin where they have fed. The grub-like larvae feed in the fruit, often causing it to fall to the ground. The larvae enter the soil to form their pupae. Emerged adults soon seek sheltered areas in which to spend the winter. Plum curculios can be controlled by applying phosmet, which is among the compounds registered for use against this pest in Connecticut, at shuck split and again about 10 days later. Consult the labels for dosage rates and safety precautions.

San Jose scale, Quadraspidiotus perniciosus.
Large infestations of the San Jose scale can cause branch and even tree death. Partially grown scales overwinter under their circular gray covering or scale on the twigs and the branches of trees. They begin to feed as the sap starts to flow. When apple trees bloom, the males emerge from under their scales to mate with the immobile females. Females are circular and cone-shaped, and their circular scales are about 1/16" in diameter, with a raised center or nipple. The males are smaller and elongate, with the nipple not centered on the scale. Females give live birth to tiny bright yellow crawlers in June, usually about 3-5 weeks after the flower petals drop. The young crawlers quickly settle, insert their long mouthparts into the twigs, and then suck sap from branches. As they grow, the crawlers secrete a waxy filament that becomes their scale or covering. Scales apparently have 2 generations per year, with the first in June and the second in August. Scales may be controlled by applying a dormant oil spray or by spraying phosmet after bloom to control crawlers. Oil and phosmet are among the compounds registered for control of this pest in Connecticut. Consult the labels for dosage rates and safety precautions. To detect the yellow crawlers, wrap black tape coated with Vaseline around small branches. Adult flights may be detected with pheromone traps.

Uglynest caterpillar, Archips cerasivoranus.
These communal leafrollers are occasional foliar pests. In spring, caterpillars hatch from eggs that were laid during the previous year. The yellow larvae feed upon both wild and cultivated cherry trees as they enclose the ends of branches in large pointed webs or nests. The adult moths, which have forewings that are yellow with brown and blue markings and about 1" from tip to tip, emerge in early summer. The females lay flattened clusters of eggs on the bark of the branches and then cover them with a glue-like material for protection. These caterpillars easily may be controlled by pruning and then destroying infested limbs.