Cherry (including sour)

Description

The wild cherry tree, Prunus avium, is a perennial tree in the family Rosaceae grown for its fruit, the cherry. Cherry trees have alternating simple oval leaves which often have serrated margins and approximately eight pairs of veins, 5–13 cm (2–5 in) long. The flowers are white and appear in clusters of about 3–5. They appear in early spring and are about one inch long. The fruit is dark red, about half an inch to a full inch, matures in early to mid summer. The bark is gray-brown, smooth and glossy and it often peels. Cherry trees can live up to 60 years, growing to a height of over 15 m (50 ft). Cherry may also be referred to as sweet cherry, gean, mazzard or wild cherry and originates from the Caspian-Black Sea region and Asia.

Sour cherry, Prunus cerasus, is closely related to Prunus avium but with fruit that is more acidic. The tree has twiggy branches with bright red to near black cherries. The tree reaches a height of 4–10 m (13.1–16.4 ft) and is believed to have originated as a natural hybrid of wild cherry (Prunus avium) and ground cherry (Prunus fruticosa) somewhere in the Caucasus Mountains, Turkey or Eastern Europe where the two species' geographic ranges overlap.


Uses

Cherries are mainly consumed as a fresh fruit or processed into jellies and juices. The wood of the cherry tree is a distinctive honey color and is used in furniture making and for musical instruments. Sour cherries are used mainly for canning and processing.


Propagation


Basic requirements
Cherries grow optimally in mild, dry climates and also have a chilling requirement to break dormancy so require cold winters. Because of the cold weather requirement, none of the Prunus family, including cherries, can grow in tropical climates. Cherry trees will grow in a variety of soils provided that they are well-draining. Soils which remain wet for prolonged periods of time and soils that become excessively dry should be avoided. Trees will perform best if planted in sandy soil with a pH of 5.5–7.5. Planting on a gentle slope is beneficial for cherry as cold air can drain away from the trees to lower areas, helping to prevent damage. Sweet cherries bloom earlier than sour cherries and can be susceptible to damage from late frosts.

Propagation
Cherry nurseries are mainly propagated by budding and grafting onto 1–2 year old seedling grown from seed. In order to grow from seed, pits should be planted in the fall (after first being chilled) and seedlings will emerge in the spring. A cherry tree will take three-four years to produce its first crop of fruit and seven years to attain full maturity.

Planting
Cherry trees should be planted in the Spring when all danger of frost has passed and the soil has warmed. If bare root plants have been purchased, be sure to keep the root ball moist prior to planting. The tree should be planted in a hole which is large enough to accommodate the root ball without bending any of the roots. Broken or damaged roots can be removed but try to avoid pruning the roots. Place the tree in the planting hole and carefully backfill with soil. The tree should be planted at the same depth as it was in the nursery. Carefully firm or tamp the soil to prevent air pockets and when the planting hole is about 2/3 filled, water the roots thoroughly before filling the remainder of the hole with top soil. The tree should be watered as needed throughout the first year of growth.

Training and pruning
Cherry trees are usually trained to a modified central leader system where the lateral limbs branch from a central trunk. Sweet cherries have a more upright growth habit than sour cherries which tend to have a more open and spreading canopy. Trees should only pruned lightly while the tree matures and reaches maximum productivity. Any dead or damaged branches should be removed.

General care and maintenance
The area around the base of the tree should be kept free from weeds either by cultivating or using a chemical weed control. In the home garden, trees are usually surrounded by turf with only a small area of soil around the trunk which is easy to keep weed free by hand. Unless grown in fertile soils, cherry trees may require the addition of some nitrogen fertilizer, the volume of which will vary with the age of the tree. The fertilizer should be applied in a band around the trunk of the tree.


References

CABI Crop Protection Compendium. (2014). Prunus avium datasheet. Available at: http://www.cabi.org/cpc/datasheet/44250. [Accessed 10 November 14]. Paid subscription required.

Ogawa, J. M., Zehr, E. I., Bird, G. W., Ritchie, D. F., Uriu, K. & Uyemoto, J. K. (Eds).(1995). Compendium of Stone Fruit Diseases. American Phytopathological Society Press. Available at: http://www.apsnet.org/apsstore/shopap.... Available for purchase from APS Press.

Roper, T. R., Mahr, D. L. & McManus, P. S. (1998). Growing Apricots, Cherries, Peaches and Plums in Wisconsin. University of Wisconsin Extension. Available at: http://learningstore.uwex.edu/assets/.... [Accessed 10 November 14]. Free to access.



Common Pests and Diseases

Spider mites (e.g. Two-spotted spider mite)
Tetranychus urticae

Symptoms
Leaves stippled with yellow; leaves may appear bronzed; webbing covering leaves; mites may be visible as tiny moving dots on the webs or underside of leaves, best viewed using a hand lens; usually not spotted until there are visible symptoms on the plant; leaves turn yellow and may drop from plant
Cause
Arachnid
Comments
Spider mites thrive in dusty conditions; water-stressed plants are more susceptible to attack
Management
In the home garden, spraying plants with a strong jet of water can help reduce buildup of spider mite populations; if mites become problematic apply insecticidal soap tor 1% horticultural oil to plants; certain chemical insecticides may actually increase mite populations by killing off natural enemies and promoting mite reproduction

Bacterial canker
Pseudomonas syringae

Symptoms
Cankers on twigs at bases of flower and leaf buds, in pruning wounds or at the base of spurs which exude amber colored gum; cankers spread upwards and form sunken areas in winter; if pathogen enters dormant buds they may be killed or open normally in Spring before collapsing in early Summer; infected buds may be symptomless
Cause
Bacterium
Comments
Disease emergence favors high moisture and low temperatures in the spring; young trees particularly susceptible; trees grown in sandy soils that drain poorly are also susceptible
Management
Ensure that a suitable cherry variety and rootstock is chosen based on geographic location and environmental conditions to prevent stress to tree which predisposes tree to canker disease; apply protective copper spray to trees before flowering; prune trees in early summer to decrease likelihood of infection

Crown gall
Agrobacterium spp

Symptoms
Galls on root and/or crown of tree which can range in size from so small they are not visible to the naked eye up to 10 cm (4 in) in diameter; galls first become visible as white, fleshy swellings that grow rapidly and become tan to brown in color; galls typically develop at the site of a wound and new galls form adjacent to old ones the next year
Cause
Bacterium
Comments
Infection with crown gall begins at the site of plant wounds; disease emergence is favored by poorly-drained, alkaline soils and previous feeding damage by nematodes
Management
Chemical control of the disease is generally ineffective; an effective bacterial biological control is available for commercial production; cultural control methods include: planting only certified, disease-free material, planting cherry in well-draining soil, rotating infected fields with a non-host before peach is planted and also using good sanitation practices

Powdery mildew
Podosphaera spp.

Symptoms
Light colored circular lesions on leaves inside tree canopy which develop a powdery appearance; lesions may coalesce to cover leaf; if infection is severe, leaves may blister and infected shoots may be distorted and stunted; infected fruits may have slightly depressed areas on the surface containing fungal hyphae (filamentous fungal structures)
Cause
Fungus
Comments
Infection of fruit is more likely if there are rainfalls close to harvest
Management
Management of powdery mildew in cherry is reliant on the application of appropriate fungicides and cultural practices which promote good air circulation around tree canopies to lower humidity

Silver leaf
Chondrosterum pupureum

Symptoms
Leaves have a silvery appearance; if infection is severe the leaves may curl upwards and become necrotic; death of individual limbs or entire tree may occur; fungal fruiting bodies appear on the surface of the dead bark
Cause
Fungus
Comments
Pathogen is spread via spores released after rainfall during periods of high humidity and can enter trees through pruning wounds; risk of infection is increased if tree is pruned during late winter or early spring; trees also susceptible when they are heavily pruned
Management
Control of silver leaf disease is difficult and infection can be widespread after rainfall in areas where the disease is present; strategies to reduce the incidence of the disease include: removing all plant debris e.g. pruning waste, stumps, and logs; pruning tree during dry periods and treating large pruning wounds with fungicidal dressing

Cherry leaf spot
Coccomyces hiemalis

Symptoms
Small, red-purple spots on upper surfaces of leaves which turn brown and may coalesce; leaves may become chlorotic if there are a few lesions present; if tree becomes severely defoliated fruit may fail to develop properly and remain light in color and watery in texture
Cause
Fungus
Comments
Fungus overwinters on infected leaves on the ground; disease development is promoted by warm temperatures and high humidity
Management
Disease can be controlled through applications of appropriate fungicides, Bordeaux mixture is also effective; no cherry varieties are resistant to leaf spot, plant less susceptible varieties if available

Black knot
Apiosporina morbosa

Symptoms
Elongated swellings (knots) on woody parts of tree which can reach up to 30 cm (12 in) long; knots are initially olive green in color with a corky texture but turn black in color and become hard and brittle; knots grow in length each year
Cause
Fungus
Comments
Infections occur on new shoots after rainfall and knots develop rapidly in second year
Management
Prune knots on twigs and branches 8-10 cm (3-4 in) below the swelling and remove the pruned branches from the orchard; remove knots on older branches by removing the knot plus 2 cm (0.8 in) of surrounding tissue; removal of knots is most effective when done in midsummer; disease can be controlled by application of appropriate fungicides, if available, during shoot elongation

Brown rot
Monilinia fructicola

Symptoms
Brown discoloration of fruit skin and inner tissue; fruit skin wrinkled; collapsed flowers exuding sap from their bases; tan cankers with dark edges on twigs; gray-brown spore masses may be present on cankers
Cause
Fungus
Comments
Fungus survives in mummified fruit on the tree, blighted blossoms, cankers and infected twigs; blossom and twig blights are promoted by periods of wet weather
Management
The currently most effective method of controlling brown rot is through the application of appropriate protective fungicides timed so that they are applied when the susceptible flower parts are exposed or after a wet period; avoiding sprinkler irrigation protects the leaves and flowers from wetness that promotes the disease. Cultural control methods include: removing mummified fruit from tree, pruning infected twigs and reducing plant stress by providing adequate levels of water and fertilizer

Verticillium wilt
Verticillium dahliae

Symptoms
Withering of leaves on one or more spurs on 1 year old wood; leaves are dull and stunted; fruit small; older cherry trees do not recover from disease
Cause
Fungus
Comments
Disease is more severe in wet soils
Management
Plant cherry in soil with no history of disease; keep trees adequately fertilized and watered

Rust
Tranzschelia discolor

Symptoms
Pale yellow-green spots on both upper and lower leaf surfaces which are angular in shape and turn bright yellow in color; spots on lower leaf surface develop orange-red spores
Cause
Fungus
Comments
Fungus overwinters in twigs or in leaves which remain attached to the tree
Management
Rust can be prevented by spraying trees with protective fungicides; application is usually carried out one, two and three months before harvest in areas prone to early season outbreaks of the disease and after harvest in areas where disease is less problematic or emerges later in the season

Peach twig borer
Anarsia lineatella

Symptoms
Death of shoot tips; feeding damage to fruit, usually at stem end; larvae are dark brown and white with a black head; adult insect is a gray-brown moth
Cause
Insect
Comments
Peach twig borers overwinter as larvae in a specialized cell known as a hibernaculum; overwintering sites are located in rough areas of bark on 1 to 4 year old wood in crotch of limbs
Management
Most effective method of treatment is well-timed applications of insecticide around time of bloom; organically acceptable insecticides include Bacillus thuringiensis or Entrust; infestations can also be treated with appropriate organophosphate or pyrethroid insecticides

Aphids (Black cherry aphid)
Myzus cerasi

Symptoms
Small soft bodied insects on underside of leaves and/or stems of plant which are shiny and black in color; if aphid infestation is heavy it may cause leaves to yellow and/or distorted, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew which encourages the growth of sooty mold on the plants
Cause
Insect
Comments
Aphids overwinter as eggs on trees and young nymphs hatch and feed at growing tips; winged aphids will migrate to plants in the mustard family during the summer months
Management
Remove any mustard volunteers growing in proximity to cherry; sturdy plants can be sprayed with a strong jet of water to knock aphids from leaves; insecticides are generally only required to treat aphids if the infestation is very high - plants generally tolerate low and medium level infestation; insecticidal soaps or oils such as neem or canola oil are usually the best method of control; always check the labels of the products for specific usage guidelines prior to use; aphids are best treated when cherry is dormant and insect is at the egg stage; if population has not been controlled by the treatment during dormancy then it should be reapplied at petal fall

Western cherry fruit fly
Rhagoletis indifferens

Symptoms
Fruit mushy and contains a single white maggot; adult insect is a fly with a black body and white bands on the abdomen and a distinctive dark banded pattern on their wings
Cause
Insect
Comments
Western cherry fruit flies are a potentially damaging pest in all western statues of the US; high populations can result in a maggot being found in every single fruit
Management
In commercial cherry plantations, western cherry fruit flies should be monitored using yellow sticky traps, the most effective being one with an ammonium carbonate lure; the insect is a quarantine pest and if a single fruit is found to be infested, treatment is warranted - even if no adults have been found on sticky traps; chemical treatments should be timed to target mature, egg-laying females in your particular region; recommended chemicals include spinosad, carbaryl, malathion, and acetamiprid; home growers should also treat trees to help control this damaging pest

X-disease
X-disease mycoplasma-like organism (MLO)

Symptoms
Rapid or slow decline of tree depending on rootstock; in hypersensitive rootstocks such as Prunus mahaleb cherry scion is rapidly girdled; cherry grafted on susceptible rootstocks exhibit a slow decline over a number of years; leaves on infected limbs are small with a red tinge; fruit may mature late and color development may be incomplete; limbs experience dieback and the tree is killed
Cause
Mycoplasma-like organism
Comments
Disease is transmitted by cherry leafhoppers
Management
Most practical control method for X-disease is to remove infected trees and other plant sources which act as a disease reservoir e.g. chokeberry

Crown and root rot
Phytophthora spp.

Symptoms
Poor new growth; leaves chlorotic, small in size and sparse; fruit may be small, brightly colored and susceptible to sunburn; shoots may suffer from dieback and tree will often die within weeks or months of first signs of infection or decline gradually over several seasons; root crown may show signs of decay which develops into a canker; bark of infected crown tissue turns dark brown; cankers may occur on aerial parts of plant
Cause
Oomycete
Comments
Symptoms can be similar to those of bacterial infections or mechanical damage; severity of disease is linked to soil moisture content; water-saturated soils promote development of disease
Management
Management of phytophthora is reliant on good management of water: cherry trees should be planted in well-draining soil to minimize the frequency and duration of water saturated soil; trees should be propagated from resistant rootstock and application of appropriate systemic fungicides may provide some protection from the disease

Cherry rasp leaf
Cherry rasp leaf virus (CRLV)

Symptoms
Leaf like growths (enations) on underside of leaves near center; symptoms spread from lower parts of tree upwards; defoliation of limbs; decline of tree
Cause
Virus
Comments
Distinguished from PNRSV by the leaves remaining green; virus is transmitted by nematodes and through grafting
Management
Fumigants to control nematodes may control cherry rasp leaf

Sour cherry yellows
Prune dwarf virus (PDV)

Symptoms
Chlorotic rings or mottled pattern on newly expanded leaves of sour cherry which become necrotic and may drop out of leaves, giving them a shot hole appearance; leaves that expand after the initial symptoms have become visible display lesser and lesser symptoms; one or more years later leaves on infected trees become yellow with green mottle and drop from tree; fruit yield may be reduced by up to 50%; sweet cherry trees develop chlorotic spots or rings with some shot holes; fruiting spurs decrease in later years as the disease progresses; fruit on infected trees are generally firmer and larger than on uninfected
Cause
Virus
Comments
Virus can infect a wide range of Prunus species
Management
No control strategies are currently known; always purchase certified, disease-free material