Peach

Description

Peach, Prunus persica, is a deciduous tree or shrub in the family Rosaceae grown for its edible fruit of the same name. The peach tree is relatively short with slender and and supple branches. The leaves are alternately arranged, slender and pointed. The tree produces pink flowers which have five petals and emerge in January and February. The fruit is a velvety, soft, fleshy red to yellow-orange fruit which is oval in shape and 3-8 cm in diameter. Peach trees can grow up to 8 m (19 ft) in height and produce fruit for 10 to 20 years. Peach may also be referred to as nectarine, the two fruits belonging to the same species, although nectarines have smooth skin, and are believed to have originated in China.


Uses

Peach trees are primarily grown for their fruit which is consumed fresh. Peach trees are also grown as ornamental plants.


Propagation


Basic requirements
Peaches grow best in areas with warm summers and require a summer temperature between 20 and 30°C (68-86°F) for the fruit to mature. The trees also have a chilling requirement to break dormancy but fruit buds can be damaged by prolonged periods below -15°C (5°F) and as such, the majority of production takes place in countries which are relatively close to the equator. In addition, peach trees bloom early and can be damaged by late frosts. Trees grow best in well-draining sandy loams in areas that receive full sun but can will grow in a variety of soils as long as water does not sit on the surface after heavy rainfall. It can be beneficial to plant the trees on elevated land to allow cold air to drain away. Trees will grow optimally in soils with a pH of 6.5.

Propagation
Peach trees are propagated vegetatively to maintain the desirable genetic characteristic of the parent. Commercial trees are usually propagated by T-budding in the summer. T-budding involves joining a bud from a desired variety onto an appropriate rootstock. Buds can also be collected late in the summer for budding during dormancy. The budwood should be collected from healthy shoots of current season growth, leaves removed and the budwood kept moist until the union with the rootstock is made. The budwood is joined to the rootstock by inserting the bud stick into a T-shaped cut on the bark of the rootstock and allowing it to grow. The rest of the tree is pruned to force the growth of the new bud which has the desired characteristics.

Planting
Peach trees should be planted in full sun. Plant bare root trees in a pre-dug hole which is slightly wider than the root ball. Backfill the hole so that the tree is planted to its original planting depth ensuring that the bud union is above the soil line. It is usually possible to identify this from changes in the color of the bark. If planting multiple trees, space them at least 7.6 m (25 ft) apart.

General care and maintenance
Peaches should be pruned annually, including the year of planting and are best trained to an open center. When the tree is bearing fruit, it is important to thin the fruits to prevent the tree from over-bearing. Aim to have 1 fruit every 8 inches. This allows fruits to become larger and prevents the tree from reducing production the following year. Trees should be watered regularly during the growing season to aid with fruit development. During dry periods, water trees every 10 to 14 days. Apply water deeply and widely, to at least the width of the canopy. Trees will also benefit from the application of a nitrogen fertilizer in Spring.


References

CABI Crop Protection Compendium. (2014). Prunus persica (peach) datasheet. Available at: http://www.cabi.org/cpc/datasheet/44340. [Accessed 05 March 15]. Paid subscription required.

Marini, R. P., Peck, J. & Smith, A. J. Growing peaches and nectarines in Virginia. Virginia Cooperative Extension. Available at: http://pubs.ext.vt.edu/422/422-019/42.... [Accessed 05 March 15]. Free to access.

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.


Common Pests and Diseases

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 peach 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

Bacterial spot
Xanthomonas campestris

Symptoms
Water soaked, angular gray lesions on the underside of the leaves which turn purple and necrotic in the center and cause a shot hole appearance if lesion center drops out; if lesions are present in high numbers on leaves they may become chlorotic and drop from tree; cankers develop on twigs either as raised blisters or as a dark area surrounding a bud that fails to open; in years of severe infection the entire fruit crop may be lost; lesions on fruit begin as small brown, water-soaked lesions which may exude gum
Cause
Bacterium
Comments
Periods of frequent rainfall during late bloom and early petal drop increase likelihood of fruit and leaf infection; infection is rare during hot, dry weather
Management
Avoid planting susceptible peach varieties in areas where disease is known; once disease is visible it can be difficult to control, protective copper applications in the Fall prior to leaf drop and/or application in early growing season may help prevent the disease; care should be taken as peach trees are very sensitive to copper

Crown gall
Agrobacterium spp

Symptoms
Galls on roots 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 peach in well-draining soil, rotating infected fields with a non-host before peach is planted and also using good sanitation practices

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

Leaf curl
Taphrina deformans

Symptoms
Yellow to red patches on young leaves in Spring which thicken and pucker causing leaf to curl; puckered parts of leaf may develop white covering; infected leaves may drop from plant or remain attached and turn dark brown; infection of fruit is rare but causes irregular, raised and wrinkled red lesions
Cause
Fungus
Comments
Emergence of leaf curl is promoted by periods of cool, wet weather during the early stages of bud development
Management
The primary method of controlling peach leaf curl is the application of appropriate fungicides and/or planting resistant peach varieties; no peach varieties are completely resistant to leaf curl

Scab
Cladosporium carpophilum

Symptoms
Small, green to olive circular spots on surface of fruit, usually close to stem end, which enlarge, darken and develop a green or yellow halo; lesions may coalesce and cause fruit surface to crack; lesions on infected green twigs are hardly visible to start off with but become brown with a raised border before turning purple or dark brown; infected leaves develop angular or circular lesions on the lower surface which are initially a similar color to the leaf but turn olive green as they mature; leaf lesions may coalesce to form chlorotic patches; defoliation may occur
Cause
Fungus
Comments
Fungus overwinters in in twig lesions or on bark surface
Management
Control currently relies completely on the use of fungicides; pruning the tree canopy promotes good air circulation and allows light to penetrate which can help control scab

Shot hole disease
Wilsonomyces carpophilus

Symptoms
Brown lesions with purple edge on fruit, twigs and buds; holes in leaves due to lesions which have dried and dropped out; brown lumps developing in the center of lesion (visible with hand lens); buds turning brown or black and exuding sap; tan lesions with brown margins which exude sap on twigs
Cause
Fungus
Comments
Disease emergence favors wet, windy conditions
Management
Application of Bordeaux mixture before rains in Fall are sufficient to protect dormant buds and twigs over winter

Silver leaf disease
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

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

Fruittree leafroller
Archips argyrospila

Symptoms
Leaves of plant rolled and tied together with silk webbing; feeding damage to rolled leaves; defoliation of plant; silk webbing may also be present on fruits and fruits may have substantial scarring from feeding damage; larvae wriggle vigorously when disturbed and may drop from plant on a silken thread
Cause
Insect
Comments
Only one generation of insect per year
Management
Monitor plants regularly for signs of infestation; remove weeds from plant bases as they can act as hosts for leafrollers; avoid planting pepper in areas where sugarbeet or alfalfa are grown nearby; Bacillus thuringiensis or Entrust SC may be applied to control insects on organically grown plants; apply sprays carefully to ensure that treatment reaches inside rolled leaves

Oriental fruit moth
Grapholitha molesta

Symptoms
Wilting shoot tips ("flagging") caused by insect feeding; insect frass may be visible around entry holes burrows in fruit which cause the fruit to be soft, mushy and discolored; adult insect is a small gray moth; larvae are initially white with a black head but turn pink with a brown head as they mature
Cause
Insect
Comments
Orietal fruit moths overwinter as mature larvae inside protective cocoons in protected areas of trees or in leaf debris on the ground; insect may undergo six or more generations per year
Management
Management of the oriental fruit moth usually involves the application of insecticides or the use of mating disruptants; commercial growers should monitor moth numbers using pheromone traps and apply insecticide if average number of moths exceeds 10 per trap; chemical sprays should not be applied within 14 days of harvest

Scale insects (White peach scale, San Jose scale)
Pseudaulacaspis pentagona
Quadraspidiotus perniciosus

Symptoms
Scale insects cause damage by feeding on twigs, branches and fruit on peach trees, injecting toxins into the plant as they do so; if the infestation is heavy, gumming may occur on the bark and twigs or entire branches can be killed; insects are flattened discs, or "scales" with no visible legs; scales produce a white waxy coating which eventually turns black (black cap stage)
Cause
Insect
Comments
Scale insects overwinter in the black cap stage; winged adult males mate with females which retain their eggs inside the body until they hatch
Management
Populations are often kept in check by natural enemies, including predacious beetles and some wasps - although broad-spectrum insecticides may result in outbreaks of scale by killing off populations of beneficial insects; peach trees can be sprayed with horticultural oils when dormant which effectively kill scales without damaging natural enemies

Phytophthora root and crown 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
Severity of disease is linked to soil moisture content; water-saturated soils promote development of fungus
Management
Management of phytophthora is reliant on good management of water: peach 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

Plum pox virus
Plum pox virus (PPV)

Symptoms
First expanding leaves exhibit chlorotic veinclearing and veinbanding; lamina twisted and distorted; fruit show dark rings, lines and spots; symptoms on fruti may disappear on ripening; fruit may be deformed
Cause
Virus
Comments
Virus is transmitted by aphids but most common method of spread is diseased plant material
Management
Plant certified healthy material; remove infected trees from orchard; chemical sprays to control aphids may prolong spread of virus