Pear

Description

The European pear, Pyrus communis, is a perennial deciduous tree in the family Rosaceae, grown for its fruit. The tree is a short deciduous tree with a tall and narrow crown and alternately arranged, simple leaves. The leaves are elliptical with finely serrated margins and defined tips and can reach 2–12 cm (0.7–4.7 in) in length. The tree produces white flowers which are 2.5 cm (1 in) in diameter and a fleshy green pyriform fruit. Pear trees can reach 9 m (30ft) and will produce fruit for about 20 years . The European pear may be referred to by name of its cultivars which include the Bartlett, d'Anjou, Kaiser Alexander and Comice pears. The European pear occurs only as cultivated trees and does not grow wild in nature. It is descendant of wild European and Asian pear trees.


Uses

The pear fruit is eaten fresh or can be cooked in a range of sweet dishes. The fruit may also be pressed for juice. The leaves of the tree can be used to produce dyes and the wood can be used in carpentry and is very durable.


Propagation


Basic requirements
Pears grow very well in areas that have a late frost and a cool, dry summer and will grow at temperatures between -26 and 45°C (-14.8–133°F). Pear trees have a chilling requirement of between 1000 and 1500 hours between 0 and 7°C (32–44.6°F) to break dormancy depending on the particular variety being grown. Generally, trees must cross pollinate with a different variety in order to successfully set fruit. Pear trees require a deep, well draining soil with a pH of 6–7 and will grow in sandy, medium or heavy soil. Pear trees are the most tolerant of all fruit trees of wet soils but roots should not be waterlogged for more than a few days at a time.

Propagation
Pear trees are propagated by budding onto suitable rootstocks. Rootstocks are usually also pear but quince is also used in warmer growing regions. Pear trees are usually acquired from the nursery as bare-rooted seedlings. They are planted by digging a whole which is large enough to accommodate the outstretched roots of the tree without bending. The graft union should be at least 10–15 cm (4–6 in) above the soil line.Trees should be spaced 4.8 m (16 ft) apart, leaving 7.5 m (25 ft) between rows. The best time for planting is in early Spring or Fall while the trees are still dormant. Young trees are susceptible to wind damage and should be provided with a wind break.

Training and pruning
Pear trees are usually trained in the same way is apple trees and often they follow a central leader system. The central leader system encourages earlier fruiting and is recommended for European pear varieties. The system consists of one main trunk which gives rise to 12 t0 16 primary scaffold branches. The tree becomes conical in shape, being wider at the bottom and narrower at the top. The shape is achieved through selective pruning of the branches in the years after planting. At time of planting, the tree is headed back by cutting the leader at a height of approximately 90 cm (36 in) from the ground. All branched lower than 76 cm (30 in) from the ground should also be removed at this time alongside and damaged or broken branches and those with narrow crotch angles. In the first winter following planting, the longest, most vigorous, vertical shoot should be selected as the leader and other vigorous shoots with narrow crotch angles removed. Branches with wide crotch angles (>40°) can be left on the tree and corrected with spacers (lengths of wire secured around the branch to correct the growth angle). Each year, while the tree is dormant, the central leader should be headed back by about 1/3 of its length and any vigorous, competing branches with narrow crotch angles removed. After the tree has fruited for two years, some branches will need removed to open up the canopy.

General care and maintenance
The amount of fertilizer that should be supplied to pear trees depends on the soil type and composition and should be checked with the aid of a soil test. Less nitrogen is supplied to pear trees than to apple as it promotes vigorous growth, increasing susceptibility to fire blight. in the first year of growth, phosphorous and potassium may be required but in subsequent years, only nitrogen is generally added to the soil. The area around the base of the pear tree should be kept free from weeds which compete for water and nutrients. In commercial plantations, appropriate herbicides may be used for weed control. In the home garden, weeds can be removed by hand. Pear trees may require fruit to be thinned to prevent over production which can lead to reduced yields in subsequent years or cause damage to the tree through excess weight. fruits should be thinned early in the season to a final density of approximately 1 fruit every 15 cm (6 in).

Harvesting
Pear fruits are usually harvested when mature, but are are ripened off of the tree. Pear allowed to ripen on the tree tend to ripen from the core outwards, resulting in fruit with mushy centers. It can be difficult to determine the correct time to harvest pears and so a variety of factors should be taken into consideration prior to picking. One of the most common indicators of maturity is the firmness of the fruit. Commercial plantations use devices called penetrometers to determine fruit firmness. Pears should be harvested when the reading is between 16 and 19 pounds.


References

CABI Crop Protection Compendium. (2010). Pyrus communis (European pear) datasheet. Available at: http://www.cabi.org/cpc/datasheet/46190. [Accessed 25 March 15]. Paid subscription required.

Lord, W. G. & Ouellette, A. (2013). Growing pears in the home garden. University of New Hampshire Cooperative Extension. Available at: https://extension.unh.edu/resources/f.... [Accessed 25 March 15]. Free to access.

Marina, R. Growing pears in Virginia. Virginia Cooperative Extension. Available at: https://pubs.ext.vt.edu/422/422-017/4.... [Accessed 25 March 15]. Free to access.

Sutton, T. B., Aldwinckle, H. S., Agnello, A. M. & Walgenbach, J. F. (eds.) (2014). Compendium of Apple and Pear Diseases and Pests. 2nd Edition. American Phytopathological Society. APS Press. Available at: http://www.apsnet.org/apsstore/shopap... Available for purchase from APS Press.



Common Pests and Diseases

Blast
Pseudomonas syringae

Symptoms
Water-soaked or black lesions on leaf petioles;which rapidly expand along the leif midrib; cankers on twigs and branches; twigs may be girdles and die; leaves turning black and dying; black lesions may be present on fruit
Cause
Bacterium
Comments
Disease emergence favors cold, wet weather
Management
In areas where disease is severe, copper fungicides should be applied in Fall and WInter

Fire blight
Erwinia amylovora

Symptoms
Shoots and blossoms turning black and shriveling; plant appears as if it has been scorched by fire; watery exudate may be present on infected areas
Cause
Bacterium
Comments
Disease emergence favors warm rainy days during bloom; care should be taken to time antibiotic application properly
Management
Cut out diseased wood; treat with Bordeaux mixture or approved fixed copper materials for organic production; streptomycin or copper application to blossoms may be necessary to prevent spread

Scab
Venturia pirina

Symptoms
Yellow or chlorotic spots on leaves; dark olive green spots on leaves and fruit; may be a velvety growth on spots on undersides of leaves; twisting of leaves; distorted leaves; severely infected leaves turn yellow and drop from tree
Cause
Fungus
Comments
Fungus overwinters on dead foliage on ground; spores dispersed by wind; high moisture encourages fungal growth
Management
Remove all leaves dropped from tree in the fall and compost to prevent any diseases surviving in debris; application of zinc and fertilizer grade urea in the Fall may be necessary to speed leaf drop, lime should then be added to fallen leaves; fungicide application may be necessary in areas where leaves remain wet for periods in excess of 9 hours; fungicides such as copper soaps and Bordeaux mixture should be applied if there is a chance of wet period as soon as leaf tips emerge

Armillaria root rot (Oak root fungus)
Armillaria mellea

Symptoms
Small, discolored leaves which drop early; death of branches; death of plant; clusters of honey-colored mushrooms may sprout at base of plant
Cause
Fungus
Comments
Fungus survives on dead roots in soil
Management
Armillaria root rot cannot be effectively controlled once it has become established in an orchard; diseased or dead plants should be uprooted and removed; planting resistant rootstocks is the most effective method of preventing the disease

Spring pear cankerworm (Fall pear cankerworms)
Paleacrita vernata
Alsophila pometaria

Symptoms
Leaves are skeletonized to nothing but the veins; young fruit have scarred depressions
Cause
Insect
Comments

Codling moth
Cydia pomonella

Symptoms
Holes and burrows in fruit; holes may be blocked with crumbly brown frass (insect excrement); wounds may be shallow or may be deep burrows extending to the fruit’s core; adult insect is a dark brown moth; larvae are pink with a brown head and may be up to 1.3 cm (0.5 in) long
Cause
Insect
Comments
Insect usually undergoes 2-4 generations per year
Management
Proper pruning methods help to open out tree canopy to ensure treatments penetrate interior of the tree and reach larvae; removal of any wild hosts or trees in abandoned orchards helps remove reservoirs of insect; organically acceptable control methods include application of Entrust and kaolin clay; small scale growers and home gardeners can remove infested fruit by hand before larvae leaves fruit to reduce insect population; successful reduction of insect population in large scale orchards is usually achieved by mating disruption by releasing pheromones over successive years

Leafrollers (Omnivorous leafroller, Redbanded leafroller, etc)
Platynota stultana
Argyrotaenia velutinana

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
Adult insect is a moth which can fly over several miles to find suitable hosts
Management
Monitor plants regularly for signs of infestation; remove weeds from plant bases as they can act as hosts for leafrollers; 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

Pear psylla
Psylla pyricola

Symptoms
Reduced tree vigor and death of trees caused by pear decline; insect is a dark red-brown insect resembling a tiny cicada
Cause
Insect
Comments
Pear psylla are a serious pest of pear and have a high capacity for developing resistance to insecticides used in their control
Management
Control of pear psylla populations is best conducted when trees are dormant; organically acceptable control methods include the use of insecticidal oils and kaolin clay; appropriate insecticidal sprays can be applied during the dormant season to reduce the populations of overwintering insects

Crown and root rot
Phytophthora spp.

Symptoms
Leaves wilting but remain attached to the tree; reduced growth; early senescence; cankers at soil level, dark discoloration of bark which is slimy when wet
Cause
Oomycete
Comments
Disease emergence favors poorly drained soil and standing water
Management
Practice good water management to prevent emergence of disease; do not over-water trees or allow water to accumulate in soil; there is no treatment for Phytophthora infection once present; no apple varieties are resistant to all strains of the pathogen

Pear decline
Pear decline phytoplasma

Symptoms
Poor shoot growth; dieback of shoots; reddening and rolling of upper leaves in canopy; premature leaf drop; reduced leaf and fruit size
Cause
Phytoplasma
Comments
Transmitted by pear psylla
Management
Plant trees which have been grafted on tolerant rootstocks; control pear psylla on trees