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Beutel, J.A. 1990. Asian pears. p. 304-309. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

Asian Pears

James A. Beutel


  1. INTRODUCTION
  2. PRODUCTION AREAS
  3. ROOTSTOCKS
  4. SPACING AND PLANTING
  5. POLLINATION
  6. BLOOM PERIOD
  7. WINTER HARDINESS
  8. TRAINING AND PRUNING
  9. DISEASES AND PESTS
  10. FRUIT THINNING
  11. HARVEST AND MATURITY
  12. ECONOMICS AND YIELDS
  13. CULTIVARS
  14. SUMMARY
  15. REFERENCES

INTRODUCTION

Asian pears comprise a large group of pears that are crisp in texture and, when mature, are good to eat as soon as harvested or for several months after picking if held in cold storage. This ready-to-eat feature may make them more acceptable to some people than European pears that are usually served when soft and juicy, which condition takes about a week to occur after removal from cold storage. Asian pears do not change texture after picking or storage as do European pears such as 'Bartlett' or 'Comice'. Often Asian pears are called apple pears because they are crisp and juicy like apples but with a different and distinctive texture. They also are called salad pears, Nashi (Japanese for "pear"), Oriental, Chinese or Japanese pears (Nihonnashi). All Asian pears today are selected seedlings or crosses made within Pyrus serotina.

Asian pears have been grown commercially in Asia for centuries. In Japan about 500,000 tonnes are grown and some fruit is exported to the United States in October and November. China and Korea also grow these pears for domestic consumption and export to the United States and Canada.

PRODUCTION AREAS

Most new Asian pear plantings in California are in Fresno, Tulare and Kern Counties. Older plantings are found in Placer and Sacramento Counties and limited new plantings are being made in the Sacramento Valley. A few plantings exist in Yakima and Wenatchee, Washington, and others are found in Hood River and Willamette Valley in Oregon. In the last few years plantings of Asian pears were made in New Zealand, Australia, Chile, France, and the eastern and southeastern United States.

It is roughly estimated that 4,000-5,000 acres of Asian pears are planted in California, Oregon and Washington. Most trees are just beginning production since most recent plantings started in 1981. Since 1984 about 100,000 trees (500 acres) of Asian pears have been planted every year in California.

ROOTSTOCKS

All Asian pear cultivars will grow on Pyrus betulaefolia, P. calleryana, P. serotina, P. ussuriensis and P. communis (seedlings of Bartlett, 'Old Home' x 'Farmingdale" or 'Winter Nelis) rootstocks. Usually P. betulaefolia is preferred for its vigor, large fruit and tolerance of wet soils. Its cold-hardiness varies with seed source. All rootstocks are satisfactory in California and the warmer winter areas of Oregon, but in Washington special cold-hardy P. betulaefolia strains are needed. Most Japanese pear cultivars are dwarfed about 50% on P. communis rootstock so California growers and nurseries prefer P. betulaefolia because they like vigorous trees that size fruit easily Chinese Asian pear cultivars such as 'Ya Li' are compatible and grow well on either P. communis or P. betulaefolia rootstock. In Japan, Asian pears are all propagated on P. serotina or P. betulaefolia. P. betulaefolia is used to prevent hard-end, a problem in some areas where P. serotina is used as a rootstock for Japanese pears. P. serotina or P. ussuriensis are cold-hardy to -40deg.F and could be used as an Asian pear rootstock for all West Coast fruit districts if a good seed source was available to nurseries. P. calleryana makes a fair Asian pear rootstock in California but lacks winter hardiness for most areas outside of California.

SPACING AND PLANTING

There is no standard accepted spacing for Asian pears on the West Coast of the United States. Plantings range from 7-1/2 by 15 feet (380 trees per acre) to 15 by 20 feet (140 trees per acre) depending on soil, rootstock, and grower preference. They generally approximate 200 trees per acre with spacing of 12 feet apart in rows and 17 to 18 feet between rows being a good planing pattern for long- and short-term production and minimum crowding of trees.

Large, ten-year-old, twelve-foot-high trees at Davis and Winters, California, cover a soil area of 150 to 225 square feet. Smaller dwarf-type 10-year-old trees on P. communis rootstock cover a soil area of 25 to 49 square feet. Space must be allowed around each tree for good light penetration and for use of orchard equipment. Thus, plantings of 145 to 200 trees per acre are recommended for vigorous selections and rootstocks-and for dwarf trees, 300 to 400 trees.

POLLINATION

Asian pear cultivars are partially self-fruitful but better crops are set where two or more cultivars are planted together. In Fresno and Tulare counties, '20th Century' or 'Shinseiki' are known to set good crops when planted alone in large blocks. In areas with cooler temperatures at bloom-time, cross-pollination by European or Asian pear cultivars will be necessary. Cross-pollinated fruit with seed tend to be larger and more uniformly, round than fruit with few seeds due to inadequate pollination.

No proven guidelines exist on the closeness of pollinizers or the use of bees for Asian pears in California. It is suggested that every 4 to 8 rows of a single cultivar have a pollinizer row or that growers plant a block of 4 to 8 rows of a second cultivar adjacent to the first. Bees may be used at a density of one to two hives per acre. Early-blooming cultivars 'Ya Li', 'Tsu Li' and 'Seuri' are compatible and should be planted together. Most of the Japanese and hybrid cultivars and selections are late blooming. Notably 'Niitaka' is pollen-sterile; 'Kikusui' does not pollinate '20th Century'; 'Seigyoku' and 'Ishiiwase' are poor pollinizers. Most other cultivars pollinate each other. Too much pollination means more thinning of fruit is necessary for proper fruit sizing.

BLOOM PERIOD

The early blooming Chinese cultivars 'Ya Li', 'Tsu Li' and 'Seuri' bloom 10 to 14 days before 'Bartlett'. In the San Joaquin and Sacramento Valleys of California, these early blooming cultivars are in full bloom by early to mid-March. They are the first pears to bloom and are most subject to frost damage. The earliest flowering Japanese cultivar is 'Chojuro' which flowers at the same time as 'Anjou' or 'Winter Nelis'. Late-flowering Japanese cultivars are '20th Century' and 'Okusankichi' which reach full bloom with 'Bartlett'. Most years the last third or half of 'Chojuro' bloom overlaps the first third or half of '20th Century bloom. Japanese and Chinese hybrids 'Shin Li' and 'Dasui' developed at the University of California bloom late in the Japanese flowering season. Thus, most Japanese pears overlap adequately to pollinate each other. The early Chinese types overlap each other but rarely overlap Japanese or European pear cultivars enough for good pollination in California. In Washington State early flowering 'D'Anjou' is well pollinated by '20th Century' and other Asian pears.

WINTER HARDINESS

Asian pear trees like '20th Century' are about as winter hardy as 'Bosc', toleratingabout -20°F, but are less hardy than 'Bartlett' and 'Anjou'. Asian pear rootstocks' tolerances for winter cold are 10°F for P. calleryana, 0° to -10°F for P. betulaefolia and -40°F for P. communis and P. serotina.

TRAINING AND PRUNING

Normally, Asian pears are trained vase-shape in California. This is generally accomplished by heading nursery trees about 25 to 30 inches high at time of planting and selecting 3 or 4 main limbs the first year and heading these new limbs about 50% leaving 12 to 24 inches of growth depending on the length of the growth the first year. This will give 6 to fairly low secondary limbs that are headed 30 to 36 inches long in the second dormant season. After fruit production starts (the third season), limbs are allowed to elongate about 18 inches per year and then they are headed to the dormant season. If trees are growing excessively then pruning should be reduced to encourage fruit spur development.

All fruit are borne on spurs on 2- to 6-year-old wood. Older wood and spurs give smaller fruit than those on 2- to 4-year-old wood. Clean pruning cuts and excess spurs should be cut off smoothly so stubs will not rub and damage fruit. Fruit sizes best on 1- to 3-year-old spurs on wood 1 to 2 inches in diameter. Fruit on small hanger wood sizes poorly Pruning should encourage several limbs with wide angle branches off main scaffold limbs. Some limb spreading to open tree centers may be desirable.

In many pear areas outside California, Asian pear trees are grown as central leaders similar to apple tree training. This is done with little or no heading of the tree and selecting wide angle limbs for framework limbs off the central leader. The final tree looks like a Christmas tree in shape. It is advisable to maintain individual tree spacing and avoid tight hedgerows for good fruit color and long-lived, productive orchards. In New Zealand, most 'Nashi' trees are central-leader-trained. In Japan, a flat-topped training system called "tanashitate" is used and trees are supported by cables and wire suspended from tag poles. This system is preferred for wind protection and to facilitate all the hand labor performed in Japanese pear production.

DISEASES AND PESTS

All Asian pear cultivars except 'Shinko' may develop fireblight (Erwinia amylovora). In areas with cold spring seasons, Asian pears will get bacterial canker (Pseudomonas spp.). When trees are planted too deep in the soil they may die of crown rot (Phytophthora spp.). Asian pears are as susceptible to fireblight as most European pears. Experienced growers usually spray antibiotic fireblight materials (Streptomycin, Terramycin, or copper) during the bloom period and later in the spring when conditions for fireblight infections are favorable, namely when average daily temperatures exceed 60deg.F and rain or dew occurs on the flowers. Antibiotic sprays for fireblight should be made at time of bloom and continued in April and May and after harvest. Frequent removal of diseased (blighted) limbs to control fireblight is necessary most years.

In Japan, black spot (Alternaria kikuchiana) is extremely damaging to fruit requiring bagging to protect certain yellow-skinned cultivars but black spot disease is not known to exist in the United States. Also, scab is a problem in Japan, but it is not the same scab species found in California on 'Bartlett' pears and apples.

Codling moth (Carpocapsa pomonella) is severe on Asian pears, requiring 3 to 4 well-timed sprays of the same insecticides used on apples and European pears at or near full dosage for control of this serious pest. Thinning clusters to single fruit also reduces codling moth infestation on fruit. Pear psylla (Psylla pyricola) can cause sticky fruit and requires at least one delayed dormant spray Many types of stink bugs and plant bugs cause injury as hard, tan-colored spots under the flesh of Asian pears. Two-spot spider mites are serious on Asian pear trees especially if the trees become water-stressed. Mite spray before harvest and frequent irrigation is essential for control of two-spot and European red mites.

FRUIT THINNING

All Asian pear cultivars require heavy thinning to obtain good fruit sizes, to insure annual cropping, and to avoid limb breakage. All thinning is done by hand since chemical thinning is not safe or reasonably effective. Some growers blossom-thin, by cutting off by hand all but 2 to 3 flowers per cluster. Most growers wait for fruit to set and then cut off all but 1 or 2 fruits per spur. This first fruit thinning is best done before the first codling moth spray and can be done by cutting off the fruit with clippers or small hand shears. A second follow-up thinning before the second codling moth spray is necessary on hard-to-size cultivars and to remove pears not properly thinned the first time. The best thinning usually requires two times to effectively leave no more than one fruit per spur, and if spurs are close together well thinned fruit are spaced four to six inches apart. Thinning up to 30 days before harvest can benefit size, but early thinning is essential for annual bearing and good fruit sizes. Thinning will require up to a half-hour per tree on younger trees and one hour plus on older trees. Trees four to five years old size fruit easily if they have only 100 to 200 per tree after thinning is finished. Crop loads of 200 to 400 fruit per tree are common on 8- to 10-year-old trees. In Japan, 500 to 700 fruit are recommended on large bearing trees or 70,000 fruit per acre.

HARVEST AND MATURITY

Harvest season in California is from mid-July through September with a few earlier or later cultivars. In Washington State and Japan, fruit are harvested August, September, and October. Most growers determine harvest time by fruit taste and color. Sugar content over 12.5% usually is adequate and fruit pressure of 8 to 11 pounds seems satisfactory. Fruit pressure is not as good a measure of maturity in Asian pears as it is in European pears. The color of russet-type fruit changes from green to brown, and the ground color of green fruit changes from green to yellow. Color and sugar content best determine time to harvest. Some green Chinese and hybrid types do not change color much at maturity. All Asian pears must be carefully handled to minimize bruising and brown marks and stem punctures. Over-mature fruit quickly show roller bruises, fingerprints and other signs of handling at harvest. Under-mature fruit are poor in flavor and ruin the market for Asian pears. At least three color picks are necessary to get mature, quality fruit from most cultivars in the central valley of California.

All Asian pear cultivars should be harvested carefully into padded picking buckets or boxes and handled gently in the packinghouse. They have tender skin that bruises, discolors and blackens a day after rough handling during picking and handling. Rough handling during picking can cause stem punctures. Many growers believe Asian pears are harder to handle than firm peaches and believe they are not suited to large, fast-moving packinghouse lines. Fruit is best field-packed from picking containers to packing boxes or trays.

In the packinghouse, placement of fruit on wide, slow-moving, smooth, clean belts will distribute fruit to packers who "eye-size" fruit and place them into plastic pack trays used to hold fruit in containers going to market. Fruit should be padded into boxes with "bubble pads" or paper-covered excelsior pads to prevent rolling while in transit.

Fruit are packed either two layers deep in 21- to 24-pound "L.A." lugs with pads and plastic packing m olds or packed one layer deep in "cherry" lugs. Fancy large fruit (12, 15, 16, 18 and 21 sizes-3- to 4-inch diameter) are packed in single-layer 11 to 12 pounds of fruit in "cherry" boxes. Medium-sized fruit are packed in two-layer boxes as sizes 48 or 50 (3-inch diameter), 54 or 56 (2-7/8 inch diameter), and 60-64 (2-5/8 inch diameter, with fruit weight of 21 to 24 pounds. Imported Japanese fruit are packed in 20-kilo cartons similar to tray-pack apples and are 3-1/2 to 4 inch diameter.

Fruit of some cultivars can be stored at 32°F for one to three months without problems. After 2-1/2 months 'Hosui' and 'Shinko' fruit gets spongy, shows some storage rot and after four months may show internal breakdown in the core area. Less mature fruit get spongy sooner than fully mature fruit. At room temperature of 70°F, the fruit begins to soften or get spongy after 14 to 21 days. Storage problems include shrivel of skin, spongy fruit, internal browning of core and skin blackening. Benefits of controlled atmosphere storage of Asian pears are unknown. Decay can occur where skin is cut and fruit stored over 60 days.

ECONOMICS AND YIELDS

In the early l980s, demand and prices for Asian pears increased greatly due to the increasing population of Asian people in the United States and Vancouver, Canada. These prices were about $1.50 per pound wholesale and thus stimulated new plantings of Asian pears in California beginning in 1982. As these early plantings began producing pears, prices declined moderately. In 1987 and 1988 with a supply of about 600,000 to 800,000 packed boxes, prices ranged from a low of $6.00 per box to a high of $20 per box. Large (3- to 4-inch diameter) fruit sold for three times as much per box as small fruit (2-1/2-inch diameter). Well colored, sweet (13% sugar) fruit brought better prices than greenish-skinned fruit. Approximate prices for #1 and fancy grade fruit in August and September were $16.00 to $20.00 per 24 pound box of 30 to 36 fruit, $11.00 to $15.00 per box of 42 to 50 fruit and $6.00 to $8.00 per box for 60 to 64 fruit. Lower grade fruit at terminal markets sold at lower prices of $5.00 to $10.00 per box depending on grade.

Yields of Asian pears are lower per acre than for 'Bartlett' or 'Bosc' because heavy fruit thinning is necessary to get sizes the market demands and pays for with premium prices. Orchards may produce a few pears the third year, better in the fourth season but yields in the fifth to seventh years range from 200 to 500 packed boxes per acre. When trees are full-sized (12 feet wide and high) at age 10-14 years old, yields may reach 800 to 1,000 packed boxes per acre of 30, 40 and 50 size fruit. Higher yields are possible but sizes will be too small for good market prices. Production costs approximate $2,500 to $3,000/acre which is greater than 'Bartletts' because of high costs to thin fruit and higher costs to pack fruit for market.

The present market for Asian pears consists of several million Asians living in the western United States, Vancouver (Canada), and major cities in the U.S.A. Future consumers are non-Asians who want to eat crisp, sweet pears that do not get soft and can be eaten as soon as picked or purchased at the supermarket.

Existing plantings of Asian pear trees probably will fill the present demand by Asians living in the U.S.A. New plantings will be necessary to fill potential demand by those who have not yet teamed about convenient, tasty, crisp, refreshing Asian pears.

CULTIVARS

Asian pear cultivars are numerous with over 25 known in California and hundreds of cultivars known in the Orient. Selection of the better cultivars for planting and future sales is a problem for all involved with this crop. The more important cultivars available in California are discussed with some ripe dates indicated for Davis, California. In Fresno, ripening will be 7 days earlier; in Oregon and Washington, about 21 to 30 days later.

There are 3 types of Asian pears. They are (1) round or flat fruit with green-to-yellow skin, (2) round or flat fruit with bronze-colored skin and a light bronze-russet (3) pear-shaped fruit with green or russet skin. Varieties are listed in order of ripening.

'Ichiban Nashi': An early-maturing, large, brown fruit ripening in mid-July ahead of 'Shinseiki', 'Shinsui' and 'Kosui.'

'Shinsui': An early-maturing, brown fruit with reasonable size, ripening in mid-July after 'Ichiban Nashi' and before 'Shinseiki'.

'Kosui': A small, flat bronze-russet early-maturing, sweet fruit with a tender skin that ripens in mid-July. A strong-growing tree with leaves sensitive to 2-spot spider mites and many sprays.

'Shinseiki': A round, yellow-skinned, firm fruit that is early-maturing (late July) plus it stores well up to three months. In appearance it resembles '20th Century' but is less flavorful. Trees are self-fruitful in the San Joaquin Valley. They require no pollinators. Fruit holds on the tree well and is often color-picked four times per season. Heavy thinning is necessary for good fruit size.

'Hosui': A very large, juicy, sweet, low acid, bronze-skinned pear that ripens in early August. The tree is extremely vigorous on P. betulaefolia and has a wild, loose growth habit. This is a very popular new cultivar in Japan and California. It gives good consumer and grower satisfaction. It is usually very susceptible to fireblight and stores for four to six weeks.

'Kikusui': A flat, yellow-green, medium-sized fruit with excellent flavor but a reputation for having, tender skin. The fruit stores well until February but the dull-colored skin makes it less attractive at harvest than '20th Century'. The fruit sizes better and has flavor and texture equal to '20th Century'. It ripens in mid-August but fruit has preharvest drop problems. Tree has average vigor.

'Yoinashi': A large, brown-skinned fruit with excellent flavor. It ripens in mid-August with '20th Century' but sizes much better.

'20th Century' ('Nijisseki'): This is the best flavored and most popular Asian pear in Japan and California. It originated in Japan in about 1900 and was responsible for the high popularity of pears in Japan. It is round, yellow-skinned, easily bruised, but stores well up to six months. The fruit is more difficult to size than other cultivars but its popularity outweighs this problem. It should not be grown on P. communis rootstock because it is severely dwarfed. The fruit ripens in mid-August. It grows well on P. betulaefolia, P. calleryana, and P. serotina. Old trees need spur removal and rejuvenating pruning to maintain fruit size. The tree is naturally well shaped and easy to handle.

'Chojuro': An old, firm, brown- to orange-skinned, flat-shaped, highly productive cultivar is losing popularity because it is not as juicy as many newer ones. It matures in mid-August, bruises easily but stores for five months. It must be picked when first yellow-brown in color or fruit is subject to severe bruising and skin discoloration.

'Shinko': The fruit is large and round to slightly flattened with a beautiful bronze-russet skin. Fruit flavor is excellent in hot climates but the fruit stores only about two months. The tree is well shaped and extremely productive, an annual bearer despite heavy crops. It matures during the first week of September and appears to be nearly resistant to fireblight.

'Niitaka': A very large, firm, brown-russet fruit. It is noted for its large size, average flavor and high production. The tree is dwarfed severely on P. communis and vigorous on P. betulaefolia. Fruit ripens in early September and stores two months. The flowers are pollen-sterile but it sets well when cross-pollinated with most varieties.

'Ya Li': A popular Chinese cultivar, is pear-shaped, has green skin and is quite tender to bruising. It is early blooming and requires cross-pollination by other early flowering cultivars such as 'Tsu Li' and 'Seuri'. The flavor is sweet and milder than other cultivars. When properly thinned and pollinated it sizes to 10 to 12 ounces. It is the most important pear cultivar in China. It stores well until February and keeps its green color. Trees are very productive and vigorous on all pear rootstocks. It ripens late in August and early September. This cultivar is slower to come into production than most Japanese cultivars.

'Tsu Li': A large, football-shaped, green fruit of only fair quality. It has long storage life (six to ten months) and gets better the longer it is stored. The fruit ripens in early to mid-September and develops a greasy feel on the skin. It must be pollinated by 'Ya Li'. 'Tsu Li' in California and 'Tsu Li' in China are not the same cultivar.

'Dasui Li' and 'Shin Li': New U.C. hybrids, very large fruit, greenish to yellow in color. They ripen in late September and early October and store well at 32°F for six months. Trees are extremely vigorous and pollinate each other. For good crops, limited pruning is essential in the second and third seasons to slow growth and encourage spur and fruit production. They grow well on P. betulaefolia or P. communis roots.

'Okusankichi': This is an old Korean and Japanese cultivar that ripens in October and stores well. The fruit is brown-russet, somewhat elongated and slightly irregular in shape. At harvest it has only fair flavor, but flavor improves in storage.

SUMMARY

Asian pears are now a newly regenerated fruit crop in California. Formerly grown on a small scale for a limited ethnic market, they have become a new crop for many consumers that do not like to ripen and eat European pears. Good cultivars developed in Japan are available for an expanding market that soon may be nearly one million packed boxes. Careful handling during picking and packing are required to avoid bruising and marking this delicate fruit. Fruit will store at 32°F in ambient air and not deteriorate in quality. Marketing and promotion make Asian pears very popular in supermarkets. Increases in production and sales during the 1980s have been eight- to ten-fold. Foreign production in Japan, China, Korea, New Zealand and Chile will certainly impact our markets in the 1990s. At the present time, quality fruit make a good profit for existing growers in California.

REFERENCES


Last update March 11, 1997 by aw