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.
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.
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.
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.
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.
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.
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.
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.
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.