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COMMERCIAL

PEAR GROWING

Agriculture Ebindbook No. 330

JAN181968

j€LTSVtiLE Emnm

Agricultural Research Service

UNITED STATES DEPARTMENT OF AGRICULTURE
CONTENTS

Page

Climatic requirements of pears 1

Pear-growing areas 2

Interior valleys of central California 3

Bottom lands of Sacramento Valley 3

Foothills east of Sacramento Valley 4

Valleys northwest of lower Sacramento

Valley 7

Lake and Mendocino Counties 7

Coastal sections of central California 8

Rogue River Valley of Oregon 8

Hood River Valley of Oregon 9

Valleys of central Washington 10

Intermountain areas of Idaho, Utah, and

Colorado 10

Central region 10

Northeastern region 10

Southern region 11

Sites and soils for pear orchards 11

Rootstocks for pears 11

Soil management and cover crops 13

Cultivation 13

Cover crops 13

Permanent sod 14

Fertilization 14

Irrigation 16

Pruning 17

Pruning young trees 17

Pruning bearing trees 17

Pollination 19

Fruit set 20

Fruit thinning 21

Hormone sprays to prevent fruit drop 21

Principal pear varieties 22

French types—Pyrus coniTnunis origin 22

Anjou 22

Bartlett 22

Bosc 22

Comice 23

Hardy 23

Maxine 23

Seckel 23

Page

Hybrid types—Pyrus coinmunis crossed with

oriental species 23

Baldwin 23

Kieffer 23

Orient 25

Waite 25

Promising new varieties 25

El Dorado 25

Packham's Triumph 25

Varieties recently introduced 25

Harvesting and handling 27

Picking maturity 27

Packing 28

Storage 29

Shipping 30

Ripening 30

Insects of pears 31

Codling moth 31

Oriental fruit moth 31

Pear psylla 32

Scale insects 32

Orchard mites 34

Sucking bugs 35

Thrips 35

Sinuate pear tree borer 35

Other insects 36

Pear diseases 37

Fire blight 37

Pseudomonas blight 39

Scab 40

Root disorders . 41

Powdery mildew 42

Leaf spot diseases 42

Virus diseases 43

Stony pit 43

Pear bark measles 43

Red leaf (curl) 43

Leaf mosaics 44

Pear decline 44

Physiological disorders 45

Hard end 45

Cork spot of Anjou 45

Literature cited 46

This publication supersedes Farmers' Bulletin 1739, Pear Growing in the Pacific Coast States.

« s. »gMi?«i«r or AsiKUiTvtt

CAUTION

If chemicals are handled or applied improperly, they may be injurious to humans,

domestic animals, desirable plants, pollinating- insects, fish, and other wildlife, and

may contaminate water supplies. Use chemicals only when needed and handle them

with care. Follow the directions and heed all precautions on the container label.

Washington, D.C. issued September 1967

For sale by the Superintendent of Documents,

Washington. D.C. 20402 —

U.S. Government Printing Office

Price 40 cents
USDA

ARS COJ^MERCIAL PEAR GROWING

Wash., D.O.

Agriculture Handbook 330

ERRATUM

Pag^ 28, column 2, line 4: Please change "approved" to disproved.*

COMMERCIAL

PEAR GROWING

By L. P. BATJER, Crops Research Division, HAROLD A. S CHôMER, Market Quality Research Division, E. J. NEWCOMER/ Entomology Research Division, and DUANE L. COYIER, Crops Research Division, Agricultural Research

Service

About 90 percent of the pear crop of the

United States is produced in the three Pacific

Coast States. Production there averages about

25 milHon bushels annually. Varieties of high

quality and European origin (Pyrus communis

L.) are grown exclusively. The major pear

areas of the Pacific Coast States are characterized by dry summers v^ith abundant sunshine.

In the better orchards 30 to 35 tons of pears

per acre are sometimes produced. The bacterial disease known as fire blight (Erwinia

amylovora (Burrill) Winslow et al.), which

makes it necessary to plant partly resistant

varieties (generally of low quality) in most

parts of the United States, can be controlled

well enough on the Pacific coast to permit

growing very choice varieties, even though they

are susceptible.

CLIMATIC REQUIREMENTS OF PEARS

Although pears will tolerate a wide range of

climatic conditions, their culture has been restricted mostly to areas that are particularly

favorable for them. On the Pacific coast, pears

are important commercially from south-central

California up into British Columbia. The

southern limit of commercial pear growing is

determined by the prevalence of high winter

temperatures. The commercial pear varieties

grown on the Pacific coast require a considerable period of low temperatures (about 1,200

hours below 45° F.) during the winter so as to

complete their dormant period and to start

off vigorously in the spring. Therefore, pears

are not adapted for commercial production in

sections where winter temperatures are so mild

that the trees do not complete this period before

blossoming. More recently varieties have been

developed that require less winter cold to break

their dormancy. This characteristic makes

them better adapted for areas where lack of

winter chilling is a limiting factor.

Most pear varieties can stand fairly low winter temperatures without much injury. If the

trees are fully dormant, temperatures as low as

—15° F. usually do not cause serious injury.

The wood and buds of pears are more subject

to injury from low temperatures than apples

under the same conditions. On the other hand,

pears are slightly more resistant to low temperatures than peaches.

In all major pear areas of the Pacific coast,

irrigation is depended on for moisture; conseRetired.

quently, rainfall does not determine the distribution of pear production. In other pear areas

where natural rainfall is depended on for soil

moisture, an average of at least 35 inches per

year is desirable.

Air drainage and freedom from spring frosts

are important in the location of a pear orchard.

Pear trees bloom relatively early. If the dormant period has been completely broken during

the winter, they normally bloom about 1 week

before apples. The blossoms are about as easily damaged by spring frosts as are those of

apples and peaches. Temperatures of 26° F.

or lower will generally kill the open blossoms.

Therefore, because of the earlier blooming season, the hazards from spring frosts are greater

for pears than for apples. In some areas pear

orchards are equipped with heaters to protect

the trees during the blooming season, particularly where orchards are located on lowland

where air drainage is not especially good. Because of the adaptation of pears to fairly heavy

soils, orchards have frequently been located on

lowland.

The most serious disease in pear production

is fire blight. On the Pacific coast this disease

is most serious in the interior valleys, particularly in California and southern Oregon, where

spring and early-summer temperatures are

likely to be high. In sections with cooler growing seasons, such as the coastal districts of

California, the Willamette and Hood River Valleys of Oregon, and the Puget Sound section of

Washington, pears are much less seriously affected by this disease.
AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

TABLE 1.—Average growing-season temperatures, by months, in commercially

important pear areas of United States

Station

Average 1temperatures in—

State and area SepMarch April May June July August tember

California: °F. ° F. ° F. ° F. ° F. °/^. op

Antelope Valley Fairmont 52.1 57.0 63.9 72.3 80.9 79.8 73.0

Auburn

^ Marysville

Sacramento

51.2 56.1 62.4 71.4 77.0 76.0 69.2

Central 54.3

54.3

59.4

58.1

64.8

63.3

72.8

69.4

77.8

73.2

76.2

72.9

71.9

69.3

^Upper Lake 49.9 54.8 59.6 66.7 73.8 72.7 66.7

San Jose 53.1 56.3 58.5 62.7 66.5 66.1 64.2

Central, coastal Santa Rosa 51.2 54.4 57.6 63.0 65.2 64.4 63.8

Michigan, southwestern.. Benton Harbor.. 34.7 47.1 57.9 68.1 72.7 71.3 64.0

New York:

Hudson River Poughkeepsie. . . 37.3 49.5 60.7 69.6 74.6 72.4 64.6

Valley.

Western Rochester 32.3 45.1 56.7 66.9 71.6 69.7 62.4

Oregon:

Hood River Valley . . Hood River 43.3 49.9 56.1 61.6 67.4 66.6 59.5

Rogue River Valley. Medford 46.7 51.6 57.7 65.2 71.8 70.8 63.1

Washington:

Wenatchee River Wenatchee 42.8 51.5 58.8 66.2 73.2 71.6 61.6

Valley.

Yakima River Yakima 44.1 52.5 59.0 66.4 71.4 69.5 61.1

Valley.

Fire blight is the major hazard in growing

pears in many areas of the East and particularly the South. In such locations it is

necessary to select varieties that are at least

partially resistant to this disease.

The climate has a definite effect on the quality of certain varieties. The Bartlett, which

is the most economically important pear variety, apparently reaches its highest dessert and

best shipping and storage qualities where temperatures are high for the 2 months preceding

harvest. When grown in hot sections, this variety ripens more slowly after harvest, remains

in prime eating or canning condition longer,

and has less tendency to break down at the

core than when it is grown in cooler sections.

The Bosc, another important variety, also appears to reach its highest dessert quality where

temperatures are high. The Anjou, the second

most important commercial variety, is well

suited to cooler conditions. This variety is well

adapted to the moderately warm valleys of the

Northwest. Average temperatures at typical

points in important pear areas are shown in

table 1.

PEAR-GROWING AREAS

Most of the commercial pear production of

the United States is restricted to areas where

growing conditions are especially favorable.

These areas are as follows : (1) Interior valleys

of central California, including the smaller

tributary valleys and adjacent slopes and foothills; (2) coastal sections of central California;

(3) Rogue River Valley of southwestern Oregon; (4) Hood River Valley of north-central

Oregon; (5) valleys of central Washington;

(6) intermountain areas of Idaho, Utah, and

Colorado; (7) central region ; (8) northeastern

region; and (9) southern region.

The pear acreage in the principal growing

areas is given in tables 2-5. The pear-growing

centers in California, Oregon, and Washington

are shown in figures 1-3.
COMMERCIAL PEAR GROWING

TABLE 2.—Pear acreage in major producing counties of California and

total for State, 1962 "^

County

Bartlett pears Other pears

Nonbearing

trees

Bearing

trees

Total Nonbearing

trees

Bearing

trees

Total

Lake

Acres

1,735

1,673

950

2,170

621

524

617

638

40

3,786

Acres

4,609

4,348

3,989

2,127

3,222

2,596

2,294

1,633

1,161

4,250

Acres

6,344

6,021

4,939

4,297

3,843

3,120

2,911

2,271

1,201

8,036

Acres

65

11

31

30

9

1

0

0

0

373

Acres

8

133

1,348

29

153

207

42

6

136

904

Acres

73

Sacramento

Santa Clara

144

1 379

Mendocino. . 59

Placer 162

El Dorado 208

Solano 42

Sonoma 6

Contra Costa 136

Other counties. 1 277

Total 12,754 30,229 42,983 520 2,966 3,486

^ Data from Calif. Dept. Agr. for California fruit and nut acreage in 1962.

TABLE 3.—Acreage of principal pear varieties

in California, 1962 ^

Variety Nonbearing

trees

Bearing

trees

Total

Bartlett

Acres

12,754

62

116

65

2

2

273

Acres

30,229

1,529

461

453

270

95

158

Acres

42,983

Hardy 1,591

Gomice 577

Winter Nelis

Bosc

518

272

Anjou 97

Other pears 431

Total 13,274 33,195 46,469

^ Data from Calif. Dept. Agr. for California fruit

and nut acreage in 1962.

Interior Valleys of Central California

Pear culture in the interior valleys of central

California is mainly restricted to a few sections,

but commercial orchards are scattered throughout almost the entire area. Approximately half

the pear trees in California are growing in this

area. The principal pear-producing sections

here include (1) the bottom lands of the Sacramento River Valley, (2) the foothills east of

this valley, (3) the valleys northwest of the

lower Sacramento River Valley, and (4) the

Clear Lake district of Lake County and the

Ukiah district of Mendocino County. All are

desirable for the production of the Bartlett

variety.

Bottom Lands of Sacramento Valley

The bottom lands of the Sacramento Valley

constitute one of the most important peargrowing sections of the Pacific slope. Between

the cities of Sacramento and Isleton pear culture is the most important fruit industry.

Practically all the pear trees in this section are

near the river.

The soils devoted to pear culture are largely

sedimentary and of recent origin, having been

deposited over a layer of peat. In some places

the overflow from the river has added to the

the depth of the soil since the early orchards

were established. Levees now prevent the river

from overflowing. The dark soil is an open,

friable, warm loam. The Bartlett, which is

grown almost to the exclusion of other varieties, produces excellent fruit here both for dessert and for canning.

All orchards of this section are equipped for

irrigation. Water from the river is easily and

cheaply obtained by means of pumps beside the

river and pipes through the river levees.

As in most other sections of California where

pears are grown, the coldest weather brings

frequent frosts but only occasional light freezes.

A large part of the pear-producing section lies

within the area where summers are moderately

hot, although tempered to some extent by cool

breezes from San Francisco Bay.
4 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

TABLE 4.—Pear acreage in principal producing areas of Oregon and Washington, 1962 ^

Variety

Hood River County,

Oreg.

Jackson County,

Oreg.

North-central

Washington

Yakima Valley,

Wash.

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Bartlett

Anjou

Bosc

Cornice

Acres

2,218

2,036

108

45

103

Acres

2,243

2,090

159

35

57

Acres

820

65

167

576

1,150

Acres

4,020

2,250

1,786

842

253

Acres

2,330

1,545

1

0

31

Acres

1,623

1,842

9

4

7

Acres

6,390

761

100

Acres

6,120

1,422

150

Other pears 177 150

Total 4,510 4,584 2,778 9,151 3,907 3,485 7,428 7,842

^ Oregon acreage calculated from data contained in Oreg. Fruit and Nut Survey, Spec. Rpt. 169, Oreg. State

Univ., 1964. Washington acreage calculated from Wash. Tree Fruit Census, Wash. State Dept. Agr., Wash. Crop

and Livestock Rptg. Serv., and Wash. Agr. Expt. Sta., 1963.

TABLE 5.—Pear acreage in principal producing

areas of Michigan and New York

Michigan ^ New York 2

Variety

Southwestern

Westcentral

Hudson

River

Valley

Western

Bartlett

Bosc

Clapps Favorite.

Seckel

Acres

5,600

500

Acres

1,700

100

Acres

825

252

247

487

102

Acres

1,920

303

152

132

Other pears.. 600 200 55

^ 1959 Mich. Tree Census ; 40 percent of total acreage

under 8 years old.

^1962 N.Y. Crop Rptg. Serv.; 36 percent of total

acreage under 8 years old.

Pears in this section mature early. The first

Bartlett shipments from the State usually originate here. The first shipments normally are

made early in July, and the fruit moves to

eastern markets for approximately 6 weeks. A

large part of the late-harvested fruit is canned.

Foothills East of Sacramento Valley

In the foothills east of the Sacramento Valley about 7,000 acres of pears are in Placer and

El Dorado Counties. The highest elevation of

orchards in this section is about 3,500 feet.

The Bartlett is by far the most important variety. The fruit reaches high dessert quality and

ships well to market. On hillsides or where the

soil is not deep, the fruit is usually smaller

than that from orchards on the deep soils of

the river bottom. Pears from lower elevations

ripen about the same time as the river pears of

the same varieties. The harvest in the higher

orchards is considerably later; therefore, fruit

from these orchards has an advantage in arriving on the market after peak shipments are

past. The Bosc, Winter Nelis, and other winter

pears are minor commercial varieties in this

section, grown mainly as pollinizers for the

Bartlett.

Most of the trees on the poorer soils in this

section are not large, and the yield is not so

heavy as on the deep bottom lands. Because

of the late ripening of the fruit, its high shipping and dessert qualities, and excellent appearance, much of the output is shipped fresh,

but some of it is canned. All the orchards are

irrigated.

Much of the soil in this section is derived

from the weathering of granite bedrock and is

open, easily worked, fertile, and well drained,

but it is low in organic matter. It is several

feet deep in some places; in others it is shallow, and outcroppings of granite are common.

In the Placerville-Camino district of El Dorado

County, pears are planted mostly on Aiken clay

loam, a residual soil from disintegrating schist

rocks. It is red, friable, and of good depth and

contains a moderate amount of organic matter.

The summers are generally hot but somewhat

shorter than along the Sacramento River or in

the districts lower in the foothills.
COMMERCIAL PEAR GROWING

^—-' I

BN-28314

FIGURE 1.—Distribution of pear growing in California; each dot represents 100 acres of pears.
AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

BN-28315

FIGURE 2.—Distribution of pear growing in Oregon; each dot represents 100 acres of pears.

BN-28316

FIGURE 3.—Distribution of pear growing in Washington; each dot represents 100 acres of pears.
COMMERCIAL PEAR GROWING

Valleys Northwest of Lower Sacramento Valley Lake and Mendocino Counties

A third section of the interior valleys of central California includes the district near Fairfield and the Vaca Valley, which is northwest

of the lower Sacramento River Valley ; both are

in Solano County. Around Fairfield the summer temperatures are more like those of the

coastal section. Little water is available for

irrigation. The Bartlett is the principal variety, and most of the fruit is shipped fresh.

In the Vaca Valley the summers are hot and

advance rapidly. The soil is a very deep, fertile, friable loam, and the trees are thrifty, but

on account of lack of moisture they do not grow

rapidly and the tonnage of fruit produced is

only moderate. The slow growth provides unfavorable conditions for fire blight development.

Some of the pear orchards are old. There are

but few new plantings, as most of the available

orchardland in this valley has been planted.

The fourth section of pear production in the

interior valleys of central California includes

the Clear Lake district around Kelseyville and

Upper Lake, both in Lake County, and the

Ukiah district in Mendocino County. In some

places the soil is a deep and easily tilled loam,

but generally it is a rather heavy black clay

that gradually slopes to the level of the lake.

It is very fertile but should be worked only at

the proper time. All the orchards are irrigated. The water is obtained largely from

wells.

The Bartlett is grown practically to the exclusion of other varieties (fig. 4). Trees grow

well and bear regularly. The fruit is large, of

good quality, and an attractive color. It ripens

later than in the principal pear sections of the

Sacramento Valley. Consequently, it reaches

the market after the heavy shipments from

FIGURE 4.—A 50-year-old Bartlett pear orchard with trees 40 feet apart in Lake County, Calif.
8 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

those sections have been sold. The fruit attains

excellent shipping quality because of the high

temperatures. Most of the crop is shipped

fresh or sent to canneries. Lake County is the

major fresh-shipment district in the State. Approximately one-half of its production moves

into fresh-fruit channels.

lem in coastal sections where the crop is largely

used for canning. Tufts and Hansen (52)^

have shown that length of fruit from the more

southerly sections averages shortest in proportion to diameter; the ratios vary from about

1.2 to 1 in central California to about 1.5 to 1

in Yakima, Wash.

Coastal Sections of Central California

The principal pear-growing sections between

the Coast Ranges and the Pacific Ocean in California are the low coastal plains adjoining San

Francisco Bay in Santa Clara, Alameda, and

Contra Costa Counties; the Napa Valley in

Napa County; and the Sonoma Valley in Sonoma County. The temperatures are much

lower than in the interior valleys because of

the ocean breezes. As a result, fire blight is

less likely to develop and the fruit ripens later.

The Bartlett is of less desirable quality for distant shipping than in sections where there are

a few weeks of high temperatures before

harvest.

This area is one of the oldest centers of commercial pear culture in California. A few of

the orchards planted in the middle of the 19th

century are still cultivated, though many of

them, as well as younger acreages, have succumbed to the rapid encroachment of residential development.

More varieties are grown commercially in

this area than in other parts of California.

Bartlett is predominant, but there are substantial acreages of Hardy, Anjou, Bosc, Winter

Nelis, and Comice. Bartlett is grown mostly

for canning, but the other varieties are shipped

fresh.

Many of the pear orchards near San Francisco Bay are at a low elevation. The soil is a

dark moderately heavy clay, which is fertile

but sticky when wet and hard when dry. Farther back from the bay and at higher elevations

the soil becomes more loamy and open and is

well adapted to the culture of other deciduous

fruits and nuts. Occasional pear orchards have

been planted on this more loamy land also, and

they generally have good tree growth and production. Practically all the orchards of this

section are irrigated. Santa Clara County

ranked third in total pear acreage in California in 1962 with 6,000 acres.

Throughout this coastal area, as well as in

the more southern sections of California, the

Bartlett pear tends to lose its characteristic

long shape. Under extreme conditions the radial diameter of the fruit almost equals its

length, and the fruit is less desirable for canning. This condition constitutes a serious probRogue River Valley of Oregon

The principal pear plantings in western Oregon are in the Rogue River Valley of Jackson

County, although there are limited plantings in

the Umpqua and Willamette River Valleys.

The Rogue River Valley area, lying west of the

center of the State and almost touching the

California line, has more than 10,000 acres of

pears. It ranges from 1,874 feet above sea

level at Ashland on the south to 935 feet at

Grants Pass on the north and is almost entirely

surrounded by mountains. Medford is the

principal shipping point. Large plantings were

made early in this century, although about half

of the present acreage has been planted since

water for irrigation was made available between 1917 and 1920.

Freezing temperatures occur throughout the

Rogue River Valley in winter. Spring frosts

are frequent, particularly on the floor of the

valley, and orchards must be protected by

heating, which is general and efficient. The

lower slopes surrounding the valley seldom have

damaging frosts during blossomtime because

of good air drainage. The summers are hot,

dry, and favorable for the ripening of pears.

The rainfall from September to the following

May totals 15 to 25 inches per year and is supplemented by irrigation during the dry season

in all but a small percentage of the orchards.

Much of the soil in this section is a rather

heavy adobe, and it is better suited to pears

than other fruits. Although the soil is fertile,

much of it is underlain by a stratum of hardpan at a depth varying from a few inches in

some of the uplands to several feet in the bottom lands. In parts of the Rogue River Valley

a high water table presents a serious problem,

requiring community drainage efforts. On the

deeper soils trees grow rapidly; on the shallower ones growth is rather slow. The slowgrowing trees are less susceptible to fire blight,

but production is also much less.

The Bartlett, Anjou, Bosc, and Comice are

the varieties most extensively planted. The

Bartlett is the most important, and recent

^ Italic numbers in parentheses refer to Literature

Cited, p. 46.
COMMERCIAL PEAR GROWING

600B7-P

FIGURE 5.—Typical Anjou pear orchard on adobe soil, Medford, Rogue River Valley, Oreg.

plantings have been largely of this variety,

Anjou, and Comice. The Bartlett produced

here has high dessert and canning qualities

and ships well. The Bosc blights badly here,

but it bears heavily and the fruit is of good

size, quality, and appearance. The Anjou is

popular because of its excellent size, appearance, and dessert and storage qualities. It is

the most blight resistant of the varieties extensively grown (fig. 5).

In the Umpqua and Willamette River Valleys

pears are grown commercially, but they are not

among the most important fruits. Summer

temperatures are lower than in the Rogue River

Valley and not warm enough for the best development of most pear varieties. Because of

the lower temperatures there is almost no loss

from blight. Winter injury has at times been

serious in the Willamette River Valley, causing the loss of many orchards.

Hood River Valley of Oregon

The Hood River Valley, about 120 miles from

the coast and at the extreme northern boundary

of Oregon, is an important pear-growing area.

The Bartlett and Anjou are the principal varieties grown (table 4). The Bartlett is used

mainly for canning, with some fresh-fruit

shipment.

The soils of this area vary considerably in

depth and texture, but not sufficiently to restrict the planting to given soil types. Pear

orchards are scattered throughout the fruitgrowing part of the valley. Most of the surface soils are sandy or silty loam, very open,

and in many places rather shallow. Water

passes through these soils rapidly. The subsoils are composed of about the same materials

as the upper soils in many places. Some of the

subsoils are very open, permitting good or
10 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

sometimes excessive drainage; others are so

compact that downward movement of water

through them is slow.

The rainfall during the summer is light, and

practically all orchards are irrigated. With

the very open and well-drained soils in one locality and compact subsoils in another, careful

observation and caution are necessary in adopting a successful irrigation program. Although

the roots of pear trees can stand excessive soil

moisture better than the roots of many other

fruit trees, they will not thrive in waterlogged

soils. Therefore, where a hard substratum is

too near the surface, care in drainage is necessary to prevent an accumulation of seepage

water from higher levels.

As the soil has a high sand and silt content

and the surface layer suited to root grov^h is

shallow in some places, the humus content needs

to be increased and maintained. Cover crops,

either cultivated plants or native vegetation,

are grown for this purpose in most orchards.

Winter injury constitutes a greater hazard

to pear production in this area than in most of

the other important pear areas of the Pacific

coast. Winters are generally mild, but occasional severe cold weather when the trees are

not thoroughly hardened has resulted in serious

damage, particularly to young trees. Fire

blight has not been serious in the Hood River

Valley.

Valleys of Central Washington

Two irrigated sections, one the Yakima River

Valley and the other along the Columbia and

Wenatchee Rivers centering around Wenatchee,

are the most important pear-producing areas

of Washington. Pear orchards are scattered

throughout these large fruit-growing belts. In

the older orchards pears and apples were often

interplanted. In both sections the soil is generally deep, fertile, and well suited to pear

growing. As the rainfall is very sparse and

occurs during the winter, all orchards are irrigated. Fire blight, although troublesome in

some years, is not so severe as in the Rogue

River Valley of Oregon and the interior-valley

sections of California. For acreages and varieties of pears grown, see table 4.

In both the Yakima and Wenatchee sections

the Bartlett attains good size, shape, and quality for canning. The fruit reaches the extreme

length in proportion to width in these northern

sections, a shape very popular for canning.

With abundant cold-storage facilities in the

area, much of the Bartlett crop is held in cold

storage and sent to canneries when they want

it. Some of it is placed on the fresh-fruit market after the California shipments are over.

Intermountain Areas of Idaho, Utah,

and Colorado

Pears are a relatively minor crop in Idaho,

Utah, and Colorado. Production is mainly restricted to the semiarid valleys and foothills

where other deciduous fruits are grown. In

Idaho, pear orchards (about 500 acres, mostly

Bartlett) are scattered throughout the southwestern part of the State in the same general

areas where apples are produced. In Utah,

most of the pears (about 1,200 acres, mostly

Bartlett) are produced in Utah County about

75 miles south of Salt Lake City in the vicinity

of Provo. Orchards are located on canyon deltas above the floor of the valley. Commercial

pear production in Colorado is limited entirely

to the western slope in Mesa and Delta

Counties.

Pears in the intermountain areas require irrigation. Climate and growing conditions are

similar to those in the lower Yakima Valley of

Washington. Bartlett and Anjou are the principal varieties grown.

Central Region

Michigan, the leading pear-producing State

of the central region, ranks fourth in production, exceeded only by California, Oregon, and

Washington. The pear industry of this State

centers in three southwestern counties—Berrien. Van Buren, and Allegan—located along

the eastern shore of Lake Michigan. The moderating effect of the lake reduces the dangers

of spring frost, and the relatively cool weather

during the early growing season aids in the

control of fire blight. Bartlett is the principal

variety.

Pear production in Illinois is scattered

through several counties in the southern third

of the State but centers in Marion County.

Other principal pear-producing States in the

central region include Ohio and Indiana. In

the former State commercial production is centered in the counties bordering on the southern

shore of Lake Erie. Pear acreage in Indiana

is widely scattered, but most of it is centered in

Posey and Gibson Counties in the extreme

southwestern corner of the State.

Northeastern Region

New England climate is generally regarded

as too severe for pear production, except a

relatively small acreage in the Connecticut

River Valley. New York, however, produces

substantial quantities of pears. The production

areas of this State are centered in western New

York and the Hudson River Valley. The lead-
COMMERCIAL PEAR GROWING 11

ing pear-producing counties of western New

York are located on the southern shore of Lake

Ontario. Climate and soil conditions in this

area are similar to those in southwestern Michigan. Pear acreages in the Hudson River Valley are located south of Albany and centered in

Columbia, Orange, Ulster, and Dutchess Counties. In New York the Bartlett constitutes

nearly 70 percent of the pear acreage.

Pear production in Pennsylvania is widely

scattered and the crop is used largely to supply

local demands. Chester and Lancaster Counties and the southeastern part of the State are

the most important areas.

Southern Region

With few exceptions high-quality Europeantype pears cannot be successfully grown in the

South because of susceptibility to fire blight.

Pears of the oriental type are far more tolerant, but their fruit quality is low and they are

best suited for cooking and preserving. Several varieties have been developed (see p. 23)

with improved quality and fire blight resistance. Most of these are hybrids between Pyrus

commnnis and oriental species, but some have

been derived entirely from P. communis varieties. Also, varieties have been developed that

require less winter cold to break dormancy

and are consequently better adapted to the

warmer areas of the South. Such pear-breeding programs are making it possible to produce better quality pears throughout the

Southern States.

Relatively few areas in the South produce

pears commercially. Most production is primarily for home consumption, with a limited

outlet for local markets. Pears are grown in

widely scattered areas throughout the Southern States. If blight-resistant varieties are

planted in well-drained soil on a site with good

air drainage, pears can be satisfactorily produced in many areas of this region.

Kieffer is perhaps the most widely planted

pear in the South. It is moderately resistant

to fire blight but is relatively low in quality.

Maxine and Waite are superior in quality to

Kieffer and somewhat more resistant to fire

blight. They are well adapted to southern conditions. Baldwin and Orient have a lower

chilling requirement than other varieties and

can be grown in the lower South, where mild

winter temperatures are insufficient to break

dormancy.

SITES AND SOILS FOR PEAR ORCHARDS

From the standpoint of air drainage for

frost protection, the slopes of rolling lands

are preferable for pears; but for the purpose

of crop diversification, these places are often

planted to fruits that blossom earlier than

pears, such as apricots, almonds, plums, and

peaches, and are therefore more susceptible

to frost injury at blossomtime. Consequently,

pears are frequently planted at the lower sites,

where artificial frost-prevention practices are

sometimes necessary. Because of better air

drainage, trees located on sloping land are less

susceptible to fire blight and the fruit is less

likely to develop serious russeting.

The best soil for pears is deep, medium textured, well drained, fertile, and easily worked.

Although pears will thrive best on such a soil,

they will do reasonably well where the soil has

a high water table, is poorly aerated, or is too

heavy in texture for most other deciduous

fruits. Pear trees seem to grow well on the

heavy soil of the Santa Clara Valley, Calif.,

and the heavy adobe in the Medford, Oreg.,

district. If grown on tolerant rootstock, they

can withstand unfavorable soil-moisture conditions. Trees growing behind the levee of the

Sacramento River have each winter a water

table within 2 feet of the surface and occasionally have stood in water for many days.

This is not an ideal situation, but does illustrate the tolerance of the pear toward unfavorable conditions.

ROOTSTOCKS FOR PEARS

Since pear varieties, like other improved

fruits, cannot be reproduced from seed, one

must plant trees that have been propagated on

seedling roots by either budding or grafting.

These seedling roots are commonly known as

rootstocks. Perhaps no other phase of pear

culture is more important than the proper

choice of a rootstock on which to grow the different varieties of pears. Extensive studies

have been made to determine the most suitable

rootstocks for propagating pear trees. It has

long been known that rootstocks vary greatly

in susceptibility to fire blight and other diseases. Also, the degree of tree vigor and of

hard end and cork spot of fruit is affected by

the kind of rootstock used (table 6). Rootstocks assumed added significance when it was

shown that the incidence of pear decline in

the Western United States depended on the

rootstock used (p. 44).
12 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

TABLE 6.—Important characteristics of pear rootstocks

Incidence of Pear Tendency Fire

Rootstock and source Vigor black end on decline Soil to produce blight

rating scion fruit resistance adaptability suckers resistance

Domestic French {Pyrus Vigorous top; None or very Very high.... Tolerates wide Great Low.

communis L., usually strong, well- rare. range of moisBartlett or Winter Nelis anchored ture and soil

seedlings). roots. texture.

Imported French (P. com- do do High do do Do

munis L., seedlings).

Old Home (variety of do do Very high.... . . .do do Very high.

P. communis L., propagated vegetatively).

Japanese pear (P. serótina Vigorous top Most varieties Low Highly sensitive

to both excesLittle IVTnHpriitp

Rehd. (P. pyrifolia when young; highly suscep-

(Burm.) seedlings older trees tible. sive and defi-

(oriental)). moderately

weak; weak

root system.

cient soil

moisture.

P. ussuriensis Maxim. Variable vigor; Moderately sus- Moderate Sensitive to both do High.

(seedlings (oriental)). moderately

weak root

system.

ceptible. excessive and

deficient soil

moisture.

P. calleryana Decne. Verv vigorous Rare High to very

high.

Tolerates wide do Do

(oriental). top; strong, range of

well-anchored moisture and

roots; lacks soil texture.

winter hardiness.

P. betulae/olia Bunge Very vigorous Moderately sus- High do do Variable

(seedlings (oriental)). top; inferior

fruit quality

on some varieties.

ceptible.

Quince .{Cydonia oblonga Slow-growing Rare Moderate to Trees need support (staking)

Great Do

Mill., propagated vege- top; weakly high.

tatively). anchored

roots.

in wet soils.

Until about World War I, most pear trees

were propagated on French seedlings. The

seeds were obtained from cider mills of continental Europe and were derived from native

trees of Pyrus communis. During and immediately after World War I, French seeds v^ere

not generally available and nurserymen used

oriental seedlings (P. serótina Rehd. and P.

ussuriensis Maxim.) almost exclusively. The

greater resistance of these stocks to fire blight

was an added incentive in bringing about their

widespread use. These stocks proved highly

desirable from the standpoint of the nurseryman. They were easy to propagate and made

a thrifty tree in the nursery row. Under good

soil and moisture conditions, trees propagated

on these stocks grew well in the orchard.

However, fruit from these trees frequently

exhibited black end, rendering it virtually

worthless for marketing purposes. Because

of this serious disorder, many orchards propagated on these stocks were eliminated.

About 1925, most propagators returned to

the use of French seedlings. In most cases

seeds were obtained from western canneries

and came from open-pollinated Bartlett, although Winter Nelis seeds were used to some

extent. Thus, about 1925 marks the beginning

of the use of domestic seedlings of P. communis, generally referred to as domestic

French. Stocks derived from this source, although susceptible to fire blight, have proved
COMMERCIAL PEAR GROWING 13

satisfactory under a wide variety of conditions,

and since 1930 have been the predominant

stock used in the Pacific Coast States.

Other stocks used to a limited extent include

P, calleryana Decne. and P. betulaefolia Bunge.

Both of these stocks of oriental origin were

introduced in 1918 by F. C. Reimer of the Oregon Agricultural Experiment Station. P. calleryana produces a vigorous tree and is fire

blight resistant although it is not winter hardy

in the more northern pear-growing areas. Varieties grown on this stock do not develop black

end. This is the preferred stock in the southern pear-growing areas. P. betulaefolia is generally regarded as an undesirable rootstock,

because it lacks hardiness and is susceptible to

blight and black end.

Extensive projects were conducted by the

Oregon Agricultural Experiment Station to develop a satisfactory pear stock resistant to fire

blight. Of many varieties and types tested,

Old Home generally proved the most satisfactory. It is highly blight resistant and is believed to be a pure form of P. communis. It

was selected by F. C. Reimer and has been

used as a trunk stock to a limited degree in

some of the pear districts of Oregon and California. The general practice has been to use

Old Home as a trunk stock by budding it on to

French seedling roots in the nursery. After 2

or 3 years in the orchard, framework branches

are grafted to the desired variety. The result

is a blight-resistant framework but with

blight-susceptible roots. Successful attempts

have been made to obtain roots on Old Home

cuttings {21), Trees developed by this means

possess blight resistance in both the roots and

trunk.

With the advent of pear decline in the Western United States, there has been considerable

interest in using Old Home as a rootstock. Observations have indicated that trees in which

Old Home trunks had scion rooted were more

resistant to pear decline than those where the

Old Home trunk had not rooted.

In recent years there has been less emphasis

on blight-resistant trunk and rootstocks. With

improved methods of blight control on the

scion variety, there is less danger of serious

losses from fire blight entering the framework

and roots. In addition, the added cost of providing a tree with a resistant trunk or roots

is also a factor.

In certain areas of the Pacific Coast States,

particularly Santa Clara County, Calif., several pear orchards have been planted on quince

roots (Cydonia oblonga Mill.). Various types

of quince have been selected, but Angers and

Provence are most generally used. Most varieties when grafted on quince do not make a

satisfactory union, and it is necessary to use

an intermediate stock, usually Hardy or Old

Home. Bartlett trees on quince roots are

rather dwarfed, attaining about half the size

of standard trees. These trees are early bearing, and because of their small stature are

more economical to prune, spray, and harvest.

However, trees on quince roots are shallow

rooted, more weakly anchored, and generally

require more exacting care.

SOIL MANAGEMENT AND COVER CROPS

Cultivation

In most commercial pear orchards some

form of cultivation is generally practiced. The

usual reasons for cultivation are as follows:

To remove noxious weeds and weed competition; to facilitate subsequent orchard operations such as irrigation, spraying, brush

removal, and harvesting; to incorporate cover

crops and manures; to prepare the soil as a

seedbed for cover crops; and to conserve

moisture.

The most common practice is to disk under

the cover crop, either volunteer or planted,

that has grown during the fall, winter, and

spring. In irrigated areas, the cultivation is

performed in advance of the first irrigation.

During the remainder of the season the frequency of cultivation will depend on the method

of irrigation and the amount of water available. In central Washington where irrigation

water is plentiful, no further cultivation is

generally practiced until after harvest. The

cover growth occurring during the summer is

usually mowed or *'ñoated down" in late summer to facilitate harvest operations. In the

Medford district of Oregon and certain areas

of California, cultivation is often performed

between each irrigation, and thus the soil is

kept relatively free of vegetation during the

growing season.

Cover Crops

A good cover crop helps to maintain organic

matter and to prevent erosion ; it improves the

physical texture of the soil and aids in water

penetration. During the fall, winter, and early

spring the growing of some cover crops to be

incorporated in the soil is an excellent practice.

The cover may be a volunteer crop of weeds or

grass, or preferably one that has been planted.
14 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

The choice of a cover crop should be determined by such environmental factors as soil,

water supply, and temperature. Among those

most commonly used are annual legumes (yellow sweetclover, common vetch, and purple

vetch), mustards, and cereals (rye, barley, and

oats). These are generally planted from the

middle of September to the middle of October

in order to be established before cold weather.

In irrigated areas an irrigation is required

after seeding to induce germination.

Permanent Sod

In some sections pear orchards have been

successfully handled in permanent sod without

cultivation. In the central Washington districts fescuegrass is the preferred cover for

this purpose. Permanent sod is particularly

suited where the sprinkler method of irrigation is used. Sod reduces runoff and increases

water percolation. Most covers require mowing at least twice a year, and it is necessary to

have sufficient water available for both trees

and cover crops.

Legume covers such as alfalfa are not preferred in most pear sections. The control of

insects is made more difficult, because legumes

are good host plants for the tarnished plant

bug (Lygus lineolaris (Palisot de Beauvois) ),

various species of mites, and other insects

harmful to pears. Furthermore, the added

nitrogen obtained from legumes makes it more

difficult to control the desired level of this element. Excessive vigor increases the difficulty

in controlling fire blight. Also, in the northern fruit areas a high nitrogen level in the fall

increases the susceptibility of the trees to low

temperatures, which may occur in late fall or

early winter.

FERTILIZATION

In many pear areas nitrogen is the only

element needed for proper nutrition of pear

trees. The amount required to maintain satisfactory growth and production will vary with

the soil type and method of culture. Mature

orchards usually require from 75 to 150 pounds

of actual nitrogen per acre. It should be applied in either late fall or early spring.

All fertilizers containing nitrogen affect the

acidity of the soil. Since slightly acid soils

are preferable for pears, all alkaline soils or

soils irrigated with hard water, which makes

the soil alkaline, should be fertilized with ammonium sulfate. Soils already acid should be

fertilized with materials having the least effect

on soil pH. These materials include ammonium nitrate, urea, and anhydrous ammonia.

In some western soils, particularly if

slightly alkaline, zinc is not available in sufficient amounts to meet the needs of the trees.

Zinc deficiency causes the condition known as

"little leaf" or "rosette." Leaves are small,

very narrow, light colored, and tend to develop

in small clusters or "rosettes." Affected leaves

also lack the normal green, particularly between the veins. This interveinal chlorosis of

leaves on limbs and branches exhibiting little

leaf or rosette is positive evidence of zinc deficiency. Zinc deficiency in an orchard can be

largely corrected by spraying the trees with

zinc sulfate solution just before the buds open

in the spring. Zinc applied to the soil is generally unavailable to the trees, because it is

largely tied up or "fixed" in the few inches of

surface soil.

Zinc deficiency of pears is most common in

central Washington, although it has been observed in some orchards in nearly all the major

pear areas of the Western States. In California zinc deficiency is most likely to occur in

the delta area of the Sacramento River.

In some orchards boron deficiency may also

be a problem, particularly in north-central

Washington. Boron deficiency may be expressed in several forms. The most common

malformity is cork development in the fruit.

If the deficiency becomes acute early in the

season, a rough scabby or russeted skin will

develop, and the fruit will generally crack without showing noticeable cork (fig. 6). If the

boron shortage occurs relatively late in the season, well-defined pitting will develop (fig. 7).

Associated with these pits are corky areas extending rather deeply into the fiesh of the

fruit. A diagnosis of the deficiency is con-

^P

BN-29824

FiGURK 6.—Young pear fruits exhibiting early-season

symptoms of boron deficiency.
COMMERCIAL PEAR GROWING 15

BN-29823

FIGURE 7.—Pitting of Bartlett pears caused by boron

deficiency (top row) ; normal fruits (below).

BN-29826

FIGURE 8.—Bartlett pear blossoms exhibiting typical

symptoms of blossom blast. Note persistence of dead

blossoms.

firmed by boron analysis. Mature fruits

should contain 10 p.p.m. or more boron and

young fruits over 20 p.p.m.

"Blossom blast" (3) is another form of boron deficiency that sometimes occurs in Washington orchards. Typical symptoms are shown

in figure 8. Generally the blossoms wilt and

die, but the leaves remain normal. The withered blossoms fail to absciss and frequently

persist until the following year. With the

more severe forms, leaves also die and the limb

may or may not put out new buds within a few

weeks after the blast occurs. If it fails to do

so, the branch dies before the next season.

Blossom blast within an orchard is random in

its distribution; rarely more than 10 to 20

percent of the trees are affected. Usually the

disorder is confined to one or two leaders on

the tree, whereas the remaining limbs are normal. Fruit set is greatly reduced on affected

limbs.

The general characteristics and conditions

associated with blossom blast suggest that the

deficiency is incipient or temporary in nature.

The following evidence tends to support this

premise (3) : Tissues of affected trees have

a relatively low boron content early in the season followed by a level of boron equal to that

in trees which do not develop the trouble;

fruits borne on affected limbs fail to develop

deficiency symptoms in the form of fruit pitting later in the season; soil applications of

boron fail to correct the disorder efl'ectively;

and blossom blast occurs chiefly on heavy soils

in seasons unfavorable for early root growth.

It has been shown that the boron requirement of pear trees suffering from all types of

boron deficiency can be effectively supplied in

the form of boron sprays, preferably applied

in late summer or early fall. Early spring

applications may fail to become effective before

blossom blast is initiated. Soil applications

are generally effective in preventing fruit

symptoms, but have no advantage over a yearly

spray application.

When soil pH values become greater than 7,

deficiencies of iron and manganese may develop. The most common of these high pH

problems is iron deficiency, or lime-induced

chlorosis. It occurs when alkaline water is

used for irrigation or when water containing

alkaline salts rises to the surface in a seepage

area. Leaves lacking iron are yellow, with a

fine network of green veins. In severe cases

the leaf dies around the edges. Although

chlorosis is sometimes diflftcult to correct, the

most effective means is soil injection of an iron

chelate solution. Iron chelate sprays applied

early in the growing season are generally less

effective than soil injections.
16 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

Manganese deficiency is rather common in

several of the pear-growing areas of the Pacific Coast States. Symptoms are found on the

leaves only, and the older leaves are affected

more than the young ones. The chlorosis is

yellow or golden in contrast to creamy white

of zinc deficiency. Leaf size is not affected as

in the case of zinc. The chlorosis pattern is

interveinal, i.e., the leaf tissue adjacent to the

major veins remains green, but the tissue between the veins turns yellow. The diagnosis

is verified by leaf analysis. Values less than

25 p.p.m. of manganese are low and less than

15 p.p.m. indicate acute deficiency.

Manganese deficiency is easily corrected with

manganese sulfate sprays, but there are few,

if any, instances where such a treatment is

necessary. The use of ammonium sulfate as a

nitrogen fertilizer provides all the control necessary by making the soil sufficiently acid to

release enough manganese to meet the requirement of the trees.

Only a few instances of potassium deficiency

have been recorded throughout the pear-growing areas of the Pacific Coast States. Potassium diminishes with depth, and where land

has been leveled to facilitate irrigation, some

deficiency may occur. Potassium deficiency is

also prevalent in a few foothill orchards of

California, where the soil is unusually light

and shallow. In certain areas of New York

and Michigan potassium deficiency frequently

occurs, particularly when young pear plantings are set in old orchard sites.

An acute shortage of this element results

in marginal leaf scorch, which appears first

on older leaves of spurs and shoots. Milder

symptoms involve a rolling of the leaf blade

upward and inward, giving the leaf a "cigarshaped" appearance. When potassium is deficient, fruit size is reduced and maturity is

accelerated. The deficiency can be positively

diagnosed by leaf analysis and can be corrected

by liberal applications of potassium salts to

the soil or the use of a mixed fertilizer containing adequate quantities of this element.

Magnesium deficiency is rather common in

parts of the South and may be a factor in certain areas of New York and Michigan. The

symptoms of magnesium deficiency are yellowing of the leaf at the margins and browning of

the margins as the leaf ages. Some varieties

show distinct interveinal chlorosis and interveinal browning. The leaves are generally

small, and in severe cases partial defoliation

occurs before harvest. Symptoms rarely develop before midsummer and are not prominent until late summer or fall. They are

usually much more pronounced on spur leaves,

though the deficiency can frequently be observed on the basal leaves of terminal shoots.

In severe cases premature defoliation occurs

and fruit size is reduced. Dolomitic limestone

is generally applied as a corrective measure.

IRRIGATION

Supplying water to the trees in irrigated

areas is one of the most important operations

in successful pear growing. If the orchard

becomes so dry that the rate of fruit growth

is reduced during the growing season, final

size of the fruit and total tonnage will be reduced in proportion to the length and severity

of the water shortage. On the other hand, use

of excessive water may lead to difficulty.

Poorly drained soils may become waterlogged

and injure roots. Because water must be

pumped and is expensive in many pear districts, it should not be wasted.

Three methods of applying water are used

in pear orchards. In California on fairly level

land of medium or heavier texture, the flooding or basin method is largely used. Small

dikes are erected as necessary to enclose an

area of approximately level land. They should

be small enough so that water can be applied

rapidly from the available supply. These basins are then filled with water sufficient to

restore soil moisture to the desired depth.

Generally 6 to 8 acre-inches will be supplied

per irrigation. This method wets all the soil

uniformly.

On moderately sloping land the rill or furrow method is generally used. Four or five

furrows, equally spaced in the center between

each tree row, are opened. Water from a head

ditch or pipeline is run into these furrows at

such a rate that it will be taken into the soil

within the length of the furrow. Furrows

must have only a moderate slope—generally 4

to 6 inches per 100 feet—to avoid erosion and

to obtain even, moderately uniform infiltration. In light-textured soils often the whole

root zone will not be wet from furrows. In

the tree row, particularly, an area of dry soil

remains. Also, with furrows it is difficult to

supply a uniform quantity of water along the

length of the furrow. Frequently excess water may accumulate at the lower end of the

furrow, or sometimes insufficient water may

reach the lower end. Skill and care are essential for uniform application of water from

furrows.

A third method of application is with sprin-
COMMERCIAL PEAR GROWING 17

klers. Light-weight aluminum pipe, with

rapid coupling devices, is used in many pear

orchards, especially where the soil is fairly

steep or so open that water enters it rapidly.

By sprinkling, all the soil is wet and response

of the trees has been very good, particularly

on sites where uniform distribution of water

by furrows or basins is difficult. Equipment

for sprinkler irrigation is expensive, but improved water distribution and tree response

are justifying its use in many orchards.

The amount of water required by pear trees

will vary with the temperature and humidity

and with the size and leaf area of the trees.

Only a small amount of water is used before

the bloom season, since there is little foliage

on the trees. Use of water increases as the

foliage develops and as the days become hotter

and generally drier.

In the interior valleys of the Pacific Coast

States, vigorous mature pear trees will use

from 5 to 6 acre-inches of water per month in

July and August and a little less in June and

September. Since some water is lost by evaporation and from other causes when irrigating, about 7 acre-inches per month may need

to be applied in July and August. On deep

soils of good water-holding capacity, this

amount can be applied in one irrigation, and

irrigating monthly will be satisfactory. On

shallow or coarse-textured soils, more frequent

and lighter watering should be practiced.

PRUNING

Pruning is necessary to obtain satisfactory

yields of good-quality fruit. The growth conditions and the various characteristics of different varieties all determine the type and

degree of pruning in a given situation. In

general, the greater the amount of pruning the

larger the fruit and the less the total yield.

Both canners and shippers prefer fruit 2%

inches in diameter and larger. To produce

fruit of adequate size and quality, moderate

pruning is required, but extreme pruning

should be avoided because of its adverse effect

on yield.

Pruning Young Trees

The i)runing of young trees is intended to

develop tree structure. By skillfully selecting

certain branches for the framework and by removing others, the pruner builds the foundation for long-lived trees that is strong enough

to carry heavy crops. With young trees, developing structure is the first concern ; producing fruit is secondary. Thus, pruning young

trees may more properly be referred to as

training. During the training process the aim

should be to develop a sturdy tree capable of

producing large crops of quality fruit.

At the time of planting, young trees should

be cut back to 24 to 30 inches from the ground

to balance the loss of roots removed in digging the trees from the nursery and also to

form a relatively low head, which is desirable

in developing a profitable tree. During the

dormant period after the first growing season

(fig. 9, A), three branches should be selected

and headed to a length of 24 to 30 inches in

order to force secondary branches. All others

should be removed. The selected branches

may emanate at about the same point on the

trunk, or they may be selected around the

trunk at a distance of 6 to 8 inches apart. The

angles of the framework branches should be

as wide as possible for added strength, but this

feature is not so important as with apples.

Pear limbs rarely break under the stress of a

heavy load.

At the second dormant pruning (fig. 9, ß),

the secondary framework branches should be

selected. Generally each of the three branches

forming the original framework will give rise

to several shoots, from which four to six secondary scaffolds are selected. All other vigorous growth is removed. Each of these

branches should be headed at the point where

a third set of branches is desired.

Beginning with the third dormant pruning

(fig. 9, C) and continuing until the framework

is complete, each of the four to six secondary

branches selected at the second pruning is

headed at the point where the next whorl of

branches is desired. The other shoots are

thinned out and left unheaded. Further heading is usually unnecessary. If the trees have

grown well, the framework should be established. Until the tree comes into bearing, only

small branches should be moderately thinned.

The lighter the pruning at this point the larger

the tree and the sooner it will fruit (fig. 10, A).

Pruning Bearing Trees

After a tree begins to bear fruit, pruning is

necessary to maintain a balance between fruit

production and vegetative growth. Although

fruit color is not a factor, branches and shoots
18 AGRICULTURE HANDBOOK 330, U.S. DEFT. OF AGRICULTURE

B

li¿ V/frm ' ' '

Sa

ê

BN-29833

FIGURE 9.—Bartlett trees before (left) and after

(right) pruning: A, 1 year old; B, 2 years old;

C, 3 years old.

should be thinned out sufficiently to allow adequate sunlight in order to maintain vigor

throughout the bearing area of the tree. Excessive heading back of shoots is likely to result in too much vegetative growth. Both

heading and spacing are usually required to

maintain a proper balance. If sufficient wood

for spur replacement is obtained and if trees

are not pruned so severely as to limit the crop,

it makes little difference whether the desired

results are obtained by thinning, heading, or

a combination of both. A well-pruned Bartlett

tree is shown in figure 10, B. Some moderate

heading of vigorous shoots was performed, but

thinning and spacing of excessive shoot growth

constituted the bulk of the pruning.

Anjou, with its characteristically light set

of fruit and consequent large leaf area per

fruit, frequently produces fruit larger than

that preferred by the trade. The ideal way to

produce smaller fruit would be to increase the

number of fruits per tree. However, since the

pruning of Anjou generally increases the percentage of blossoms setting fruit more than

enough to compensate for the reduction in

number of flower buds incident to pruning,

many growers rely on rather heavy pruning.

Although satisfactory in some seasons, such

heavy pruning stimulates the rate of fruit

growth so much that with a moderate crop the

final fruit is often larger than desired. Furthermore, with repeated heavy pruning, the

yield per tree in some years may be considerably less than that of trees with annual light

pruning.

Experimental evidence indicates that over a

period of years annual light pruning will produce as great a total yield and with vigorous

trees a slightly greater yield than annual heavy

pruning. The advantages of the lighter pruning include less cork spot (see p. 45) where

cork is a problem, more desirable fruit size,

and the opportunity for greater yield per tree.

In pruning pear trees, particularly Anjou,

emphasis should be placed on the removal of

limbs with spurs over 4 or 5 years old. To renew these limbs, an excess of new water

sprouts should be left each year. These should

be thinned out when they are 2 years old, leaving those that have or, if still needed, those

that will set fruit spurs in the coming years.

The remainder are removed. These renewal

shoots should be left until they have produced

one or two crops and then replaced with new

or younger fruiting shoots. By a rotation system of this type old spurs are not permitted to

develop. Where this system has been rigidly

followed, the cost of pruning is not excessive and fruit set and yield have been very

satisfactory.
COMMERCIAL PEAR GROWING 19

BN-29832

FIGURE 10.—Bartlett trees after pruning: A, 5 years old; B, mature.

POLLINATION

Numerous pollination experiments show that

Bartlett and Anjou are virtually self-sterile.

They also show that these varieties may be

highly self-fruitful in the West because of the

production of parthenocarpic fruits (without

seed). However, cross-pollination generally

aids in the setting of fruit by all important pear varieties under some, if not all,

conditions.

In the Western States good crops of Bartlett and Anjou are harvested where no provision is made for cross-pollination. The degree

of self-fruitfulness of these varieties depends

on the season and growth status of the tree.

If temperatures are relatively cool during the

bloom period and immediately following, fruit

set in solid blocks of these varieties will be

much lower relatively than where cross-pollination is provided. Likewise, the lower the

vigor the more likely fruit set will be adversely

affected where there is no provision for crosspollination.

Even where vigor and weather conditions

are optimum, cross-pollination generally results in a greater fruit set. This may not be

an advantage if the increased set is not needed

for an adequate crop, because such a situation

would necessitate the removal of surplus fruit

in order to obtain adequate size. However, in

many fruit areas, particularly in the Northwest, cross-pollination will pay large dividends

by increasing yields in more years than not.

Also, there are areas in California where Bartlett will benefit in most years with cross-pollination, even though there are many successful

orchards of this variety grown in solid blocks.

Most of the fruit in these orchards is seedless and generally has the desirable feature of

being longer in proportion to its diameter.

The overall size of seedless pears may not be

so great as seeded fruit (cross-pollinated),

though the experimental information on this

point is inconclusive. Seedless pears are more

prone to harvest drop than those with seed.
20 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

but this can be prevented through the use of

hormone sprays (see p. 21).

Griggs and Iwakiri (16) in a comprehensive

study determined whether a seedless Bartlett

was the result of stimulative parthenocarpy,

caused by the stimulus of self-pollination, or

whether fruit set was due to vegetative parthenocarpy, which occurs without any pollination. During four seasons of experiments

these workers found that stimulative parthenocarpy failed to result in a significantly higher

set than when pollen was not involved (vegetative parthenocarpy).

Additional evidence was obtained by caging

trees with tight mosquito netting, either with

or without a colony of bees enclosed. These

tests showed that bees working the blossoms

failed to increase the self-fruitfulness of the

Bartlett pear. It may be concluded, therefore,

that bees are of doubtful value in Bartlett orchards unless other varieties are interplanted

or are within bee-flight range so that crosspollination is possible. In the East, Bartlett

and most other varieties cannot be depended

on to set fruit without cross-pollination.

In providing for cross-polHnation one should

consider the commercial value of the pollinizer

and when it blooms in relation to the variety

to be pollinated. All important pear varieties

that produce viable pollen are compatible. The

Waite and Magness varieties are pollen sterile

and obviously will not function as pollinizers.

The pollinizer and the main variety must

bloom concurrently or their blossoming period

must overlap. If sufficient chilling to break

the rest period occurs during the dormant

season, most pear varieties overlap reasonably

well.

Bartlett has a relatively long chilling requirement, whereas Winter Nelis requires

much less chilling to break dormancy. Thus,

when mild winters occur in the Sacramento

Valley, Winter Nelis bloom may be too early

to adequately pollinate the later opening Bartlett blossoms. In such instances Hardy is a

preferred pollinizer, since this variety has a

chilling requirement similar to that of Bartlett

and is likely to bloom at about the same time

whether the winter is mild or cold.

Varieties grown in southern regions may

vary considerably in time of bloom. For example, Baldwin and Orient, because of their

short chilling requirement, may bloom too early

to pollinate Maxine or Waite.

In colder areas the chilling requirement of

a variety is of no consequence, because the

winters are always cold enough to adequately

satisfy all varieties. In the Western States

both Bartlett and Anjou are important varieties and are considered good pollinizers for

each other. In Michigan and New York, Bosc

is frequently used as a pollinizer for Bartlett.

Often a grower is interested in planting only

one variety and would like to have as few pollinizers as possible. In most areas every fourth

tree in every fourth row is adequate. With

this pattern only 6 percent of the trees are

pollinizers, and two diagonal spaces represent

the maximum distances from the main variety

to a pollinizer. When pollinizers are provided,

it is necessary to have an adequate supply of

bees to transfer pollen from one variety to another. One strong colony for every 2 acres is

generally adequate.

The best time to place bees in the orchard is

when the first blossoms open. Pear blossoms

are not particularly attractive to bees, and

placing them in the orchard earlier encourages

the bees to go elsewhere. It is not necessary

to distribute the hives singly throughout the

orchard. Placing them in groups of 5 to 10 in

a warm protected place not only promotes optimum activity but also facilitates handling.

FRUIT SET

Even under optimum conditions of pruning,

cross-pollination, and general culture, Anjou

pears with heavy bloom in the Pacific Coast

States frequently fail to set a capacity crop of

fruit. Various types of chemical sprays have

been tested to increase fruit set on this variety.

Batjer and Thompson (5) working in central

Washington found that boron sprays (50 to

100 p.p.m. of boron) applied during the bloom

period appreciably increased the set of Anjou

under certain conditions. In speculating on

the mechanism involved, these workers concluded that a probable explanation was the correction of an incipient or temporary deficiency

of boron.

In later work Degman and Batjer (10)

found that a 7.5 p.p.m. concentration spray

of 2,4,5-trichlorophenoxypropionic acid (2,4,5-

TP) when appHed to Anjou immediately prior

to or after harvest generally resulted in a

marked increase in fruit set the following year.

During years when unsprayed check trees set

a full crop, very little benefit was obtained

from the spray treatment, but in vears when

the checks set a light crop, 2,4,5-TP spray resulted in a moderate increase in set and yield.
COMMERCIAL PEAR GROWING 21

In several districts of central Washington the

use of 2,4,5-TP has become standard commercial practice on Anjou. Bartlett is rather sensitive to 2,4,5-TP, and if the treatment is used

on this variety, the concentration should not

exceed 3 to 4 p.p.m.

With the advent of naphthaleneacetic acid

(NAA) to prevent harvest drop on Bartlett,

several experienced grov^ers reported that

these sprays also increased fruit set. Although

experimental evidence is lacking, extensive observations indicate that this may be true.

After the discovery that 2,4,5-TP increased

fruit set, it would seem logical that NAA

sprays, though less effective, could act in a

similar manner.

FRUIT THINNING

Many varieties of pears set heavy crops that

do not develop to good marketable size, particularly Winter Nelis, Bosc, and Bartlett. If

medium to large fruit is desired, part of the

crop from such trees should be thinned in

order to have a larger leaf area per fruit.

In California, thinning of Bartlett is seldom

necessary.

Many pear varieties, such as Bartlett,

Hardy, and Bosc, tend to set the fruit in clusters, often three to five fruits on a single spur.

If the set of fruit on the tree as a whole is

excessive, these clusters should be reduced to

one or two fruits each by removing the smaller

ones. On the other hand, if the set of fruit

on the tree as a whole is not excessive, fruit in

these clusters will reach satisfactory size and

quality without thinning.

It is impossible to lay down hard-and-fast

rules for the thinning of pears. The number of

fruits a tree will develop to good marketable

size will vary with its vigor and growing conditions. Experiments indicate that with nearly

all varieties from 30 to 40 good leaves per

fruit are essential for the manufacture of materials that produce fruit. However, these

leaves need not be directly adjacent to the fruit.

With extremely heavy sets of fruit, thinning

to reduce the amount of fruit in proportion to

the leaf system is essential if fruit of best size

and quality is to be obtained. Since fruit that

is small at thinning time tends to remain so, it

should be removed at that time.

As the natural drop is usually over about 6

weeks after bloom, the earlier the thinning is

done after this the greater is the effect on improving the size of the remaining fruit. At 50

days from full bloom, fruit size of Bartlett is

about 10 percent of harvest size and at 70 days

growth has increased to only 20 percent of the

ultimate size. Thus the size of the remaining

fruit can be favorably affected but to a less degree with relatively late thinning.

In some areas, particularly California, growers rely solely on selective picking to supply

the necessary thinning. When pears of 2%

inches in diameter and larger are removed in

the first picking, the fruit remaining on the

tree will likely increase in volume at a daily

rate of about 2 percent. Thus, about 1 week

is required to obtain an increase of Vs-inch

diameter for the remaining fruit. Bartlett

pears, however, should not be permitted to remain too long on the trees for size increase,

since both shipping and canning quality may

be seriously impaired (see section on harvesting and handling).

HORMONE SPRAYS TO PREVENT FRUIT DROP

Dropping of fruit before or during harvest

causes considerable loss in some years. This

is especially true in solid blocks of Bartlett

rendered seedless for lack of cross-pollination.

This loss can be greatly reduced by the use of

hormone sprays on most varieties where drop

is a serious problem.

Such sprays are now used generally by commercial pear growers. NAA has been effective

for this purpose when used at a strength of 5

to 10 p.p.m. In most sections of California

NAA is usually incorporated in a mite spray,

which is applied 2 to 7 days before harvest.

The spray becomes effective within 2 or 3 days

and generally controls drop for 3 to 5 weeks.

Another hormone, 2,4-dichlorophenoxyacetic

acid (2,4-D), may also be used to prevent drop.

From 10 to 14 days may be required for 2,4-D

to become effective, but the effect lasts considerably longer than NAA. Pears are sensitive to 2,4-D and injury may result if more

than 3 to 5 p.p.m. are used. Formulations containing the ester or high volatile types of 2,4-D

should be avoided.

When hormone sprays are used to prevent

the natural drop of fruit, it is important that

the fruit be harvested at the proper stage of

maturity ; it should not be allowed to remain on

the tree too long. Overripe pears, particularly Bartlett, break down soon after harvest.
22 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

PRINCIPAL PEAR VARIETIES

Pear varieties may be classified into two

broad groups—the French types, or those of

European origin (Pyrus communis L.), and

the hybrid types, which originated as crosses

between European varieties and oriental

species. In general, the European varieties

are much higher in quality but more susceptible to fire blight. Because of this, the hybrid

types are better adapted to southern conditions.

French Types—Pyrus communis Origin

Anjou

Anjou (fig. 11), a large green pear of

French origin, has been grown in the Pacific

Coast States over a long period, but most

plantings have been made since 1920. It is the

most important winter pear and second only to

Bartlett in total production. Anjou is grown

mainly in Washington and Oregon, with limited plantings in California.

The fruit is attractive and high in dessert

quality. It keeps well in storage until March

or April or slightly longer in sealed polyethyBN-29825

FIGURE 11.—Important pear varieties of European

origin: A, Anjou; B, Bartlett; C, Bosc; D, Cornice.

lene liners, and may be marketed over a long

period. The entire commercial crop is marketed as fresh fruit. The tree is vigorous and

grows large. This variety is more resistant to

fire blight than other large high-quality varieties. It is a consistent bearer but a slow producer. Rather heavy and detailed pruning

improves fruit set on older trees.

Bartlett

Bartlett (fig. 11) is grown on almost threefourths of the pear acreage of the Western

States. It is also an important commercial

variety in Michigan and New York. Nearly

two-thirds of the crop is canned. About onethird is sold as fresh fruit and is shipped to all

parts of the United States. Small quantities

are dried.

The trees are adapted to a wide geographical range and to a great diversity of soil and

climatic conditions. They are prolific, bear

regularly, and endure neglect, abuse, and

uncongenial surroundings surprisingly well.

These characteristics, combined with the quality and uses of the fruit, make Bartlett a remarkable variety.

When well grown, Bartlett is generally considered the standard of excellence by which

other pears for fresh-fruit shipment are measured. It is the only variety in the West to be

used for all purposes. In flavor and texture it

is unsurpassed among the major commercial

varieties. It is the first of these varieties to

ripen. The picking season ranges from early

July in the valleys of central California to late

August or early September in other areas

where this variety is grown.

The fruit may be held successfully up to 2^/2

months in conventional cold storage. It is normally off the fresh-fruit markets by the middle

of October. Bartlett is best both in dessert

and in storage and handling qualities when

grown under fairly hot summer conditions. In

the coastal sections of all the Pacific Coast

States where summers are very cool, the fruit

does not keep so well after harvest as in the

hotter interior sections and usually is less rich

in flavor. Fruit from these coastal sections is

generally canned or used locally, as the carrying quality is not sufficiently good to allow

shipment to distant markets.

Bosc

Bosc (fig. 11) is grown on about 2,000 acres,

mainly in the Rogue River Valley of Oregon

where the fruit is excellent. It is also an important variety in New York and Michigan.
COMMERCIAL PEAR GROWING 23

The fruit grows to good size. The yellow

skin, which is almost covered with a brown

russet, is particularly attractive. It is a fall

and early-winter fruit, reaching prime market

condition in October and November. The tree

bears rather early and produces heavy crops.

The tree, particularly while young, is difficult to shape by pruning. The branches produce vigorous new shoots from their terminals.

These remain rather slender for a considerable

time and branch but little, so that the tree

remains open and often becomes ungainly

and willowy by the spreading of the slender

branches. Special attention is required to

maintain a tree of desirable shape.

Trees of this variety are attacked by fire

blight about as seriously as those of any other

commercial variety. The fruit may be seriously affected by stony pit virus. The tree is

less tolerant of poor soil drainage than many

other varieties.

Cornice

In the Santa Clara Valley of California and

the Rogue River Valley of southern Oregon,

Comice (fig. 11) is grown on nearly 2,000

acres. This tree is open and rather easily managed by pruning, but it is not so consistent in

bearing habits as many other varieties, often

setting very light crops.

The fruit is large, light greenish yellow, and

of excellent dessert quality. In flavor it is

among the very best of the pears. It keeps

well if handled carefully and can be held in

cold storage into January. However, it is one

of the most easily bruised of the commercial

varieties. The skin is tender and easily punctured, and even light bruises at picking time

will result in darkened areas on the fruit. It

is also readily injured by the rubbing of the

leaves and branches. In recent years much of

the crop has been marketed for gift packages

and other channels where special handling can

be given.

Hardy

Hardy is grown on about 1,500 acres, mainly

near San Francisco Bay and in the Santa Clara

and San Juan Valleys of California. The tree

grows well, is a heavy bearer, and appears to

be more resistant to fire blight than Bartlett.

It is rather easily handled by pruning, because it is not inclined to branch freely and

remains open. Much of the new growth takes

place at the terminals of fruiting branches or

where branches are headed back or removed.

Numerous large fruiting spurs instead of

shoots develop along the fruiting branches and

remain vigorous and productive for many

years. The wood unites well with quince and

is frequently budded on quince roots and then

topworked to other varieties.

The fruit is of good size and shape, keeps

and handles fairly well in storage, and attains an attractive flavor. It ripens soon after

Bartlett and before Bosc and Anjou. It was

a favorite for export prior to World War II,

but now it is largely used in canned fruit

mixes and baby foods.

Maxine

Maxine is well adapted to most areas of the

South. It ripens in mid-September between

Orient and Kieifer. The fruit is large, attractive in shape, and yellow when ripe. The flesh

is average in firmness and moderately gritty,

with flavor and quality above the average of

hybrid pears. It is suitable for eating fresh

and rated high as a canned product. The tree

is vigorous, productive, and generally rather

tolerant to fire blight.

Seckel

Seckel is more tolerant to fire blight than

any of the principal varieties of the French

type. Because of this characteristic it can be

grown successfully under a wide variety of

climatic conditions, including areas throughout the South. The fruit is small but of excellent flavor and quality. The tree comes into

bearing late, but is usually very productive as

a mature tree. This variety is of limited commercial value because of its small fruit, but

it is highly prized for home use and local

markets.

Hybrid Types—Pyrus communis Crossed

With Oriental Species

Baldwin

Baldwin (fig. 12) because of its low cold

requirement to break dormancy is an excellent variety for the lower South. If planted

m the middle and upper South, however, it

may bloom too early, and consequently spring

frosts are likely to cause loss of crop. The

fruit is almost round and golden yellow when

ripe. Its fresh and processed qualities are

considered good for a hybrid variety.

Kieffer

Kieifer (fig. 12) is perhaps the most widely

planted pear in the Southern and lower Midwestern States. It is grown chiefly for home

consumption.

The trees are vigorous and well adapted to

a wide geographical range and to a great di-
24 AGRICULTURE HANDBOOK 330, U.S. DEFT. OF AGRICULTURE

BN-29812

FIGURE 12.—Hybrid-type varieties adapted for southern areas: A, Baldwin; B, Kieifer; C, Orient; B, Waite.
COMMERCIAL PEAR GROWING 25

versity of soil and climatic conditions. Its

moderate fire blight resistance makes it possible to grow this variety in areas where many

European varieties will succumb to this disease. Kieffer blossoms relatively early and

is unfruitful with its own pollen. It therefore

requires the presence of another variety blossoming at about the same time in order to set

heavy crops of fruit.

Kieffer matures in late September or October, depending on the area. The fruit is medium to large, developing an attractive color

when ripened properly. Its flesh is firm, moderately juicy, and gritty. Although the dessert

quality is low, the canned product is usually

good.

Orient

Orient (fig. 12) ripens in late August or

early September. It blooms several days earlier than Kieffer and has outstanding resistance to fire blight.

The fruit is large, nearly round, and greenish, with juicy flesh that is firm and only moderately gritty. It is only fair as a fresh fruit,

but the canned product is attractive in appearance and of good quality. The tree is vigorous and productive, with a willowy type of

growth becoming almost weeping under a full

crop of fruit. Orient is recommended for

planting throughout the Southern States.

Waite

This variety (fig. 12) possesses a high degree of fire blight resistance and is well

adapted to the middle and upper South. Waite

was introduced by the U.S. Department of

Agriculture in 1938. Its fruit resembles that

of Bartlett in size and shape. The quality is

fair to good. The seasons of Waite and Kieffer are the same.

PROMISING NEW VARIETIES

El Dorado

El Dorado (fig. 13) originated about 1925 as

a chance seedling near Placerville, Calif. During the past few years considerable interest

has developed in this variety, and several hundred acres have been planted in Oregon and

Washington.

El Dorado is a winter-type pear of European

origin, which fits well into the late marketing

season. It is harvested just after Anjou and

usually with Comice. The fruit is distinctly

pyriform in shape, often resembling the Bartlett variety, clear skinned, and with a moderately long, flexible stem. The fruit is as

large as that of Bartlett, and the flesh is essentially free of stone cells. The skin becomes

an attractive pale yellow when the fruit is

ripened.

In limited storage tests El Dorado has not

developed scald or core breakdown. The fruit

has stored well at 30° F. until April and May.

Taste tests indicate that it has excellent quality.

The fruit is moderately free of blemishes

and russeting and resists mechanical injury

as well as that of Bartlett and Anjou. Shelf

life is as long as that of Anjou and longer

than Comice or Packham's Triumph. The

fruit also resists pressure and friction bruising.

This variety has not been widely tested and

should be planted only on a trial basis until

more is known of its performance.

Packham's Triumph

Packham's Triumph (fig. 13) originated in

New South Wales, Australia, and was introduced there commercially about 1900. It is a

European-type pear. It was introduced into

the United States about 1945. Several commercial plantings have been made in Oregon

and Washington.

The fruit is large and similar to that of

Bartlett in shape, except that the surface is

likely to be rough and irregular, particularly

on the larger fruit. The skin is lemon yellow

when ripe. The flesh is fine textured and

juicy, with a particularly rich and pleasing

flavor. Packham's Triumph matures about 30

days after Bartlett and keeps well in cold storage for 4 to 5 months. The tree is upright,

vigorous, and a good producer, but highly susceptible to fire blight.

Varieties Recently Introduced

The Agricultural Research Service of the

U.S. Department of Agriculture recently introduced Magness, Moonglow, and Dawn, which

were developed at Beltsville, Md., from 8,000

seedlings of the pear-breeding program. They

were all derived from European varieties. The

first two are fire blight resistant, and all

three are considered good to excellent in quality. These varieties have not been widely
26 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

BN-29831

FIGURE 13.—Promising new pear varieties currently being evaluated: A, El Dorado; B, Packham's Triumph.

tested and should therefore be planted on a

trial basis until more is known of their performance.

The picking maturity of Magness is 10 to 14

days later than that of Bartlett. The fruit is

lightly covered with russet, medium size, and

generally oval. The flesh is soft, very juicy,

and almost free of grit cells. The mature fruit

has a sweet flavor and is highly aromatic.

When in prime condition it rates with the highest quality pears. It can be held in storage up

to 3 months and ripens with good quality. The

tree is very vigorous and spreading; it possesses a high degree of fire blight resistance.

Magness is pollen sterile.

Moonglow is mature for picking about 7

days before Bartlett. The fruit is attractive,

has rather soft flesh, is moderately juicy, and

is nearly free of grit cells. The flavor is mild

and subacid. The fruit is considered good for

processing as well as fresh consumption. The

tree is vigorous, upright in habit, and resistant

to flre blight. Both Moonglow and Magness

are recommended for trial, especially in areas

where fire blight is a major problem.

Dawn matures about 10 days earlier than

Bartlett. The fruit is pyriform, generally resembling Bartlett in shape. It will average

slightly smaller than Bartlett. The fruit is

very good in quality and is aromatic, sweet,

and very juicy. It is almost entirely free of

grit cells. The tree is only moderately vigorous and perhaps is no more resistant to fire

blight than Bartlett. It is recommended for

trial as a relatively early variety in areas

where Bartlett can be grown satisfactorily.
COMMERCIAL PEAR GROWING 27

HARVESTING AND HANDLING

To attain their highest quality, pears must

be harvested before they are ripe. However,

if picked v^hen too immature, they are undersized and often shrivel in storage. They lack

sv^eetness and flavor and are susceptible to

storage scald. On the other hand, if picked

too late, the fruit ripens quickly and has a

short storage potential. It often is gritty in

texture, lacks juiciness, and is subject to core

breakdown.

Picking Maturity

Flesh firmness is the most satisfactory single

index of pear maturity. The optimum picking

pressure will vary somewhat under different

growing conditions, but the pressure test is a

valuable aid in determining the proper time

for picking in any district.

Flesh firmness is determined with a Magness-Taylor pressure tester, which indicates

the amount of pressure in pounds required to

force a rounded plunger five-sixteenths inch in

diameter into the pared flesh of the pear to a

depth of five-sixteenths inch. The measurement should be made at two or three locations

on the circumference of the fruit. Russeted

and blushed areas should be avoided, because

readings from them are usually higher than

from other parts of the fruit.

In cool districts or cool seasons and with

ample moisture, pears tend to be softer and

greener than those grown in hotter districts,

especially if there is a shortage of water.

Pears grown in hot weather tend to be yellow

and remain firm in texture.

Magness and others (S^) reported that in

the hot districts of central California, especially when accompanied by a shortage of water, Bartlett pears were a distinct yellow when

of proper picking maturity and tested as high

as 23 pounds' pressure. Pears from the cooler

growing districts, with suflScient soil moisture,

were greener and softer when mature enough

to harvest, and high quality was obtained only

when the fruit was picked with pressure tests

under 20 pounds; pears testing between 17

and 19 pounds generally have the best quality.

Abnormally cool growing seasons may also

affect the harvest date. Hansen (17) found

that premature ripening of Bartlett pears in

the Hood River area occurred in districts with

comparatively cool growing seasons and only

in years when temperatures were below average. The several weeks prior to harvest were

more critical than those earlier in the growing

season. The earliest indication of premature

ripening in the orchard appears as pink coloration near the calyx. Affected fruits soften and

break down in the core area and fail to ripen

normally. When the symptom first appears on

some of the fruits, the crop should be harvested, and even though firmer than recommended, the fruits may be handled normally

and will usually ripen to fair quality.

Recommendations for proper pressure-test

readings for different pear varieties are listed

in table 7.

There are other valuable indices of maturity

in addition to pressure tests. Color, corking

of the lenticels, and general finish aid in determining proper picking time. Lenticels of

immature pears are white, and as cork cells

develop, they become brown and shallow. The

brown in the lenticels is a good indication that

the fruit will ripen without shriveling. Color

between the lenticels also becomes lighter green

than at the lenticels. A characteristic waxiness of the skin and the rounding out of the

fruit are also guides in determining the optimum picking maturity.

Of various physiological tests for maturity,

the soluble solids test is the most indicative of

quality. A close correlation exists between

flavor and soluble solids. In California the

Bartlett Pear Commodity Committee has established a combination firmness-soluble solids

test in its maturity regulations. A pressure

test of 21 pounds, reported to the nearest half

pound, is the maximum allowable, and then

only if the soluble solids are at least 10 perTABLE 7.—Flesh-firmness recommendations for

harvesting pear varieties

Variety

Firmness *

Maximum Optimum Minimum

Anjou

Pounds

15

19

16

13

11

15

18

15

Pounds

13

17

13

11

10

13-14

16

12.5

Pounds

10-11

Bartlett 215

Bosc 11

Cornice 9

Hardy 9

Kieffer 12

Seckel 14

Winter Nelis 11

^ Magness-Taylor pressure tester with %6-inch-diameter plunger.

^ See p. 28 for modification.
28 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

cent.^ General picking may start at 20 pounds

irrespective of solids content.

Bartlett is the variety commercially canned

almost exclusively in the Pacific Coast States.

Pears for canning are usually picked at a lower

pressure-test reading than are those for fresh

consumption. Canners usually specify the

range of sizes and the grade, and the trees are

selectively picked three or four times at 7- or

10-day intervals to meet requirements.

In a study of maturity and handling of

Bartlett pears for canning in the Pacific Northwest, Ezell and Diehl (12) concluded that fruit

picked at a pressure test of 15 to 17 pounds

was the most desirable. These pressures ordinarily permitted the harvesting of maximum

tonnage, and the fruit was best suited for the

storage and ripening procedures involved with

processing. Pears picked at higher pressures

darkened more when cut and continued to

darken during preparation for canning. At

pressure tests of 14 pounds and lower, the

pears tended to break down at the core before

they had reached the desired softness for canning. This tendency developed rather rapidly

below 14 pounds' pressure.

Climatic conditions modify these figures for

optimum maturity. Pears may soften very

slowly during a hot season or in a hot production area, although they may change from

green to yellowish and soluble solids may increase. In some California districts with hot,

dry growing seasons, a desirable maturity

may be reached when the flesh firmness is 21

pounds or slightly higher. In such cases maturity indices, such as color, finish, and soluble

solids, must be considered.

Packing

Pears destined for immediate consumption

on the fresh market may be packed and shipped

without precooling or without being held in

cold storage previous to shipping. It is usually desirable that this fruit arrive on the market in a condition that will quickly reach the

eating-ripe stage.

For pears that are not to be shipped immediately after harvest, the best practice is to

pack them as they come from the orchard and

cool to a core temperature of 29° to 31° F. to

arrest ripening. However, packing operations

often cannot keep pace with harvest, and accumulated pears should be placed immediately

in cold storage and packed as promptly as is

feasible.

The belief among many pear shippers that

^ L. L. Claypool. Personal communication. Univ.

Calif., Davis.

handling pears while cold results in skin blemishes, variously known as ^'finger prints,"

"abrasions," "scald," and similar descriptive

terms, has been approved. Smith (51) reported that refrigeration did not make Bartlett and Anjou fruits more susceptible to

surface abrasions, but that resistance of the

skin to injuries declined with advancing age in

storage. Bartlett pears promptly cooled and

held at a core temperature of 31° F. for up to

4 weeks were not more susceptible to surface

blemishes after this interval in storage. Thus,

with prompt and adequate refrigeration, the

packing season for Bartlett pears may be

safely extended for 2 or 3 weeks and that of

Anjou pears for 6 to 7 weeks after the fruit has

been picked. Fruit so handled may be washed

and packed without previous warming.

Most of the pear tonnage for the fresh market is packed in standard wooden pear boxes,

which have inside measurements of 18 inches

long, 111/2 inches wide, and 8^/2 inches deep.

The packed box weighs from 53 to 55 pounds

and the net weight of the fruit is from 47 to

49 pounds. Lug boxes of wood or fiberboard

with approximate inside dimensions of 13^/2

by 16 by 6y2 inches are frequently used for

large pears, and recently the use of traypacked boxes has increased. The tray packs

are identical with those used for apples and

consist of paper-pulp trays in fiberboard

boxes.

Several new types of packs, which may eventually accommodate a large percentage of the

pear tonnage, are still in the developmental

stage. Prepackaged trays overwrapped with

shrinkable films and packed in fiberboard boxes

have been tested experimentally, and limited

numbers of commercial shipments have been

made (13). Some shippers report good results

with pears wrapped and packed in standard

fiberboard boxes, eliminating the cost of trays.

The height of these boxes is slightly reduced

to accommodate a net weight of 45 pounds. A

**tight fill" fiberboard box is also being used

commercially, chiefly for Bartlett pears in California. It is a labor-saving pack in which the

boxes are filled from the ends of belts and

tightly packed by vibration. Box lids, fixed by

staples or other means, produce a compressed

pack, which prevents movement of the pears

in handling and transit.

Since 1952, when sealed polyethylene film

liners were first used commercially for pear

storage, nearly all pears in the Western States

destined for the fresh market are packed in

"poly liners." In the liners an atmosphere

develops in which carbon dioxide accumulates

and oxygen diminishes. Both conditions contribute to an extension of storage life if the
COMMERCIAL PEAR GROWING 29

resultant levels are in the proper range. The

respiration rate is lowered and the fruit maintains greater firmness and has a lower content

of soluble pectin. Moisture loss from the pears

is held to a low level (i^). Film bags of the

desired dimensions are used to line each box.

After the box is packed, the top of the bag is

sealed by tying, heat sealing, or folding and

taping. Thickness of the films may vary from

1 to iy2 mils.

The tolerance of pears to carbon dioxide is

limited, and levels above 2 to 3 percent may

cause core browning, cell dehydration, and

death. Cavities occur in the dried tissue and

the affected areas have a brown pithy appearance. The disorder may also extend into the

fleshy part of the pear.

In the early use of polyethylene film for pear

liners, the permeability to carbon dioxide was

in the desired range and allowed from 1 to 3.5

percent to accumulate within the bag at 31^ F.,

while the oxygen level varied from 13 to 18

percent (15), Later supplies of film were less

permeable, and carbon dioxide concentrations

of 5 to 10 percent were common. Consequently, the film liners required perforating or

the use of a carbon dioxide absorbent within

the packages. Liners with about 100 needlepoint perforations are commonly used commercially. They allow an accumulation of carbon

dioxide within the package of about 1 to 2

percent and do not significantly change the

moisture retentiveness of the film.

A recent development for holding the carbon

dioxide at a low level involves its absorption

by hydrated lime, packaged in envelopes, and

used as a pad within the liners. The carbon

dioxide is held at a low level, and at the same

time benefits from low oxygen are obtained.

The oxygen is generally below 12 percent, but

does not reach levels low enough to cause injury (18).

When sealed polyethylene liners are used,

be sure that the film is slit when the fruit

is transferred from cold storage to warmer

temperatures.

Pears are usually wrapped in Hartman

wraps, which contain mineral oil to retard

scald development and a copper compound to

prevent spread of infection from a decaying

fruit to adjacent ones. Recently some chemicals have been found that control Anjou scald

more effectively than mineral oil. Ethoxyquin

(Stop Scald) ^ is the most effective of these

* Trade names are used in this publication solely to

provide specific information. Mention of a trade name

does not constitute a warranty or an endorsement of

the product by the U.S. Department of Agriculture to

the exclusion of other products not mentioned.

chemicals and may be applied to the fruit in a

water dip or spray in the packing line or in

paper wraps when the fruit is packed. Since

the effectiveness of ethoxyquin is dependent

on contact with the fruit, the treatment if applied in a dip or spray must not be followed

with a water rinse.

Storage

When pears are to be stored for a long time,

they should be cooled immediately after picking. If the fruit is to be consumed within a

few weeks after harvest, immediate refrigeration is of less importance. For maximum storage life, pears should be held at about 30° F.

The length of time pears may be held in cold

storage varies with the varieties. The storage

life of each variety is fairly definite, and when

pears are held beyond their normal storage

life, they will not ripen properly upon removal. Even though they appear to be in good

condition, the flesh will not soften, the skin

''scalds" or turns brown, and breakdown may

occur.

The storage life of pears may be affected by

several factors, such as conditions under which

the fruit was grown, maturity at time of harvest, time lapse before being thoroughly cooled,

and temperature in storage. Thermocouples

may be placed in fruit and air at selected locations in the cold-storage room while the fruit

is being placed in storage. Accurate records

can then be obtained during the cooling and

storage periods and the information used for

adjustment of refrigeration capacity, air circulation, and stacking patterns (37, i7). The

length of time that pear varieties may be held

in storage at 30° to 31° F. if picked at the

proper maturity and stored promptly is given

in table 8.

Bartlett pears for canning, when held for

15 to 30 days in cold storage, have better color

and texture when canned than either those

ripened without storage or those stored for

longer periods. However, fruit harvested at

proper maturity and cooled promptly gives a

fairly good product even when stored for 2

months before canning (12),

Benefits from controlled-atmosphere storage

of pears have been recognized for years (2),

but this type of storage has not been extensively adopted commercially. This is probably

T3ecause similar effects have been obtained

with polyethylene liners. An atmosphere containing about 2 percent oxygen and 1 percent

carbon dioxide is recommended for fruit stored

at 30° to 31° F,
30 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

Variety

Maximum storage life in boxes—

Without

liners

With sealed

polyethylene

liners

Anjou

Days

175-185

70- 85

90-100

90-105

75-140

90-120

90-100

175-230

Days

214-216

ßartlett 107-126

Bosc 120-130

Comice 120-135

Hardv

Kieffer

Seckel. .

Winfpr NAII«

Shipping

TABLE 8.—Storage life of pear varieties held ing in transit may be initiated by the use of

at 30° to 31° F, in boxes without and with thermostatically controlled heaters. The recpolyethylene liners ommended thermostat setting is 47.5° F. (4^2,

M' Because of the low temperatures that

usually prevail in transit during late fall and

winter, no significant warming of the fruit

occurs from its own metabolism; therefore,

heaters must be used. In shipments of pears

from the Northwest, heaters installed at Chicago raised fruit temperatures to 50°-60° by

the time of arrival in New York. Pears in

these cars were then ripe enough for distribution 18 to 36 hours sooner than those in

nonheated cars. Other tests indicated the

feasibility of ripening pears by heating in rail

fan cars after arrival at market (car fans operated by portable motors) and thus eliminating the extra handling required to move the

fruit through ripening rooms.

If the pears are to be stored at terminal

markets or transshipped overseas, they should

be held in cold storage during transit. Fruit

shipped immediately after harvest should be

thoroughly precooled and shipped at temperaPears may go into immediate distribution tures as near 32° F. as feasible,

and consumption after harvest, into cold storage in the production areas, or into storage at

the terminal markets. The protective services

for pears in transit are determined by the

disposition to be made of the fruit upon arrival

at its destination.

If the fruit is to go into immediate consumption, temperatures that permit some ripening in transit may be used. For early

varieties such as Bartlett, Bosc, and Comice,

shipped immediately after harvest, modified

icing services should be used to provide temperatures of 45° to 55° F. for the first 5 to 6

days in transit (i3). This will start the conditioning or preripening of pears, which is

vital to the satisfactory marketing of the fruit.

For transit periods of less than 6 days, the

fruit may be treated with ethylene gas before

or during shipment to hasten ripening (i6).

Pears shipped early in the season require

longer to ripen than those shipped later.

The extent of ripening initiated in transit

may be regulated by the transit temperature

and correlated with the time required to ripen

the fruit after it reaches its destination. Mechanically refrigerated cars and Ice Tempco

cars, which use ice as a refrigerant and have

thermostatically controlled fans, are well

adapted for temperature control (19, 20).

Midseason and late pears are generally room

or car precooled or are shipped from cold storage in the production areas. When shipped

from cold storage in the fall and winter, ripenRipening

For best dessert quality, most varieties of

pears should be ripened at 60° to 70° F. and

a relative humidity of 80 to 85 percent. Ripening temperatures higher than 70° are not desirable and may result in poorly flavored and

textured pears or in losses from decay before

softening.

The fastest ripening temperature for Bartlett pears is about 75° F., but ripening at 68°

to 70° is only slightly slower. The fruit ripened at the lower temperature may be slightly

better flavored. It also ripens to excellent

quality at 60° to 68°, but for canning, the

more rapid ripening may be desired because

of the processing schedule. At a ripening

temperature of about 85°, quality is sacrificed

and the pears often become mealy, whereas at

higher temperatures they may fail to ripen

and often break down. Kieffer pears should

be ripened at 60° to 65°.

Although pears may color and soften in storage, they cannot be assumed to have ripened

normally unless they have developed full flavor

and are very soft and juicy. The ability of

pears to ripen depends on the storage temperature and the length of time they have been

stored. Pears have a definite and limited storage life beyond which they will not ripen normally when removed to higher temperatures.
COMMERCIAL PEAR GROWING 31

INSECTS OF PEARS

Pears cannot be grown profitably without

adequate control of insect pests. It is essential

to identify the insects in order to know what

measures to take against them. For additional

information on pear insects, see U.S. Department of Agriculture Handbook 306, Insect

Pests of Deciduous Fruits in the West. Information on insecticides to be used, dosages, and

timing of applications may be obtained from

the county agricultural agent, State agricultural experiment station, or the U.S. Departmention of Agriculture.

Codling Moth

One of the most serious insect pests of pears

is the codling moth (Carpocapsa pomonella

(L.)). It must be controlled with a regular

annual spray program, carefully timed and

thoroughly applied. The insect is injurious

only in the larval, or worm, stage. Young

worms burrow into the fruit, either through

the calyx end or in the side, usually at points

where two fruits touch or where a leaf touches

a fruit. After feeding beneath the skin for a

few days, the worms go to the center of the

fruit, where they feed on the seeds and core.

When full grown, they tunnel to the surface

and leave the fruit. Their presence is often

evident from the brown frass that plugs the

holes. Wormy fruit is of no value.

Codling moths winter as mature worms in

cocoons under the loose bark of trees (fig. 14),

in cracks, crevices, or bark wounds, and in

litter on the ground. In the spring the worms

pupate, and in a short time the adult moths

(fig. 15) begin to appear, usually soon after

BN-29813

FIGURE 15.—Codling moth adult.

BN-29830

FIGURE 14.—Codling moth larva and pupa in cocoons.

the trees have bloomed. They continue to

emerge for some weeks, the period extending

through part of May and June. Moths are inconspicuous and are most active at twilight.

Eggs are laid on fruit and leaves on evenings

when the temperature is above 60° F. They

hatch in 6 to 14 days, depending on the temperature, and the worms feed in the fruit for

3 weeks or longer. In the northern peargrowing areas there may be only one generation and a partial second, but in some areas

with longer growing seasons, as on the Pacific coast, there may be as many as three

generations.

Oriental Fruit Moth

The oriental fruit moth (Grapholitha molesta

(Busck) ) occurs in most of the pear-growing

districts of the United States. It attacks pear

as well as other deciduous fruits. The pinkishwhite worms burrow into the fruit in much

the same way as those of the codling moth, and

they cannot be readily diiïerentiated. These

pests hibernate in cocoons as full-grown

worms, and there are several generations in a

season. Ordinarily if the codling moth is controlled on pears, the oriental fruit moth will

not cause much damage.
82 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

Pear Psylla

The pear psylla {Psylla pyricola Foerster)

is a serious pest of pear, sometimes even more

injurious than the codling moth. It has been

in the Eastern States for over 100 years and

appeared about 1939 in Washington. From

there it spread to practically all pear-growing

districts on the Pacific coast. Injury is limited to pears. Honeydew secreted by these

insects runs down over the foliage and fruit,

and a sooty fungus grows in it. This causes

the skin of fruits to become blackened and

scarred, and the foliage develops brown spots.

Heavy infestations may cause partial defoliation of the trees, reducing vitality and preventing the formation of fruit buds. There is

strong evidence that the psylla is associated

with the development and spread of pear decline disease.

Pear psylla adults (fig. 16) have somewhat

the appearance of miniature cicadas, with

transparent wings sloping over the body.

They are about one-tenth inch long and dark

reddish brown. They can ñy suddenly from

where they are resting, giving the impression

that they have jumped. Adults of the overwintering form are larger and darker than

those of the summer form. They hibernate in

crevices in the bark and on the ground. The

adults may become active at any time when

the temperature is above 40° F.

The elongated whitish or yellow eggs are deposited in March or sometimes even earlier in

the small crevices about the buds, and they

hatch in 10 to 30 days. After the foliage is

BN-29814

FIGURE 16.—Pear psylla adult.

out, many eggs are deposited on the leaves.

The young nymphs migrate to the axil of the

leaves or to the opening leaves themselves to

feed. They are yellowish and ñattened and

soon cover themselves with the honeydew that

they secrete. After going through four successively larger stages and becoming greenish,

they reach the last, or "hard-shell," stage (fig.

17), from which they molt into adults. There

may be three to five generations a year, the

first one lasting about 45 days and the later

ones about 30 days. Adequate control is often

difficult to obtain, and any treatment must be

carefully timed and thoroughly applied.

Scale Insects

The San Jose scale (Aspidiotus perniciosus

Comstock) may cause serious loss of pears if

not controlled, for it infests not only the bark

and foliage but also the fruit itself (fig. 18).

It causes small reddish spots on fruit and foliage. Trees may be partially or entirely killed

and the fruit becomes unmarketable. Actually this pest is not difficult to control and does

little damage if recommended sprays are applied annually.

The scales are about one-twelfth inch in

diameter, with yellow bodies protected by circular, grayish, scalelike coverings. Each mature female produces several hundred small,

louselike, yellow crawlers, which migrate to

new locations. These crawlers may be scattered about by wind, birds, or other means.

Feeding is through a sucking beak. Growth is

completed in about 6 weeks, the insect remaining in the same location. There are two or

more generations a year.

In California, pears may be infested with the

Italian pear scale {Epidiaspis piricola (Del

Guercio)), which has habits and a superficial

appearance similar to the San Jose scale.

However, the soft bodies beneath the scales

are reddish purple instead of yellow. Two

other scale insects, the calico scale {Lecanium

cerasorum Gockerell) and the European fruit

lecanium {Lecanium corni Bouché), attack

pears in California, and the latter may occasionally be found in the Northwest. They are

one-eighth to three-eighths inch in diameter.

They are convex, brown, and, in the case of the

calico scale have irregular white marks. The

adults live only on the twigs or limbs, but the

flattened young usually feed on the leaves,

where they produce large amounts of honeydew in which a black fungus grows. Control

of these scales, if done during the dormant

period, is not difficult.
COMMERCIAL PEAR GROWING 33

. >

r^

::: Äi-^^-.

BN-29822

FIGURE 17.—Pear psylla nymphs: A-E, Young stages; F, fifth, or "hard shell," stage on pear twig.

The cottony maple scale (Pulvinaria innumerabilis (Rathvon) ) sometimes becomes a

pest on Winter Nelis and Anjou, but is seldom

seen on Bartlett. It is primarily a pest of

maple. This scale is easily recognized by the

cottony egg sac produced early in the summer.

About 3,000 eggs are laid in this sac and they

hatch during June and July. The young scales

settle on the underside of leaves, and the partly

grown females later migrate to the twigs,

hibernating there and completing their growth

in the spring. At this time they are brown,
34 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

BN-29821

FIGURE 18.—Pear infested with San Jose scale.

mite (Tetranychus urticae (Koch)), and the

McDaniel spider mite (Tetranychus mcdanieli

McGregor). The first two winter in the egg

stage on trees. The red eggs usually hatch

before the blossoms open, and the young mites

feed on the developing foliage. The European

red mite adult is velvety red and very convex.

The brown mite is dull red to greenish, flattened, and has longer legs. The brown mite

feeds mostly at night, congregating on twigs

and branches during the day.

The two spider mites winter as bright-yellow

or orange adults under bark scales and in debris on the ground, migrating to the new foliage as soon as it develops and feeding first

on the leaves nearest the trunk. When feeding, they are yellowish or greenish, often with

two dark spots on the back. They spin considerable webbing.

Development of orchard mites is rapid in

warm weather and there may be eight or more

generations in a season. This makes control

difficult and measures must be taken before

serious injury occurs. The damage caused by

convex, and about one-eighth inch in diameter.

After the egg sac is formed and the eggs are

laid in it, the female dies. There is only one

generation a year. Applications of dormant

sprays, as for the San Jose scale, control this

scale very well. Several other species of scale

insects occasionally may be found on pears.

The grape mealybug (Pseudococcus maritimus (Ehrhorn) ) is found throughout the Pacific Coast States and is an important pest of

pear in California. These insects overwinter

on the scaffold limbs in egg sacs as young

crawlers. They migrate early in the spring and

start feeding on the tender growth. When

full grown, they are about one-fourth inch

long, dark purple, and covered with a white

powdery wax. Oviposition occurs late in June

beneath the bark scales and at the base of new

growth. This generation becomes adult by

late summer. Injury results from honeydew

dripping onto the fruit. Some of the mealybugs may also crawl into the calyx end, where

their feeding breaks down the tissues. Control

is more difficult than with the other scale insects on pear.

Orchard Mites

Orchard mites are important pests of

pear, often doing great harm. Included are

the European red mite (Panonychus ulmi

(Koch) ), the brown mite (Bryobia rubrioculus

(Scheuten)) (fig. 19), the two-spotted spider

BN-29810

FIGURE 19.—Brown mite adult.
COMMERCIAL PEAR GROWING 35

BN-29816

FIGURE 20.—Adults of pear leaf blister mite.

these mites is primarily to the foliage, which

becomes bronzed or blackened ; defoliation may

occur, and serious interference with the normal development of the fruit results.

There are two other much smaller mites that

live on pear—the pear leaf blister mite {Eriophyes pyri (Pagenstecher) ) (fig. 20) and the

pear rust mite (Epitrimerus pyri (Nalepa)).

Neither can be seen easily without a hand lens.

The pear leaf blister mites winter under bud

scales, and the young of the new generation

form characteristic blisters on the unfolding

leaves in which the mites live. They also feed

on the young fruit. Damage is usually severe

only on young trees; on older trees the fruit

may become russeted. Control may be obtained with fall or early spring spraying.

The pear rust mites winter behind leaf scales

and in small crevices on twigs. They become

active in the spring as the new growth develops, and feed on leaf surfaces and also on

the fruit, which may become russeted. Sprays

similar to those used for the pear leaf blister

mite should give effective control.

Sucking Bugs

Several kinds of sucking bugs may attack

pear fruit. Among these are lygus bugs (Lygus spp.) (fig. 21). They are small grayish

or greenish bugs about one-fourth inch long.

They may cause buds to drop in the spring or

the fruit to become misshapen. Boxelder bugs

(Leptocoris trivittatus (Say)) are larger and

are black and red. They are more likely to

attack the ripening fruit. The consperse stink

bugs (Euschistus conspersus Uhler) are still

larger, about one-half inch long, shield shaped,

and gray brown. They are covered with small

black dots. Local information should be obtained as to how to control these bugs.

BN-29818

FIGURE 21.—Lygus bug.

Thrips

The pear thrips (Taeniothrips inconsequens

(Uzel) ) is usually held in check by control

measures used against other pests. These insects are about one twenty-fifth inch long,

slim, and dark brown. The adults may be

found in the opening buds, where they may

prevent the blossoms from producing fruit.

Later the white larvae feed on the developing

pears and cause russeting. Another species,

the bean thrips (Caliothrips fasciatus (Pergande) ), is occasionally a pest of pear in some

parts of California.

Sinuate Pear Tree Borer

In some of the Eastern States the sinuate

pear tree borer {Agrilus simmtus (Olivier) )

attacks pear. The larvae burrow into the inner bark and sapwood. They are slender,

whitish, and when full grown may be IVz

inches long. There is one brood a year, the

adult beetles emerging in May and June. They

are slender, purplish bronze, and about one-
86 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

third inch long. Occasionally entire plantings

of young pears may be killed by this pest.

Control consists chiefly in cutting out and destroying infested trees and branches during

the winter. Insecticides applied for other pests

in May and June will destroy many of the

beetles.

Other Insects

The orange tortrix {Argyrotaenia citrana

(Fernald) ) sometimes occurs on pears, particularly in the coastal districts of California.

The active, greenish, black-headed caterpillars

of this leaf-roller moth feed on the surface of

the fruit. There are several generations a

year.

In the coastal areas of Oregon and Washington the syneta leaf beetle (Syneta albida LeConte) (fig. 22) attacks the young fruit (ñg.

23) and foliage. These beetles are about onefourth inch long and gray or yellowish. Both

BN-29817

FIGURE 22.—Syneta leaf beetle male and female.

pests are normally controlled with sprays applied against the codling moth.

The pear midge {Contarinia pyrivora (Riley) ), resembling a mosquito, is a small insect

that occurs in the Eastern States. It emerges

when the blossom buds begin to show color

and deposits eggs in them. The eggs hatch

in a few days, and the small whitish larvae

feed in the developing ovaries, causing the

young fruit to be deformed. When full grown,

the larvae leave the fruit and enter the soil to

spin cocoons, in which they remain until they

transform to adults the following spring. Insecticides applied to the trees when the adults

are emerging will control this pest effectively.

The pear-slug (Caliroa cerasi (L.)) (fig.

24) is slimy, olive green or black, and about

one-half inch long when full grown. These

slugs feed on the foliage. Other leaf feeders

include the fruit-tree leaf roller {Archies argyrospilus (Walker)), a tentiform leaf miner

(Lithocolletis sp.), the California pear-slug

{Pristiphora abbreviata (Hartig)) (fig. 25),

the spring cankerworm (Paleacrita vernata

(Peck)), and the fall cankerworm (Alsophila

pometaria (Harris)). All these leaf feeders

are likely to be controlled with spray programs

used against the codling moth and the pear

psylla.

Aphids are occasionally found on pear, including the woolly pear aphid {Eriosoma pyricola Baker & Davidson), the melon aphid

(Aphis gossypii Glover), the apple aphid

(Aphis pomi heGeer), the green peach aphid

BN-29816

FIGURE 23.—Young pears injured by syneta leaf beetle.

1

! -.

i

• /

/

ä \ ',. -'

FIGURE 24.—Pear-slug and its injury.
COMMERCIAL PEAR GROWING 37

BN-29811

FIGURE 25.—California pear-slug: A, Injury to leaf; B, egg in tissue and young larva feeding;

C, full-grown larva.

(Myzus persicae (Sulzer) ), and the bean aphid

(Aphis fabae Scopoli). Control of aphids is

usually not difficult.

The shot-hole borer {Scolytus rugulosus

(Ratzeburg) ) and sometimes another species,

Anisandrus pyri (Peck), also may be found in

pear trees, usually those in poor condition.

The American plum borer (Euzophera semifuneralls (Walker) ) and the Pacific fiatheaded

borer (Chrysobothris mail Horn) may also attack trees in poor condition. Keeping trees

healthy will prevent most of these attacks.

The grubs of rain beetles (Pleocoma spp.)

attack the roots of pear in Hood River County,

Oreg., and occasionally elsewhere. They are

whitish with brown heads and may be 2V2

inches long when full grown. The buffalo

treehopper (Stictocephala bubalus (F.)) and

sometimes other species attack young pear

trees in northern California and in the Northwest. Injury to the bark results when the

females slit it to lay their eggs. Clean cultivation about the trees will usually prevent most

of this injury.

PEAR DISEASES

Fire Blight

Fire blight is one of the most destructive

pear diseases (fig. 26). Losses vary from blossom blight to destruction of large branches

and entire trees. The extent of damage depends on such factors as varietal susceptibility,

weather conditions, cultural practices, and control measures.

The disease was first recorded in the Hudson

River Valley of New York in 1780. Nearly

100 years later the bacterium Erwinia amylovora (Burrill) Winslow et al. was found to be

the causal agent.
38 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

Í ^:££r'

FIGURE 26.—Fire blight of pear.

BN-29g28

The disease usually appears first as a blossom blight, and later infection spreads to

shoot growth and developing young fruits. The

blossom-blight symptoms are confused in some

areas with those caused by Pseudomonas syringae Van Hall (p. 39). As the bacteria invade

the spurs and branches, the tissues turn dark

green and become water soaked. Affected

parts eventually turn brown, then black, and

remain firmly attached to the tree. Under

favorable conditions the bacteria move very

rapidly. If left unchecked, they will advance

from the blighted blossoms to the main

branches, down the trunk, and into the roots.

The bacteria may overwinter in cankers, which

act as inoculum sources the following spring.

Aifected parts often produce droplets of clear,

milky, or amber-colored exúdate containing numerous bacteria, which are readily disseminated to susceptible tissue.

Insects disseminate the bacteria. Honey

bees contaminate their mouth parts by feeding on oozing exúdate from cankers and are

often responsible for blossom infections during their search for nectar. Other insects may

also cause blossom infections by accidental contact with bacterial exúdate followed by later

visitation to flowers.

Rain and windblown mist transfer bacteria

from diseased to healthy plant parts. Blight

epidemics often follow hail storms. The injury from hail apparently provides an entry

point for the bacteria. Any means involving

physical transfer of the bacteria to susceptible

plant parts can also spread blight, provided

other conditions are favorable. Control measures are designed to reduce inoculum and protect susceptible tissue.

Usually control necessitates removal of all

infected spurs and branches as soon as they

appear as well as aifected areas on large

branches, crotches, trunks, and roots during

the dormant season. Cuts should be made well

below the infected areas as soon as possible

after they appear, regardless of the size of the

wood. In these operations cutting tools should

be disinfected between each cut to prevent possible transmission of the causal bacteria.

Corrosive sublimate and Reimer's solution

have been used extensively as disinfectants but
COMMERCIAL PEAR GROWING 39

are sometimes difficult to obtain. Streptomycin dips have been used in some areas also.

Household chlorine bleaches containing 5 percent sodium hypochlorite diluted to one-tenth of

the proprietary strength are more convenient,

easy to obtain, and satisfactory. However,

sodium hypochlorite is extremely corrosive to

metal. Pruning tools are either dipped or

w^iped with a sponge that is saturated with

the disinfectant between each cut. All tools

treated with disinfectant should be thoroughly

rinsed and dried when reuse is not anticipated

within several hours. Infected wood must be

removed from the orchard after pruning and

burned promptly. Under' no circumstances

should these prunings be shredded and left

for mulch as is commonly practiced in many

orchards.

Helpful preventive measures include removal

of all root suckers and succulent water sprouts

that might become infected and carry the bacteria into the body of the tree. Cultural and

pruning practices that discourage vigorous

growth tend to reduce susceptibility to fire

blight.

Application of chemicals in sprays or dusts

has aided in blight control when used in combination with other control measures. Various

forms of copper have been recommended for

fire blight control {22, 30, 4-5). Bordeaux mixture has provided relief from the disease on

pears. However, its value on apple for fire

blight control has been less beneficial. All

coppers, even the fixed forms, have been effective in certain localities but may russet

some varieties. Dust formulations often have

been less injurious than spray applications

with the same chemicals. Anjou is especially

sensitive to copper, and in recent years antibiotics have provided more satisfactory control

on this variety.

Kienholz (27) demonstrated the effectiveness of streptomycin on the highly susceptible

variety Forelle. However, fire blight must be

severe or the crop of sufficient value to warrant costly antibiotic applications. Until safer

and more economical chemicals become available, growers must rely primarily on other

means for fire blight control.

Most of the commercially grown pear varieties are susceptible to fire blight. Nearly 80

species of the family Rosaceae are hosts of the

disease. However, there are known sources of

resistance in pears and apples, and plant

breeders have developed new varieties with

commercial potential. The widely grown Bartlett variety is one of the most susceptible and

cannot be grown commercially in the warmer

areas of the United States.

Fire blight is the most serious disease affecting pears and limits the production of the

older high-quality varieties to the cooler growing areas of the Pacific coast, the higher elevations in the Mountain States, and small areas

along the Great Lakes. Even in these areas

much effort is necessary in the use of blossom

sprays, prompt canker removal, good growing

practices, and community cooperation to keep

the disease in check.

Pseudonionas Blight

Another frequently troublesome bacterial

disease of pears is caused by Pseudomonas

syringae Van Hall (fig. 27). This disease has

been known by many names, including blossom

blast, lilac blight, false fire blight, and Pseudomonas blight. The last name is preferred because it distinguishes this disease from fire

blight. These two diseases bear striking similarities, particularly in the blossom stages of

infection. However, they can be readily separated by following the progress of symptoms

beginning with the initial stage of infection.

Panagopoulos and Crosse (38) compared,

symptoms of the two diseases as follows:

BN-29820

FIGURE 27.—Pseudomonas canker on stem of young

Bartlett tree.
40 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

"Pseudomonas blight begins as one or more

discrete black lesions on the exterior surfaces

of floral organs, e.g., sepals, receptacles, and

pedicels. The lesions enlarge quickly, turning

tissues black as they do so. Fire blight infections, on the other hand, originate through the

nectariferous tissue in the calyx cup and spread

rapidly into the receptacle and then via the

pedicel into the spurs and branches. The infected tissues are at first dark green and water

soaked, but after a few days they turn brown

and take on a varnished appearance due to the

spread of bacterial ooze over the surfaces."

Bacterial ooze has not been observed in association with infection by P. syringae. Calyxcup infections are common and occur independent of blossom blast. Weather conditions

were suggested as a predisposing factor of

blossoms to the blight phase, and frost was

shown to increase susceptibility to P. syringae

{39). This would help to account for the

sporadic appearance of the disease in many

fruit-growing areas.

Symptoms of the disease in the twigs and

larger wood of pear trees in California were

described by Wilson {53). He noted that

brownish streaks extended several inches

through the cortex and outer phloem beyond

the outwardly visible canker. Similar streaks

are rare or entirely lacking when the wood is

invaded by fire blight bacteria.

P. syringae has been associated with pear

buds. However, the method or time of infection has not been established (39). In stone

fruits, Dye (11) suggested that P. syringae

enters the plant during the autumn and causes

serious loss of young trees in the spring. Control of the disease in the Pacific Coast States

has been based on the theory that most of the

infection occurs during the fall and application

of two bordeaux sprays is commonly recommended. The first spray should be applied

when the leaves begin to fall and the second

when most of the leaves are gone. These

sprays have not been completely satisfactory

and further testing is in progress to find more

effective means of combating the disease.

Scab

Scab caused by Venturia pyrina (Aderh.)

(fig. 28) is an important disease of pears in

some areas of the United States, and when

control measures are not practiced, losses are

high. Its severity is dependent on environmental conditions and spore carryover from

the previous year.

The general appearance of pear scab is similar to apple scab, the disease caused by the

BN-29819

FIGURE 28.—Pear scab.

closely related fungus Venturia inaequalis

(Cke.) Wint. apud Thuem. Leaves, fruits, and

succulent young twigs are susceptible to attack. During seasons when rainfall is abundant at bloomtime, dark, velvety, or sooty

spots begin to appear on the young fruits about

petal fall. Fruits infected early usually drop,

whereas those infected later remain on the tree

and may be severely misshapen by harvesttime.

Malformation of the fruit is caused by cessation of growth in the region attacked by the

fungus while healthy tissue continues growth.

Early infections may cover the entire side of

the fruit, whereas later infections usually result in numerous small spots. The area in the

center of a scab lesion may die and slough off,

leaving a russeted area on the skin. It is common to find this corky area surrounded by

sooty patches of active scab at the edge of the

lesion.

Leaves often display dark velvety patches of

the fungus similar to those found on the fruit.

These spots generally are more prevalent on

the lower leaf surface, although süots on the

upper surface are also common. Leaf lesions

are often found along the midrib, and as the

affected part ceases grovi^th, puckering and

twisting commonly occur. Leaves infected
COMMERCIAL PEAR GROWING 41

early in the season usually drop, and under

epidemic conditions severe defoliation may seriously weaken the tree. The remaining infected leaves decrease their rate of food

manufacture and contribute little to the buildup

of reserves. Consequently, bud formation is

decreased and the next year's crop may be

adversely affected.

Infection of twigs may occur at any time

during the growing season. New twig lesions

appear as small blisters or pustules, which

often slough off as the twig produces a corky

underlayer. The remaining pustules are an

important source of inoculum the following

spring. Overwintering pustules rupture during moist weather in the spring and liberate

spores (conidia), which are readily dispersed

by rain and wind to cause new infections. The

infection cycle may be repeated several times

during the growing season, and fruits are susceptible until harvesttime. Fruits infected

shortly before they are picked will appear normal when harvested, but may develop small

pinpoint lesions during the storage period. Infection of the fruit after harvest has not been

demonstrated.

Most features of pear scab are similar to

those of apple scab. In addition to the production of conidia (summer spores), the fungus also produces perithecia on fallen leaves.

The perithecia mature during the winter and

early spring and develop ascospores, which

are forcibly discharged and carried about by

air currents during moist weather.

According to Kienholz and Childs (28) ^

"continual moisture for periods of 5 to 48

hours is necessary for the spores to germinate

and infect susceptible pear tissue. If the temperature during the rainy period is about

75° F., a spore may germinate and infect the

plant within approximately 5 hours. At lower

temperatures, moisture must persist for a correspondingly longer time so that at 40° F. a

wet period of approximately 48 hours is required before infection occurs. After infection has taken place, an incubation period of

12 to 25 days is required for the fungus to

become visible to the naked eye. That is why

scab lesions often appear during periods that

seem unfavorable for scab infection.''

All the commonly grown commercial varieties of pear are susceptible to scab. Kienholz

and Childs (28) stated: "Fruits of Anjou,

Bartlett, Comice, Winter Nelis, Easter Beurre,

Forelle, Seckel, and Flemish Beauty are often

severely affected. Bosc fruits are very susceptible in the young stage, or until they shed

their pubescence; afterwards they become

highly resistant. Often a variety only lightly

affected in one district may be the most seriously affected of all varieties in another."

Langford and Keitt (29) showed that strains

of the fungus exist and thus would account

for such apparent differences in varietal

susceptibility.

Control of this disease is complicated by the

overwintering of the fungus on current-season

twig growth, in contrast to the apple scab

fungus, which overwinters exclusively on the

fallen leaves. Plowing under the fallen pear

leaves was recommended as a control measure

in Australia, where it was demonstrated that

leaves buried for 70 days were no longer capable of producing ascospores. Control measures

in the current season are designed primarily

to protect young fruits and leaves as they develop. Early-season efforts are imperative to

successful pear scab control. Many control

schedules recommend the application of lime

sulfur in the dormant period just as buds begin to swell. Lime sulfur, ferbam, and dodine

are fungicides most commonly recommended

during the bloom period and into the growing

season. Dodine has been more effective and

less injurious than other materials after the

dormant spray.

Root Disorders

Various root diseases are found in most

pear-growing regions of the United States and

have been referred to as collar rot, crown rot,

and root rot. The primary pathogens are several species of the fungus Phytophthora. Collar rot on pear trees was reported in British

Columbia by Mclntosh (SI). He showed that

P, cactorum (Leb. & Cohn) Schroet. on pear

trees was the causal agent. More recently

Mclntosh (33) showed that two other species

of Phytophthora were capable of infecting pear

rootlets. Cameron (7) demonstrated that P.

cinnamomi Rands was pathogenic on pear roots.

Trees infected by species of Phytophthora

are characterized by generally poor growth.

Those attacked by P. cactorum may eventually

die because of a girdling of the trunk at or

below the ground line. P. cinnamomi kills

young feeder rootlets, but is not pathogenic

on the larger roots and crown tissue. Mclntosh (32) stated that nursery stock infected

with Phytophthora resulted in a high percentage of unthrifty trees. Some trees produced

little or no growth for several seasons after

planting.

Although differences in varietal susceptibility have been observed, little information on

the subject is available. Cameron (7) reported a lower percentage of infection in Old

Home, Old Home X Farmingdale seedlings,
42 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

and Pyrus calleryana Decne. than in Winter

Nelis and Bartlett. Until more research on

varietal susceptibility is completed, control

measures are dependent on means other than

resistance.

Collar rot losses can be reduced if the disease is detected before damage to the cambium

occurs. Infected tissue should be exposed to

the air and allowed to dry thoroughly. However, this practice would be of no value where

young rootlets are rotted by P, cinnamomi.

The area adjacent to the trunk should be kept

free of weeds and debris so that rapid drying

will occur after rain or irrigation. Proper irrigation is of prime importance and may vary

considerably under localized conditions.

The fungus is especially sensitive to copper,

and painting or spraying the trunks at the

ground line with copper fungicides has been

helpful. Applications should not be repeated

at frequent intervals because copper toxicity

may develop. In Washington, where collar rot

has recently become a severe problem, it is

recommended that the soil be removed from

around the trunk and replaced with pumice.

To help prevent root and crown disorders,

shallow planting is desirable. Successful control of collar rot depends primarily on the

maintenance of well-aerated soil and prevention of free-water accumulation.

Armillaria root rot, also known as oak root

fungus, crown rot, and shoestring root rot, is

caused by the fungus Armillaria mellea Vahl

ex Fr. The disease is not considered an economic problem generally, but in some localities

it is troublesome. Pear trees of all ages are

susceptible to attack by the fungus. Masses of

fungus mycelium known as rhizomorphs penetrate the root of the host plant. These structures attach themselves to the host root and

apparently enter through a combination of

chemical and mechanical means. The rhizomorphs grow rapidly throughout the root between the bark and the wood, forming a white

fingerlike growth. Large areas of the root are

killed by the action of the fungus, and as the

crown becomes girdled the tree declines and

eventually dies.

The fungus can live saprophytically in the

soil or may parasitize a wide range of host

plants. Resistance to Armillaria is known, but

it is not a commercial pear-growing practice

for control of this disease. Soil fumigation

with chloropicrin or carbon disulfide has been

successful on light soils, but only provides partial control on heavier soil types. When practical, newly cleared forest land should be

avoided for new pear plantings if Armillaria

is a problem.

Powdery Mildew

Powdery mildew of pears is caused by Podosphaera leucotricha (Ell. & Ev.) Salm. Although this fungus is more common on apple,

it is readily spread from this host to pears.

The fungus commonly overwinters on infected

apple buds and is disseminated to pears in the

spring. In Oregon the fungus is capable of

overwintering on infected buds of pear seedlings and invades the new shoots as they develop. Infected tissue becomes covered with

a white ñuffy mycelial growth, on which conidia

(spores) are borne. These spores can infect

tender young fruits, leaves, and shoots. The

disease cycle may be repeated every 5 to 7 days

under ideal environmental conditions. Symptoms on pears are identical to those on apples,

but often mycelial growth and spore production are more limited. Buds weakened by

powdery mildew are more susceptible to winter damage and are often severely injured during cold weather. Early infection of the young

fruit may cause serious russeting and render

it unsalable by harvesttime.

Control of powdery mildew is usually

achieved by several fungicide applications

beginning at the prepink stage. Lime sulfur

and various other sulfur compounds are sometimes used for powdery mildew control on

pears. However, Kienholz (25) demonstrated

that wettable sulfur fungicides reduced fruit

set of Anjou when applied from the pink stage

through three or four cover sprays.

Leaf Spot Diseases

Two leaf spot diseases of pear are found

throughout the United States, but more frequently are troublesome in areas east of the

Mississippi River. Early leaf spot is caused

by the fungus Fabraea macúlala Atk., and appears in early spring (usually April). The

spots are mostly circular in outline and dark

brown to nearly black with purplish margins.

Spotted leaves turn yellow and drop, often

causing profuse bloom in early fall. The fruits

of some varieties, such as Garber, may develop

black cankers and cracks after infection.

Late leaf spot is caused by Cercospora minima Tracy & Earle. Symptoms usually appear

in August as indefinite, angular, brown to

grayish spots without definite outline and follow the areas between major veins. Severe infection of pear trees by C. minima may cause

defoliation.

Ferbam sprays control early blight and

should be applied when the spots begin to appear in April, followed by one or two sprays
COMMERCIAL PEAR GROWING 43

at 3-week intervals. Late leaf spot may be

controlled with a similar spray program, with

application of the first spray in late July.

Copper sprays should be used only in severe

infection because of risk of fruit russet. Sanitation measures, such as plowing under or removing fallen leaves, help to reduce the incidence of these two leaf spot diseases.

Virus Diseases

Virus diseases are a major threat to the pear

industry. Losses may take various forms.

The overall effects are reduced tree vigor and

fruit quality, lower yields, and even death of

trees. Virus diseases of pear have not been

so intensively investigated as those of stone

fruits or apples.

Until recently the only virus disease of major importance on pears was stony pit, described by Kienholz {2Jf). Posnette {íl)

listed five groups of pear virus symptoms in

addition to those of stony pit. Pear ^'blister

canker'' was shown by Cropley {9) to be

caused by a virus. Millecan and others {36)

reported a wood-pitting disorder in pear trees

and showed it to be of virus origin. Further

transmission tests will most likely reveal other

virus diseases of pear.

Several accounts of virus transmission in

pear trees, exclusive of pear decline, by means

other than graft union of diseased to healthy

tissue are reported {8, iO). Observation of the

spread of virus diseases in pear orchards often

suggests transmission by vectors, such as insects or nematodes, but this has not been confirmed by experimental evidence. Growers

should be aware of the virus diseases known to

affect pears and the steps necessary to prevent

their spread to healthy trees. The following

description of pear virus diseases should be

helpful in recognizing these problems as they

exist in the orchard.

Stony Pit

Stony pit is characterized by stony tissue in

the pear fruit, usually at the base of dimples

and depressions. Severely affected fruits are

misshapen, malformed, and unsalable. Bosc

is the most severely affected, but symptoms

occur on other varieties.

In Oregon stony pit symptoms have not been

observed on Bartlett fruits, even where this

variety has been topworked on affected Bosc.

In California severe symptoms have been seen

on fruits of a few Bartlett trees, indicating the

possible existence of a virus strain capable of

infecting this variety.

The tissue develops early in the growth of

pear fruits. Dark-green areas are formed just

beneath the peel 10 days to a month after petal

fall. Rapid development of surrounding normal tissue results in depressions or pits. When

several of these occur together, pear fruits become drastically distorted. Cutting into the

pitted area reveals stony masses of grit cells.

The severity of stony pit symptoms is variable

among fruits on an affected tree and among

trees of a single variety. Symptoms vary in

severity from one year to the next. Trees

with severe symptoms one year may show moderate symptoms in another year, but the relationship of symptoms from tree to tree will

usually be in the same proportion. Symptoms

of stony pit should not be confused with those

caused by the tarnished plant bug (Lygus

lineolaris (Palisot de Beauvois)), cork spot,

or boron deficiency.

Kienholz (26) described chlorotic flecking,

leaf banding, and rough bark symptoms, which

he associated with stony pit. Subsequent work

has indicated that these symptoms are caused

by other viruses occurring concurrently with

the stony pit virus.

Control of this disease consists primarily of

propagation from stony pit-free trees. No

methods for curing affected trees in the orchard or for reducing the severity of fruit

symptoms are known. Some growers have

followed the practice of topworking affected

Bosc to Bartlett or other unaffected varieties.

Some evidence indicates spread from tree to

tree, but this needs to be substantiated.

Pear Bark Measles

This disease is characterized by the formation of blisters followed by longitudinal splitting and cracking of the bark on the stems of

young trees. Necrosis of the underlying

phloem tissue accompanies development of this

virus disease and may eventually cause death

of the tree. Cordy and MacSwan (8) suggested that it may be seed transmissible.

Red Leaf (Curl)

''CurF' is the name associated with a red

leaf condition of pear trees, which appears in

late summer and is not associated with pear

decline. The disease is reported from California (35) and, although not yet proved, this

disorder suggests a virus as the causal agent.

Affected trees have undulated reddish-purple

leaves, the tips of which typically curl under

and toward the midrib. They may be shaken

from the trees easier than those from healthy

trees, but not so easy as those affected with
44 AGRICULTURE HANDBOOK 330, U.S. DEFT. OF AGRICULTURE

pear decline. Red leaf or curl affects all varieties of pear trees and shows some diiferential

in symptom severity between trees and different rootstocks. The number of affected trees

is still small, but the disorder is regarded with

much concern.

Premature reddening of pear leaves may also

result from other causes, such as girdling by

rodents or various other root injuries.

Leaf Mosaics

Posnette (H) Hsted leaf mosaic, vein yellows, and red mottle as virus diseases of pear.

Quince veinbanding and hawthorn ring pattern

occur as latent viruses of pear. Symptoms of

pear leaf mosaic are irregular, chlorotic, greenish-yellow areas on dark-green healthy tissue.

These areas are usually associated with the

veins, but are distinguishable from symptoms

of the veinbanding virus, in which yellowing

is confined to the area adjacent to the veins.

Chlorosis caused by veinbanding is usually

found as narrow, yellow, continuous bands

along smaller veins, and is generally more severe in young rather than in mature trees.

There is no practical means of curing virusinfected pear trees in the orchard. However,

it is possible to obtain virus-free varieties by

special heat treatment. Programs to supply

nurseries with virus-free stock are not yet

completely developed, but such material will

eventually become available. Economical operation of pear orchards in the future may well

depend on the planting and maintenance of

trees that are free of the major virus diseases.

Pear Decline^

Pear decline is caused by a virus spread by

the pear psylla (Psylla pyricola Foerster) (6,

23, 48, 50), The disease was recognized as

early as 1946 in central Washington and was

reported in 1948 in British Columbia (^.9).

During the next 10 years pear decline spread

to all the commercial growing areas of Washington. It was recognized and reported in

Oregon in 1957 and appeared in California in

1959. In all these areas it has spread rapidly,

with the loss of many thousands of trees.

The symptoms of pear decline are similar

to those of the moria disease of pears described

from Italy, and the two diseases are considered

identical (^P). The causal virus was probably

brought into the United States on symptomless,

nonsensitive pear stocks, where it had existed

without symptom expression for a long time

^ Prepared by L. C. Cochran, Crops Research Division, Agricultural Research Service.

in the absence of an insect vector. The pear

psylla became established in the early 1940's

in British Columbia, from where it spread into

the United States. Pear decline has spread

almost coincident with the spread of the pear

psylla in the Western United States. Pear

decline currently has not been recognized anywhere in the United States except in Washington, Oregon, and California.

Symptoms of pear decline are generally of

two types: (1) Quick wilting and death of

trees, in some cases within a week, and (2)

slow decline, characterized by cessation of normal growth shortly after spring foliation, failure of fruit set or failure of fruit to mature

normally, progressive weakening of trees, and

often death after one to several years. Both

types are associated with sieve-tube necrosis

just above the bud union (^). The rapid death

type was spectacular where the disease invaded

new areas, especially during the height of the

growing season in the hot interior valleys of

California.

Many otherwise normal trees in infected

areas develop striking preseason autumnal red

and yellow coloration. These trees are regarded to be in incipient stages of infection

and show decline symptoms the following year.

Symptoms of pear decline are somewhat nondescriptive and hence are easily confused^ with

those resulting from other causes that interfere with normal growth.

Infected trees generally are growing on the

so-called oriental pear rootstocks—Pyrus serótina and P, ussitriensis. Some diseased trees

have been found on P. calleryana and to a less

extent on P. communis. Orchards on domestic

(P. communis), particularly Bartlett, seedlings

grown from seed collected in orchards where

Bartlett was pollinated with Anjou have not

been aifected. Trees on Old Home, a fire

blight-resistant variety used as a rootstock or

as a body stock and planted deep to allow its

own rooting, have also not been affected. Some

affected trees have occurred on French rootstock, which supposedly is P. communis. Such

seed lots may be mixed or could be hybrids

with pear decline-sensitive parents. P. serótina and P. ussuriensis were widely used after

World War I because of their vigor and blight

resistance, but fortunately were nearly discontinued in the early 1940's after hard end was

shown to be associated with P. serótina.

The use of nonsensitive rootstocks, such as

seedlings of Bartlett pollinated by Anjou, is

currently the best recommendation for control.

Affected trees do not recover sufficiently to produce economic crops and should be replaced

with trees on tolerant rootstocks. The pear

psylla is a prodigious feeder on pear species,
COMMERCIAL PEAR GROWING 45

and therefore the causal virus of pear decline

will probably become universal in susceptible

species in infected areas.

Physiological Disorders

Hard End

Hard end or black end makes fruit hard,

rounded, or often black over the blossom end

as it approaches maturity (fig. 29). This disorder occurs almost exclusively on trees

propagated on oriental stock. It is generally

attributed to unfavorable water relationship

within the plants and fruits. Ackley (1) found

that the water-supplying power of the Japanese

rootstock is not so great as that of the French

stock. If this is the case, an intense competition for water may exist among the organs of

the Japanese rooted trees during hot periods

when water loss is excessive.

Hard end has ceased to be a serious problem

in western pear culture, since most of the

trees on susceptible stocks have succumbed to

pear decline. The disorder may be largely

avoided by using the proper rootstocks (see

table 6).

Cork Spot of Anjou

In certain instances Anjou pears develop a

serious fruit disorder known as cork spot. Affected fruits develop internal necrotic spots,

which are often associated with external sunken areas, giving the fruit a bumpy appearance (ñg. 30). Such pears are unmarketable.

Frequently insufficient symptoms on the surface prevent detection when the fruit is graded.

Cork spot is more serious when trees are

propagated on oriental roots. Also, relatively

light crops of large fruits are more prone to

develop the disorder. In this respect it is

similar to bitter pit in apples. During periods

of moisture stress (hot days) the leaves apparently pull moisture from the fruit, resulting in the death of cells in the flesh and the

formation of cork spots. Cork spot can be

largely avoided by the use of French rootstocks

and the employment of cultural practices that

will be conducive to a heavy set of fruit.

FIGURE 29.—Bartlett pears showing two stages of hard

end disorder: Left, normal; center, hard end; right,

black end. (After Ackley {!).) FIGURE 30.—Cork spot of Anjou.
46 AGRICULTURE HANDBOOK 330, U.S. DEPT. OF AGRICULTURE

LITERATURE CITED

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1949. EFFECT OF BORIC ACID SPRAYS APPLIED DURING BLOOM UPON THE SET OF PEAR FRUITS.

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1960. INFECTION OF PEAR ROOT WITH PHYTOPHTHORA CINNAMOMI. (Abs.) Phytopathology 50: 630.

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1961. SOME EVIDENCE THAT PEAR BARK MEASLES

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1956. SUGGESTIONS FOR CONTROLLING BLAST OF

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1955. USE OF FILM BOX LINERS TO EXTEND STORAGE

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i:^ U.S. GOVERNMENT PRINTING OFFICE: 1967 O 249-917
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