^^ AH 526/8/78

PEAR

PRODUCTION

1

L-.

t.-v^

/^^ UNITED STATES AGRICULTURE PREPARED BY

({iàM DEPARTMENT OF HANDBOOK SCIENCE AND

^'^^ AGRICULTURE NUMBER 526 EDUCATION

ADMINISTRATION

ACKNOWLEDGMENTS

Appreciation is expressed to Tom van der Zwet, Science and Education Administration, Beltsville, Md., and to M. N. Westwood and Porter Lombard, Oregon

State University, Corvallis, for preparing sections on fireblight, rootstocks, and new

varieties, respectively. We also thank the county extension agents in the various

pear-growing States who contributed data on pear acreages reported in this handbook.

Trade names and the names of commercial companies are used in this publication solely to provide specific information. Mention of a trade name or

manufacturer does not constitute a guarantee or warranty of the product by

the U.S. Department of Agriculture nor an endorsement by the Department

over other products not mentioned.

On January 24, 1978, four USDA agencies—Agricultural Research Service

(ARS), Cooperative State Research Service (CSRS), Extension Service (ES),

and the National Agricultural Library (NAL)—merged to become a new

organization, the Science and Education Administration (SEA), U.S.

Department of Agriculture.

This publication was prepared by the Science and Education Administration's Federal Research staff, which was formerly the Agricultural Research

Service.
CONTENTS

Page Page

Introduction 1

Climatic requirements of pears 1

Pear-growing areas 3

Production and utilization of pears 3

Interior valleys of central California 3

Coastal sections of central California 7

Rogue River Valley of Oregon 9

Hood River Valley of Oregon 9

Valleys of central Washington 11

Intermountain areas of Idaho, Utah, and

Colorado H

Central region 11

Northeastern region 11

Southern region 11

Sites and soils for pear orchards 12

Rootstocks for pears 12

Soil management and cover crops 13

Cultivation 13

Cover crops 14

Permanent sod 14

Fertilization 15

Irrigation 17

Pruning 18

Pruning young trees 18

Pruning bearing trees ... ; 18

Pollination 19

Fruit set 21

Fruit thinning 22

Chemical fruit thinning 23

Size thinning of fruit and harvest size

prediction 24

Hormone sprays to prevent fruit drop 25

Principal pear varieties 25

French types—Pyrus communis origin 25

Hybrid types—Pyrus communis crossed with

oriental species 27

New varieties 28

El Dorado 28

Packham's Triumph 28

Varieties recently introduced 29

Asian pears 30

Pear insects 31

CodHng moth 31

Oriental fruit moth 31

LeafroUers 32

Pear psylla 32

Scale insects 33

Orchard mites 34

Sucking bugs 35

Thrips 36

Other insects 35

Pear diseases 37

Fire blight 37

Pseudomonas blight 49

Scab 41

Root disorders 42

Powdery mildew 43

Leaf spot diseases 44

Physiological disorders 44

Virus diseases 45

Diseases caused by mycoplasmalike organisms 47

Harvesting and handling 48

Picking maturity 48

Packing 49

Storage 49

Shipping 50

Ripening 50

Suggested supplemental reading 50

Fruit set and thinning 50

Varieties 51

Rootstocks 51

Powdery mildew 51

Leaf spot diseases 51

Fire blight 51

Pseudomonas blight 51

Pear scab 52

Root disorders 52

Virus diseases 52

Physiological disorders 52

Storage and handUng 52

Insect control 53

This publication supersedes Agriculture Handbook No. 330, Commercial Pear Growing.

Washington, D.C. Issued August 1978

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402

Stock No. 001-000-03813-3
PEAR PRODUCTION

By Max W. Williams, H. Melvin Couey, Harold Moffitt,¡and Duane L. Coyier'

INTRODUCTION

About 93 percent of the pear crop of the United

States is produced in the three Pacific Coast States,

Cahfornia, Oregon, and Washington. Production

there averages about 700,000 tons annually, as compared with about 750,000 tons for the entire United

States. 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 with 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

growing. 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 period of low

temperatures (about 1,200 hours below 45° F (7.2°

C)) during the winter to complete their dormant

period.

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.

Most pear varieties can withstand fairly low winter

'Williams, research leader and plant physiologist, and Couey,

research leader and plant physiologist, Hilo, Hawaii; Moffitt,

research leader and entomologist, Yakima, Wash.; and Coyier,

research plant pathologist, Corvallis, Oreg., Science and Education Administration (SEA), U.S. Department of AgricuUure

(USDA).

temperatures without much injury. If the trees are

fully dormant, temperatures as low as -15° F (-26°

C) 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 more resistant to low temperatures than peaches.

All major pear areas of the Pacific coast are

dependent on irrigation for moisture; consequently,

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 (-3.3° C) 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

1
AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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 poor. 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 high. In sections with

cooler growing seasons, such as the coastal districts

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

Washington, pears are much less seriously affected

by this disease.

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.

Table 1.—Average growing season temperatures, by months, in commercially important U.S. pear areas

State and area Station

Average temperatures in

March April May June July August September

California:

Central ,

Central, coastal . .

ÍAuburn

Marysville

Sacramento

Upper Lake

iSan Jose

(Santa Rosa

Op, O^ Op O^ Op O^ Op

51.2 10.7 56.1 13.4 62.4 16.9 71.4 21.9 77.0 25.0

54.3 12.4 59.4 15.2 64.8 18.2 72.8 22.7 77.8 25.4

54.3 12.4 58.1 14.5 63.3 17.4 69.4 20.8 73.2 22.9

49.9 9.9 54.8 12.7 59.6 15.3 66.7 19.3 73.8 23.2

53.1 11.9 56.3 13.5 58.5 14.7 62.7 17.0 66.5 19.2

51.2 10.7 54.4 12.4 57.6 14.2 63.0 17.2 65.2 18.4

76.0 24.4 69.2 20.7

76.2 24.6 71.9 22.2

72.9 22.7 69.3 20.7

72.7 22.6 66.7 19.3

66.1 18.9 64.2 17.9

64.4 18.0 63.8 17.7

Michigan,

southwestern Benton Harbor

New York:

Hudson River

Valley Poughkeepsie

Western Rochester

Oregon:

Hood River

Valley Hood River

Rogue River

Valley Medford

Washington:

Wenatchee River

Valley Wenatchee

Yakima River

Valley Yakima

34.7 1.5 47.1 8.4 57.9 14.4 68.1 20.0 72.7 22.6 71.3 21.8 64.0 17.í

37.3 2.9 49.5 9.7 60.7 15.9 69.6 20.9 74.6 23.7

32.3 0.2 45.1 7.3 56.7 13.7 66.9 19.4 71.6 22.0

43.3 6.3 49.9 9.9 56.1 13.4 61.6 16.4 67.4 19.7

46.7 8.2 51.6 10.9 57.7 14.3 65.2 18.4 71.8 22.1

42.8 6.0 51.5 10.8 58.8 14.9 66.2 19.0 73.2 22.9

44.1 6.7 52.5 11.4 59.0 15.0 66.4 19.1 71.4 21.9

72.4 22.4 64.6 18.1

69.7 20.9 62.4 16.9

66.6 19.2 59.5 15.3

70.8 21.6 63.1 17.3

71.6 22.0 61.6 16.4

69.5 20.8 61.1 16.2
PEAR PRODUCTION

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.

Production and Utilization

of Pears

The number of pears sold commercially in the

United States by State and by Pacific coast area for

1973, 1974, and 1975 is given in table 2. The trends

in production and use for 1963 through 1974 are

shown in table 3. The pear acreage in the principal

growing areas is given in tables 3 to 6. The peargrowing centers in California, Oregon and Washington are shown in figures 1 to 3.

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 grow in this area. The principal pearproducing 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.

Table 2.—Utilized production of pears by States and Pacific coast, variety

composition, 1973-75^

State 1973 1974 1975 Pacific coast 1973 1974 1975

Connecticut

New York .

Pennsylvania

Michigan . .

Idaho

Tons Tons Tons

1,500 1,400 1,900 Washington:

Bartlett .

12,600 14,000 17,500 Other . .

Tons Tons Tons

123,500 126,400 154,500

63,800 86,900 85,500

1,800 3,200 3,400 Total 187,300 213,300 240,000

9,500 10,500 15,000 Oregon:

Bartlett

Other .

1,300 1,050 1,650

Total

73,000 72,000

98,000 103,000

79,000

93,000

171,000 175,000 172,000

Colorado 5,510 4,590 6,000

California:

Utah , . . 5,830 3,200 4,100 Bartlett

Other .

Washington 187,300 213,300 240,000

Total

Oregon 171,000 175,000 172,000

3 States:

California 327,300 310,900 300,350 Bartlett

Other

Total United States 723,640 737,140 761,750

Total

317,000 297,000 294,000

10,300 13,900 6,350

327,300 310,900 300,350

513,500 495,400 527,500

172,100 203,800 184,850

685,600 699,200 712,350

^ Taken from Fruit situation, Economic Research Service, USDA, TFS-198, March 1976.
AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Table 3.-Pears: Production and utilization, by States,

crop of 1975 (preliminary)*

1Jtilization

State

and Not Pro- Processed (fresh basis)

variety utilized^ duction^ Fresh^ -

Canned^ Dried

Tons Tons Tons Tons Tons

California, all 300,350 C) C) (')

Bartlett . . 294,000 66,400 221,900 5,700

Other . . . 6,350 C) C)

Colorado . . . 6,000 C) C)

Connecticut . 1,900 1,900

Idaho 1,650 C) C)

Michigan . . . 15,000 C) C)

New York . . 2,500 17,500 C) e)

Oregon, all . . 3,000 170,000 98,500 C) (')

Bartlett . . 79,000 17,500 61,500 (^)

Other . . . 3,000 91,000 81,000 10,000

Pennsylvania 3,400 3,400

Utah 800 4,100 4,100

Washington, all 219,000 C) (') (')

Bartlett . . 133,500 50,700 82,800

Other . . . 85,500 C) C) C)

United States 6,300 738,900 326,900 406,150 5,850

* Taken horn Agricultural Statistics 1976, USDA.

^Quantities not harvested for economic reasons and excess

cuUage of harvested fruit.

^Production is the quantity sold or utilized.

^Includes ''Home use."

^Some quantities otherwise processed are included in

''Canned" to avoid disclosure of individual operations.

^Data not published to avoid disclosure of individual

operations, but included in U.S. totals.

Bottom Lands of Sacramento Valley

The bottom lands of the Sacramento Valley constitute one of the most important pear-growing 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 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.

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.
PEAR PRODUCTION

Foothills East of Sacramento Valley

In the foothills east of the Sacramento Valley,

about 3,000 acres of pears are grown 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.

Table 4.—Pear acreage in major producing counties of

California and total for Stäte ^

Bartletts Other pears

County

Nonbearing Bearing Total Nonbearing Bearing Total

Acres Acres Acres Acres Acres Acres

Lake 1,105 7,550 8,655 20 35 55

Sacramento 255 6,137 6,392 0 98 98

Mendocino 372 4,053 4,425 39 32 71

Solano 452 3,221 3,673 1 2 3

El Dorado 233 2,117 2,350 5 121 126

Santa Clara 150 1,540 1,690 62 355 417

Sonoma 107 1,555 1,662 3 2 5

Yuba 287 1,484 1,771 10 93 103

Other counties . . . 439 8,522 9,661 369 554 923

Total 4,100 36,179 40,279 509 1,292 1,801

^ Data from California Department of Agriculture for fruit and nut acreage, 1974.

Table 5.—Pear acreage in principal producing areas of Oregon and Washington^

Hood River County,

Oregon

Jackson County,

Oregon

North-central

Washington

Yakima Valley,

Washington

Variety

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Nonbearing

trees

Bearing

trees

Acres Acres Acres Acres Acres Acres Acres Acres

Bartlett . . . 1,120 3,360 100 4,400 1,545 1,623 1,390 7,075

Anjou . . . . 1,147 2,952 0 1,900 1,330 2,055 761 1,422

Bosc 118 303 250 1,950 1 9 100 150

Comice . . . 45 35 280 120 0 4 - -

Other pears . 46 117 10 435 31 7 177 150

Total . . . . 2,476 6J61 650 9,805 2,907 3,698 2,428 8,797

1976 estimated pear acreage supplied by county extension agents for various pear districts based on earlier tree censuses.
AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Table 6.-Pear acreage in principal producing areas

of Michigan and New York

Michigan* New York^

Variety

South- WestHudson

River Western

western central Valley

Acres Acres Acres Acres

Bartlett . . 5,800 2,765 996 2,591

Bosc .... 233 72 323 432

Qapps Favorite . . 98 58 108 178

Seckel . . . - - 24 74

Other pears 366 8 239 20

Total^ . . 6,496 2,903 1,690 3,295

M 973 Michigan Tree Census.

^ 1975 New York Crop Reporting Service.

^Includes 285 acres of Kieffer pears.

On hillsides or where the soil is not deep, the fruit is

usually smaller than 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 as 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.

Valleys Northwest of Lower Sacramento Valley

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. The trees are thrifty, but due to 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. New

plantings are few because most of the available

orchardland in this valley has been planted.

Lake and Mendocino Counties

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 generally 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. 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 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 freshshipment district in the State. Approximately onehalf of its production moves into fresh-fruit channels.
PEAR PRODUCTION

fotLNcn/itSHirou

Figure 1.—Distribution of pear growing in California; each dot represents 100 acres of pears.

Coastal Sections of Central

California

The principal pear-growing sections between the

Coast Ranges and the Pacific Ocean in CaUfornia

are the low coastal plains adjoining San Francisco

Bay in Santa Clara, Santa Benito, 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 than usual. The Bartlett is of less desirable

quahty 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 ostly for canning, but the other varieties are

shipped fresh.
AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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

Figure 3.—Distribution of pear growing in Washington; each dot represents 100 acres of pears.
PEAR PRODUCTION

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 also been planted on this more loamy

land, 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

problem in coastal sections where the crop is largely

used for canning. 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.

Rogue River Valley of Oregon

The principal pear plantings in western Oregon are

in the Rogue River Valley of Jackson County. Limited plantings are 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 10,500 acres of pears. It

ranges from 1,874 feet above sea level near 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 the

most limiting production problem, particularly in the

valley floor with poorer air drainage than the foothills. About 6,500 acres are protected by fuel oil

heaters; 2,000 acres are protected by an overhead

irrigation sprinkler system developed locally during

the past 12 years. The system provides 0.15 to 0.17

inch of precipitation per hour during critical temperatures.

Pear trees grow and produce best on the deeper

volcanic clay as well as the deep sandy loam soils

along Bear Creek and the Rogue River. 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, the water

table is high and the soil is heavy, thus drainage is

required. Extensive early apple plantings have gradually been replaced with pear trees, which will withstand these conditions more successfully.

The Bartlett, Anjou, Bosc, and Comice are the

varieties most extensively planted. About 37 percent

of the acreage is the Bartlett variety with about onehalf shipped fresh and one-half canned. They have

high dessert quality, which can be retained for up to

8 weeks of storage. A few Seckel, Eldorado, Packham, and red varieties are also produced successfully.

The area is best known for its high-quality winter

varieties. A good quality, blight resistant Anjou has

good market acceptance, but acreage is declining

slowly due to lower yields than the Anjou pear districts to the north (fig. 4). Bosc acreage is increasing

due to excellent eating quality, classical uniform russetting, and good yields. The Comice acreage is also

increasing due to the extensive gift pack industry in

Medford. The climate and soils produce superior

quality, sweet, juicy fruit, which is gaining sales in

the commercial 46-pound carton as well as gift packs

sold primarily in the Thanksgiving-to-Christmas season.

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 5). The Bartlett is used mainly for canning,

with some fresh-fruit shipment.

The soils of this area vary considerably in depth
10 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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W:..::êéêêêê.^

50057-P

Figure 4.—Typical Anjou pear orchard on adobe soil, Medford, Rogue River Valley, Oreg.

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 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 growth 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 purnose 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.
PEAR PRODUCTION 11

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 5.

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

(table 6).

Pear production in Illinois is scattered through

several counties in the southern third of the State but

centers in Marion County. Other principal pearproducing 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 for 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 leading 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 (table 6).

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 European-type

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 with improved quality and fire blight

resistance. Most of these are hybrids between Pyrus
12 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

communis 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 it does illustrate the tolerance of the pear toward unfavorable conditions.

ROOTSTOCKS FOR PEARS

Pear varieties, like other orchard fruits, do not

reproduce true from seed and thus must be budded

or grafted to seedling or clonal rootstocks. Perhaps

no other phase of pear culture is more important

than the proper choice of a rootstock. Extensive

studies have been made to determine the most suitable stocks for specific climates, soil conditions, disease resistance, growth control, and fruit quality.

Rootstocks and their specific traits are given in table

7. Rootstocks assumed added significance when it

was shown that the incidence and severity of pear

decline in the Western United States depended

directly upon the genetics of the rootstock used. Pear

decline is now known to be caused by a mycoplasma,

which, when transmitted to the tree by psylla insects,

moves down the living bark to the graft union where

it causes tissue death (and girdling) of trees on susceptible roots. The most susceptible stocks are Pyrus

pyrifolia (Burm.) Nak. (Japanese or Serotina pear)

and P. ussuriensis Max. (Chinese pear). These

should not be used as rootstocks for domestic (European) pear.

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 were not generally available and nurserymen

used oriental seedlings {P. pyrifolia and P.

ussuriensis) 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 for the nurseryman. They

were easy to propagate and made a thrifty tree in the
PEAR PRODUCTION 13

nursery. 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.

Because of this, 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, 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, proved satisfactory under a wide

variety of conditions and, since 1930, have been the

predominant stock used in the Pacific Coast States.

Other stocks used include quince {Cydonia

oblonga Mill.), P. calleryana Decne., P. betulaefolia

Bunge, and P. communis types, including Winter

NeUs seedling, self-rooted Old Home, and Old Home

X Farmingdale (OH x F). The interest in the Chinese

species and blight-resistant Old Home and OH x F

started with F. C. Reimer at the Southern Oregon

Experiment Station. In about 1915, he initiated work

on blight-resistant rootstocks and trunkstocks, which

lasted more than 40 years. Not only did he collect all

available domestic sources of blight resistance, but

he also made two trips to China, Korea, and Japan

to collect native wild species. P. calleryana was naturally blight resistant, but P. betulaefolia was not;

however, Reimer selected four seedling clones, which

are blight resistant and produce resistant seedlings.

Much of Reimer's material formed the basis for

new studies started in 1960 to find decline-resistant

stocks. P. calleryana and seedlings of Bartlett and

Nelis are nominally tolerant of decline, whereas

clonal East Mailing Quince A (M Quince A), Lepage

Series C Provence Quince (Provence Quince C), Old

Home, and OH x F are resistant. P. betulaefolia

seedling stock are completely resistant to decline and

are the most vigorous of all stocks tested. Imported

French seedlings and P. caucásica Fed. from Eastern

Europe are more susceptible to decline than domestic

seedlings.

Factors other than blight and decline also may

influence choice of a rootstock. Trees grafted on

quince, P, calleryana, or P. betulaefolia, are not as

hardy as those grafted on P. communis types and

find their greatest use in the mild areas of Oregon,

California, and the Southern States. Most cultivars

are not compatible with quince and need a compatible interstem. Both Old Home and Hardy can be

used, but those with Old Home interstem have been

more productive. Comice and Anjou may be grafted

directly to quince, as can one strain of Bartlett

(called Swiss Compatible). Recent work with P.

betulaefolia indicates that it does not cause hard end

as earlier reported. However, it should not be used

with Anjou because the extreme vigor and light cropping tendency result in cork spot of the fruit. P. pyrifolia (that is, Serotina, Japanese Sand Pear) and P.

ussuriensis should not be used because they are susceptible to pear decline and show a high incidence of

hard end. Old Home (scion rooted) results in a fine

healthy tree but is slow bearing compared with

several selected OH x F clones. High-yielding clones

of OH X F, which are resistant to blight and decline,

have been selected and are now being propagated.

Some clones are low enough in vigor to result in a

semidwarf tree, while others are even more vigorous

than Old Home. P. calleryana and P. betulaefolia are

the best adapted to wet, poorly drained soils. Quince

can be grown on clay soils if surface and internal

drainage are good, but should be planted shallow in

furrows rather than glazed holes dug with an auger.

Table 7 indicates the general traits of the common

rootstocks used in the United States.

SOIL MANAGEMENT AND COVER CROPS

Cultivation

Cultivation is often practiced in commercial pear

orchards 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
14 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Table 7.—Important characteristics of pear rootstocks

Rootstock Vigor

Sou

adaptability

Winter

hardiness

Pear root

aphid

Root

sprouting

Tolerance to

pear decline

Resistance to

fire blight

Pyrus communis types:

Domestic seedling . Moderate Wide range,

moisture,

and texture

Hardy Susceptible High Good Low.

Imported French .. . -do- -do- -do- -do- -do- Fair Low.

Old Home clone ... High -do- -do- -do~ -^o- Very high Very high.

OH X F clones Low-high -do- ~do- -do- Variable -do- High.

Quince Low Dry, noncalcareous

Not hardy Resistant High High Low.

P. calleryana Moderate Wide range

except

high pH

Slightly

hardy

-^o- Low Good High.

P. betulaefolia Very high -do- Moderately

hardy

Moderately

resistant

-do- Very high Very high.

P. pyrifolia Moderate Poor in

wet soils

-do- Variable -^o- Low Moderate.

P. ussuriensis -do- -do- Hardy Moderately

resistant

-do- -do- Very high.

plentiful, no further cultivation is generally practiced

until after harvest. The cover growth occurring

during the summer is usually mowed or "floated

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. 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
PEAR PRODUCTION 15

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. 5). If the boron

BN-29824

Figure 5.—Young pear fruits exhibiting early season symptoms of

boron deficiency.

shortage occurs relatively late in the season, welldefined pitting will develop (fig. 6). Associated with

these pits are corky areas extending rather deeply

into the flesh of the fruit. A diagnosis of the deficiency is confirmed by boron analysis. Mature fruits

should contain 10 parts per miUion (p/m) or more

boron and young fruits over 20 p/m.

"Blossom blast" is another form of boron defiBN-29823

Figure 6.—Pitting of Bartlett pears caused by boron deficiency

(top row); normal fruits (below).
16 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

ciency that sometimes occurs in Washington

orchards. Typical symptoms are shown in figure 7.

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: 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 effectively; and blossom blast occurs

chiefly on heavy soils in seasons unfavorable for

early root growth.

BN-29826

Figure 7.—Bartlett pear blossoms exhibiting typical symptoms of

blossom blast. Note persistence of dead blossoms.

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 difficult 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.

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 the

creamy white of zinc deficiency. Leaf size is not

affected as in the case of zinc. The chlorosis pattern

is interveinal; 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/m of manganese are low

and less than 15 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.
PEAR PRODUCTION 17

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.

Four 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 sprinklers.

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 fourth method is trickle irrigation in which

water is emitted through small, regulated orifices in

plastic pipe. This method is useful when the water

supply is limited.

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 acreinches 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 irri-
18 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

gating, about 7 acre-inches per month may need to

be apphed in July and August. On deep soils of good

water-holding capacity, this amount can be appUed

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 2-3/8 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 pruning 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, 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 emnate 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 Umbs rarely break

under the stress of a heavy load.

At the second dormant pruning, 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 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.

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 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 8, 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
PEAR PRODUCTION 19

Figure 8.—Bartlett trees after pruning: A, 5 years old; B, mature.

BN-29832

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 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 to 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.

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 par-
20 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

thenocarpic fruits (without seed). However, crosspollination 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 cross-pollination.

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 (crosspollinated), though the experimental information on

this point is inconclusive. Seedless pears are more

prone to harvest drop than those with seed.

A comprehensive study determined if a seedless

Bartlett was the result of stimulative parthenocarpy,

caused by the stimulus of self-pollination, or if fruil

set was due to vegetative parthenocarpy, which

occurs without any pollination. During four seasons

of experiments, 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 cross-pollination is

possible. In the East, Bartlett and most other varieties cannot be depended on to set fruit without

cross-pollination.

In providing for cross-pollination, 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 producing viable

pollen are compatible. Bartlett (fig. 9A), like most

varieties, produces large blossoms with abundant

pollen. The varieties Waite and Magness (fig. 9B) are

completely male 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 requirements, 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. However, when practical, closer proximity of pollinizers in Anjou blocks

will increase yield (fig. 10). 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 par-
PEAR PRODUCTION 21

PN-5765

Figure 9.—Portion of pear tree in full bloom and individual flower (insert) of; A, Bartlett, showing numerous clusters of wide open blossoms with fully developed anthers and abundant pollen; and B, Magness, showing sparse individual clusters of smaller, cup-shaped

flowers with aborted anthers and no pollen.

ticularly attractive to bees, and placing them in the

orchard before blossoming encourages the bees to go

elsewhere. Hives do not have to be distributed 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, crosspollination, 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 varieiy. In central Washington, boron sprays

(50 to 100 p/m) applied during the bloom period

appreciably increased the set of Anjou. A probable

explanation of the mechanism involved is the correction of an incipient or temporary deficiency of

boron.

Fruit set of pears can be increased by cultural

management such as pruning, fertilization, and limb

positioning. The most effective practice is spreading

limbs to the 45° position with the trunk. Limb girdling 2 to 3 weeks after bloom also increases set but

may cause girdled area to be more susceptible to

winter injury. If used, girdling or scoring should be
22 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

1,000 done on limbs and not on main trunks or scaffolds

to avoid danger of winter injury.

Fruit set can also be influenced by applying

growth regulators. This work is still in the experimental stages, but holds considerable promise for the

future, especially on Anjou.

Figure 10.^Anjou pear yield (and average annual yield for 30

years) as related to distance from Bartlett pollinizers (from

Westwood and Grim, 1972).

Spaces From Pollinizer Row

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
PEAR PRODUCTION 23

the greater is the effect on improving the size of the

remaining fruit.

In some areas, particularly California, growers rely

solely on selective picking to supply the necessary

thinning. When pears of 2-3/8 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 1/8-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. This

practice is seldom used in Oregon or Washington.

Chemical Fruit Thinning

High labor costs have encouraged the use of chemicals for thinning Bartlett pears. The ideal practice is

to remove most of the excess fruit with chemical

sprays and use supplemental hand thinning to adjust

the fruit load. Quality of remaining fruit is improved

by hand removal of the small, marked, and misshapen fruit.

Fruit set and size of Bartlett pears have been determined after spraying with different rates of naphthaleneacetic acid (NAA) and naphthaleneacetamide

(NAAm). Both NAA and NAAm reduce fruit set

(table 8). NAAm is used at a rate of 10 to 15 p/m.

NAA is used at a rate of 15 to 20 p/m. The most

effective time of application is at 15 to 20 days after

full bloom. NAAm sometimes causes overthinning.

NAA usually will not cause overthinning. Chemical

thinning can increase size of remaining fruit by up to'

18 percent. However, the increase in size of the fruit

is generally small considering the earliness of thinning and the amount of thinning obtained (table 8).

The grower should know at hand-thinning time

which fruit will be large enough at harvest to satisfy

the market requirements. After chemical thinning

Table 8.-Fruit set and increase in size of remaining fruit after chemical thinning

of Bartlett pear orchards in 3 different years^

Orchard

Year, chemical,

and concentration (parts

per miUion)

First year:

Check

NAA 5

10

NAAm 10

20

Fruit

set^

Size

increment^

Size

Fruit Increset ment

Size

Fruit Increset ment

Size

Fruit Increset ment

Number Percent Number Percent Number Percent Number Percent

60

53

44

55

39

55

43

39

34

33

0

6

11

9

6

42

43

44

40

38

0

0

6

4

4

Second year:

Check

NAA 10

NAAm 15

45

35

25

0 51

5 35

12 25

0

7

15

60

40

22

0

11

11

60

40

25

0

4

15

Third year:

Check

NAA 15 .

NAAm 10 .

62

32

34

18

9

' Sprayed 14 days after bloom with NAA, naphthaleneacetic acid, or NAAm, naphthaleneacetamide

as indicated.

^Number of fruit per 100 blossoming clusters.

^ Based on 100 fruit measured at random from each of 5 trees per treatment.
24 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

and in light crop years, the tendency is to overthin

the remaining fruit and seriously reduce profits.

Many growers space-thin pears, using the same

spacing of 8 to 10 inches as used for apples, with the

assumption that a similar increase in size of

remaining fruit is obtained with pears as with apples.

Research on fruit growth after chemical and hand

thinning indicates that pears do not benefit from

thinning to the same extent as apples. Therefore, the

practice of heavy thinning by spacing of fruit to

increase fruit size should be avoided, especially on

young, healthy trees.

Size Thinning of Fruit and Harvest

Size Prediction

A method of predicting harvest size at thinning

time has been developed and is presented as a guide

for size thinning Bartlett pears. Table 9 is used for

predicting the final size of fruit at harvesttime. The

data are from 10 years of actual fruit measurements

at Wenatchee, Wash., and are useful in determining

which fruits will be too small to meet grade standards at harvest. If a 2-1/4-inch-diameter pear is

desired at a harvesttime of 125 days from bloom, the

fruit should be a minimum of 1.06 inches in diameter

at 60 days from bloom (table 9). If harvest date is

advanced to 110 days from bloom, the fruit should

be 1.26 inches in diameter at 60 days from bloom to

meet the desired harvest size of 2-1/4 inches. All

fruits smaller than these measurements should be

removed at thinning time. A small pear grows at

about the same rate as a large one, but because it is

small to begin with it will be smaller at harvesttime

regardless of the amount of thinning done.

The correlation between early fruit size and final

harvest size is very high. At 60 days after bloom, the

final size can be predicted to within one-eighth inch

in diameter 90 percent of the time. This close correlation is undoubtedly due to the uniform growth

rate of pears. Because of this close correlation, the

data in table 9 can be used as an excellent guide for

size thinning Bartlett pears. Some variation in results

will occur in different pear districts because of climatic differences and specific cultural practices such

as frequency of irrigation and fertilization. However,

adjustments can be made by the individual grower at

thinning time to allow for the effect of climate, high

or low tree vigor, and cultural practices on fruit

growth. For example, it may be necessary to leave

Table 9.-Harvest size predictions for Bartlett pears

Fruit size at designated days from full bloom

Size prediction period Harvest period

60 65 70 75 100 110 120 125

Inches in diameter

1.06 1.17 1.28 L37 1.87 2.04 2.19 2.25

1.17 1.28 1.39 1.49 1.98 2.15 2.30 2.36

1.26 1.37 1.48 1.58 2.10 2.27 2.43 2.49

1.34 1.46 1.57 1.68 2.22 2.40 2.55 2.62

1.43 1.55 1.66 1.78 2.33 2.52 2.68 2.74

1.51 1.63 1.75 1.87 2.44 2.63 2.80 2.87

1.63 1.75 1.87 1.99 2.56 2.76 2,93 3.00

1.75 1.87 1.99 2.11 2.68 2.88 3.04 3.12

only the fruit which is large enough at 60 days from

bloom to obtain 2-1/2-inch pears at harvest, rather

than smaller ones predicted to be 2-1/4 inches in

diameter. This would allow a margin of safety for

adverse growing conditions.

Hand thinning of Bartlett pears after 70 days from

bloom does not result in an appreciable increase in

size of the remaining fruit. Most of the benefit from

thinning at that time is in removal of cull fruit and,

in some cases, larger sound fruit to prevent limb

breakage. Contrary to popular belief, Bartlett pears

on healthy trees can be left in clusters of two or three

and still attain desirable quality and harvest size,

provided the tree is healthy and the limb will support

the fruit load. This can be done because improved

spray practices control insect pests, and the increase

in fruit size obtained from space thinning or thinning

to one fruit per spur is small.

Many growers are using size thinning to improve

quality and yield of pear fruit. On a given day, a

thinning crew can be given a sample fruit and

instructed to remove all fruit smaller than the sample

fruit and if necessary do some space thinning to

reduce limb breakage. This system prevents overthinning of trees capable of carrying and sizing heavy

crop loads.
PEAR PRODUCTION 25

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

pears growers. NAA has been effective for this purpose when used at a strength of 5 to 10 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.

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.

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 polyethylene 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 three-fourths

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 one-third 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 2-1/2

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
26 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Figure 11.—Important pear varieties of European origin: A, Anjou; B, Bartlett, C, Bosc; D, Cornice. BN-29825
PEAR PRODUCTION 27

the fruit is excellent. It is also an important variety in

New York and Michigan.

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 Kieffer. 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 commerical 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, because of its low cold requirement to

break dormancy, is an excellent variety for the lower

South. If planted in 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.
28 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Kieffer

Kieffer 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 diversity of soil

and climatic conditions. Its moderate fire blight

resistance makes it possible to grow this variety in

areas where many European varieties 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 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 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 possesses a high degree of fire blight

resistance and is well adapted to the middle and

upper South. Waite was introduced by USDA in

1938. Its fruit resembles that of Moonglow but is

smaller in size. The quality is fair to good. The seasons of Waite and Kieffer are the same. Waite

flowers are male sterile.

NEW VARIETIES

El Dorado

El Dorado orginated 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 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 will store

well at 30° F (-1.1° C) until April and May. Taste

tests indicate it has excellent quality.

The fruit is moderately free of blemishes and russeting and resists mechanical injury as well as Bartlett and Anjou. Shelf life for Eldorado is as long as

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 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 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.
PEAR PRODUCTION 29

Varieties Recentiy introduced

ARS introduced Magness, Moonglow, and Dawn

(fig. 12), which were developed at Beltsville, Md.,

from 8,000 seedlings of the pear-breeding program.

They were all derived from European varieties. All

three are moderately to highly fire blight resistant,

and the fruit are considered good to excellent in

quality. These varieties have not been widely 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 and highly fire blight

resistant; however, in Maryland trees have died from

trunk blight (fig. 23 Q. Magness is male 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 fire blight. Moonglow is 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.

Some more recent selections are red-fruited

mutants of the green or yellow pear varieties, and

other selections are from breeding programs of individuals and institutions. The following are the best

introductions and a description of them by storage

season:

Very Early Storage Season (Less Than 1 Month)

Starkcrimson is a red sport of Clapp's Favorite

with equivalent shape, quality, and handling as

Clapp's. It has an attractive red fruit with good

eating quality of melting texture and sweet juicy flavor. It blooms with Bartlett, but should be harvested

1 week before Bartlett harvest.

PN-5766

Figure 12.—Pear varieties released bv U.S. Department of Agriculture: A, Magness; B, Dawn; and C, Moonglow.
30 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Early Storage Season (2-1/2 to 4 Months)

Butirra Précoce Morettini is an Italian variety of

excellent quality, precedes Bartlett harvest by a

week, but stores as long as Bartlett (2-1/2 months).

The fruit is about 2-3/4 inches in diameter and pyriform in shape with a bright, blushed, yellow skin.

The fruit should be picked at 15 to 17 pounds pressure. When ripened, it has a melting texture and tart

flavor (soluble solids 14 percent). The tree crops well

and regularly with cross pollination.

Butirra Rosata Morettini is an Italian variety with

slightly less quality than Précoce Morettini, but is

harvested during Bartlett season at 15 to 17 pounds

and stored 2-1/2 months. It is larger (3 inches in

diameter) and coarser in texture but handles better

than Bartlett or Précoce.

Sensation Red Bartlett or Mock's William is a redfruited sport of Bartlett with similar characteristics

to the Max's Red Bartlett except that fruit quality,

skin color, and handling are superior. Reversion to

green Bartlett has not been as likely as with Max's

Red.

Rosired Bartlett is another red sport of Bartlett

with similar characteristics except with a solid

maroon skin. Harvesting should be made about 1

week after Bartlett.

Reimer Red is a Comice x Max Red Bartlett

hybrid developed by Reimer in the Rogue River Valley. To keep well in storage through December, the

red blush fruit should be harvested at time of late

Anjou or early Comice harvest. The fruit is pyriform

in shape, 2-1/2 inches in diameter, and juicy and

sweet (soluble solids 15 percent). The tree crops

moderately and regularly.

California (Max Red Bartlett x Cornice hybrid)

came from the University of California at Davis

breeding program. To keep well in storage through

December, the fruit should be harvested at 15 to 18

pounds pressure at time of Bartlett harvest. Fruit

diameter is 3 inches, and fruit shape is variable, oval,

obtuse, and pyriform. The fruit skin has a green

ground color at harvest, which becomes yellow with

red blush whenripe. The texture, juiciness, and

soluble solids (15 percent) are similar to Comice.

Bloom occurs slightly earlier than Bartlett.

Midstorage Season (5 Months)

Butirra di Roma is an Italian variety of excellent

quality with a blushed yellow skin. The fruit is about

2-3/4 inches in diameter with a pyriform shape if

picked at time of Bartlett harvest at 16 to 18 pounds

pressure. The fruit is moderately resistant to abrasive

marks, making handHng comparable to Bosc. The

fruit is melting with some grittiness, juicy, and sweet

(soluble solids 14 percent).

Red Comice is a red fruit mutant of Comice. It has

the same characteristics as Comice except with

slightly longer fruit with red stripes. Red Comice has

been compatibly grafted on quince rootstock.

Late Storage Season (8 months)

Red Anjou is the red sport mutation of Anjou

with the same fruit characteristics except with a solid

red skin. The fruit is small (2-1/4 inch diameter) if

picked during Anjou harvest for late storage, but

Red Anjou can be picked 2 weeks later for better size

at the expense of a shorter storage. Red Anjou trees

have lacked vigor like some of the other red varieties.

Rogue Red (Comice x Seckel x Farmingdale

hybrid) was developed by the Southern Oregon

Experiment Station. Rogue Red fruit is as sweet as

(soluble solids 17 percent), but drier and grittier than

Comice and can be kept in storage as late as Anjou.

The red blush fruit varies in shape and is large (3

inches in djameter). Rogue Red can be picked during

Comice and Bosc harvest at 13 to 15 pounds pressure. Harvests of Rogue Red are generally improved

with cross pollination. Rogue Red is compatible on

quince. Bloom occurs at some time between that of

Anjou and Bartlett, or later.

Asian Pears

Asian pear varieties from China and Japan are P.

serótina and P. ussuriensis or their hybrids. Several

have been tested and grown throughout a number of

U.S. regions. These pears are called "apple-pears" in

the U.S. markets because the fruit is aromatic, crisp,

juicy, and sweet, and the subacid flavor is unlike

"European" pears. The trees of these "Oriental" varieties are quite resistant to fire blight and bacterial

canker, but the Japanese varieties are more attractive

to pear psylla than are the Chinese varieties.

The major variety grown in Yakima and in the

Sacramento Valley is Nijisseiki (Twentieth Century),

which is harvested in early September and can be

stored at temperatures above 32° F (0° C) for

several months. The fruit is round and has pale, yellow, waxy skin. A few promising varieties, which

could replace Nijisseiki, have been tested and grown

in Japan and the west coast of the United States.

Two varieties are Shinseiki (New Century), which is

smaller fruited and matures 10 days earlier, and
PEAR PRODUCTION 31

Chojuro, which has the same shape, size, and harvest

date as Nijisseiki but with russetted skin.

Of the Chinese varieties tested in Cahfornia and

Oregon, Tsu Li and Ya Li show the most promise.

Tsu Li has a large (3 inches in diameter), blocky.

pyriform, Hght-green fruit with russetted lenticels. It

matures in early October and can be stored for 5

months in above-freezing temperatures. Ya Li is similar but smoother and more pyriform. Trees of both

varieties have been vigorous and productive.

PEAR INSECTS

Pears cannot be grown profitably on a commercial

basis without adequate control of insect and mite

pests. Before satisfactory control measures can be

applied, the pest species must be identified. Because

control programs may change rapidly and should be

adapted to conditions present in your growing area,

information on specific control programs, trapping,

and other pertinent information should be obtained

from a licensed pest control consultant, county agricultural agent, or personnel of the State agricultural

experiment station or the USDA.

Codling Moth

One of the most serious insect pests of pears is the

codling moth (Laspeyresia pomonella (L.)), which

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 larvae burrow into the fruit, either through

the stem or calyx ends 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 larvae 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 larvae in cocoons

under the loose bark of trees (fig. 13), in cracks, crevices, or bark wounds, and in litter on the ground. In

the spring the larvae pupate, and in a short time the

adult moths (fig. 14) begin to appear, usually soon

after 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 (15.6° C). They hatch in 6 to 14 days,

depending on the temperature, and the larvae feed in

the fruit for 3 weeks or longer. In 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 l\/loth

The oriental fruit moth {Grapholitha molesta

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

PN-5767

Figure 13.—Codling moth larva and pupa in cocoons.

Figure 14
32 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

of the United States. It attacks pear as well as other

deciduous fruits. The pinkish-white worms burrow

into the fruit in much the same way as those of the

codling moth, and they cannot be readily differentiated. These pests hibernate in cocoons as fullgrown 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. Sex pheromone baited traps are also available for the oriental fruit moth. These traps can be

useful in a manner similar to that for the codling

moth.

Leafrollers

Several species of leafroller moths attack pear fruit

in various areas of the United States. In recent years,

infestations of the fruittree leafroller {Archips

argyrospilus (Walker)) have become more common

in western pear orchards. Fruittree leafrollers overwinter as egg masses on the twigs and limbs. The

eggs hatch in early spring and the young larvae feed

on leaves, tying them together or folding over an

edge of a single leaf and tying it down with silk. The

larva lives within the tunnel thus created. The adults

emerge in late spring or early summer depending

upon geographic location and lay eggs which will

give rise to the second generation. Damage caused by

the feeding of the larvae on the fruit consists of deep,

irregular holes with rough scar tissue. Young fruits,

which are fed upon, may remain small and become

misshapen.

The redbanded leafroller (Argyrotaenia velutinana

(Walker)) is primarily a pest of apple in the Eastern

United States but will also attack pear. Redbanded

leafrollers overwinter as pupae within a folded leaf in

the ground cover. Adults emerge in mid- to late

spring, and the eggs are laid in masses on the trunk

and scaffold branches shortly after emergence. The

larvae feed on both leaves and fruit. Damage caused

to the fruit is similar to that caused by the fruittree

leafroller. Two full generations are produced in New

York.

Treatments applied for control of codling moth

usually will also control leafrollers. Where standard

control programs are modified, a treatment at petal

fall may have to be applied for control of these pests.

Sex pheromone baited traps are available for some

of these leafrollers, and when properly used they can

furnish information on presence of a given species,

occurrence and timing of flights, relative abundance,

and effectiveness of control programs.

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. Honeydew secreted by these insects runs down over the

foliage and fruit, and a sooty fungus grows in it. This

causes the skin of the fruit 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 pyslla

is associated with the development and spread of

pear decline disease.

Pear psylla adults (fig. 15) have somewhat the

appearance of miniature cicadas, with transparent

wings sloping over the body. They are about oneFigure 15.—Pear psylla adult.

BN-29814
PEAR PRODUCTION 33

tenth inch long and dark reddish brown. They can

fly suddenly from where they are resting, giving the

impression 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 (4.4° C).

The elongated whitish or yellow eggs are deposited

in March or sometimes earlier in small crevices

about the buds and hatch in 10 to 30 days. After the

foliage is 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 flattened and soon cover themselves

with the honeydew they secrete. After going through

four successively larger stages and becoming greenish, they reach the last, or "hard-shell" stage (fig. 16),

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 {Quadraspidiotus perniciosus

(Comstock)) may cause serious loss of pears if not

controlled, for it infests not only the bark and foliage

but also the fruit (fig. 17). The scale occurs in most

pear-growing areas and has a wide host range,

including many ornamental trees and shrubs as well

as deciduous fruit trees. Trees may be partially or

entirely killed by heavy infestations. Under light

infestations, damaged fruit can be culled out.

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. There are two or

more generations a year.

In the Pacific States, the dormant or delayed dormant sprays are most important in control of San

Jose scale. In heavy infestation situations, one or two

sprays, in addition to the dormant or delayed dormant stages and directed towards the crawler stages,

should be applied when crawlers are active in the

summer.

In California, pears may be infested with the

Italian pear scale {Epidiaspis leperii (Signoret)),

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 (Cockerell)) and the European

fruit lecanium (L. corni Bouche), attack pears in California, and the latter may occasionally be found in

the Northwest. They are 1/8 to 3/8 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.

The cottony maple scale {Pulvinaria innumerabilis

(Rathvon)) sometimes becomes a pest on Winter

Nelis and Anjou, but is seldom seen on Bartlett. Cottony maple scale 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, 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 used 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, but good control can be achieved by properly

timed and applied sprays directed towards the

crawlers in spring and summer.
34 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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. 18), the two

spotted spider mite {Tetranychus urticae Koch), the

McDaniel spider mite {T.mcdaniel McGregor), and

the yellow spider mite {Eotetranychus carpini borealis (Ewing)). The first two winter in the egg stage on

Figure 16.—Pear psylla nymphs: A,— E, Young stages; F, fifth, or "hard shell" stage on pear twig. BN-29822
PEAR PRODUCTION 35

which the mites live. Damage usually first appears on

the foliage as blisters; feeding on the fruit before and

during the blossom period produces depressed, russeted spots. The postharvest and delayed-dormant

stages are the best times to apply sprays for control

of the pearleaf blister mite. While early postbloom

sprays also help to control infestations, sprays

applied at this stage may be too late to prevent injury

to the fruit and foliage.

The pear rust mite is an important pest of pears in

most areas of the West. These mites overwinter

behind loose bud scales or in crevices in the bark.

They become active in the spring as new plant

growth develops and feed on leaf surfaces and on the

fruit. Infested foliage bronzes as the mites feed; on

fruit, damage takes the form of a smooth russeting of

the skin, usually first appearing below the calyx later

spreading over the fruit surface. Detection of rust

Figure 17.—Pear infested with San Jose scale.

BN-29821

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 spider mites winter as bright-yellow or orange

adults under bark scales and in debris on the ground,

migrating to the buds or new foliage as soon as it

develops, 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. 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 these mites is primarily to the

foliage, which becomes bronzed in appearance;

defoliation may occur and seriously interfere with

the normal development of the fruit.

Two other much smaller mites live on pear—the

pearleaf blister mite {Eriophyes pyri (Pagenstecher))

(fig. 19) and the pear rust mite {Epitrimerus pyri

(Nalepa)). Neither can be seen easily without a hand

lens. The pearleaf blister mites winter under bud

scales, and the young of the new generation form

characteristic blisters on the unfolding leaves in Figure 18.—Brown mite adult.

BN-29810
36 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

BN-29816

Figure 19.—Adult of pear leaf blister mite.

mites before fruit injury occurs requires careful

examination of buds, leaves, and fruits with a highpower hand lens or under a dissecting microscope.

As with the pearleaf blister mite, the postharvest

period is the best time to apply control measures.

However, delayed-dormant, prepink or summer

sprays may also be required to prevent damage to

the fruit.

Sucking Bugs

Several kinds of sucking bugs may attack pear

fruit. Among these are lygus bugs (Lygus spp.) (fig.

20). 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 stink bugs, including the consperse stink bug {Euschistus conspersus Uhler) and

Say's stink bug {Chlorochroa sayi Stal), are somewhat larger, about one-half inch long and shield

shaped. The consperse stink bug is gray- brown and

covered with small black dots whereas Say's stink

bug is bright green covered with white dots.

Infestations of these sucking plant bugs are usually

local and may occur anytime during the season.

Thrips

The pear thrips ( Taeniothrips inconsequens (Uzel))

is usually held in check by control measures used

against other pests. These insects are about onetwenty-fifth inch long, slim, and dark brown. The

adults may be found in the opening buds, where they

Figure 20.—Lygus bug.

BN-29818

may prevent the blossoms from producing fruit.

Later, the white larvae feed on the developing pears

and cause russeting. Several other species, the bean

thrips (Caliothrips fasciatus (Pergande)) and the

western flower thrips {Frankliniella occidentalis (Pergande)), are occasional pests of pear in some areas of

California. While the pear thrips and bean thrips

have not been considered major problems in recent

years, significant changes in pest control programs

could result in the reappearance of these thrips as

pests.

Other Insects

The orange tortrix (Argyrotaenia citrana (Fernaid)) sometimes occurs on pears, particularly in the

coastal districts of California. The active, greenish,

black-headed caterpillars of this leafroller moth feed

on the surface of the fruit. There are several generations a year.
PEAR PRODUCTION 37

The plum curculio (Conotrachelus nenuphar

(Herbst)) is an occasional pest of pear in the Eastern

United States. This weevil overwinters as an adult in

fallen leaves and other debris in and around

orchards. The adults become active in early spring

and feed upon flowers, leaves, buds, and developing

fruits. The eggs are laid in the fruit, and the developing larva feed inside. Damage consists of deformities caused by egg deposition punctures and

feeding holes in the young fruit and feeding holes in

mature fruit. In the northern areas, there is only one

generation per year while there may be several in the

southern areas.

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.

The pearslug {Caliroa cerasi (L.)) (fig. 21) 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 a tentiform leaf miner

{Lithocolletis sp.), the California pear sawfly {Pristiphora abbreviata (Hartig) (fig. 22), 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 {A. pomi DeGeer), the green peach

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

(A. fabae Scopoli). Control of aphids is usually not

difficult.

The shothole borer {Scolytus rugulosus (Ratzeburg)) may also be found in pear trees, usually

BN-29827

Figure 21.—Pear-slug and its injury.

those in poor condition. The American plum borer

(Euzophera semifuneralis (Walker) and the Pacific

flatheaded borer {Chrysobothris mali 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 2-1/2 inches long when full grown.

The buffalo treehopper {Stictocephala bubalus (F.))

and 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. 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.
38 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Figure 22.—California pear sawfly: A, Injury to leaf; B, egg in tissue and young larva feeding; C, full-grown larva.

BN-29811

The disease was first recorded in the Hudson River

Valley of New York in 1780. Nearly 100 years later

the bacterium, Erwinia amylouora, was found to be

the causal agent.

The disease usually appears first as a blossom

blight (fig. 23 Ä). Later, infection spreads to shoot

growth and developing fruit (fig. 23 B). The blossomblight symptoms are confused in some areas with

those caused by Pseudomonas syringae. 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 usually

remain firmly attached to the tree. Under favorable

conditions, the bacteria move very rapidly. If left

unchecked, they advance from the blighted blossoms

to the main branches, down the trunk (fig. 23 C) and

into the roots. In Beltsville, Md., many Magness

trees have died from blight that started in the trunk

and later girdled the entire tree. The bacteria may

overwinter in cankers, which may act as inoculum

sources the following spring. Affected parts often

produce droplets of clear, milky, or amber-colored

exúdate. Numerous bacteria, contained in the

exúdate, are readily disseminated to susceptible

tissue by insects.

Insects disseminate the bacteria. Honey bees contaminate their bodies by visiting blighted blossoms

and are often responsible for carrying the pathogen

from blighted to healthy flowers. 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. Injury caused by hail apparently provides entry points 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 innoculum and protect

susceptible tissue.
PEAR PRODUCTION 39

PN-5768

Figure 23.—Fire blight of pear: A, Severe blossom blight; B, advanced fruit blight, showing typical water soaked margin along necrotic

area with many ooze droplets; and C, characteristic streaking on tree trunk, resulting from profuse production of bacterial ooze.

Control usually necessitates removal of all infected

spurs and branches as soon as they appear. Affected

areas on large branches, crotches, trunks, and roots,

should be removed immediately, regardless of size, to

prevent spread to healthy parts of the tree. Cuts

should be made well below the infected areas to

insure removal of all tissue which might contain fire

blight bacteria. In these operations, cutting tools

should be disinfected between each cut to prevent

possible transmission of the causal organism.

Mercury compounds are no longer allowed for use

as disinfectants. Household chlorine bleaches containing 5 percent sodium hypochlorite diluted to onetenth of the proprietary strength, are more convenient, easy to obtain, and satisfactory. However,

sodium hypochlorite is extremely corrosive to metal.

Other disinfectants include various denatured alcohols. Pruning tools are either dipped or wiped 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.

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. Overstimulation of growth

by fertihzation should be avoided.

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. 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
40 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

especially sensitive to copper, and in recent years

antibiotics have provided more satisfactory control

on this variety.

Streptomycin has provided very effective control

of fire blight in Oregon and California on the highly

susceptible variety Forelle. In Maryland, a 6-year

field study showed that, under epiphytotic blight

conditions, fire blight in Bartlett pears could be controlled with streptomycin. However, resistance to

antibiotics has been reported and local authorities

should be consulted before using them for fire blight

control. No single practice will control fire blight,

but a combination of all available practices will

undoubtedly reduce damage.

Most of the commercially grown pear varieties are

susceptible to fire blight. More than 100 species of

the family Rosaceae are hosts of the disease. However, sources of resistance are known 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 highquality 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. A comprehensive review of

fire blight was recently completed and is included in

the selected reading material listed in back of this

handbook.

Pseudomonas Blight

Another frequently troublesome bacterial disease

of pears is caused by Pseudomonas syringae (fig. 24).

This disease has been known by many names,

including blossom blast, lilac blight, false fire blight,

and Pseudomonas blight. The latter 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.

Bacterial ooze is not normally associated with

infection by P. syringae, but an unidentified fluoFigure 24.-

BN-29820

Pseudomonas canker on stem of young Bartlett tree.

rescent Pseudomonas sp. was isolated from infected

pear buds in 1969 by researchers in Beltsville, Md.

Therefore, this characteristic is no longer a reliable

means of separating fire blight symptoms from those

of Pseudomonas blight.

In California, Pseudomonas blight is reported to

cause brownish streaks, which extend 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. In apple, however, it was observed in

New York that discolored streaks extended in the

xylem in advance of externally visible lesions following artificial inoculation. Although P. syringae

has commonly been associated with pear trees, the

most crucial period for protection of the plant

against invasion by the bacterium has not been

established. The literature on P. syringae suggests

that both spring and fall infections occur. Systemic
PEAR PRODUCTION 41

invasion of the tree may result from infection at any

time and pathogenic P. syringae bacteria have been

isolated from apparently healthy pear trees. Systemically infected trees make control measures extremely

difficult. Therefore, young trees must be adequately

protected during periods of cool, wet weather

because these conditions are most favorable for disease development.

Control of the disease in the Pacific Coast States

has been based on the theory that most of the infection occurs in 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.

Early spring sprays, applied while the trees are still

dormant, may also be helpful. However, their use

should be restricted to young, nonbearing trees to

avoid injury to the fruit of copper-sensitive varieties.

Antibiotic sprays have not proven successful, and

treatments more effective than copper are needed.

Symptoms of Pseudomonas blight typically begin

as one or more minute, black lesions on the flower

parts. The lesions enlarge, turn black very rapidly,

and often coalesce to form larger necrotic areas. In

contrast, infections which result from invasion by

fire blight bacteria begin at the nectiferous tissue of

the flower and spread rapidly through the calyx cup

and into the receptacle. They continue to move rapidly into the spurs and branches. The affected parts

develop a dark-green, water-soaked appearance, but

later become dark brown and often appear shiny as

the bacterial ooze dries on the surface of the infected

tissue. Calyx cup infections due to P. syringae are

common and may occur independent of blossom

blast.

Both Pseudomonas blight and fire blight are

favored by moist conditions, but optimum temperatures for disease development vary markedly.

Fire blight is generally favored by higher temperatures than Pseudomonas blight, and exposure of

pear blossoms to frost has been shown to cause a

marked increase in their susceptibility to P. syringae.

Conversely, fire blight development is delayed by the

intervention of frost during the blossom period. The

differential response to frost may help explain the

often sporadic development of these two diseases in

fruit-growing areas.

Scab

Scab, caused by Venturia pyrina (fig. 25), is an

important disease of pears in some areas of the

BN-29819

Figure 25.—Pear scab.

United States, and when control measures are not

practiced, losses are high. Its severity is dependent

upon environmental conditions and spore carryover

from the previous year.

The general appearance of pear scab is similar to

apple scab, a disease caused by the closely related

fungus V. inaequalis. 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 harvest time. 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. This corky

area is commonly surrounded by sooty patches of

active scab at the edge of the lesion.

Leaves often display dark, velvety patches of the
42 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

fungus similar to those found on the fruit. These

spots are generally more prevalent on the lower leaf

surface, although spots on the upper surface are also

common. Leaf lesions are often found along the midrib, and as the affected part ceases growth, puckering

and twisting com^monly occur. Leaves infected 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 harvest may appear normal,

but often 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 and in infected twig lesions. 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.

Continual moisture is necessary for spores to germinate and cause infection. At the optimum temperature (75° F or 23.9° C) for growth of the pear

scab fungus, a continual wet period of 5 hours is adequate for the infection process to proceed. At higher

or lower temperatures, a correspondingly longer continuous moist period is necessary at 40° F (4.4° C),

48 hours is required to establish infection. An incubation period of 12 to 25 days is required for the

fungus to become visible to the naked eye. This

accounts for the appearance of the disease at times

which may appear unfavorable for its development.

All commonly grown commercial pear varieties

are susceptible to scab. Bosc fruits are very susceptible in the immature stages, but become

highly resistant after they have shed their

pubsecence. It is not uncommon for a variety to

be severely affected in one area and only lightly

affected in another. This may be due to the existence of fungus strains which vary in their pathogenicity. The occurrence of such strains has been

reported in the United States and thus would

account for 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 m the dormant period just as

buds begin to swell. Lime sulfur, ferbam, and

dodine are fungicides most commonly recommended during the early spring and into the

growing season. Dodine has been more effective

and less injurious than other materials after the

dormant spray. Reports of apple scab fungus

resistance to dodine are common, and the occurrence of similar resistance by the pear scab fungus

would not be surprising. Local authorities should

be consulted before planning a spray program to

determine which control methods and materials

have provided satisfactory control in any given

area.

Root Disorders

Various root diseases are found in most peargrowing 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 was reported on pear trees

in British Columbia in 1959 where it was shown that

P. cactorum was the causal agent. More recently, it

was demonstrated that two other species of Phytophthora {P. cryptogea and P. cambivora) were

capable of infecting pear rootlets. Research in

Oregon showed that P. cinnamoni was pathogenic

on pear roots.
PEAR PRODUCTION 43

Trees infected by species of Phytophthora are

characterized by generally poor growth. Those

attacked by P. cactorum may eventually die because

of a girdUng of the trunk at or below the ground line.

P. cinnamoni kills young feeder rootlets, but is not

pathogenic on the larger roots and crown tissue.

Nursery stock infected with Phytophthora often

results in a high percentage of unthrifty trees, which

commonly produce little or no growth for several

seasons after planting.

Although differences in varietal susceptibility have

been observed, little information on the subject is

available. Oregon reports indicate that a lower percentage of infection occurs in Old Home, Old Home

X Farmingdale seedlings, and Pyrus calleryana 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. The area adjacent to the

trunk should be kept free of weeds and debris so that

rapid drying will occur after rain or irrigation. However, these practices would be of little value where

young rootlets are rotted by P. cinnamoni.

In Washington, where collar rot is frequently a

severe problem in pear orchards, soil should be temporarily removed from the crown area of infected

trees in early spring. This practice may check the

progress of collar rot and enhance recovery of the

tree if it is completed during the early stages of infection. The soil should be replaced as the trees enter

the dormant season to reduce exposure of the crown

area during the winter months. Irrigation should be

carefully managed during the growing season, and

extended wetting of the crown should be avoided.

Successful control of collar rot depends primarily on

the maintenance of well-aerated soil and prevention

of free-water accumulation. Chemical control of

collar rot has met with little success but treatment of

the crown area with copper sprays or paints has been

recommended. Although the fungus is especially sensitive to copper, these treatments should not be

repeated at frequent intervals because copper may

accumulate in the soil and cause phytotoxicity.

Armillaria root rot, also known as oak root fungus, crown rot, and shoestring root rot, is caused by

the fungus Armillaria mellea. The disease is not generally considered an economic problem, 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 resistant rootstocks are not used in commercial pear growing 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 infected hosts previously occupied the

area.

Powdery Mildew

Powdery mildew of pears is caused by Podosphaera leucotricha. Although this fungus is more

common on apples, 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, fluffy 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. The

optimum temperature for disease development is 70°

F (21° C). Most fungi require free water for spore

germination and continued development, but water

inhibits germination and growth of the pear powdery

mildew fungus. However, relative humidities between

95 and 99 percent do favor this disease.

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
44 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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, sulfur fungicides may

reduce fruit set of Anjou when applied after the buds

begin to open in the spring.

Dinocap is more commonly used for control of

powdery mildew of pears, but recommendations of

local authorities should be followed closely. Under

no circumstances should dinocap be applied during

the full-bloom period because this fungicide may

interfere with pollination. Sprays to control powdery

mildew should be applied immediately after petal

fall. In the Pacific Coast States, two spray applications at a 10 to 14-day interval should provide economic control of the disease and reduce fruit russet

due to fungus infection, unless conditions are

extremely favorable for powdery mildew development. Spray recommendations in Oregon include

a combination of dinocap, dodine, and streptomycin

during the postbloom period to control powdery mildew, scab, and fire blight. Serious fruit damage may

result from the use of dinocap plus streptomycin

during the postbloom period if dodine is omitted

from the combination. Therefore, dodine should

always be included in the mixture, even if scab is not

a problem.

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 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.

Symptoms usually appear in August as indefinite,

angular, brown to grayish spots without definite outline and follow the areas between major veins. Severe

infection by C. minima may defoliate pear trees.

Ferbam sprays control early blight and should be

applied when the spots begin to appear in April, followed by one or two sprays 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.

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. 26). This disorder occurs almost exclusively on trees propagated on oriental stock. It is

generally attributed to unfavorable water

relationship within the plants and fruits. The ability

of the Japanese rootstock to supply water to the

scion is reportedly less than 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 7).

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 (fig. 27). Such pears are

unmarketable. Frequently, insufficient symptoms on

the surface prevent detection when the fruit is

graded.

PN-6365

Figure 26.—Bartlett pears showing two stages of hard end disorder: Left, Normal; Center, hard end; right, black end. After

Ackley; see "Suggested Supplemental Reading."
PEAR PRODUCTION 45

Figure 27.—Cork spot of Anjou.

BN-29829

Cork spot is more serious when trees are propagated on oriental roots. Relatively light crops of

large fruits are more prone to develop the disorder.

In this respect, cork spot 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.

Virus Diseases

Virus diseases are a major threat to the pear

industry and losses may take various forms. The

overall effects of virus infection in pear trees often

involve a reduction in tree vigor, fruit quality, and

yield. Virus diseases of pear have not been studied as

thoroughly as those of stone fruits and apples, but

various investigators have shown that several viruses

attack pears and present serious problems for pear

growers.

Stony pit was the first virus described on pear

trees. Many other virus-induced diseases of pear

have since been reported, including those which

cause leaf mosaics, bark disorders, and fruit blemishes. More recently, several latent (symptomless)

virus diseases of pear have also been described.

Pear vein yellows is probably the greatest threat to

the pear industry because it is widely distributed,

severely affects young trees, and causes a significant

reduction in yield. A 13-year study in England

revealed that trees infected with pear vein yellows

produced 30 percent less fruit than healthy trees. A

40-percent yield reduction occurred when trees were

infected with both pear vein yellows and ring pattern

mosaic (apple chlorotic ring spot). Several latent

viruses have also been reported in pear trees. Viruses

in this group produce no detectable symptoms in

pear, but when isolated from pear and inoculated to

indicator hosts, produce symptoms which are readily

recognized. Although pear decline was previously

described as a virus disease, it is now believed to be

caused by a mycoplasmalike organism and will be

discussed separately.

Transmission of pear viruses by insect or nematode vectors is sometimes offered as an explanation

for apparent spread of these diseases in the field.

However, no experimental evidence has been

reported to confirm these observations. Because vegetative propagation is the only proven method of

transmitting virus diseases from one pear tree to

another, extreme care should be exercised in the

selection of material for this purpose. Although

reports of seed transmission of pear virus diseases

have appeared in the literature, they are not confirmed by further experimental evidence. The following descriptions of several pears viruses should be

helpful in recognizing these diseases as they exist in

the orchard. It is not intended as a complete list of

all virus diseases on pears.
46 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

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. The abnormal 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 branch of an infected tree and among individual trees in an orchard. Symptom severity may

vary from one year to the next on an individual tree,

but the relationship of symptoms from tree to tree

will usually remain constant. Stony pit symptoms

should not be confused with those caused by the tarnished plant bug {Lygus lineolaris), cork spot, or

boron deficiency.

Chlorotic flecking, leaf banding, and rough bark

symptoms have also been associated with stony pitinfected trees. However, in most cases, these symptoms probably are caused by other viruses, which

may occur concurrently with the stony pit virus.

Bosc is the most severely affected, but symptoms also

appear on Anjou and other varieties. Although Bartlett fruits rarely display stony pit symptoms, they

have been observed on this variety in Oregon and

California. This suggests the possibility of a new

strain of the virus, since it has been common practice

to topwork infected Bosc and Anjou trees to Bartlett.

This recommendation was made when it was discovered that Bartlett did not express stony pit symptoms

following budding or grafting of trees severely

infected with the virus. The maintenance of a virus

reservoir in the orchard is not good management,

and infected trees should be replaced as soon as

practical. No method for reducing the severity of

symptoms or curing infected trees in the orchard is

known.

areas develop red coloration due to necrosis of the

cells. Whether this is caused by a strain of vein yellows or is the result of infection by two different

viruses is uncertain. Sources of vein yellows without

red mottle have been discovered, but no material has

been found to be infected with red mottle and free of

vein yellows. Local environmental conditions have a

marked influence on symptom expression in pear

trees infected with the virus. Although seed transmission was reported for this disease, it has not been

confirmed. Only grafting techniques are well documented as methods of transmission of the virus.

Most of the commonly grown commercial varieties

are susceptible, but do not display symptoms of

equal intensity. Various surveys have shown that

pear vein yellows is widely distributed in commercial

pear plantings in the United States and other countries. The substantial reduction in yield caused by

pear vein yellows infection makes this disease of

great economic importance to pear growers.

Pear ring pattern mosaic is caused by the same

virus that induces the disease in apples known as

apple chlorotic leaf spot. Infected trees produce

leaves that are characterized by light-green to greenish-yellow rings and lines. The symptoms usually

occur near the main or secondary veins, but most

often appear completely at random over the leaf surface. The leaves of some of the more sensitive cultivars may be twisted or curled. Only rarely do symptoms occur in the fruits as faint green rings. No

deformity of the fruit or damage to the flesh has

been observed.

Transmission of the virus is readily accomplished

by budding or grafting, and probably all pear varieties are susceptible. Surveys in The Netherlands

indicated that 20 to 23 percent of pear trees tested in

1963 were infected with pear ring pattern virus. A

survey conducted in Washington 10 years later did

not reveal a single infected tree. The disease does not

appear to spread in the field, and no effect on yield

has been observed; however, it may reduce the grade

in cultivars which develop symptoms on the fruit.

Leaf Mosaics

Pear vein yellows virus causes chlorotic bands to

form along the smaller veins of infected leaves. Usually, only short sections of the veinlets are affected,

and the symptoms are most pronounced during the

scion's first year of growth. Mature trees do not ordinarily display symptoms. Red mottle virus of pear

causes similar symptoms except that the affected

Other Virus Diseases

Several virus diseases of pear which cause disorders of the bark have been reported. Pear bUster

canker in England, pear rough bark in Norway, and

pear bark measles in the United States cause similar

symptoms in pear trees. All are transmissible from

pear to pear. Although no comparative studies have

been reported, these diseases may all be caused by
PEAR PRODUCTION 47

the same virus or possibly by different strains of a

single virus. The extent of damage caused by bark

canker diseases is not known, but infected trees are

typically poor producers and their growth is

restricted.

Symptoms first appear as small blisters on the

bark of 1- to 2-year-old stems during early spring.

The bark later splits and cracks as the lesions enlarge

and coalesce to form larger cankers. Young trees

often succumb to attack by this virus. Those that

survive for 3 years usually continue to grow, but may

be stunted and unproductive.

These diseases are readily transmitted by budding

and grafting. Therefore, it is essential that stock and

scion varieties be virus free. Contrary to the reported

seed transmission of pear bark measles, this theory is

not generally accepted. Control measures for trees

infected with the virus are not known.

Although other virus diseases have been reported

on pears throughout the world, they either do not

occur or are not of economic importance in the

United States and will not be discussed here. Several

latent virus diseases in pear have been demonstrated

by indexing on suitable indicator plants. Very little

information is available on the effects these viruses

may have on their pear hosts, and they are not considered of practical importance to the commercial

pear grower.

Disease Caused by Mycoplasmalike

Organisms

Pear Decline

Although pear decline was previously described as

a virus-induced disease, it is now known that a

mycoplasmalike organism is the causal agent. Like a

virus disease, this pathogen can be moved from pear

to pear by budding and grafting. However, success

by this means is generally low. The pear psylla

{Psylla pyricola) can transmit the disease, and pear

decline has historically followed introduction of this

insect pest into pear-producing areas. The disease

was first recognized in central Washington about

1946 and was reported in British Columbia in 1948.

During the next 10 years, pear decline spread to all

pear-growing areas of Washington and was reported

in Oregon in 1957. By 1959, it had moved to California. It spread rapidly in all these areas and thousands of trees were lost. Because pear decline causes

the most severe reaction on trees grown on oriental

rootstocks, the areas where these rootstocks were

widely planted suffered the most severe losses.

The symptoms of pear decline parallel those of

moria disease in Italy and the two diseases are

probably identical. The causal agent was probably

introduced into the United States on symptomless,

nonsensitive stocks, where it may have existed for

some time in the absence of a suitable vector. After

establishment of the pear psylla in British Columbia

and its subsequent migration to Washington, pear

trees planted on sensitive oriental rootstocks readily

developed pear decline symptoms.

Symptom expression on infected trees is also

directly related to the sensitivity of the rootstock and

to cultural care. Heavy infestations of pear psylla

accentuate disease symptoms, while horticultural

practices, which tend to reduce stress to the tree, generally result in less symptom expression.

Unlike diseases caused by viruses, control of the

pear decline complex has proven feasible through the

use of antibiotics. In California, over 300,000 trees

are treated annually with oxytetracycline hydrochloride. The antibiotic is administered by transfusing it through small holes drilled into the trunk.

Severely infected trees have been restored to normal

or near normal condition following two to three

annual postharvest treatments. This control method

should not be used without first consulting experienced and qualified applicators. Oxytetracycline

HCl, like other pesticides, must be registered for use

on pears by State and Federal agencies before it can

be legally used on pear trees.

Pear decline disease is characterized by the following three basic syndromes: quick decline or tree

collapse, slow decline, and leaf curl. Both rapid and

slow tree decline result from damage to the phloem

tissue at the union of the stock and scion and are

usually associated with trees on Fyrus serótina or P.

ussuriensis rootstocks. Pear trees on the more tolerant P. communis, P. betulaefolia, and P. calleryana rootstocks usually develop leaf curl symptoms

when infected with the pear decline organism. Leaf

curl is characterized by leaves which curl downward

from tip to midrib, develop a reddish to purple cast,

and drop prematurely. Infected trees display leaf curl

symptoms in late summer or early fall, well before

healthy trees develop normal fall color. Other characteristic symptoms include poor shoot and spur

growth and smaller leaves, which are typically rolled

upward along the longitudinal axis. Infected trees

normally produce fewer and smaller fruit than
48 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

healthy trees and often develop extensive dieback of

the branches.

Recent studies in California indicated that reduction in vigor of leaf curl infected trees may be due to

causes other than stock scion incompatibility.

Reduced translocation of soluble carbohydrates from

the leaves was noted and may explain reduced vigor

and productivity, as well as the difficulty often

encountered in establishing young trees.

HARVESTING AND HANDLING

To attain highest quality, pears must be harvested

before they are ripe. However, if picked when too

immature, they are undersized and often shrivel in

storage, lack sweetness 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, is gritty in texture, lacks

juiciness, and is subject to core breakdown.

Picking IVIaturity

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 MagnessTaylor 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. Recommendations for

proper pressure-test readings for different pear varieties are listed in table 10.

Other valuable indices of maturity, in addition to

pressure tests, include 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 the various physiological tests for maturity, the

soluble solids test is the most indicative of quality. A

close correlation exists between flavor and soluble

Table 10.-Flesh-firmness recommendations for

harvesting pear varieties

Firmness^

Variety

Maximum Optimum Minimum

Pounds Pounds Pounds

Anjou 15 13 10

Bartlett 19 17 15

Bosc 16 13 11

Comice 13 U 9

Hardy 11 10 9

Kieffer 15 14 12

Seckel 18 16 14

Winter Nelis 15 12 11

^ As measured by a Magness-Taylor pressure tester with a

5/16-inch plunger tip.

solids. In California, the Bartlett Pear Commodity

Committee has established a combination firmnesssoluble 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 percent. 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 to meet requirements.

In the Pacific Northwest, Bartlett pears for canning should be picked at a pressure test of 15 to 17

pounds. These pressures ordinarily permit the harvesting of maximum tonnage, and the fruit is best

suited for the storage and ripening procedures

involved with processing. Pears picked at higher

pressures darken more when cut and continue to

darken during preparation for canning. At pressure

tests of 14 pounds and lower, the pears tend to break
PEAR PRODUCTION 49

down at the core before they reach the desired softness for canning. This tendency develops rather rapidly below 14 pounds of 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 more

yellow shades 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.

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.

Abnormally cool growing seasons can also affect

the harvest date. Premature ripening of Bartlett

pears in the Hood River area occurs in districts with

comparatively cool growing seasons and only in

years when temperatures are below average. The

several weeks before 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. Premature ripening is induced by

continuous exposure of pears to 45° F (7.1° C) or

colder night temperatures and 70° F (21° C) day

temperatures for 2 days or 50° F (9.9° C) night and

70° F (21° C) day temperatures for 9 days during the

month immediately preceding harvest. Premature

ripening does not develop with night temperatures of

55° F (12.6° C) and 70° F (21° C) days, or 45° F

(7.1° C) nights and 90° F (32.1° C) days. When premature ripening first appears on a few 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.

Packing

Pears destined for immediate consumption on the

fresh market may be packed and shipped without

precooling or without being held in cold storage

before shipping. This fruit should 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 (-1.6° to -0.6° C) 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.

Bartlett pears promptly cooled and held at a core

temperature of 31° F (-0.6° C) for up to 4 weeks are

not susceptible to surface blemishes. With prompt

and adequate refrigeration, the packing season for

Bartlett pears may be safely extended for 4 to 6

weeks and for Anjou pears, 12 to 16 weeks after the

fruit has been picked. Fruit handled this way can be

washed and packed without previous warming.

Most of the pears are wrapped and place packed

in two-piece full-telescoping corrugated fiberboard

containers. Some are wrapped and tray packed in

slightly deeper, two-piece, full-telescoping corrugated

fiberboard containers.

A "tight fill" fiberboard box is also used commercially, chiefly for Bartlett pears in California. It is a

laborsaving 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.

Nearly all pears destined for the fresh market are

packed in vented polyethylene liners, which minimize

moisture loss but do not induce carbon dioxide levels

that would injure the pears.

The Hartman wraps contain copper to prevent

spread of decay organisms and ethoxyquin to control

scald in Anjou. Ethoxyquin may also be applied in a

flood applicator at harvest, as a line spray, or in wax

at packing time.

Several types of decay, including Blue Mold, Bullseye Rot, and Side Rot, can be controlled by benomyl or thiabendazole applied in a flood applicator

at harvest, in a line spray, or in wax at packing time.

These materials do not control Mucor or Alternaria

rots, so good sanitation and care in handling are very

important.

As the packing season is extended, danger of siuffmg and bruising increases. If it is necessary to store

for more than a few weeks before packing, controlled

atmosphere storage reduces the susceptibility to scuffing and bruising.

Storage

When pears are stored for a long time, they are

cooled immediately after picking. If the fruit is con-
50 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

sumed within a few weeks after harvest, immediate

refrigeration is of less importance. For maximum

storage iife, pears are held at about 30° F (-1.1° C)

in an atmosphere containing 2 percent oxygen and 1

percent carbon dioxide.

The length of time pears can be held in cold

storage varies with the varieties. The storage life of

each variety is fairly definite. 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 can 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.

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.

Some cold-storage operators are using a new

technique to lengthen the storage life of Anjou

pears by as much as 2 months. Immediately after

harvest, the fruit is stored, but must be free of surface water. Carbon dioxide is then released in the

storeroom until a 12-percent concentration is

reached. The oxygen in the storeroom will level

off and should be maintained at 12 to 15 percent.

Fans should be used to prevent carbon dioxide

layering. After 2 weeks, the oxygen and carbon

dioxide must be reduced to the normal storage

concentration of 2-percent oxygen and 1-percent

carbon dioxide to avoid carbon dioxide injury to

the fruit.

Shipping

Pears should be shipped as near the recommended

storage temperature as possible. Most rail carriers

recommend thermostat settings of 33° or 34° F (0.5°

or 1.1° C) because the equipment will not permit

lower settings without danger of freezing.

Ripening

For best dessert quality, most varieties of pears

should be ripened at 60° to 70° F (15.6 to 21° C) and

a relative humidity of 80 to 85 percent. Ripening

temperatures higher than 70° F (21° C) 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 (23.8° C), but ripening at 68° to 70° F

(19.9° to 21° C) 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° F (15.6° to 19.9° C), but for canning, the more

rapid ripening may be desired because of the processing schedule. At a ripening temperature of about

85° F (29.3° C), 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° F (15.6° to

18.2° C).

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.

SUGGESTED SUPPLEMENTAL READING

Fruit Set and Thinning

Batjer, L. P., Rogers, B. L., and Thompson, A. H.

1954. Blossom blast of pears: an incipient boron deficiency.

Amer. Soc. Hort. Sei. Proc. 52: 192-204.

and Thompson, A. H.

1949. Effect of boric acid sprays applied during bloom upon

the set of pear fruits. Amer. Soc. Hort. Sei. Proc. 53:141-

142.

Griggs, W. H., and Iwakiri, B. T.

1954. Poüination and parthenocarpy in the production of

Bartlett pears in California. Hilgardia 22:643-678.
PEAR PRODUCTION 51

Tufts, W. P., and Hansen, C. J.

1931. Variations in shape of Bartlett pears. Amer. Soc. Hort.

Sei. Proc. 28:627-633.

Westwood, M. N., and Grim, J.

1962. Effect of pollinizer placement on long term yield of

Anjou, Bartlett and Bosc pears. Amer. Soc. Hort. Sei.

Proc. 81:103-107.

Williams, M. W.

1973. Chemical thinning and guide for size-thinning Bartlett

pears. Wash. State Hort. Assoc. Proc. 1973:55-59.

Bilhngsley, H. D., and Batjer, L. P.

1969. Early season harvest size prediction of 'Bartlett' pears.

Amer. Soc. Hort. Sei. J. 94(6):596-598.

Varieties

Covey, R. P.

1969. Effect of extreme cold on the over-wintering of Podosphaera leucotricha. Plant Dis. Rptr. 53:710.

Coyier, D. L.

1967. The biology and control of tree fruit powdery mildews.

Utah State Hort. Soc. Proc. 1967:17-19.

1971. Control of powdery mildew on apples with various fungicides as influenced by seasonal temperature. Plant Dis.

Rptr. 55:263-266.

and Mellenthin, W. M.

1969. Effect of lime-sulfur-oil sprays on dAnjou pear. Hort .

Sei. 4:91-92.

Roosje, G. S.

1962. The importance of short time intervals between sprays

against apple powdery mildew. Brit. Insecticide Fungicide

Conf. Proc. 1961. I, 185.

Griggs, W. H., and Iwakiri, B. T.

1977. Asian pears in California. Calif. Agr. 31(1):8-12.

Ihorniley, J. M.

1976. The pears of Asia. Oreg. Hort. Soc. Proc. 67:156

Rootstocks

Reimer, F. C.

1925. Blight resistance in pears and characteristics of pear species and stocks. Oreg. Expt. Sta. Bui. 214, 99 pp.

Stebbins, R. L., Westwood, M. N., and Lombard, P. B.

1972. Pear rootstocks for Oregon. Oreg. Ext. Fact Sheet 61:1-

2.

Westwood, M. N.

1970. Rootstock-scion relationships in hardiness of deciduous

fruit trees. Hort Science 5:418-421.

Raabe, R. D.

1967. Variation in pathogenicity and virulence in Armillariû

me/lea. Phytopathology 57:73-76.

Leaf Spot Diseases

Powdery l\/lildew

Baker, J, V.

1962. The life history of apple mildew and the field assessment

of the disease. Brit. Insecticide Fungicide Conf. Proc. 1961,

I, 173.

Burchill, R. T.

i958. Observations on the mode of perennation of apple mildew. Agri. Hort. Res. Sta. Bristol Rpt. for 1957, p. 114.

Goldsworthy, M. C, and Smith, M. A.

1938. Ihe comparative importance of leaves and twigs as

overwintering infection sources of the pear leaf blight

pathogen, Fahraea maculata. Phytopathology 28:574-582.

Plakidas, A. B.

1941. The mode of overwintering of Entomosporium maculatum in Louisiana. Phytopathology 28:938.

Westwood, M. N., Cameron, H. R., Lombard, P. B., and Cordy,

C. B.

1971. Effects of trunk and rootstock on decline, growth and

performance of pear. Amer. Soc. Hort. Sei. J. 96:147-150.

Lombard, P. B., and Bjornstad, H. O.

1976. Performance of Bartlett pear on standard and Old

Home x Farmingdale rootstocks. Amer. Soc. Hort. Sei. J.

101:161-164.

Fire Blight

Keil, H. L., and Zwet, T. van der.

1967. Sodium hypochlorite as a disinfectant of pruning tools

for fire blight control. Plant Dis. Rptr. 51:753-755.

Kienholz, J. R.

1955. Control of fire blight on Forelle pears with antibiotics at

Hood River, Oregon. Plant Dis. Rptr. 39:208-209.

Zwet, T. van der, and Keil, H. L.

1977. Fire blight. U.S. Dept. Agr. Handbook. 510.

1960. Ihe role oí secondary infections in the spread of apple

powdery mildew {Podosphaera leucotricha (Ell. & Ev.)

Salm.) J. Hort. Sei. 35:66.

Butt, D. J.

197 L Ihe role of the apple spray programme in the protection

of fruit buds from powdery mildew. Ann. Appl. Biol.

68:149-157.

Pseudomonas Blight

Panagopoulos, C G., and Crosse, J. E.

1964. Blossom blight and related symptoms caused by Pseudomonas syringae van Hall on pear trees. East Mailing

(Kent) Res. Sta. Ann. Rpt. 1963:119-122.
52 AGRICULTURE HANDBOOK 526, U.S. DEPT. OF AGRICULTURE

Pear Scab

Kienholz, J. R., and Childs, L.

1951. Pear scab in Oregon. Greg. Agr. Expt. Sta. Tech. Bui.

21, 31 pp.

Smith, K. M.

1972. A textbook of plant virus diseases. Ed. 3, 684 pp. Academic Press, Inc.

Westigard, P. H., and Zwick, R. W.

1972. The pear psylla in Oregon. Oreg. State Univ. Agr. Expt.

Sta. Tech. Bui. 122, 22 pp.

Root Disorders Physiological Disorders

Cameron, H. R.

1960. Infection of pear root with Phytophthora cinnamoni.

(Abs.) Phytopathology 50:630.

Mclntosh, D. L.

1959. Collar rot of pear trees in British Columbia. Phytopathology 49:795-797.

1960. The infection of pear rootlets by Phytophthora

cactorum. Plant Dis. Rptr. 44:262-264.

Virus Diseases

Ackley, W. B.

1954. Hard-end of the Bartlett pear and its possible association with various water relationships of the fruit and

leaves. Wash. Agr. Expt. Sta. Tech. Bui. 15, 35 pp.

Hansen, E.

1961. Climate in relation to post harvest physiological disorders of apples and pears. Oreg. State Hort. Soc. Ann. Rpt.

53: 54-58.

Storage and Handling

Catlin, P. B., Olsson, E. A., and Beutel, J. A.

1975. Reduced translocation of carbon and nitrogen from

leaves with symptoms of pear curl. Amer. Soc. Hort. Sei. J.

100:184-187.

Cropley, R., and Posnette, A. F.

1973. The effect of viruses on the growth and cropping of pear

trees. Ann. Appl. Biol. 73: 39-43.

Wolfswinkel, L. D. and Posnette, A. F.

1963. The identification of some viruses infecting apple, pear,

and quince. 5th Europ. Symposium Fruit Tree Virus Dis.

Proc. In Phytopath. Mediterránea 2, pp. 132-136.

Fridlund, P. R.

1973. Incidence, systemic nature, and spread of the pear vein

yellows virus in the Yakima Valley, Washington. Plant Dis.

Rptr. 57: 483-486.

Jensen, D. D., Griggs, W. H., Gonzales, C. Q., and Schneider, H.

1964. Pear psylla proven carrier of pear decline virus. Calif.

Agr. 18(3): 2-3.

Kienholz, J. R.

1939. Stony pit, a transmissible disease of pears. Phytopathology 29: 260-267.

1953. Stony pit of pears. U.S. Dept. Agr. Yearbook 1953: 670-

673.

Nyland, G., and Möller, W. J.

1973. Control of pear decline with tetracycline. Plant Dis.

Rptr. 57: 634-637.

and Möller, W. J.

1974. Postharvest treatment of pear trees for control of pear

decline. Calif. Univ. Bui. AXT-446, August 1974, 3 pp.

Posnette, A. F.

1963. Virus diseases of apple and pear. Commonwealth Agr.

Bur. Tech. Comm. 30, 141 pp.

Shalla, T. A., Carroll, T. W., and Chiarappa, L.

1964. Transmission of pear decline by grafting. Calif. Agr.

18(3):4-5.

Allen, F. W., and Claypool, L. L.

1948. Modified atmospheres in relation to the storage life of

Bartlett pears. Amer. Soc. Hort. Sei. Proc. 52:192-204.

Ezell, B. D., and Diehl, H. C

1934. Relation of maturity and handling of Bartlett pears in

the Pacific Northwest to quality of the canned product.

U.S. Dept. Agr. Tech. Bui. 450, 24 pp.

Fountain, J. B., and Chapogas, G.

1966. Prepackaging pears at shipping point. U.S. Dept. Agr.

Mktg. Res. Rpt. 758, 13 pp.

Gerhardt, F.

1955. Use of film box liners to extend storage life of pears and

apples. U.S. Dept. Agr. Cir. 965, 28 pp.

and Schomer, H. A.

1954. Film liners for boxes of pears and apples. Pre-Pack-Age

7(5):14-17.

Hansen, E.

1963. Control of CO 2 concentration in sealed polyethylene

pear box liners by use of packaged hydrated lime inserts.

Amer. Soc. Hort. Sei. Proc. 83:210-216.

Magness, J. R., Diehl, H. C, and Allen, F. W.

1929. Investigations on the handling of Bartlett pears from

Pacific Coast district. U.S. Dept. Agr. Tech. Bui. 148, 28

pp.

Olsen, K. L., Patchen, G. O., and Schomer, H. A.

1960. Cooling rates of apples packed in fiberboard boxes as

influenced by vents, perforated trays, and stacking pattern.

Wash. State Hort. Assoc. Proc. 56: 214-220.

Pierson, C F., Ceponis, M. J., and McColloch, L. P.

1971. Market diseases of apples, pears, and quinces. U.S.

Dept. Agr. Handbook 376, 112 pp.

Redit, W. H., and Hamer, A. A.

1961. Protection of rail shipments of fruit and vegetables. U.S.

Dept. Agr. Handbook 195, 108 pp.

Sainsbury, G. F., and Schomer, H. A.

1957. Influence of carton stacking patterns on pear cooling

rates. U.S. Dept. Agr. Mktg. Res. Rpt. 171, 10 pp.
PEAR PRODUCTION 53

Smith, E.

1946. Handling injuries on pears following cold storage.

Amer. Soc. Hort. Sei. Proc. 47:79-83.

Wang, C. Y., and Mellenthin, W. M.

1972. Induction period and threshold temperatures for premature ripening in Bartlett pear. Amer. Soc. Hort. Sei. J.

97:557-600.

and Mellenthin, W. M.

1975. Effect of short term high CO2 treatment on storage of

D'Anjou pear. Amer. Soc. Hort. Sei. J. 100(5):492-495.

Insect Control

Barnett, W. W., Moorehead, G. W., Davis, C. S., Joos, J. L.,

Bearden, B. E., and Berlowitz, A.

1976. True bugs cause severe pear damage. Calif. Agr.

30(10):20-23.

Madsen, H. P., and Barnes, M. M.

1959. Pests of pear in California. Calif, Agr. Expt. Sta. Ext.

Serv. Circ. 478, 40 pp.

Metcalf, C. L., Flint, W. P., and Metcalf, R. L.

1962. Destructive and useful insects. McGraw-Hill, New York.

Pear Insects, pp. 741-747.

Newcomer, E. J.

1966. Insect pests of deciduous fruits in the West. U.S. Dept.

Agr. Handbook 306, 28 pp.

T^ U. S. GOVERNMENT PRINTING OFFICE : 1978 O - 269-315