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Chapter 6. PROGRESS AND PROBLEMS IN TREE FRUIT AND NUT PRODUCTION
H. J. BROOKS, H. W. FOGLE, AND J. W. M C K A Y
1726 one settlement of 40 families near Boston, Massachusetts, made
10,OOO barrels of cider.
Fruit nurseries were slow to become established in the new colonies,
and many new plantings were grown from seed. The better of these
seedlings were then propagated asexually and many new local apple and
pear cultivars (varieties) were carried west with the advance of the
frontier. Nearly every homestead had its own collection of apple and
Perhaps it was well that new apple and pear plantings were from
seed rather than from asexual propagation of possibly unadapted European varieties. A vast number of apple and pear cultivars were described
in the early pomological literature, and many more local cultivars served
the needs of frontier families without the benefit of a varietal description.
A survey of the literature (Ragan, 1905, 1908) shows that about 13,000
apple cultivars and 8,500 pear cultivars were mentioned in American
publications from 1804 to 1904.
Both apples and pears were so well established in America by the
colonists that it is difficult today to realize that these fruits were not
native to this country, Both fruits remain a part of the American diet,
and with increased population there is increased demand for production.
The major problems associated with the commercial production of pome
fruits are discussed.
The United States produces more apples than any other country in
the world, about 125 million bushels annually. This figure represents
about one-fifth of the total world production. In this country, apples are
grown commercially in 34 States, Washington producing about one-fifth
of the total commercial crop. The leading apple-producing States are
Washington, New York, Michigan, Virginia, California, and Pennsylvania
in that order (Pubols, 1964). The four general areas of apple production,
in order of their total production, are: the Pacific Northwest, the New
York-New England areas, the Appalachian area, and the Midwest. Of the
125 million bushels of apples produced annually in ,the United States, 97
per cent are used for domestic consumption. About 62 per cent of the
apples sold are for fresh market, the remaining 38 per cent being
processed. On a weight basis, about 55 per cent of the processed apples
go into applesauce, about 20 per cent into juice, and about 13 per cent
The average per capimta use of fresh apples in the United States is
about 20 pounds per year. This consumption is about the same as that
TREE FRUIT AND NUT PRODUCTION
of bananas but less than that of all citrus fruits combined. On a farmweight equivalent, the per capita consumption of all apple products
is about 27 of the 190 pound per capita consumption of all fresh and
processed fruit ( U.S. Dept. Agr., 1964).
The important apple cultivars in the United States, in the approximate
order of their production, are DELICIOUS, MCINTOSH, GOLDEN DELICIOUS,
ROME, JONATHAN, WINESAP, and YORK IMPERIAL. The DELICIOUS cultivar
is used primarily for fresh market, while the YORK IMPERIAL cultivar,
which is grown only in the Appalachian area, is used almost exclusively
for processing. GOLDENDELICIOUS can be used either for the fresh market
or as a processing apple. This partly accounts for the rapid increase in
popularity of this cultivar, which was not introduced commercially
until 1916. MCINTOSHis grown commercially in New York, New England,
and Michigan, while Washington State is the major producing area of
the WINESAP cultivar.
2. Trends in Production
The apple barrel in every cellar of early days is no longer typical of
the American home, but the popularity of the apple remains. This
popularity is undoubtedly associated primarily with quality and secondly
with availability. Whereas the apple earlier had little competition from
other fresh fruits in the fall and winter season, today it is in strong
competition with many kinds of fruit. As a consequence, there has been
a gradual change in apple cultivars, storage techniques, packaging, and
and merchandizing. These changes continue and influence trends in
The RUSSET or WINTER RUSSET type of apple was as familiar to the
housewife of sixty years ago as the DELICIOUS apple is to the housewife of
today. The RUSSET was a small unattractive apple that remained firm
through the winter and into the spring, and no good housewife would
start the winter without a barrel of RUSSET apples. This choice of cultivar
was simply one of availability because no other apple would keep as
long, The housewife of today no longer needs to store her own apples,
New cultivars and methods of commercial storage make apples available
on the market through the winter and spring months. Her attention now
centers more on the attractiveness and quality of the apple compared to
that of the other fruits offered for sale.
The apples being offered today may be attractive but of poorer
quality than is desired by the informed consumer. The color sports
or mutations of the DELICIOUS apple demonstrate this trend toward greater
emphasis on appearance than on quality. There are more than 75 strains
of the DELICIOUS or RED DELICIOUS apple which color earlier than the
H. J. BROOKS, H. W. FOGLE, AND J. W. MCKAY
standard DELICIOUS or RED DELICIOUS cultivars (Blodgett and Aichele,
1W).These strains of DELICIOUS do not necessarily mature earlier than
the standard DELICIOUS, but because they color early in the season, they
are found displayed in the fresh fruit markets before the standard
DELICIOUS cultivar. The early harvest and sale of immature color sports
obviously is because of appearance, not fruit quality.
The commercial apple industry in the United States is now attempting
to adjust to the demands for better quality in the fresh market. The
high-quality GOLDEN DELICIOUS cultivar is being planted in increasing
numbers. Some states prohibit the shipment of RED DELICIOUS prior to a
given date, thus attempting to keep immature apples off the market.
Improved techniques of harvesting, storaging, and packaging are all
designed to make the apple more competitive with the other fruits.
Controlled-atmosphere storage has made apples available as a fresh
fruit the year round.
The competition of the apple with other fresh fruit during the last
fifty years is reflected in the data on per capita consumption. The relative
consumption in comparison with oranges, grapefruit, and bananas is
shown in Table I. Commercial production of apples is expected to
increase considerably when new young plantings in the major appleproducing States come into full production around 1970. With increased
availability, per capita consumption is expected to increase ( Pubols,
The methods of displaying apples in the food market have changed
considerably since 1950. Prior to 1950, all apples were displayed in
bulk. Small stores displayed apples in containers placed on the floor,
while larger stores displayed apples in bins or on counters. Since 1950,
prepackaged apples have increased in popularity. Prepackaging has the
advantages of reducing spoilage, extending shelf life because of less
customer handling, reducing labor required to maintain displays, and
lowering customer selection time (Bums et al., 1963). Once having
been exposed to prepackaged apples, it is expected that the customer will
not object to the small premium for this added convenience.
There has been a gradual increase in processed apples over the last
twenty years; about 38 per cent of the commercial crop is now processed
(U.S. Dept. Agr., 1964).There has been a pronounced increase in canned
apple products, and this trend is expected to continue. New plantings now
being made of the GOLDEN DELICIOUS cultivar, which can be used both
for processing and the fresh market, ensure the increase in commercial
apple production in the United States for the next decade. With cultivars
such as GOLDEN DELICIOUS and with better control of premature harvest
of RED DELICIOUS strains, there is every reason to believe that the apple
Average Yearly per Capita Consumption (Pounds) of Fresh Fruits, Farm Weight, 1910-19635
Compiled from U.S.Dept. Agr. ( 1964), Table 7.
H. J. BROOKS, H. W. FOGLE, AND J. W. M C K A Y
will remain popular with the American housewife and that it will successfully compete with other fresh and processed fruit.
Beyond the next decade, the trend of apple production may depend
upon the success of scientists currently engaged in research in anticipating and meeting the future needs of the industry.
3. Major Problems and Research Contributions
The major production problems of the fruit industry today are closely
associated with the economics of the country. The increase in population,
sprawling suburbs, and land speculation have denied to orchard production the use of large acreages of land. Even in the smaller communities,
the orchardist and the home owner are competing for the same sites; sites
that are fertile and high in elevation with good water and air drainage.
Taxes on potential orchard sites which are also potential homesites are
often too high to permit orcharding.
The young orchard is expensive to establish and to maintain during
the nonproductive years. It may not show a profit before the tenth year.
Expensive specialized spray equipment is needed to control diseases and
insects, making small orchard operations no longer economical. As a
consequence, there is a tendency toward consolidation of existing
orchards and an increase in the size of new orchard operations.
The availability of labor for the cultural and harvest operations of
the orchard is becoming increasingly acute. Some areas grow only a few
apple cultivars which mature in a short period, thus creating a peak
demand for harvest labor. As a result many apples cannot be harvested
at the proper stage of maturity. Proper harvest maturity is a critical
problem in Washington State, which has a high production density of
the RED DELICIOUS and WINESAP cultivars.
Because of the labor shortage, there has been considerable research
devoted to mechanical harvesting and handling of apples. Bulk bins
have been used successfully for moving apples from the orchard (Burt,
196l),but the problem of mechanically removing the apples from the
tree and into the bins has not yet been resolved (Quackenbush et al.,
1962). Hydraulic devices to lift and move apple pickers about in the
tree have been developed, but these devices are expensive and are in
operation only during the short period of apple harvest. Experiments
with mechanical shaker devices to harvest apples have resulted in excessive fruit injury. It is conceivable that mechanical devices may be
developed to remove apples from the tree, but until they are perfected,
the orchardist must continue to rely upon the techniques that have
prevailed since the introduction of apples into America 300 years agothose involving the laborer with a ladder and a picking basket,
TREE FRUIT AND NUT PRODUCTION
The ideal apple orchard of the future would be one in which the
young trees would be planted at the high density of about 250 trees per
acre instead of the current 50 to 100 trees. The trees would be forced
into early production, and once in production, would be maintained at
a relatively small size to facilitate harvesting. If the trees were maintained
at a height of 12 to 14 feet, all the fruit could be harvested from a 6 to 8
foot stepladder. This would reduce the hazards and inefficiency of
harvesting apples from the tops of large trees which are so common in
today’s commercial orchards. At present, there is no effective way of
controlling size except by constant and laborious pruning. There has been
considerable research on the use of size-controlling rootstocks, but in this
country, dwarfing rootstocks have not been completely satisfactory
(Tukey, 1964). In Europe, size-controlling or dwarfing rootstocks have
been used with considerable success, but laborious pruning, training,
and staking or trellising of the trees is necessary.
Recent advances have been made in the use of chemicals for controlling the size of young apple trees. Growth-controlling chemicals have
been generally successful on ornamental plants (Cathey, lW)and
of these experimental chemicals, B-Nine ( N-dimethylamino succinamic
acid) markedly reduced the vegetative growth of apple trees to less than
half and increased flowering (Batjer et d.,1964). If chemicals can be
used to reduce tree growth and maintain production in high-density
plantings, the efficiency of harvest operations will be greatly enhanced.
Spur-type mutations of leading apple cultivars have recently been
discovered in the United States (Blodgett and Aichele, 1960). Trees
propagated from these mutant forms have shortened growth and tend to
produce fruit earlier in the life of the tree than do standard trees. Additional experience is needed with these spur-type apple trees before
their potential use can be properly estimated, but it appears that spurtype apple bees can be used to good advantage in high density plantings.
Bringing young orchards into earlier bearing is a major problem that
has received little attention. Certain clonal rootstocks are known to dwarf
young trees and bring them into earlier bearing, but physiological disorders develop as the trees become older. Ringing with a knife or otherwise girdling the trunks of young apple trees has been used with limited
success to induce early flowering. Chemical growth regulators have been
observed to promote flowering in apple trees (Stahly and Piringer, 1962)
but are still in experimental stages. When the physiology of flowering is
generally better understood, controlled flowering and fruiting of apple
trees may be possible.
Alternate bearing in the apple tree has always been a serious problem.
Some apple cultivars are worse in this respect than others, but all cultivars
11. J. BROOKS, 11. W. FOGLE, AND J.
have a tendency to overbear one year and bear a small crop the next. If
too much fruit is left to develop on the tree during a given year, there are
insufficient flower buds formed for the following spring. Research leading
to an understanding of the biochemistry involved in flowering may
provide an answer to the problem of alternate bearing. Recent work on
the use of chemical fruit-thinning compounds ( Batjer and Billingsley,
1964) has indicated that chemical thinning of apples will reduce alternate bearing.
Nutrition, though still a problem in commercial apple production, is
no longer a major problem. The results of a large amount of nutrition
research are now available to growers (Childers, 1954), but the apple
tree is slow to respond to changes in nutrient supply, and nutritional
imbalances continue to plague the apple grower. Soil analysis does not
always show the fertilizer requirements of the trees in the orchard, and
leaf analysis is now being used as the basis for determining the fertilizer
requirements of individual orchards. Nitrogen application with respect
to rate and time of application is perhaps the most important aspect of
orchard fertilization. Excessive nitrogen applications in the spring will
cause excessive amounts of vegetative growth which may not develop
flower buds the following year. Summer applications of nitrogen will
cause a delay in fruit coloring and maturity. Minor element deficiency
symptoms have been described (Cain and Shear, 1964) but generally
deficiencies are not serious problems in commercial apple areas.
Insect and disease control continue to be major problems in spite of
the many new pesticides available. With some insects, particularly with
orchard mites, the development of resistant strains keeps abreast of
the development of new insecticides. Powdery mildew ( Podosphaera
Zeucotricha ) and fire blight ( Erzcinia amylovora ) are major apple diseases
for which we do not have completely effective controls.
Apple measles is a physiological disorder affecting increasing numbers of young apple trees, particularly trees of the RED DELICIOUS variety.
The disorder is associated with low calcium and high manganese, but
the cause of the disorder is not yet completely understood. York spot is
another disorder the cause of which is not understood. It causes corking
of the apple tissues (Fig. 1 ) and is particularly serious in the YORK
I h m m A L apple cultivar. The areas of cork tissue are often undetected
until the apples are sliced for processing. Additional research is needed
on both the measles and York spot disorders.
The importance of viruses to commercial applr production is not
fully understood. Several latent viruses are known to be widely distributed in commercial apple cultivars, but the extent to which these
viruses influence production is not known. Several other viruses that
TREE FRUIT AND NUT PRODUCTION
seriously damage apples are of limited distribution and stand as potential
threats if a natural vector should be introduced.
The complex genetic composition of apples, the eight years required
from hybridization to fruiting, and the extensive land requirements to
test progeny make apple improvement by breeding a slow and expensive program. Apple breeding programs at many State experiment stations
have been discontinued because of the time and expense involved, but
some still continue. The New York Agricultural Experiment Station, for
example, has been engaged in apple breeding for the last 72 years. The
FIG. 1. York spot disorder on
progress made by the apple-scab-resistance program (Shay et al., 1953)
clearly indicates that it is possible to breed apple cultivars that are
resistant to apple scab. Success of this breeding program may stimulate
efforts to develop apple cultivars resistant to insects and other diseases.
As with apples, the average production of dessert pears in the United
States is higher than in any other country in the world. The average annual production in the United States is about 28 million bushels, nearly all
of which is consumed in this country. In addition, the United States
annually imports about 300 thousand bushels of pears. The average annual per capita consumption of pears as fresh fruit is about 3 pounds;
it ranks seventh behind bananas, apples, oranges, peaches, grapefruit,
and grapes in freshfruit consumption (U.S. Dept. Agr., 1964). An equal
amount of processed pears is consumed and, in total value of production,
pears rank third behind apples and peaches.
H. J . BROOKS, H. W. FOGLE, AND J. W. MCKAY
Pears can be grown throughout most of the United States, but commercial production is limited to certain geographic locations where the
ravages of fire blight (Erwiniu umylovoru), a bacterial disease, are less
severe. This disease was first observed in the Hudson River valley in
1780 and since that time has spread to all parts of the United States and
to several foreign countries. Large pear plantings in the eastern. southern,
and central States were destroyed by fire blight prior to 1900, and no
satisfactory control of the disease is presently known.
Pear fire blight develops and spreads rapidly in warm climates. In
the cooler climates of the Pacific Coast and around the Great Lakes the
natural spread of the disease can be reduced by pruning out diseased
branches and by the use of antibiotic protective sprays. In certain areas
of the Pacific Coast States, the high diurnal temperature change providing cool nights apparently reduces the natural spread of the disease.
Therefore, most of the commercial pear production in the United States
is located in these coastal areas, California produces about half of the
pears grown in this country; Oregon, Washington, Michigan, and New
York follow in that order. These five States produce about 94 per cent
of the total commercial pear production.
The BARTLETT is the most important pear cultivar grown in the
United States and comprises more than 70 per cent of the total pear
production. There are about 14 million bushels of BARTLETT pears produced annually in California alone. More than half of the commercial
pears produced in the country are canned, and most of the canned pears
are of the BARTLETT cultivar. The ANJOU pear is the second leading commercial cultivar. It is grown mostly in Oregon and Washington for use
as a fresh fruit on the winter market. The BARTLETT pear does not store
well and is not used as a winter pear. The BOSC, COMICE, and HARDY cultivars are grown to a lesser extent, but are important cultivars in some
pear-growing areas. The KIEFFER cultivar is grown locally in some
southern and eastern States because of its tolerance to fire blight, but it
is of poor quality and is not found in commercial production.
2. Trends in Production
Since fire blight has become the limiting factor in commercial pear
production in most of the rest of the United States, production increases
are in the three Pacific Coast States, particularly in California. BARTLETT
continues to be the leading cultivar planted and is expected to continue
to be the major cultivar in the United States for many years to come,
The production and utilization of processed pears has increased steadily in recent years (Pubols, 1964), and this upward trend is expected
to continue. Most of the increase in the production of processed pears
TREE FRUIT AND NUT PRODUCTION
is in the State of California, where the amount of canned pears has
quadrupled since 1946 (U.S. Dept. Agr., 1963).
There is increased grower interest in pear production in the central
and eastern States. The United States Department of Agriculture and
several State experiment stations have pear-breeding programs, and
high quality, blight-resistant pear cultivars are expected to be introduced
during the next thirty years. Tree fruit breeding is a slow process, but
sources of blight resistance are known and it is only a matter of time
until blight-resistant cultivars will be available.
The pear, unlike the apple, is sold on its merits of quality rather than
appearance. The consumer will accept a russeted pear cultivar like the
BOSC or a green pear like the ANJOU whereas a similarly russeted or
colored apple cultivar would be unacceptable. If it were not for fire
blight, pears would be abundant and priced competitively with the
apple. The pear probably commands less of the market potential than
any other fresh fruit sold in the United States. As soon as high quality
blight-resistant pear cultivars become available, a considerable increase
in commercial pear production is expected in the United States and the
commercial pear acreage is expected to be more evenly distributed
throughout the country.
3. Maior Problems and Research Contributions
Without question, fire blight is the major production problem limiting
pear production in this country. Much research on this disease has been
carried out during the last eighty years, but no adequate control has yet
been found. Bees are necessary for pollinating fruit trees, yet bees are
important initial vectors which spread the disease through the pear
orchard. Antibiotics are not effective in controlling the natural spread of
fire blight in the areas of the country where the disease is most serious.
The environmental factors that influence the spread of the fire blight
disease are not well understood. The occurrence of the disease is erratic;
it may not appear for several years in a given area, and then, following
certain climatic conditions, there may be an outbreak of epidemic proportions. Hailstorms are often associated with these outbreaks. Recent
research has shown that the fire blight organism can remain on the
surface of the pear tree for long periods without causing obvious infection (Keil et al., 1964). Hailstorms apparently injure the leaf and stem
tissues of the tree sufficiently to provide entrance points for the organism,
Once inside the stem, it multiplies and spreads rapidly. Whole trees
may be killed if blight infections are not removed promptly.
The United States Department of Agriculture is emphasizing research
studies on pear fire blight resistance. New biochemical techniques are
H. J. BROOKS, H. W. FOGLE, AND J. W. M C K A Y
being developed to distinguish the susceptible and resistant seedlings in
progenies of the pear-breeding program. Some pear seedlings do not
produce fruit until they are 9 years of age; early elimination of susceptible seedlings by a biochemical screening technique would greatly
increase the efficiency of the breeding program. About 20,OOO seedlings
can be maintained and evaluated in the field plantings at Beltsville,
Maryland. As fast as the seedlings are evaluated, new seedlings are
planted, In 1960, two blight-resistant cultivars, MAGNESS and MOONGLOW,
were introduced from this breeding program, but many thousands of
seedlings are expected to be grown before additional cultivars can be
selected, evaluated, and introduced.
Pear decline, another disease, has killed several million pear trees on
the Pacific Coast. This disease kills trees growing on certain oriental
pear rootstocks. It now has been proved to be a virus ( Jansen et al.,
and the pear psylla has been demonstrated to be the insect
vector. The disease appears to be very similar to the “Moria disease”
known in Italy. The causal virus may have been imported in pear species
material, where it existed until it was picked up and carried by the psylla
as the insects spread from the Canadian border through the States of
Washington and Oregon and into California. Pear decline was first
observed in Washington in the 1940’s. It was first recognized in Oregon
in 1957 and in California in 1959.
Pear decline injury can be reduced by the use of decline-tolerant
rootstocks. Seedlings of BARTLETL’ pollinated with AN JOU have proved to
be resistant to the pear decline virus, and most new pear plantings are
being made on this stock. In addition to being an insect carrier of the
pear decline virus, the psylla itself is an economic insect which must be
Fruit handling and ripening is also a problem of the pear industry.
Unlike most other fruits, pears will not ripen properly on the tree. The
fruits must be harvested while still hard and then ripened for about
6 to 10 days at 65 to 70°F. Pears which have been improperly stored may
develop a breakdown in the internal tissues when the fruit are ripened.
This is particularly true of the ANJOU pear, but a reduction in the concentration of carbon dioxide during storage will reduce internal breakdown (Hansen, 1957). Much additional research must be done, however,
both in developing better cultivars and solving the problems of pear
storage, before pears can be available as a fresh fruit the year round.
Pear trees grow more slowly than apple and are slower to come into
production. Once in production, a pear orchard will produce more fruit
to the acre than an apple orchard, and a pear orchard may stay in commercial production for more than seventy years. Growth-retarding chem-