Orlando tangelo

Material Information

Orlando tangelo production and utilization in Florida
Series Title:
Circular Florida Cooperative Extension Service
Crocker, T. E ( Timothy Eugene ), 1944-
Wardowski, Wilfred F
Florida Cooperative Extension Service
University of Florida -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville Fla
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Physical Description:
11 p. : ; 23 cm.


Subjects / Keywords:
Tangelo -- Florida ( lcsh )
City of Orlando ( local )
Tangelos ( jstor )
Rootstocks ( jstor )
Pollinators ( jstor )
government publication (state, provincial, terriorial, dependent) ( marcgt )
bibliography ( marcgt )
non-fiction ( marcgt )


Includes bibliographical references (p. 11).
General Note:
Cover title.
General Note:
"12-1M-80"--P. 4 of cover.
Circular (Florida Cooperative Extension Service) ;
Statement of Responsibility:
T.E. Crocker and W.F. Wardowski.

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
51253263 ( OCLC )


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:~cBP, ;P



Florida Cooperative Extension Service
Instiutte of Food and Agricultural Sciences
University of Florids, Gairesv'.lle


T. E. Crocker and W. F. Wardowski'

One of the most important citrus hybrids ever produced by
man has been the tangelo, a cross between grapefruit and tan-
gerine. The name tangelo was derived from the first part of
"tangerine" and the last part of "pomelo" (an old name for
grapefruit) (14). The first tangerine X grapefruit crosses were
made between 1893-1914. Since then, more than a dozen hybrids
with desirable characteristics have been named and described,
but none has attained the commercial popularity of the 'Orlando'.
The 'Orlando' tangelo is a hybrid of 'Duncan' grapefruit and
'Dancy' tangerine. It originated from one of many crosses made
in Florida between 1908 and 1912 by W. T. Swingle and his as-
sistants, E. M. Savage and F. W. Savage. It was first named 'Lake'
because of it's first fruiting at Eustis in Lake County (14).
Because of the confusion associated with this name, it was later
renamed 'Orlando'. It's characteristics include early maturity,
good shipping quality, attractive appearance and pleasant flavor.
Together, these factors have made the 'Orlando' tangelo a com-
mercially important fruit in Florida.

Economic Position of the 'Orlando' Tangelo
Until the mid-60's the 'Orlando' tangelo produced high returns.
Total production was low and marketing was controlled by a small
group of producers. The high prices and the cold-hardiness ex-
hibited by the 'Orlando' in the 1962- 1963 freeze attracted many
additional growers, so that the carefully controlled market was
lost. Increased volume contributed in large part to the decline
in prices during the last decade (Table 1). Also, the 'K-Early', a
low quality tangelo maturing earlier than the 'Orlando', was sent
to market in sufficient quantities to depress later tangelo sales.
The high quality 'Robinson' tangerine was introduced in 1959.
'Robinson' matures earlier than 'Orlando', but the seasons over-
lap appreciably so that 'Robinson' competes with 'Orlando'. Re-
cent releases of new tangerine hybrids such as 'Nova' may result
in even greater competition in the future.

1 Extension Horticulturists

Because of the development of poor flavor in extracted juice,
only small quantities of 'Orlando' juice can be blended with that
of sweet orange and there is no current market demand for tan-
gelo juice alone. Thus, even though increasing amounts of tan-
gelos are being used in processing (Table 2), prices are so low
that this outlet is not profitable. The future of the 'Orlando'
tangelo, therefore, is bleak unless new products or increased
market demands for processed and fresh fruit can be developed.
With the present price structure 'Orlando' tangelo growers
are confronted with a serious economic problem for which there
is no simple, short-term solution. The purpose of this bulletin
is to offer 'Orlando' tangelo producers a summary of the best in-
formation on producing, harvesting and utilizing 'Orlando' tan-
gelos in an attempt to help maximize profits.
Description: The fruit of the 'Orlando' tangelo has been de-
scribed (3) as being oblate in form with the fruit size medium
to large (21/2" to 2/4" wide). The fruit is without neck. It is
seedy when cross-pollinated. The rind is light orange to orange
in color, thin and slightly pebbled. The skin is held tightly and
is not free peeling. Segments number 12 to 14. The axis is small
and hollow. The flesh of the 'Orlando' tangelo is orange colored,
tender and very juicy. The flavor is mildly sweet when fruit
are properly grown and mature. Fruit matures in time to be
shipped for the Thanksgiving market.
A unique foliage characteristic which the 'Orlando' has in
common with many other tangelos is the cupped or "boat" shaped
leaves. 'Orlando' leaves are more cupped than leaves of most
other tangelos with the exception of the 'K-Early'. The 'Orlando'
has inherited from its grapefruit parent a spreading habit of
growth rather than the upright growth of the tangerine. It has,.
however, inherited from the tangerine brittle wood and a ten-
dency to bear fruit on the extremities of the limbs rather than
on the inside like the grapefruit. This combination of brittle
wood and fruiting habit can result in severe limb breakage if a
large crop is set. These characteristics have definite implications
for the spacing and pruning of the 'Orlando'.
The 'Orlando' often fails to set adequate crops of fruit. Re-
search has shown that the 'Orlando' is weakly parthenocarpic
and sexually self-incompatible (6). It is necessary, therefore,
to stimulate fruit setting on 'Orlando' by cross-pollination, gir-
dling or use of GA sprays.
The 'Orlando' is more cold-resistant than sweet orange cultivars
and is probably more cold-resistant than some other tangelos
(3). Thus it is well adapted for planting in the colder citrus areas
of the state.

Vigor is probably equal to that of its grapefruit parent. It is
more vigorous than 'Nova' and 'Thornton' tangelos and is less
vigorous than the 'Minneola' and 'Sampson' (3).

Selection of Trees and Rootstocks
The sections on selections of trees and rootstocks which follow
are intended to provide information for selection of replacement
trees needed to maintain the grove in economical production.
'Orlando' is very susceptible, regardless of rootstock, to a
damaging virus disease called xyloporosis. The 'Orlando' tangelo
is so susceptible to the xyloporosis virus that is is used by the
Florida Budwood Registration Program as the official indicator
plant in indexing for this disease. Since xyloporosis is transmitted
only through infected budwood, this problem can be eliminated
through the use of budwood free of xyloporosis. Registered xylo-
porosis-free budwood is readily available to Florida nurserymen.
No rootstock will provide tolerance or resistance to 'Orlando'
trees infected with xyloporosis.
The most popular rootstock for 'Orlando' as well as most man-
darins and mandarin hybrids except for 'Dancy' tangerines, is
'Cleopatra' mandarin (Citrus reshni). 'Orlando' trees budded
on this rootstock produce good quality fruit and have good cold-
hardiness. This rootstock is resistant to tristeza and exocortis,
but is not as resistant to footrot as sour orange. Yield on 'Cleo-
patra' is initially low with small fruit size. The 'Orlando' grows
slowly during the first six to 10 years, therefore, requiring some
time to come into economical production (10). With 'Cleopatra'
rootstock good production practices are necessary for produc-
tion. It is best suited for heavier, well-drained soils.
Rough lemon (Citrus jambhiri) has been the most widely-
planted citrus rootstock in Florida in years past. 'Orlando' on
rough lemon produces high yields, but low quality fruit that
tends to dry on the tree if held past maturity. Rough lemon
should not be used as a rootstock for 'Orlando', at least until
young tree decline disease is more clearly understood.
Sour orange (Citrus aurantium) is resistant to footrot and is
tolerant to exocortis. 'Orlando' trees on this rootstock have good
cold tolerance and produce high quality fruit. Sour orange is
susceptible to the tristeza virus, produces generally small fruit
size and is not as prolific as rough lemon or sweet lime. This
rootstock is not as resistant to drought as rough lemon and is
not suited for deep coarse sands. It is usually planted on fine-
textured soils, and in colder regions of the state.
Other rootstocks that might be tried for 'Orlando' are 'Car-

rizo' and 'Rusk' citrange (C. sinensis X P. trifoliata), sweet
lime (Citrus limettoides), and trifoliate orange (P. trifoliata).
These rootstocks have not been extensively planted, but have
been tried with 'Orlando' with some success (10).
Obviously no one rootstock can be recommended for all situ-
ations; each has good and bad characteristics which must be
taken into account for a given location. Climate, soil type, virus
diseases, and cultural practices, including the availability of
irrigation, must be taken into consideration when choosing a

Increasing Fruit Set
The 'Orlando', as mentioned before, is weakly parthenocarpic
and self-incompatible. Although some 'Orland6' trees on very
fertile and with fine-textured soils and under favorable environ-
mental conditions produce good crops of seedless fruit, generally
some method to increase fruit set is needed to insure good pro-
duction. This can be achieved by cross-pollinating, girdling or
gibberellic acid (GA) treatments (7,9).
When cross-pollination is used, a variety compatible with 'Or-
lando' is interplanted to insure cross-pollination. This results in
increased yields of seedy fruit. Some major requirements for an
effective pollinator are: 1) It must naturally be cross-compatible
with 'Orlando'. 2) The variety must produce sufficient pollen
to insure cross-pollination. Some varieties, e.g. 'Robinson', pro-
duce viable, but only small amounts of pollen. 3) The blooming
period of the pollinator must overlap with 'Orlando' to insure
a pollen source when the 'Orlando' is receptive. 4) The pollina-
tor should bloom annually and have a consistent amount of bloom
each year.
Other cultural requirements should also be considered. The
pollinator should be compatible with the fertilizer, insect and
disease control program and weather requirements of the 'Or-
lando'. Some growers prefer pollinators which mature fruit at
the same time as 'Orlando' for ease of harvest; others prefer a
pollinator with a different fruit maturity time to reduce mixing
of varieties at harvest. Another factor to consider is the value
of the fruit and whether it will be sold as a fresh or processed
Research is currently underway to further evaluate pollinators
for 'Orlando'. To date 'Lee', 'Temple' and 'Robinson' have been
satisfactory pollinators for 'Orlando' (1,11). 'Temple' is general-
ly used because it is an important specialty fruit and an effective
pollinator. It has the disadvantage of being susceptible to scab,

susceptible to cold and it cannot be top-worked on to 'Orlando'
because of xyloporosis. 'Lee' is a good pollinator for 'Orlando'
but it does not have much promise as a commercial variety. 'Rob-
inson' is a low pollen producer and usually 'Orlando' is used as a
pollinator for it.
'Clementine', 'Osceola', and 'Nova' have been investigated as
pollinators with no conclusive results. 'Murcott' and 'Dancy' tan-
gerines are unsatisfactory most years because time of flowering
does not overlap with 'Orlando' and the sweet oranges usually
give inconsistent results. Grapefruit blooms irregularly and is
sometimes sprayed with arsenic which may contaminate the tan-
gelos with an illegal residue on the fruit.
Generally, the pollinator is not very effective at distances
greater than 2 tree rows away. Therefore, the planting scheme
for pollinators should be to plant the pollinator in the third row
into the grove and then in every fifth row thereafter through
the remaining area of the grove. Other planting schemes may
be used to facilitate cultural practices and harvesting, such as
2 adjacent rows of pollinators rather than a single row.
Girdling has been used to increase the yield of seedless fruit
on 'Orlando' (5,8,12). This is done by using a hook-bladed knife
and cutting through the bark and into the wood, completely
around the trunk of the tree. The time for girdling is from full
bloom to petal fall, but girdling is effective up to two weeks
after petal fall if flower abscission has not occurred. Fruit from
girdled trees are equal in size to naturally seedless fruit from a
comparable size crop. The effect of girdling lasts only one season
and must be repeated each year. Girdling done commercially is
generally less effective than experimental girdling. This is be-
cause the experimenter probably used greater care in making the
cut on the trunk of the tree and chose vigorous trees because
they respond best to girdling. Also, grove laborers do not like
the job because it is rigorous work and requires crawling be-
neath the tree, moving limbs and other debris before girdling
may be done. For these reasons, girdling may ultimately prove to
be too expensive.
Gibberellic acid (GA) is used to increase yields of seedless
fruit on 'Orlando' and is cleared for use in Florida on all tangelos.
Fruit on trees sprayed with this growth regulator are generally
smaller and are delayed approximately 2 weeks in development
of orange peel color as compared to non-treated fruit. The yields
from GA-sprayed trees are about the same as those from girdled
trees. The time of application is from full bloom to two-thirds
petal fall at a concentration of 15 parts per million (ppm) GA.

At concentration above 25 ppm, fruit yields are reduced and ab-
normal fruit are produced. GA is normally applied as a dilute
spray until the tree is thoroughly wetted. Although little is
known about response to a concentrated GA spray, it is usually
better to apply growth regulators as a dilute spray, because a
small error in mixing a concentrate spray can either result in
damage to the trees or an ineffective application.

Cultural Practices
Irrigation-Most citrus responds favorably to irrigation and
since the 'Orlando' is weakly parthenocarpic, almost any condi-
tions which produce tree stress in the post-bloom period will
cause some fruit loss. This has been observed in 'Orlando' groves
where trees near a lake or on very fertile soil produced a larger
crop than trees in less desirable areas. Therefore, the tree should
be protected from moisture stress particularly during the period
from bloom to summer rains.
Spacing of 'Orlando' trees in the orchard should be determined
by rootstock and soil type as well as other environmental condi-
tions that affect tree growth. With the vigor and spreading type
growth that 'Orlando' inherited from its grapefruit parent, it is
unlikely to perform well if placed closer than 15 feet in the row.
Since the 'Orlando' responds well to hedging, it should be main-
tained as hedged rows of closely spaced trees. A general rule to
use when planting 'Orlando' would be to plant the trees on the
more vigorous rootstocks (rough lemon, sweet lime) at a spac-
ing of 25' X 25' or 20' X 25', and to plant those on rootstocks that
will produce smaller trees at least 15' X 20'.
Fertilization-A survey of 'Orlando' groves (2) has indicated
that relatively high rates of N are needed for the best fruit
yields. These applications of N must be made in split applications
and must be applied the previous year for the fertilizer to be
effective. If sufficient N is not applied to 'Orlando', a condition
known as "winter chlorosis," a yellowing of the leaves due to N
translocation, occurs during the fall and winter. For this reason,
N at rates of 200-300 #/acre, which is heavier than normal for
most citrus, is applied in 2 or more applications per year.
Pruning-Pruning of 'Orlando' is used to control tree size and
shape, to increase yields, and to improve fruit size, quality, pack-
out and color. It also facilitates orchard operations such as spray-
ing, cultivation, fertilization and harvesting by opening drive
middles in the grove. 'Orlando' responds well to pruning because
of its spreading growth habit, brittle wood and tendency to bear
fruit on its extremeties.

Hedging helps to control the spreading type growth and allows
the brittle wood of 'Orlando' to thicken so that it will be capable
of supporting a heavy crop of fruit without breaking. Hedging
also helps keep the tree growing vigorously and producing new
fruiting wood. Since the fruit is mature in early winter, hedging
and topping are usually completed before bloom. Hedging should
be done as early as possible after the fruit is removed and the
danger of freezes is past. The angle of hedging should be between
10-15 degrees from the vertical. This increases light reaching
lower branches and prevents skirt loss due to shading by rapid
regrowth at the shoulder of the tree.
Many growers use annual light hedging on all four sides (two
sides if hedged rows) on vigorous 'Orlando' groves with good
results. Others use a two-year cycle in which every other middle
is hedged every other year. Both methods provide good results.
'Orlando' should be topped before the trees require severe cutting
(no wood larger than three inches in diameter). The height
of topping varies from nine to 12 feet at the shoulders and from
10 to 15 feet at the center.
Again, optimum tree size will depend on rootstock, spacing and
vigor of the individual grove. Since the fruit will probably have
to be spot picked and clipped, lower tree heights are better for
the harvesting operation.
Topping is usually done on a two to three year cycle, depending
on the amount of regrowth that has occurred. For further in-
formation on equipment cost and brush removal consult Extension
Circular 388 "Maintenance Pruning of Florida Citrus".
Insect and Disease Control-'Orlando' tangelos are susceptible
to many of the insects and diseases that attack other Florida
citrus varieties. Complete recommendations for insect and disease
control can be found in the "Florida Citrus Spray and Dust
Schedule" (Extension Circular 393).
'Orlando' fruit usually is grown for the fresh market; there-
fore, it requires a more precise insect and disease control pro-
gram than does fruit grown primarily for concentrate. A par-
ticular problem observed by many growers is that 'Orlando' fruit
is even more attractive to mites than most other types of citrus.
These pests must be controlled for quality fruit and good fruit
yields. Also, the 'Orlando' seems to be severely damaged by greasy
spot which should be controlled with fungicidal sprays. Scab may
be a problem in some areas, but melanose has not been as serious
a problem as with other citrus varieties such as grapefruit. Oil
sprays should not be used on 'Orlando' later than 60 days before
harvest because these may retard development of good color.
Topworking-If the ecomonic situation discussed previously
does not improve, top-working may be a desirable alternative

for the producer of 'Orlando' tangelo. Top-working involves re-
moving the top portions of the trees and grafting or budding
a new scion variety on these limbs. This practice has several
limitations. It is difficult to find skilled laborers who are willing
to do this kind of work. A great deal of aftercare is required.
The cost of the top-working operation is great. The topworked
trees for the first few years are very susceptible to cold damage.
Topworking has been done in a variety of ways on many acres
of Florida citrus. The tree may be cut back to scaffold branches
and a graft used to attach the scion wood to the limbs. However,
the best way is to allow sprouts to develop from the cut-back
scaffold branches and then bud these.
The after-care of topworking is very important. First, the
trees must be whitewashed as this may reduce the amount of
suckering and minimize sunscald injury to the bark. Hand suck-
ering and selective pruning are essential to remove the 'Orlando'
suckers from the tree and to train the new scion properly. The
new shoot from each graft or bud should be clipped before it
exceeds 18" to 24" in length to promote early branching. Choose
only those branches with the widest crotch angles to reduce limb
breakage when the crop is matured.
Selecting the proper variety to use for topworking 'Orlando'
is very important because of the brittle wood of 'Orlando'. It is
unlikely that the 'Orlando' tree frame would be able to support
successfully a grapefruit scion without limb breakage with a
heavy crop. Only budwood free from xyloporosis and other
viruses should be used. 'Temple' would not be a good choice be-
cause xyloporosis-free budwood is not readily available.
Again, it must be stressed that topworking is expensive from
a labor standpoint because of the budding or grafting and the
amount of aftercare the grove will require.
Maturity: The 'Orlando' tangelo matures in November and
December with a bright orange color and a subacid flavor. Ninety-
five percent of all Florida tangelos (mainly 'Orlando') sold as
fresh fruit in the 1971-72 season, were shipped in November, De-
cember and January (5). Maturity standards are based on Brix,
acid and Brix/acid ratio. Juice content is not regulated. Unlike
oranges, higher standards are not required for color-added tan-
gelos. Specific figures for maturity standards are subject to
change; hence, Florida Department of Citrus regulations should
be consulted for current standards.
Harvesting: Clipping should be used for harvesting 'Orlando'
tangelos. Proper clipping, i.e, avoiding clipper cuts and short
stems which puncture other fruit will reduce losses from decay.

Harvesting without clipping tends to result in plugging (a por-
tion of the peel pulling out with the stem). Harvesting in January
and February would reduce the need for clippers due to a natural
loosening as the fruit matures, but holding fruit this late may
result in reduced yield the next year. Spot picking large fruit
with suitable color for the fresh market is sometimes economical-
ly justified particularly when sizes are heavy to 125 and below.
The main sizes shipped are 64, 80, 100 and 125 (number of fruit
per /45 bushel carton). Market prices are usually consistent for
the three larger sizes with a lower price for the smaller 125 size.
Processing: The use of tangelos for processing has been limited
to the percent of mandarin type juice currently allowed in frozen
concentrated orange juice. Cold-pressed tangelo oil is similar to
tangerine oil, according to taste panelists, with about half the
strength of tangerine oil (4). Tangelo oil has received good prices
when sold as a distinctive product, but commonly oranges and
tangelos are mixed before processing and this results in a blend
of citrus oils. On-tree prices of tangelos for processing are ap-
preciably lower than those for fresh fruit (Table 2).
Fresh Fruit Handling: 'Orlando' tangelos mature internally be-
fore desirable skin color has developed, therefore, degreening is
often necessary. Degreening with ethylene destroys chlorophyll
in the peel, thus allowing the orange color to predominate. Test
pickings for degreening are advisable to assure that a profitable
packout is feasible. Details of degreening room conditions are
found in Extenison Circular 289, "Recommendations for Degreen-
ing Florida Fresh Citrus Fruit."
Recent research (13) has shown that 'Orlando' has the peel
pigments that respond to "'cool coloring." In this technique the
fruit are held at cool temperatures (between 65 and 75 degrees
F) with very low (1 ppm or less) ethylene levels for one to two
weeks. Under such conditions, pale yellow or greenish 'Orlando'
tangelos develop a deep red-orange color without loss of internal
quality. This treatment is, however absolutely dependent on very
careful picking as the minor nicks and scratches encountered
in "normal" picking darken and tend to decay during "cool
Delayed handling between harvest and waxing contributes to
the peel injury, stem-end rind breakdown (SERB). SERB can
often be controlled by handling the fruit as quickly as possible
from the field through the packing house. When delays are en-
countered, fruit should be held in degreening rooms at 90 to 96
percent relative humidity without the addition of heat or ethy-
lene. More information may be found in Extension Circular 286,

"Practical Measures for Control of Stemend Rind Breakdown of
Decay control of Florida citrus is primarily accomplished by
postharvest application of approved fungicides and refrigeration.
Extension Circular 259, "Postharvest Decay Control Recom-
mendations for Fresh Citrus Fruit," lists the currently approved
fungicides with suggested rates and methods of application as
well as refrigeration temperatures.
Gentle handling of 'Orlando tangelo fruit is a means of assur-
ing a high quality fresh fruit in stores and homes. This gentle
handling includes all the steps from harvesting through market-
Table 1. Florida tangelo production
Total On Tree
Crop Year Production Price Per Box
(Boxes)* (Dollars)
1963-64 900,000 4.83
1964-65 1,000,000 4.00
1965-66 1,200,000 2.85
1966-67 1,700,000 1.64
1967-68 1,700,000 3.22
1968-69 1,800,000 2.47
1969-70 2,500,000 1.13
1970-71 2,700,000 1.04
1971-72 3,900,000 1.76
1972-73 3,500,000 1.25
Florida Crop and Livestock Reporting Service
1222 Woodward Street, Orlando, Florida
Florida Field Box=90 Ibs.

Table 2. Utilization and on-tree price per box of Florida tangelos*
Utilization of Production
Total Fresh Processed
Crop 1,000 Price Per 1,000 Price Per 1,000 Price Per
Year Boxes Box $ Boxes Box $ Boxes Box $
1967-68 1,700 3.22 1,415 3.73 285 .69
1968-69 1,800 2.47 1,214 3.40 586 .55
1969-70 2,500 1.13 1,397 1.89 1,103 .17
1970-71 2,700 1.04 1,607 1.65 1,093 .15
1971-72 3,900 1.76 1,896 2.55 2,004 1.01
1972-73 3,500 1.25 1,707 2.45 1,793 .10
Florida Crop and Livestock Reporting Service
1222 Woodward Street, Orlando, Florida
* Florida Field Box= 90 Ibs.

Literature Cited
1. Brown, H.D. and A.H. Krezdorn. 1969. Hand pollination tests and field
evaluation and pollinators for citrus. Proc. Fla. State Hort. Soc. 82:43-48.
2. Cooper, Talber, Jr., A.H. Krezdorn and R.C. Koo. 1969. The nutritional
status of the 'Orlando' tangelo (Citrus paradise macf. 'Duncan' X C.
reticulata Blanco 'Dancy'). Proc. Fla. State Hort. Soc. 82-34-38.
3. Hodgson, R.W. 1967. Horticutural varieties of citrus. In The Citrus
Industry. Vol. 1, Ch. 4. Reuther, W., H.J. Webber and L.D. Batchelor
(eds). University of California, Berkeley, California.
4. Kesterson, J.W. and R. Hendrickson. 1969. Florida expressed tangelo
oil. Amer. Perf. and Cosmetics 84(5) :51-54.
5. Krezdorn, A.H. 1960. The influence of girdling on the fruiting of 'Or-
lando' tangelos and navel oranges. Proc. Fla. State Hort. Soc. 73:49-52.
6. Krezdorn, A.H. 1967. The influence of seeds and pollen source on the
size of fruit. Proc. Fla. State Hort. Soc. 80:37-42.
7. Krezdorn, A.H. 1969. The use of growth regulators to improve the
fruit set of citrus. Proc. First Int. Citrus Symp. 3:1113-1119.
8. Krezdorn, A.H. and H.D. Brown. 1970. Increasing yields of the 'Min-
neola', 'Robinson' and 'Osceloa' varieties with gibberellic acid sprays
and girdling. Proc. Fla. State Hort. Soc. 83:29-34.
9. Krezdorn, A.H. and M. Cohen. 1962. The influence of chemical fruit-set
sprays on yield and quality of citrus. Proc. Fla. State Hort. Soc.
75: 53-69.
10. Krezdorn, A.H. and W.J. Phillips. 1970. The influence of rootstocks on
tree growth, fruiting, and fruit quality of 'Orlando' tangelos. Proc. Fla.
State Hort. Soc. 83-110-116.
11. Krezdorn, A.H. and F.A. Robinson. 1958. Unfruitfulness in the 'Or-
lando' tangelo. Proc. Fla. State Hort. Soc. 71:86-91.
12. Krezdorn, A.H. and W. J. Wiltbank. 1968. Annual girdling of 'Orlando'
tangelos over an eight-year period. Proc. Fla. State Hort. Soc. 81:29-35.
13. Stewart, Ivan and T.A. Wheaton. 1971. Effects of ethylene and tem-
perature on carotenoid pigmentation of citrus peel. Proc. Fla. State
Hort. Soc. 84:264-266.
14. Swingle, W.T., T. Ralph Robinson and E.M. Savage. 1931. New citrus
hybrids. U.S. Agr. Cir. No. 181.

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This public document was promulgated at an annual cost of
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production and utilization of a variety of Florida fruit.

Institute ol Food and Agricultural Sciences


Uiversity of Fm l


(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
Joe N. Busby, Dean