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Group Title: Circular - University of Florida Institute of Food and Agricultural Sciences ; 430
Title: Citrus nursery practices
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Full Citation
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Permanent Link: http://ufdc.ufl.edu/UF00067091/00001
 Material Information
Title: Citrus nursery practices
Series Title: Circular
Physical Description: 21 p. : ill. ; 23 cm.
Language: English
Creator: Tucker, D. P. H
Youtsey, C. O
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1980?
 Subjects
Subject: Citrus fruits -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Bibliography: p. 20-21.
Statement of Responsibility: D.P.H. Tucker and C.O. Youtsey.
General Note: Cover title.
Funding: Circular (Florida Cooperative Extension Service) ;
 Record Information
Bibliographic ID: UF00067091
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 19644171

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Full Text





HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida





Circular 430


Citrus Nursery

Practices

D. P. H. Tucker and C. O. Youtsey


WI:: .
SCl~r
'tc


Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
John T. Woeste, Dean for Extension


























































Cover photo Young budded citrus trees in nursery row




2






Introduction


This publication is primarily for those who are new to the
citrus nursery business. However, the experienced nurseryman
as well as the novice should find much helpful information pre-
sented here.
Consult your county Extension agent and the Florida Depart-
ment of Agriculture plant specialist in your area for current
recommendations and quarantine regulations concerning citrus
nursery stock production. The Florida Department of Agricul-
ture Citrus Budwood Registration Bureau in Winter Haven will
suggest sources of registered selections of virus-tested and horti-
culturally proven propagation material, including true-to-type
seed sources.
The commercial citrus grower requiring nursery trees for re-
plants or new grove plantings, should consider carefully the
advantages of obtaining them from reputable commercial nur-
series employing the most advanced propagation techniques and
utilizing the best horticultural selections. The profitable produc-
tion of well-grown nursery stock requires knowledgeable super-
vision, considerable labor, and a large investment in machinery
and equipment.

Site Selection
Nursery site selection is of great importance. A nursery site
is best located away from developed areas in a place where the
frost hazard is minimal. Well drained, virgin soil is preferred
and an adequate supply of good quality water is essential. Good
access roads to the site and within it are desirable for inspection,
cultural operations, digging and transportation. The site should
also be free of parasitic nematodes which attack citrus, such as
the burrowing nematode and citrus nematode. Before planting,
citrus nursery sites must be approved by the Division of Plant
Industry, Department of Agriculture and Consumer Services.

Nursery Site Hygiene
Aspects of disease control will be discussed elsewhere, but it
is important to understand the role that sanitation plays in the
overall control of disease problems. The single, most destructive

1Extension Horticulturist, Fruit Crops Department, IFAS, University of Florida, Gainesville.
2Plant Specialist Supervisor, Bureau of Citrus Budwood Registration, Division of Plant
Industry, Winter Haven, Florida.







disease encountered in the nursery is Phytophthora parasitica.
This fungal organism is one of a group of "water molds," so-
called because they spread and grow rapidly under high mois-
ture conditions. Rhizoctonia is another fungus that frequently
causes "damping-off" in seedbeds in warm weather. Phyto-
phthora is a common soil inhabitant widely distributed even
where not producing visible symptoms. Under favorable condi-
tions these organisms cause damage to the roots and lower stems
of seedlings, rendering them unfit for further use. They are
spread by the movement of infested soil, splashing of rain and
irrigation water, or by heavy run-off from infested areas.
Sanitation practices incorporated into the daily work schedule
as suggested below can greatly reduce disease incidence in the
nursery:
1. Clean equipment before bringing it into the nursery and
confine it to nursery use.
2. Do not move contaminated soil or equipment into fumigated
areas.
3. Remove diseased plants and isolate the area before the
disease can be spread.
4. Remove plant residues as soon as possible after digging
trees.
5. Use only healthy seedlings for lining-out, discarding any
plants with evidence of root or stem rot.
6. Keep storage or holding areas free of debris and periodi-
cally treat with fungicides to reduce disease spread.
In addition to soil fungi, the exocortis viroid presents a special
sanitation problem. This disease, when present in the plant, can
be spread on budding knives, clippers and hedging shears. To
prevent this, each budder should be supplied with a small con-
tainer of sterilant (10 percent household bleach, the active in-
gredient of which is sodium hypochlorite), to disinfect knives
and clippers when propagating or pruning. This should become
a closely supervised procedure as this disease affects many scion
rootstock combinations that can result in unproductive grove
trees.

Seed Bed
The seed bed should be located preferably on sloping land in
an area separated from the main nursery (Fig. 1). This will
avoid accumulation of run-off from irrigation or heavy rain that
may transport disease organisms into the growing area or re-
sult in excess moisture in the root zone. The soil should be fumi-












4 I

rl 4 K


Figure 1. Citrus seedlings in seedbed


gated for the control of nematodes, diseases and weeds, especi-
ally if previously cropped. Soil acidity should be adjusted to pH
6.5 to 7.0 during land preparation. Consult your county Exten-
sion agent or Department of Agriculture plant specialist for soil
testing, fumigant type and rate recommendations.
Seedbed fumigants have at times resulted in irregular seedling
growth following germination which may be characterized by
stunting and nutrient deficiency symptoms, primarily those of
phosphorus. The problem has been associated with the lack of
mycorrhizal fungi in fumigated nurseries as these fungi are very
sensitive to methyl bromide. Experimental inoculation of citrus
seedlings with such fungi in fumigated soil has virtually elimi-
nated the problem and actually resulted in spectacular growth
increases in California. While some inoculation work has been
conducted in Florida, large scale field trials have not been con-
clusive. Seedbed aeration by cultivation following fumigation
and heavy preplant applications of phosphate have been found
to reduce the occurrence of this problem. Seedlings should be
closely observed for poor growth and bronzed leaves.
The careful selection of seed for planting is a very important
factor in the ultimate performance of the tree. Some varieties
are capable of transmitting psorosis virus to seedlings through
the seed from infected mother trees. Seedlings from off-type
trees do not react to diseases and growing conditions in the same







way as standard true-to-type selections. For these reasons seed
should be selected from established seed source plantings chosen
for uniformity and freedom from viruses.
While citrus seed may be planted at any time of the year, late
winter and spring are most suitable. Strong winds during this
period may cause damage to young seedlings from blowing sand;
therefore, the planting of cover crops such as oats and rye be-
tween rows is commonly practiced to reduce this effect. Seeds
planted after May l15-30 will emerge under weather conditions
most favorable for the development of "damping-off" diseases,
possibly resulting in a poor survival of young seedlings.
Seed may be planted by hand in open furrows approximately
1 inch deep, scattered evenly in the bottom of the furrow, or a
planting board may be used to ensure that seed is spaced evenly
at a uniform depth. While this method takes considerable time,
it results in straighter, more uniform seedlings with less benched
root formation, and makes maximum use of available seed.
Broadleaf types such as sour orange, rough lemon and C. macro-
ph ylla should be planted further apart than varieties with small
leaves such as 'Carrizo' citrange, P. trifoliata or 'Cleopatra'
mandarin. Width of rows should be adapted to equipment used
for nursery operations. Commercial seed planters are available
but must be adapted for use in citrus seed beds.
While the best seed germination may be expected when seeds
are planted immediately after extraction, storage is often neces-
sary in order to plant certain species at the desired time. Seeds
should be extracted and washed with clean water and surface-
dried in a cool, shady place on a clean wood or screen surface.
The Florida Department of Agriculture Bureau of Citrus Bud-
wood Registration, Winter Haven, offers a hot water seed treat-
ment service for the prevention of seed-borne Phytophthora
parasitic infection. For small quantities, a dip treatment of
8-hydroxyquinoline sulfate (1 'per gal of water) for 2 minutes
is suggested. Seeds may be stored for several weeks in the refrig-
ertor at 45 F packaged in plastic refrigerator bags. There are
sources of true-to-type virus indexed seed in Florida and Cali-
fornia, the locations of which may be obtained from the Citrus
Budwood Registration Bureau.

Irrigation
Most commercial citrus nurseries are irrigated by permanent
overhead sprinkler systems. The design of such systems is im-
portant to ensure the even distribution of water. Such even dis-







tribution assumes additional importance if the system is to be
used for the application of fertilizers. Uneven distribution will
lead to considerable differences in amounts applied, with con-
sequent injury to or deficiency in plants receiving the higher
or lower amounts.
A carefully managed water regime is essential for the produc-
tion for healthy seedlings. The use of excessive irrigation has
been determined to be the cause of many nursery problems. The
frequency of seedbed irrigation depends on soil type, tempera-
ture, rainfall and size of seedlings. Frequent light watering is re-
quired for newly planted seedbeds. As seedlings become well
established, less frequent heavier applications should be made
to maintain maximum growth. Prolonged wet soil conditions,
high humidity, and crowded seedbed conditions are conducive
to the development of soilborne Phytophthora and Rhizoctonia
fungi with resulting severe seedling losses. Certain citrus species
such as sweet orange, rough lemon, 'Milam', 'Carrizo' citrange,
and 'Cleopatra' mandarin are more susceptible to root diseases
than others and demand careful attention. After seedlings have
emerged, irrigation should supplement rainfall to maintain soil
moisture.

Disease Control
One of the keys to the maintenance of disease-free conditions
is the prudent use of irrigation. The incidence of "damping-off"
can be reduced by the use of pre-plant fumigation practices.
Fungicidal drenches of Benlate have also been evaluated for the
control of "damping-off"; however, specific recommendations are
not available at this time. Where drench operations prove im-
practicable, spray applications at high volume may be made so
that the spray deposit eventually reaches the soil. The disease,
Alternaria, to which rough lemon and to a lesser extent 'Rang-
pur' lime rootstocks are susceptible, may be controlled by the
use of copper or Difolatan sprays. Sour orange scab, which is a
serious problem with sour orange, rough lemon, 'Milam,' and
occasionally other rootstocks, may be effectively controlled with
Benlate or Difolatan. In soils where copper levels are above
50 lb/A, the use of copper fungicides is discouraged. The use
of Difolatan at full dosage rates may cause foliage damage on
certain varieties; therefore, precaution is advisable. Fungicides
should be applied judiciously, with more frequent applications
being required during periods of active growth and frequent
rainfall periods, particularly during the summer months. Con-







trol of fungus diseases can be most effective when sprays are
applied on a regular basis before infection is apparent. Consult
the current Florida Citrus Spray and Dust Schedule for recom-
mendations on materials and rates for control of all pests and
diseases.

Fertilization
Fertilizer programs are difficult to formulate in citrus nur-
series because of the rapidly changing growth stages. Rates
given represent guidelines only and individual nurserymen will
formulate their individual programs. Since excessive fertilizer
applications have been the rule rather than the exception, it is
prudent to note that continual luxury consumption of nutrients
and resulting vigorous vegetative growth will enhance the in-
cidence of disease, especially in seedbeds. Soil tests should be
made at least once a year to determine the status of pH, calcium,
phosphorus, copper, and total soluble salts.
When the seedlings are 1 to 11/2 inches high, the first light
application of a low analysis mixed fertilizer should be made to
the seed bed. Use approximately 200 to 500 pounds of fertilizer
per acre, depending upon natural soil fertility. Fertilizer is best
applied prior to or following an irrigation or good rain. Foliage
should be thoroughly dry before application to prevent leaf burn.
Fertilizer should be applied at 3-to 4- week intervals, with a
gradual increase to a maximum of 500 to 1,000 pounds per acre
when the seedlings are approximately 12 months old. A ratio of
1-1-1, with 15 to 20 percent of the nitrogen derived from organic
sources, is recommended.


Lining Out
The area to be used for growing the nursery trees should be
thoroughly tilled, leveled and cleared of all roots and perennial
weed residues. Necessary soil amendments should be added at
this time to adjust the pH to 6.5 to 7.0. As with the seedbed,
this site should be in a carefully selected location.
When seedlings have reached 3/16 to 14 inch in diameter,
they are ready to be transplanted or "lined out" in rows for
budding. Seedlings held in the seedbed for as long as a year
are more likely to be infected with root diseases and scale in-
sects due to crowding. Large seedlings, especially those of tri-
foliate hybrids, are harder to transplant successfully, with the
resultant expense of resetting.







Seedlings should be dug from the row with spades or mechan-
ical equipment. Care should be taken to leave as many roots
undamaged as possible. Tops should be pruned to 8 to 10 inches
and extremely long or damaged roots removed. Seedling roots
should be dipped in a fungicide such as Captan 50 W (! 11b 100
gal) after trimming.
When digging, "off-type" seedlings should be discarded, and
plants showing any degree of diseased roots or stems culled at
this point. Use of diseased seedlings can only result in produc-
tion of diseased trees. Seedlings should te graded into 2 or
3 sizes and planted in the nursery rows by size groups. This
procedure results in uniform seedlings that will reach the same
growth stage at the same time and will be ready for similar
treatments. This practice will require less labor and yield a
higher percentage of salable trees.
The size of the nursery area and type of cultivation will dic-
tate to a large extent the row spacing and distance in the row
that seedlings should be set. Current practice is to plant seed-
lings as close as 4-6 inches apart in the rows as opposed to the
former practice of 12 inches. While close planting makes maxi-
mum use of available land, trees that are to be held more than
one season in the nursery may be more susceptible to scale in-
sects and diseases as a result of shading and poor air circulation
near the soil surface. Effective spray coverage is also less likely
to be achieved under crowded conditions.
Liners may be set at any time of the year; however, small
seedlings set in March or April are often large enough to bud by
fall. Dormant buds can be forced'in the spring and grown to a
size large enough to move by mid to late summer. Seedlings as
large as l1/1 to :!I inch set in the late summer or fall can be well
established by March or April of the following year, so that
trees budded at that time will be ready for movement by fall.
The soil should contain adequate moisture before lining out
for planting furrows to remain open. Liners may be set mechan-
ically or by hand; however, with either method it is important
not to plant liners any deeper than they grew in the seed bed.
The soil should le packed firmly around the roots leaving no air
pockets. Frequent light irrigation, :l to-1 inch per application,
should be applied until seedlings become established. This is es-
pecially important during the warm summer months. Irrigations
can then be scheduled at 2/ to 1 inch per week as needed to
supplement rainfall.
Seedlings should be fertilized within 2 to 1 weeks after lining
out, with an initial application of about 50 pounds per 1,000







seedings of an 8-2-8 mixture or approximate equivalent analysis.
The seedlings should be fertilized every 3 to 4 weeks and when
approximately 3 months old, may receive 75 to 100 pounds of
fertilizer per 1,000 trees. High analysis fertilizers should be used
with caution as plant damage can occur.

Weed Control
In the past, weed control has undoubtedly been the most
costly production practice in the nursery operation. Although
fumigation offers excellent weed control for some weeks after
the operation, severe weed reinfestation will follow. Such weed
growth will quickly get out of hand, compete with seedlings, and
hinder nursery operations. Although costly, hand weeding oper-
ations are sometimes necessary. Cultivation is practiced with
equipment modified for nursery use; however, care must be
taken not to damage the plants and tillage depth should be kept
to a minimum. While herbicides are now used in commercial
nurseries with increasing frequency, it should be remembered
that citrus in young stages of growth in the nursey is very sus-
ceptible to these materials. Pesticide manufacturers are hesitant
to seek herbicide registrations for nursery use due to the low
volume usage compared with the high per acre dollar value of
the crop.
Suggestions for weed control may be obtained from a Univer-
sity of Florida Extension weed specialist. It is essential that
weed growth be controlled at very early stages, preferably at
germination, since lower herbicide dosage rates are likely to be
more satisfactory. Spot treatment of isolated dense areas of
weed growth may be done using contact or sytemic-type herbi-
cides provided young seedlings and budlings are adequately
shielded from the spray. The application of herbicides through
the sprinkler system is not an approved method of application.

Budding the Nursery
Plants propagated by budding offer many advantages over
plants propagated from seeds, layers or cuttings. Budding allows
the grower to choose a given scion on a rootstock so that it will
be better adapted to certain conditions. Benefits from the root-
stock include vigor, productivity, fruit quality and disease or
nematode resistance. In addition, a budded plant will flower and
produce fruit at an earlier age than seedling plants. Plants pro-
pagated from the same budwood source will usually be geneti-
cally uniform and true-to-type.







The first step in preparation for budding a citrus nursery is
the selection of budwood (Fig. 2). This is perhaps one of the
most important steps in developing a superior nursery tree.
When possible, budwood should be selected under the supervision
of a Division of Plant Industry representative, and it should be
registered free from as many virus or virus-like diseases as
possible. Full participation in the Budwood Registration Pro-
gram, sponsored by the Division of Plant Industry, is strongly
advised.


Figure 2. Selection of suitable budwood


Budwood should be selected from trees known to be free of
bud-transmitted diseases or other bud-propagated disorders that
may seriously affect the productivity of the tree on the partic-
ular rootstock selected. Budwood should be taken from true-to-
type trees known to possess the ability to produce large quanti-
ties of high quality fruit. Bud sticks are usually taken from
mature wood of the previous flush of growth, but less mature and
more angular wood can be used with good results if particular
care is taken when wrapping. It is preferable that budwood be
dormant with well-developed buds. Each bundle of budwood
should be clearly marked as to variety and tree from which it
was taken.







Best results will be obtained when budwood is used fresh.
However, if storage is desired so that the budding operation
may be conducted at a later date, it is suggested that sticks be
tied together in small, properly labeled bundles, packed in clean,
damp (not wet), coarse sawdust, and stored in a cool dry place.
Buds may also be packaged in plastic bags with damp sphagnum
moss and stored in the refrigerator at 45 to 50F. Do not at-
tempt to store budwood longer than 1 to 2 months under these
conditions.
Citrus can be budded whenever the bark will "slip" or sepa-
rate readily from the wood. This condition exists during periods
of spring, summer, and fall when most nurserymen bud trees.
Budding of larger size seedlings can be done after the stock is
established long enough to facilitate efficient handling (usually
6 to 8 weeks after lining out). Since the benefits derived
from disease resistance of the rootstock may be negated by
placing the bud too near the soil, the preferred budding height
is 6 inches above ground level. High budding takes advantage
of rootstock tolerance to Phytophthora parasitica.
One method of budding citrus is to insert a shield into an in-
verted "T" slot cut into the bark of the stock. The trunk of a
seedling, %8 to :V, inch caliper, should be pruned clean of thorns
and limbs ahead of the budder to save time. A sharp budding
knife is used to make a downward cut about 11/ inches long.
This is a vertical cut through the bark, deep enough into the
wood to be certain that the bark has been completely cut. A
cross cut is then made at the bottom of the vertical cut, thus
forming the inverted "T." In making this cut, the back of the
knife blade is turned slightly downward so that the cut is a little
upward as well as across the stock. At the finish of the cross cut,
the knife blade is turned slightly upward and given a slight
twist to open the bark at the junction of the horizontal and
vertical cuts (Fig. 3).
The bud is now cut from a budstick held with the terminal
end away from the budder. The cut is toward the budder and is
made parallel with the axis of the budwood, using a slightly
rotating motion. The knife is held with the blade almost parallel
to the axis of the budwood, and the thumb of the knife hand is
used to steady the budwood while making the cut. This will give
a shield-shaped piece of bark and wood about 'i, to 1 inch long
with a flat, smooth cut surface (Fig. 4). The bud should not be
scooped out as this causes too much wood to be taken with the
bud. The bud should be handled between the thumb and the,
knife blade and inserted in the stock. (Figs. 5, 6)


































Figure 3. Preparing seedling for budding


Figure 4. Removal of bud from stick.


4~ 1




















Figure 5. Insertion of bud into incision on seedling


OM


Figure 6. Bud in place ready for wrapping
14


A







Another method of budding which has become popular with
many budders is known as the "hanging bud." In this method,
the budder cuts a section of the bark from the stem about the
size of the bud which is to be used. A "lip" is made at the upper
end of the cut in order to hold the bud in place. The bud is cut
in the same manner as described for the inverted "T" method.
In addition, the top of the bud should be steeply tapered by cut-
ting off the front surface. The tapered cut forms a surface which
can be easily inserted under the "lip" that has been cut on the
stock. The most popular means of wrapping a bud is with 3-mil
polyethylene plastic strips approximately 5/ inches wide and
6 to 10 inches long depending upon the size of the stock. The
wrap is started below the bud and pulled firmly but not too
tightly around the plant to just above the vertical cut. There,
the end is placed beneath the last circular wind of the wrap and
pulled tightly in place (Figs. 7, 8).

Nursery Care
Following spring budding, wraps may be removed after 14
to 18 days, and should not be left on for more than 30 days.
Inspect for callus formation around the edge of the bud before
unwrapping. After the wrapping is removed, the seedling top
may be lopped over and allowed to remain, nourishing the root-
stock as the new bud sprouts and reducing the shock to the plant.











S







Figure 7. Wrapping bud with budding tape




















A4


Figure 8. Wrapped bud

In lopping, the seedling is cut approximately % the distance
through the stem 11/2 to 21/2 inches above the bud, and the top is
pushed over and laid on the ground (Fig. 9). Some prefer to
remove the top completely after the bud is several inches high,


Figure 9. Lopped seedlings with established bud








while others bend the seedling over to the ground and pin the
top to the soil with wire or tie in position with string.
Well callused buds from dormant budding in late October or
November may be unwrapped before banking. Should trees have
to be banked before unwrapping, buds under banks should be
inspected at intervals during the winter to determine that no
abnormal loss is, occurring. The bank is usually removed in
February or early March as soon as the danger of frost has
passed. The wrap is removed and the top of the seedling is
lopped above the bud, allowing the bud to grow. When growth is
2 to 4 inches long, a stake is placed beside the bud for protection
and support. When 4 to 6 inches high, the bud may be tied to
the stake with string or plastic to help prevent breakage. Where
wire ties are used, girdling may result if they are not loosened
or removed periodically. After 12 to 16 inches of growth the
seedling tops may be removed by cutting smoothly just above
the bud union. Such bops serve to harbor insects, mites and
foliage diseases if left too long in the nursery. The young shoot
is trained to the stake until it is 18 to 20 inches tall (Fig. 10).
At this point, the top should be pinched or cut in order to stimu-
late lateral growth.


Figure 10. Young nursery trees with shoots trained to stakes







During the growth of the tree, weed growth should be kept
under control, using extreme care not to injure the bud. In the
absence of rainfall, 1 to 112 inches of supplemental irrigation
should be applied each 7 to 10 days. Rootstock sprouts should be
broken or cut as soon as they develop since they retard the
vigor of the young bud. Rough removal of large sprouts will re-
sult in open wounds through which disease organisms may gain
entrance. A non-asphalt base formulation of naphaleneacetic
acid (NAA) at concentrations of 1/2 to 1 percent has shown some
promise in controlling rootstock sprout growth on established
budlings; however, it is not approved for such a use at this time.
When the bud is 3 to 5 inches in length, fertilizer may be
applied at the rate of 50 pounds of a 6-6-6-4-0.5-0.5 (N-P-K-
MgO-MnO-CuO) or equivalent analysis mixture per 1,000 trees.
By the time the bud reaches the top of the stake, a similar
fertilizer may be applied at the rate of 100 pounds per 1,000
trees every 4 to 6 weeks until about September 15. From time
to time during the growth of the nursery tree, nutritional sprays
may be applied if soil tests (for copper) and visual symptoms
(zinc and manganese) so indicate. Insect populations and di-
sease pressure must be kept at a minimum during the growth
of the young nursery trees to insure their healthy and vigor-
ous condition. Consult the current Florida Citrus Spray and Dust
Schedule for recommendations.

Cold Protection
Most commercial nurserymen in central Florida employ cold
protection practices, with both irrigation and heat being used
as the need arises depending on environmental conditions. At
the lining out (liner) and budling stages of growth, trees are
more susceptible to cold damage than established trees in groves.
Investment in a good heating system is, therefore, entirely justi-
fled. Permanent automatic heating systems are the obvious
choice rather than those requiring high labor input. More de-
tailed information on local frost and freeze warning services,
and critical temperatures at which cold protection operations
should be initiated may be obtained from your county exten-
sion agent.

Equipment
Much of the equipment used in Florida citrus nurseries has
been developed through the modification of existing equipment,







or is specifically designed by individual nurserymen. Such equip-
ment is best observed by visiting some of the larger commercial
nurseries.

Digging, Preparation and Shipment of Nursery Trees
Quite often, priorities of labor, land preparation and equip-
ment use will dictate the time of grove planting. The time of
cutting back and digging the trees in relation to the growth
cycle should be considered. Trees cut back and dug just before
the new growth cycle usually respond best after transplanting
in the grove. Those dug during or immediately after the growth
flush may result in weaker growth. This difference in growth
performance of the tree may be explained by a maximum storage
of carbohydrates in the roots in the first case and a depletion
in the later. The use of anti-transpirants (materials which re-
duce water loss from trees) sprayed on trees after cutting back,
but before digging, has shown some promise for improving the
performance of trees after transplanting into the field.
Shortly before digging trees, tops should be cut back to the
scaffold branches (hat-racking) preferably leaving some foliage
intact. Trees are then dug mechanically with a tractor-drawn
subsoil blade in most larger commercial nurseries, or with a
straight-edged nursery shovel. Root systems should be dipped
in a fungicidal solution of Captan and water to reduce the spread
of fungal infection to healthy trees. Trees should then be stored
in a closed truck body or in the shade under cover and subjected
to continual sprinkling with water to ensure that root systems
are not allowed to dry out.
In many instances, the death or unsatisfactory growth of
recently planted young grove trees has been attributed to negli-
gence in handling at some stage between the nursery operation
and tree planting. Desiccation of the feeder root system due to
inadequate watering, exposure to wind and heat after digging,
during transport and before planting will result in root death
and consequent inability of the young tree to recover from the
shock of moving. Great care should be taken to ensure that
trees are delivered to the planting site in a healthy condition,
and that the grower is adopting sound planting and post-plant-
ing care procedures. This, of course, includes the very critical
watering phase of the operation. When tree mortality occurs
some weeks after planting, it is always difficult to determine
whether the grower or the nurseryman should accept responsi-
bility. The grower or some other knowledgeable individual







should be present at the planting site to inspect the trees on
arrival and determine whether they are in satisfactory condition.
Spring, summer and fall planting should be associated with
certain problems, including extended periods of drought, intense
heat stress and the advent of cold weather, respectively. In-
stances of tree loss during the months of July, August and
September have been attributed to heat stress, associated with
an insufficient frequency of rainfall or supplemental irrigation.

Summary
Citrus nursery practices are adapted to the individual nursery
operation, and will vary with location, soil type, varieties, root-
stocks, and available labor and equipment. Hopefully, the infor-
mation contained in this publication can be combined with
practical experience to improve nursery management practices,
increase returns to nurserymen, and produce superior trees for
the citrus industry.

The listing of specific trade names here does not consti-
tute endorsement of these products in preference to others
containing the same active chemical ingredients.

Recommended Reading
Baker, W. F. Ed. 1957. The UC system for producing healthy,
container-grown plants Manual 23. Calif. Agr. Exp. Sta.,
Ext. Service. Div. of Agr. Sci., Univ. of Calif., Berkeley,
Calif.
Florida Citrus Spray and Dust Schedule. 1977. Cir. 393-C. Fla.
Coop. Ext. Service, IFAS, Univ. of Fla., Gainesville, Fla.
Grimm, Gordon R. and Rodney Whidden. 1966. Preventing
infection from the foot rot fungus. Proc. Fla. State Hort.
Sci. 79: 73-75.
Knorr, L. C. 1973. Citrus diseases and disorders. The Univ.
Presses of Fla., Gainesville, Fla.
Newcomb, D. A. 1973. Citrus nursery operations. Proc. First
Intl. Citrus Short Course. 152-158. Fla. Coop. Ext. Service,
IFAS, Univ. of Fla. Gainesville, Fla.
Opitz, K. W., R. A. Platt and E. F. Frolich. 1968. Propagation
of citrus. Cir. 546. Calif. Agr. Exp Sta., Ext. Service,
Div. of Agr. Sci., Univ. of Calif., Berkeley, Calif.
Pratt, Robert M. 1958. Florida guide to citrus insects, di-
seases and nutritional disorders in color. Agr. Exp. Sta.,
Univ. of Fla., Gainesville, Fla.







Reuther, W. Ed. Citrus Industry. Vol. 1. 1967. History, world
distribution, botany, varieties. Vol. 2. 1968. Anatomy,
physiology, mineral nutrition, seed reproduction, genetics,
growth regulators. Vol. 3. 1973. Propagation, planting,
weed control, soils, fertilizing, pruning, irrigating, cli-
mate, frost protection. Revised edition. Div. of Agr. Sci.,
Univ. of Calif., Berkeley, Calif.
Whiteside, J. 0. 1971. Some factors Affecting the Occurrence
and Development of Foot Rot on Citrus Trees. Phyto-
pathology, Vol. 61, No. 10, 1233-1238.
Whiteside, J. 0. 1972. Foot Rot of Citrus Trees The impor-
tance of high budding as a preventive measure. The
Citrus Industry. April. pp. 14-19.






































































22































This publication was promulgated at a cost of $701.59, or
.14 cents per copy, to inform nurserymen, growers and
production personnel about citrus nursery practices.





Single copies are free to residents of Florida and may be obtained
from the County Extension Office. Bulk rates are available upon
request. Please submit details of the request to C.M. Hinton, Publi-
cation Distribution Center, IFAS Building 664, University of
Florida, Gainesville, Florida 32611.




6-5M-77



COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
K. R. Tefertiller, Director
























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