Citrus Experiment Station
Mimeo Report CES-67-20
200-1/5/67 Lake Alfred, Fla.
ECONOMICAL CITRUS PRODUCTION PRACTICES
Herman J. Reitz
and the Citrus Experiment Station Staff
Citrus growers today have two overriding interests. One is to find profitable
markets for the large crop of fruit currently on trees, and the second is to use the
most economical grove production practices available, consistent with good grove
health and adequate yield of high quality fruit. On a dollars and cents basis,
there has always been ample reason for utilizing the most economical practices. If
fruit prices are high, this is a way to make additional profits. When fruit prices
are low, use of these practices is a necessity.
One of the most savored cliches in the citrus industry holds that there are as
many production programs as there are grove owners, and it is frequently added that
all these programs make money for the grove owner. This may be nearly true in
times of high prices, but when prices are low the choice of money-making practices
is much more greatly limited.
Most growers are in the business on a permanent basis, and must take a long-
term view and weather the occasional poor year. Efforts toward good management now
need to be intensified on all fronts, including the keeping of accurate grove
records, the efficient scheduling of grove operations, the economical purchasing of
all supplies, the competent handling of more or less fixed costs such as financing
and taxes, the marketing of the crop, and the actual making of choices of grove
practices to employ. Only the latter of these items is in the scope of this
Whether prices are high or low, groves must be maintained in a highly produc-
tive condition. The only return a grower receives from a grove operation comes
from the sale of fruit, and the more good quality fruit he has to sell, the greater
are his chances of making money on his grove. Certainly no one can now afford to
spend money on unnecessary grove operations of any kind or for frills, fads, patent
medicine, or magical remedies.
High fruit quality is as important as high yield. Fruit with the highest yield
of solids per box will find ready acceptance in the chilled juice and frozen concen-
trate outlets. Fruit with highest exterior quality, in desirable sizes, will find
an outlet in the fresh fruit market. Large amounts of money can be lost by running
scarred, disfigured, and green fruit through packinghouses. For fresh fruit, a high
pack-out is mandatory for a profitable operation. This is a much more important fac-
tor in years of low prices than in years of high prices, when all fruit, including
packinghouse eliminations, will pay a good return at the cannery. Crops of fruit
with low soluble solids, green color, disfigured by melanose and rust mite, will be
discriminated against in all the channels of the trade, and when fruit is plentiful
may never find a market outlet. In past years, there has been economic abandonment
of oranges, grapefruit, and tangerines in Florida, and low quality fruit is most
likely to meet this fate.
A grower may find it economically impossible to maintain a Spartan but ade-
quate program on all the groves under his management. In such cases, he might do
well to concentrate his resources into a thoroughly effective program on his most
valuable varieties, his highest producing individual blocks, and those most eco-
nomical to operate, while abandoning blocks affected with disease such as spread-
ing decline, fringe areas chronically affected adversely by water damage or recur-
ring cold injury, or blocks with undesirable varieties. This would be preferable
to scattering his resources over his entire acreage in a skimpy, ineffectual pro-
gram that would result in low yields or poor quality fruit.
For many years, the Citrus Experiment Station has joined with other agencies
in issuing recommendations on cultural practices. Some of the more widely
distributed of these are Bulletin 536B, "Recommended Fertilizers and Nutritional
Sprays for Citrus," the "Better Fruit Program Spray and Dust Schedule," and the
"Citrus Insect Control" series of articles issued quarterly, published in
The Citrus Industry. Numerous articles have been written on a timely basis as re-
search results became available. These recommendations have always been issued on
the basis of most economical production costs, whether fruit prices were high or low.
In the remaining portion of this article, the essential elements of an economi-
cal production program will be emphasized.
Spraying.- Spraying is the most difficult and costly of all the production prac-
tices in the grove. There are many species of insects and mites, several fungus dis-
eases, and at times nutritional deficiencies that must be brought under control.
There are numerous chemicals available to be chosen to fit individual situations.
Also, the operation of the spraying machinery requires great attention to details.
However difficult or expensive the operation may be, it is still necessary if high
yields of high quality fruit are to be produced, and productivity of the grove is
to be maintained.
The elements of a successful spraying operation include: grove inspection,
timing of the application, choice of materials, and operation of the equipment to
obtain good coverage.
Thorough inspection of the grove before spraying is necessary to learn which
pests actually exist in the grove, so that when the decision is made to spray, all
compatible materials needed to control the existing or threatening pests can be
included. It is much more economical to spray for a combination of conditions at
one time than to make repeated applications.
Timing of the postbloom and summer sprays is generally fixed by the stage of
tree growth or by the calendar. It is a very reasonable assumption that spray
applications will be needed in most groves at these two times. Inspection should be
sufficiently thorough to ensure that all threatening conditions are covered when the
application is made. During the remainder of the year, timing of sprays is more de-
pendent upon inspections to determine when the pests, primarily mites, are present.
In rust mite control, it is very important to spray before an increasing population
gets established on the fruit.
Considerable money will be expended for spray materials. Consequently, before
making a decision, a clear idea should be obtained as to the relative costs of ma-
terials for accomplishing the control of the pests present in the grove. This does
not necessarily mean that the cheapest materials are the best. For example, sulfur
is a cheap material and gives quick control of rust mite, but reinfestations fre-
quently occur in a short time. Further, scales and spider mites may also become
more troublesome if sulfur is used excessively. Therefore, sulfur should be used
only as an emergency treatment between the postbloom, summer, or fall mite sprays,
as discussed in the Spray Schedule.
Operation of the spray machinery should not be casually turned over to poorly
trained, indifferent help. This is especially true for low gallonage (high concen-
trate) applications. Calibration of the equipment to deliver the proper gallonage
is of the utmost importance. The spray pattern should be continuous and cover the
entire height of the tree. Approximately two-thirds of the spray should be de-
posited in the upper half of the tree. Competent personnel should ensure that the
calibration and rate of travel of the machine are as described in the Better Fruit
Program Spray and Dust Schedule. A good rule of thumb for gallonage per tree is
to use the number of gallons per tree equivalent to the height of the tree plus 5.
Thus, a 15-foot tree would require 20 gallons of dilute spray. Economies can be
made by concentrate sprays, but correspondingly, higher quality and better trained
help must be used in this kind of operation.
A great deal of money can be lost needlessly in the spraying operation, either
by putting on unnecessary materials or amounts of sprays, or by making inadequate ap-
plications. If, in hopes of saving money, a sprayer is sent into a grove to make a
skimpy, inadequate application, the grower might do well to cancel the entire opera-
tion and save all the expense. The results in pest control may be about the same.
Fertilizing.- Costoof fertilizing have been held down fairly well in the past
several years. One of the most common mistakes growers have made in recent years has
been excessive use of fertilizer. Groves do not need more than the amount of fer-
tilizer recommended in Bulletin 536B, and money need not be spent on fertilizers in
the more or less blind faith that some intangible benefit will be attained. Avoid
purchase and use of materials that do not carry a complete guaranteed analysis on
the fertilizer tag.
Most mature trees need not be fertilized more than twice a year. On finer tex-
tured soils in coastal areas, very satisfactory results will be obtained from one
application per year. Possibly the Orlando tangelo or the lemon, which seem to be-
come nitrogen deficient more readily than other varieties, would benefit from three
applications, but these varieties are exceptional. An application should be made in
late fall or winter and followed by one between the postbloom and summer sprays.
Timing is not very important and fertilizers should be applied when labor is avail-
able between other operations such as spraying, in which timeliness is of critical
For young bearing and mature bearing trees, 100 to 200 pounds of nitrogen per
acre per year and an equivalent amount of potash are recommended. Magnesium should
be used at the same ratio as recommended in Bulletin 536B. If phosphate is used
during the first few years in the life of a young grove, it can then be safely
omitted from many groves for several years. A soil test such as described in
Bulletin 536B will give assurance as to the adequacy of the phosphate status of the
As a general rule, it is more economical to use high-analysis fertilizer or
straight materials than to use low analysis fertilizers. Some growers still do not
distinguish between the cost of fertilizer on a per-ton basis and the cost on a per-
acre basis. It is the per-acre cost that is important. Growers should select the
cheapest fertilizer based on the recommended amounts of plant nutrients per acre.
For greatest economy, the materials used should be those that can be purchased by
the individual in his specific case for the least money per acre. Each grower will
have to determine what this is. All nitrogen sources have nearly the same value
when low or moderate application rates are used.
In most cases, the minor elements can be omitted until actual deficiency symp-
toms appear. For greatest economy, do not use zinc in sprays until at least some
traces of zinc deficiency appear in the grove.
It is not necessary to use manganese unless persistent manganese deficiency
symptoms appear on the foliage. Spray applications of manganese are likely to be
necessary only on calcareous soils. In groves with acid soils receiving mixed fer-
tilizers, manganese should be applied as manganese sulfate in the mixed fertilizer.
This simplifies the spraying program, and by reducing spray residue on leaves, tends
to decrease the numbers of insect and mite pests.
Unless actual copper deficiency symptoms appear, copper should be regarded
primarily as a fungicide. Where copper deficiency symptoms appear, the copper ap-
plication should be planned to utilize the fungicidal properties along with the
nutritional effect. This means the use of copper only as a fungicide in the spray
Boron deficiency cannot be readily identified by symptoms until damage to
fruit has occurred. Hence a preventive boron application should be included on a
yearly basis, either in sprays or fertilizers. The small amount of borax needed
in sprays will not upset insect and mite control very appreciably.
Liming in all cases should be based on a soil test. Whenever an application is
made, use not less than 1 ton per acre. It is not economical to make light, fre-
quent applications. In groves with high copper soil conditions, the use of high cal-
cium limestone is recommended to bring the pH up to an adequate level.
Irrigation.- Use of irrigation has greatly increased in central Florida in the
past few years, because research has proven that proper irrigation will increase
yield of most varieties. Irrigation should be used between the months of January and
June to prevent tree damage or production loss from drought. Irrigation between the
months of July and December does very little to increase yield, and should be used
in this period only to offset the occurrence of severe drought conditions that may
weaken the tree and lead to loss of the crop. Marsh grapefruit responds most strik-
ingly to irrigation, followed by Hamlin oranges, Valencia oranges, and Dancy
tangerines. Pineapple oranges respond very little to irrigation and should not be
irrigated in preference to making needed application on the other varieties.
Most irrigation has been done in the past by perforated, portable pipe. The
rate of application by this system is high and the system is entirely satisfactory
on fairly level land, except for high labor costs.
More recently, permanent systems have been installed widely. These are
fairly expensive to install, but quite economical to operate, primarily because of
the low labor cost. These systems are designed to deliver water at a very low rate,
of approximately 0.15 inch per hour, thus requiring 10 to 20 hours for each
Long duration of sprinkling has some disadvantages. If the application is made
during the day, wind frequently prevents a uniform application over the entire grove
area. Evaporative losses during dry, windy days may carry away over half the water
pumped. Under these conditions, salts may accumulate on the leaves to toxic
proportions. This is not important unless the total salt content of the water ex-
ceeds about 1000 ppm. If the sprinkling is done at night, fungus diseases such as
scab, melanose, and greasy spot are encouraged. Some of the fungi bringing about
biological control of scales and mites are also to some extent encouraged, a bene-
The best practice seems to be irrigation at night, when usually the trees will
be wet with dew for several hours even without irrigation. The irrigation should be
terminated sometime during the following morning, so that the trees will dry off
thoroughly before the following night. This will interrupt the development of the
fungus disease organisms.
Excessive irrigation must be avoided. Weekly applications of irrigation water,
no matter how economically they are applied, are detrimental. Frequent irrigations
unnecessarily encourage the development of fungus diseases and are highly detrimental
to fruit quality, both internal and external. When an application is made, it should
be done with 1.5 to 2.5 inches so that the water needs of the tree will be adequately
supplied for several weeks. Usually no more than five or six applications per year
are needed, even in dry years.
If a grove must be sprayed and also needs irrigation, irrigate thoroughly first,
then spray. This avoids washing off the deposits of pesticides which have been
placed on the trees at considerable cost.
Cultivation.- Cultivation is beneficial only through control of weeds, and
should be held to a minimum. Clean cultivation as required to control weeds in late
fall, winter, and during the spring drought period will conserve soil moisture,
eliminate fire hazard, make the grove slightly warmer on cold nights, and facilitate
harvesting operations. Cultivation, mowing, or chopping during the summer may be
necessary to permit effective spraying, or even effective inspection of the grove.
Minimum cultivation of perhaps two times during the dry season and one additional
time during the summer to facilitate spraying would be just as satisfactory as any
other cultivation procedure and would be most economical.
Young, non-bearing trees must be relieved of serious competition from weeds and
from the hazard of foot rot infection during the summer growing season, either by
cultivation or by herbicides. The use of herbicides is new and cannot be adequately
discussed in this article. Several useful herbicides are recommended in Extension
Circular 303. Federal approval for the use of several others is hoped for in the
near future. For economical grove operation, growers should keep themselves
thoroughly informed on the latest developments in this field. Growth of weeds or
other cover crops in the middles between young trees is beneficial in reducing wind
erosion and sandblasting, particularly during the spring.
Grove Heating.- Cheap fruit will not pay much of a grove heating bill. However,
in case of a generally severe freeze, fruit might no longer be cheap. Also, growers
would be well advised to protect themselves against loss of bearing surface, since as
noted above, the only possible way to obtain an income from a grove operation is by
selling fruit. Generalized recommendations would indicate that for fruit protection,
firing should be considered if the temperature is predicted to fall below 280 for
four hours or more, and firing for protection of the tree is indicated if a few
hours below 240 is predicted. See Extension Circular 287 for more details about
the time to light heaters.
Replanting of Vacant Spaces.- Nursery trees today are not in short supply.
Fixed costs per acre are much the same, whether a grove has no skips or many skips.
Replanting in vacant spaces has always been a good idea, since eventually the
yield per acre will be almost directly proportional to the number of healthy trees
present. While it is too late now to increase production in the next few years by
replanting skips, the present economic conditions emphasize how important this
consideration is over the long-run. Nothing but the highest quality, virus-free
trees should be used and all replants should be of the same variety as the
balance of the block.
Pruning.- Hedging and topping of bearing groves should be continued. Hedging
facilitates the movement of equipment in the grove and facilitates effective spray-
ing. Topping tall trees eliminates the difficult and expensive operation of spray-
ing into the tops and also makes for lower cost of harvesting. Both operations
usually result in improved fruit size and color in tangerines, and increased fruit
size in grapefruit, thus improving pack-out.
Ideally, the removal of all deadwood is desirable for disease control, but
this operation appears to be uneconomic due to high cost of wages. Watersprouts
need not be removed from the center of the tree. They may produce fruit if not
Hedging and topping should be done before crowding occurs. Then only light
cutting is required, little crop loss results, and brush removal is not a serious
problem. Hedging or topping of tall, crowded trees is very expensive, and appre-
ciable reduction of the next crop can usually be expected. Light frequent pruning
is better than severe pruning at intervals of several years.