This document provides information on citrus agronomy. It describes the botanical details of citrus plants, including their native distribution, major production areas, flowers, leaves, fruits, and varieties. It discusses propagation through budding, nursery management activities like pruning, irrigation, fertilizing, weeding and pest control. For mature orchards, it outlines pruning, irrigation, weeding, fertilizer application, and control of pests like citrus rust mites, scale insects, aphids, and fruit flies through both chemical and biological methods.

1. CITRUS
AGRONOMY
BY
Dennis Owusu Boateng (Technical officer)
BUNSO COCOA COLLEGE
CSSVD CONTROL UNIT (COCOBOD)

2. Introduction
• Botanical name for sweet orange is citrus senensis
• Citrus, common name for several related evergreen
trees and shrubs of the Rue family, and generally
for the fruits they produce, including the citron,
grapefruit, lemon, lime, orange, shaddock,
tangerine, and bergamot (A pear shaped orange).
• The plants are characterized by wing like
appendages on the leaf stalks, white or purplish
flowers, and fruit with a spongy and a juicy pulp
divided in sections.
• The leaves, flowers, and rind of the fruit abound
in volatile oil and emit a sharp fragrance. Many
citrus plants have thorny branches.

3. Distribution
 Citrus are subtropical, with
growing temperatures ideally at 24-27 ºC and
intolerant of frost.
 Native to Southeast Asia
 Site selection, always an important
consideration, is particularly critical in regions
subject to cold winter temperatures.

4.  Major citrus production worldwide

5. That is the biological description of a
plant.
The citrus tree consists of Shoot,
Leaves,
Flowers, Fruits and Roots.
Botany

6. Flowers
 Reproductive organ of most seed-bearing
plants. Flowers carry out the multiple roles of
sexual reproduction, seed development,
and fruit production.
 The flowers are solitary or in small
corymbs, each flower 2–4 cm diameter, with
five (rarely four) white petals and numerous
stamens; they are often very strongly scented.

7. Leafs
 A leaf is an extension of a plant's branch.
 A plant leaf helps in transpiration
and guttation, both of which remove excess
water from the plant, and respiration, the
process by which a plant obtains oxygen and
energy.
 Leaves also may store food and water and
provide structural support.
 These plants are large shrubs, reaching 5–15 m
tall, with spiny shoots and alternately arranged
evergreen leaves with an entire margin.

8.  Leaf Arrangement

9. Fruits
 The fruit is a hesperidium, a specialised berry,
globose to elongated, 4–30 cm long and 4–20
cm diameter, with a leathery rind surrounding
segments filled with pulp vesicles.
contained in the rind, and most are juice-laden.
 The juice contains a high quantity of citric acid
giving them their characteristic sharp flavour.
 Citrus fruits are notable for their fragrance,
partly due to flavonoids and limonoids

10. • Citrus consists of many species, some of
which are not even edible. Some varieties of the
edible ones have however been recommended
to the public.
• These include:
– Sweet Orange
– Grapefruit
– Tangerine
– Tangelo
– Lemon
– Lime
Varieties

11. Propagation
 Citrus is almost entirely propagated
by budding. Planting unbudded seedlings may
not be true-to-type, and often takes a long time
to fruit.
 They are also susceptible to disease attack.
 Obtain buding by selecting a required bud and
uniting this with a suitable rootstock.
 Most trees are propagated in the nursery by T-
budding.

12. Picture showing T budding

13.  ROOTSTOCKS
 Traits most important in rootstock selection
include:
– compatibility with scion
– adaptation to soil and climatic conditions
– ease and uniformity in propagation
– influence on precocity, consistent
cropping and yield, and fruit
quality
– influence on winter hardiness
– suckering tendency
– sensitivity to disease, pests, and replant problems.

14. Selecting a site for Nursery
 The site should be level.
 It should be safe from erosion, floods or heavy winds—that
is, you will need windbreaks.
 It must be fenced to protect it against damage from animals.
 It needs a permanent water supply.
 It must be near a road for transport of inputs and plants and
ready access by clients.
 The soil used must be free of soil borne diseases and pests,
such as nematodes.
 Local construction materials, such as wood, bricks, poles
and banana stems, should be available.
 Labour to manage the nursery must be available.
 Well-rotted farmyard manure, sand or decomposed sawdust,
compost or fertile topsoil for soil mixture must be available.

17. Site selection and Preparation
• Sandy loam is best for the cultivation of Citrus.
• The most important factor in the choice of site
is free from high drainage of water.
• Soils with an underlying hardpan of about 1m
or less to the top mock soils, or slain sites are
not suitable. Apart from these, citrus can
be grown on a wide range of soil types.
• Citrus is not shade loving, therefore clear
the site of all tree stumps and plough
before setting in the plants.

18.  Citrus can develop a large number of nutrient
deficiencies, including N, P, K, Mg, Ca,
Mn, Zn, Cu, Fe, B and Mo.
 The level of N fertility has more influence on
the growth, yield, and quality of citrus
than any other single plant nutrient.
 Adequate supplies of N are necessary
to optimize growth and development of
newly planted citrus trees.
 Compost, animal manure and green manure
can be worked into the soil to a depth of 1 m,
to serve as pre plant fertilizer.

19. Orchard Establishment
• Plant the orchard when the rainy season has
fully set in.
• Clear the land of any bush.
• Complete planting holes, well
in advance, before
purchasing the budding.
• Always ensure that the
trees are plantedno
deeper than they had grown in the nursery.
• Citrus has a planting distance of 3m x 3m

20. How to Plant
 Prepare the planting hole
– Dig a hole only as large as necessary to
accommodate the root system.
– Trees should be planted with
their top major roots even with the soil
line.
– Prune any damaged roots back beyond the
damaged area.
– If container-grown trees have a tap root
curled in the bottom of a container, cut this root
off at the point where it begins to curl.

21. – Separate and trim the roots of container trees that
may be root-bound.
– Save the soil from the hole to use as
backfill.
•Position the tree
– Place the tree in the hole at the same depth it was
growing previously.
Filling the hole
– Remove any debris from the dug-up soil. Back-
fill with the same soil that was removed from the
hole. Never back-fill with an amended soil mix
of a lighter texture. Such a practice will create
drainage problems and cause tree roots to suffocate
during periods of excessive moisture.

22.  Water
– After the tree is planted, water well. Check
the original soil line one last time.
– If the tree does settle, now is the time to move it
back to the correct position with the soil level .
Stake if needed
– Unless the tree bends over, it will not need support
from staking.
– If stakes are needed, place them on opposite sides
of the tree, perpendicular to the direction of
the prevailing wind.

23. Before Planting After planting

24. Maintenance Operations
1. Training and Pruning (Nursery)
– The tree must produce a canopy of sufficient size
before economic fruit production begins.
What to do during training and pruning.
– Remove shoots (i.e. suckers) originating from the
rootstock and low on the scion (i.e. water sprouts)
– Remove branches that cross from one
side of the tree to the other.
This will produce an abundance of vegetative
growth that will, in turn, assist in producing
new vegetative growth.

25. 2. Irrigation(Nursery)
– Young trees seldom need watering in the fall. For
young trees, it is best to water twice per week,
from March through June is to maintain optimum
moisture in the upper soil layer where most of
the roots are, especially during the crucial period
of leaf expansion, bloom, fruit set and fruit
enlargement –(January/February to June,
usually).
– Soil type will affect how well the soil holds the
water.

26. –
– Proper growth and fruiting it is essential that
trees receive water in ‘on time’.
– To ensure adequate moisture the soil should be
thoroughly wet before wilting occurs.
– To avoid overwatering, excess water must drain
away.
Alternate wetting and drying allows oxygen
necessary for root growth to enter the soil.
 Good irrigation help

27. 3. Fertilizing (Nursing)
– Mineral nutrients are classified as macronutrients
and micronutrients.
– The term "macronutrients" refers to
those elements that plants require in large
amounts (N, P, K, Ca, Mg, S).
– The term "micronutrients" (or “trace
elements”) applies to plant nutrients that are
essential to plants but are needed only in small
amounts (Fe, Zn, Mn, B, Cu, Mo, Ni, Cl).
– Visual deficiency symptoms of N, P, K, Ca, Mg,
Fe, Zn, Mn, B, Cu, and Mo can usually be
recognized by distinctive symptoms with lack of
nutrients.

28.  Types of fertilizer to use:
Generally, only two types of fertilizers are
required:
–A balanced fertilizer (8-8-8, 13-13-13), and
–A nitrogen fertilizer such as ammonium nitrate (33-
0-0), or ammonium sulfate (21-0-0). Urea (46- 0-0)
is a good source of nitrogen. The nitrogen fertilizer
stimulates vegetative growth later in the year. The
numbers 8-8-8 or 13-13-13 represent the percentage
of nitrogen-phosphorus-potassium the fertilizer has.

29. 4. Weeds Removal (Nursing)
– Hand pick weed and unwanted plants from the
nursery.
– These weeds compete with the citrus for
nutrients which may end up killing the seedlings.
5. Pest Control (Nursing)
5. Young Plants at nursery are affected by a lot of
stem borers, Leaf Chewers and leaf miners.
6. Recommended insecticide such as Green Light
Spinosad can be sprayed

30. The activities for citrus management
include:
Pruning
Irrigation Weed Control
Fertilizer Application
Pests, Parasites and Diseases , and their
control
Orchard Management

31.  Pruning (Matured Stage)
– For a matured tree, we do want is called
maintenance pruning. This is a situation were
we do selective pruning; If heavy pruning of
large wood is required, pruning half of the
trees in the first year, and the second half next
year will reduce the impact of crop loss.
Annual pruning of diseased and pest
attacked branches is also done in the
matured stage.
To avoid damage to the fruit, mature fruit
trees should not be pruned immediately
before harvest, or when mature fruit are on

32.  Irrigation (Matured Stage)
– Citrus trees will wilt and yield will be depressed
unless moisture is provided during the long dry
season of November to February.
– Therefore, make sure that the trees are watered
during this period.
– Ten liters of water (stream water, well water, tap
water, etc.) delivered at the base of the trees
twice a week is sufficient for good development
and yield.

34.  Weeding (Matured Stage)
– Absolute weed control under a hot, humid climate
may be very expensive, nevertheless there is need
for some level of weed control.
– Slash the orchard at least 3 times in the year with
a hoe, the last being at the on-set of the dry
season.
– In addition, ring weed individual trees constantly.
Ring-apply Diuron or Paracol to check weed
growth.

35.  Fertilizer Application (Matured Stage)
– 2–4 years of age:
• 500 grams of compound fertilizer N.P.K (15:15:15) per
trees, twice in the year.
– 5–10 years of age:
• 2 kg (15:15:15) + 600 grams per tree, twice in the year.
– 10 years and above:
• 3 kg (15:15:15) + 800 grams per tree, twice in the year.
These applications should be done in June
and September to obtain maximum benefit.

36. Pests of citrus
 Citrus Rust Mites
 Main Species
– Citrus bud mites
– Citrus red mites
 Symptoms of Damage
– causing external blemishing and, in extreme
infestations, smaller fruits, pre-mature falling
and even shedding of leaves. disfigure
the surface of the fruit and the foliage mainly in
the winter and during droughts

37. floridana) help to eradicate rust mites and the
Texas citrus mite.
Chemical Control
– To control Citrus Bud Mites spray the tree
with Bug Buster or Trounce.
 Biological Control
– Mass rearing and release of parasitic fungi
Triplosporium
(Hirsutella thompsonii and

38. Picture of Citrus Rust Mites

39. Citrus Scale Insects
 Main Species
– Snow scale, Purple scale, Red scale and glover
scale.
 Symptoms of damage
– Affect woody portions of the tree, suck sap
from the branches, twigs, leaves and
fruit, induce shedding of fruit and foliage,
produces green spots on the fruit, infests young
trees.

40.  Biological control
– Maintaining populations of the Vedalia lady
beetle in
effective
Parasitic
nurseries and groves is a
means of controlling this
fairly
scale,
wasps (Aphytis spp.) are able to
control Citrus snow scale, purple scale and
Florida red scale.
Chemical Control
– To effectively control scale insects and
limit damage, Horticultural Oil should be
sprayed on the tree. The Horticultural oil
serves to suffocate the scale and eggs. In the
spring if the crawling nymphs are present,
spray the trees with Bug Buster to prevent
the new nymphs from further infecting the
tree.

41. Picture of Citrus Scale insect

42. Citrus Aphids (Plant lice)
 Main Species
– Brown Citrus aphid, Toxoptera citricidus
– Citrus Whitefly
– Orange dog caterpillar
 Symptoms of Damage
– Aphids (plant lice) cause leaves to curl,
crinkled with puckered marks, yellowing
and the twisting of the leaves, which gives
the appearance of deformed leaves. As the
severity of the aphid infestation increases, leaf
drop and twig and branch die back can be seen.

43.  Chemical control
– Use a specific aphicide or horticultural
spray oil. Always check the label before
spraying, as not all oils are registered for use in
citrus. Oils can also cause phytotoxic damage
if not used correctly.
Biological control
– Predators, parasites, and fungal diseases attack
aphids and occur naturally in the orchard. The
honeydew produced by the aphids provides
a good food source for many natural enemies.

44. Picture of Citrus Aphid

45. Fruit Flies
 Main Species
– Queensland fruit fly
– Mediterranean fruit fly
– Papaya fruit fly
 Symptoms of damage
– Infested fruit usually falls from the tree as
a result of the activity of the larvae in it.
The style of damage by fruit fly larvae
tunnelling in fruit varies with the type and
maturity of the fruit, the number of the larvae
in it, and the

46. – weather
. Frequently citrus fruits, although
stung, do not develop larvae, but the stung fruit
sometimes fall.
Control
– Traps
• Traps are used to monitor male fruit fly populations
in orchards. The lures in the traps attract only
the male fruit fly, which are then killed.
• The traps, commonly called Dak-pots, contain a
mixture of the male attractant or parapheremone and
an insecticide.
• The traps are normally hung in trees. The traps are
effective and convenient but do not control it.

47. • Bait mixture is prepared using an attractant (protein
source) and an insecticide. Flies are attracted to the
protein which they require for egg maturation.
• As they feed they are killed by the insecticide. Bait
spray components include the insecticides maldison
or chlorpyrifos and yeast autolysate or
hydrolysate as the attractant.
Chemical spray
• Registrations also exist for the chemicals dimethoate
and fenthion for cover sprays for Qld fruit fly
control in citrus.
– Baits

48. Picture of Citrus Fruit Fly

49. Diseases of Citrus
 Citrus Canker
 Causative organism-Bacterium
 Symptoms
– formation of scabs (similar to halo lesions) in
the leaves, branches and fruits causing yellow
halo-like lesions or scabs on the fruit, leaves
and twigs of citrus trees. Severe infections can
cause leaf loss, blemished fruit, fruit drop and
die back.

50.  Control
– This contagious disease is treated by applying
antibiotic formulation.
– Management
susceptible citrus
options include replacing
resistant
cultivars with
cultivars, applying preventive sprays of copper-
based bactericides, and destroying infected
trees and all surrounding trees within an
appropriate radius.

51. Picture of Citrus Canker

52.  Citrus Sooty Mold
 Causative organism-fungus
 Symptoms
– Characterized by black coloration of the
affected citrus tree leaves. The black color is
nothing but the spores of sooty mold.
– The mold forms on the leaves as a result
of honeydew secretions from insects such
as whiteflies, aphids and mealybugs.
Control
– Using formulations of neem oil, which is
an organic broad spectrum insecticide,
fungicide and miticide such as orthene,
malathion, or diazinon

53. Picture of Citrus Sooty Mold

54.  Citrus Greasy Spot
 Causative organism-fungus
 Symptoms
– After infection takes place, the fungal spores
germinate within the leaf tissues, causing the
lower leaf portion to develop slightly raised
blisters.
– Telltale signs include yellowish-brownish
blister spots on leaves, often on the
underside of the leaf. As the disease
develops, the spots develop into oily looking
blisters.

55. Control
– Spraying copper fungicide two times in
summer help in controlling this fungal disease.
Spraying petroleum oil at the rate of 5-10 gallons
per acre is generally applied.

56. Picture of Citrus Greasy Spot

57.  Citrus Melanose
 Causative Organism-fungus
 Symptoms
– Darkly colored, raised, corky pustules
appear after leaf infection. The pustules
may be surrounded by yellowed leaf tissue
or yellow halos. The yellow color may later
turn green. Severely infected shoot apices
may become distorted or die back.
– Fully expanded, mature leaves resist
infection. On fruits infection appears as
darkly colored and usually raised pustules of
various sizes

58.  Control
– Cultural control by periodically pruning
away dead branches. This will reduce
pathogen survival, increase air circulation to
dry out the canopy, and allow for more effective
fungicide penetration and coverage of the
foliage.
– Sprays of
and leaves may be necessary for disease
copper fungicides to young fruits
management. Where the disease tends to be
severe, frequent fungicide applications may be
required

59. Picture of Citrus Melanose

60.  Citrus Root Rot Disease
 Causative organism-Fungus
 Symptoms
– Notable signs include developing brown
browning of citrus fruits.
– Over time, as the disease advances the
bark dries, cracks and dies. The infected area is
then left as a dark sunken canker. The
disease can also cause browning and decaying
on the fruit and yellowing and die-back on the
foliage.
patches in bark, oozing of plant sap, leaf
turning yellow, premature leaf fall and

61.  Control
– Cultural control such as trimming down all the
affected twigs and spray appropriate
fungicide in correct dose. To control the
brown rot it is important to remove all
leaves and damaged fruit when it falls to
the ground; prune of all lower branches off
the tree so that the tree branches are more
than 2 feet from the ground;
– Chemical control can be done by spraying
the tree with a fungicide such as Agri-Fos
and Captan

62. Picture of Citrus Root Rot

63. Parasite
 Mistletoes
– Mistletoes are plant parasites that live on other
plants to obtain food and water.
 Carrier organism- Birds, squirrels and
porcupines
 Symptoms
– The symptoms are difficult to note at the early
stage because the leaves mimic that of citrus. it
can really be seen when the parasitic plant bears
yellow or red flowers at the adult stage.

64.  Control
– Cultural control is so far the only method that is
effective; chemicals are not effective, as it
is impossible to apply them safely and
efficiently. This is done with a standard pruner
– The recommended time is when the Mistletoe is
in flower as this makes it easier to spot them in
the cocoa canopy.

65. Picture of Mistletoes

66. Harvest
 Citrus must be clipped, not pulled from the
tree, to prevent plugging the peel. It is best
to harvest citrus on a clear, sunny day with
low humidity. The fruit should be harvested
as soon as the dew has evaporated. On
a cloudy day, the fruit should be harvested
in the afternoon. Fruit should not be
harvested at all on a rainy day.

67. Storage
 Only fruit which have not been damaged in
harvest are used for storage. Citrus may be
stored for periods of up to 1-2 months
at low temperatures (0-4.4 °C).
 Plastic crates or boxes are used for
storing fruit. Boxes should be stacked
inside the storage room in a way that
maintains good ventilation. Fruit will store
longer if kept cold. Sunlight should not
be able to penetrate inside the storage
room. Any rotting fruit should be removed.

68. Uses
 Food Value
– Their juice is used as an ingredient in a variety of
dishes; it can commonly used in salad dressings
and squeezed over cooked meat or vegetables.
– A variety of flavours can be derived from different
parts and
– Marmalade, a condiment derived from cooked
orange and lemon to produce a jam-
– Lemon or lime is commonly used as a garnish for
water, soft drinks, or cocktails.
– The colourful outer skin of some citrus fruits, known as
zest, is used as a flavouring in cooking;

69.  Medical Value
– Citrus juice also has medical uses; lemon juice is used
to relieve the pain of bee stings.
– Oranges were historically used for their high content of
vitamin C, which prevents scurvy.
– After consumption, the peel is
sometimes used as a facial cleanser.
– A peel of lemonsor orange is
commonly used as a means to moisten
medical cannabis when stored with it.
– Before the development of fermentation-based
processes, lemons were the primary commercial source
of citric acid.
– Orangejuice may help preventcalcium
oxalatestone formation

70. ME’DAASE