1. The document discusses various physiological disorders that affect mandarin trees, including frost damage, sunburn, fruit splitting, puff and crease, peteca of lemon, rind disorders, hail damage, wind scarring, chimera, and fruit drop caused by factors like summer drop, pruning, drought stress, and temperature changes. 2. It also covers nutrient disorders like nitrogen, phosphorus, potassium, manganese, zinc, iron, and copper deficiencies as well as deficiencies of molybdenum and boron. 3. Additional topics include physiological issues like salt injury, herbicide damage from diuron and simazine, and mesophyll collapse from water stress. Each disorder is described and

2. Manadrin Physiological Disorders
A
Lecture To ToT trainees ( FFS)
By
Mr. Allah Dad Khan
Provincial Coordinator IPM KPK
MINFAL Pakistan

4. Frost
Identification tip: Frost dieback
 Brown dead leaves remain
attached to trees damaged by cold
weather, giving plants a scorched
appearance. Certain other leaf and
twig diseases and disorderscause
similar damage. With cold injury,
damage is most prevalent on outer,
exposed branches. Young trees
are especially susceptible to cold.

5. Sunburn discoloring
Identification tip:
 Exposure to hot sun can kill parts
of leaves and fruit, resulting in
yellow-to-brown blotches. Sunburn
also causes bark cankers (not
shown). Injury is most prevalent on
the south and west sides of the
tree if sun exposure is the cause of
damage.

6. Fruit Splitting:
Identification tip:
 Rinds split at the bottom of
fruit after tree stress, such as
extreme weather, inappropriate
irrigation, and potassium
deficiency. Decay fungi such as
Alternaria rot or blue and green
mold often invade wounded
fruit.

7. Puff and crease
Identification tip:
 An uneven appearance
develops on the outer surface
of rinds when the outer rind has
separated from inner fruit. The
apparent cause is different
growth rates between the inner
fruit (endocarp) and the white
layer (albedo) under the peel
Puff and crease

8. Peteca of lemon
Identification tip:
 This lemon malady causes
depressions in the rind, which
become discolored or brownish

9. Rind disorder
Identification tip:
 Brown, water-soaked blotches
or dark, sunken areas develop
on the rind after rainy weather
and as fruit matures and turns
orange. Secondary fungi may
colonize affected areas as the
fruit breaks down. This
physiological problem (abiotic
disorder) is a problem in
California on Satsuma
mandarins.

10. Hail damage
Identification tip:
 Hail impact causes discolored
scars on fruit and twigs and
tears or shreds leaves.
Damage occurs on the
exposed side of fruit, including
locations not likely to have
been impacted by equipment.

11. Wind scarring
Identification tip:
During persistent winds, fruit may rub
against twigs or thorns and develop
scars.
 Shallow, discolored scars on
the rind occur when fruit rub
against twigs or thorns,
especially on lemon trees at
exposed locations

12. Chimera
Identification tip:
 A raised section in fruit,
typically in a wedge-shape, is
usually from chimera. This
genetic mutation is of minor
importance.

13. Fruit Drop
Summer Drop
 During the late spring and early
summer, most citrus trees will
naturally drop tiny, marble-sized
fruit. Citrus trees lose some of
the developing fruits to prevent
the tree from being weighed
down by an excessive amount
of ripening fruit. Unless your
citrus tree has another problem
and you are losing fruit in May,
June or July, the cause is likely
natural and unavoidable..

14. Pruning
Symptoms
 Too much pruning may cause a
loss of young fruit from your
tree. Citrus trees rarely need
heavy pruning. For the best
results from your tree, prune it
to remove branches that are
dead, diseased, decaying or in
danger of harming other
branches by contact. The best
time to prune is after the last
frost in the spring or during the
summer before August, to
prevent cold damage on any
new growth that appears after
pruning.

15. Drought Stress
Symptoms
 Inadequate watering of a citrus
tree tends to put the tree under
stress. A drought-stressed tree
may jettison its fruit to ensure
the survival of the food-making
leaves, branches and
remaining fruit. Make sure the
tree is well watered. Mulch
around the base of the tree to
help conserve water in the soil.

16. Temperature Changes
Symptoms
 Sudden, drastic temperature
swings, especially right after
fruit set, could cause the tree to
drop immature fruit. High
temperatures helps to sweeten
citrus fruit, but they should be
later in the summer, after the
young fruit has begun to grow.
During periods of high heat,
you will also need to pay
attention to the amount and
frequency of watering. If the
citrus trees are in pots, they
may need daily watering during
warm weather.

17. leocellosis:
leocellosis::
 It is caused by rind oil release
when oil cells get ruptured during
harvesting or during handling from
the field to the pack house. It is
more common in crop taken in
'Mrig' bahar and harvested during
February- March. Careful
harvesting and handling reduces
incidence of oleocellosis. Rind oil
from ruptured cells discolours the
skin making the fruit unmarketable.
 Control : Best way to reduce its
incidence is to cure the fruit
overnight at a temperature of 18-
20 C for 12-24 hrs, before the fruit
is moved from the field to the pack
house

18. Nutrient Disorders
Identification tip:
Iron deficiency symptoms on young citrus
leaves.
 Leaf discoloring occurs
between distinctly greener
veins when nutrient disorders
such as a deficiency of iron
(shown here), potassium, or
zinc are the cause

19. Nitrogen deficiency
Identification tip:
 Foliage is pale overall when
nitrogen is deficient. The
causes include a true
deficiency of nitrogen, adverse
soil conditions, or unhealthy
roots

20. Phosphorus Deficiency
Symptoms
Figure 4. Phosphorus deficiency
[Click thumbnail to enlarge.]
 Fruit are rather coarse with
thick rinds (Fig. 4) and have
lower juice content which is
higher in acid. Although rarely
observed, foliage may exhibit a
bronze appearance.
Phosphorus deficiency is
unlikely to occur in groves that
have received regular P
applications in the past.
However, new plantings on
previously uncropped land
usually require substantial
initial phosphorus applications

21. Potassium Deficiency
Symptoms
Figure 5. Potassium deficiency (3 levels of K
deficiency with the smallest fruit being the
most deficient.)
 Fruit are smaller, have
smoother, thinner rinds and
may be subject to splitting
and/or drop (Fig. 5). Potassium
deficiency is likely to occur on
calcareous soils due to
elemental antagonism, and
where large crops of fruit are
produced with high nitrogen
rates. A rarely observed
bronzing of foliage may
sometimes be observed,
particularly on lemons.

22. Manganese Deficiency
Symptoms
Figure 7. Manganese
deficiency
 Deficiency appears as dark green bands
along the midrib and main veins surrounded
by light green interveinal areas giving a
mottled appearance (Fig. 7). As severity
increases, the light green interveinal areas
give way to a yellow-bronze coloration. Both
manganese and zinc deficiencies may occur
on calcareous soil and may be more severe
on trees with highly pH-sensitive rootstocks.
Incipient manganese symptoms may
sometimes disappear as the season
progresses, so leaves should be observed
several times before remedial action is taken.
Soil and foliar applications may be effective
in correction of manganese deficiency

23. Role of Soil pH
Symptoms
 Lemon trees perform best in a soil with a
pH level more acidic than many plants
require, between 5.5 and 6.2. Yellowing
among the veins on a leaf that signals an
iron deficiency may not arise because the
soil lacks iron. The true reason might be
that the soil tends toward the alkaline side
and cannot put the iron into a usable form
for the plant. A home soil test or a test
sent to a soil-testing laboratory will report
your soil's current pH level. If the soil tests
too high for a lemon's acidic preference,
add elemental sulfur. To lower the pH by
one point, for example, from 6.5 to 5.5,
use 2 1/2 pounds per 100 square feet in
loamy soil. If your soil is sandy, reduce the
application by one-third. For clays,
increase the amount of sulfur added by 50
percent. Work it thoroughly into the top 6
inches of the soil.

24. Sunscald

25. Foliage Symptoms
Symptoms
 Since similar symptoms, such as yellowing
of leaves, can indicate too little of a number
of different nutrients or micronutrients, you
should submit or take a take home soil test
before supplementing. Insufficient water
contributes to nutrient deficiencies, as can
soil pH imbalance. Nitrogen inadequacy, the
most common deficiency, results in foliage
turning yellow from the lower leaves up.
Iron, manganese and zinc deficiencies often
appear together as lighter splotches
between the veins of a leaf. If this
abnormality only shows up on the south side
of the tree, it may signal a shortage of zinc.
Occurring on the north side, a manganese
deficiency is the likeliest culprit. In
overwatered, poorly drained soil, yellow
splotches probably indicate that the tree
does not receive enough iron. A symptom of
magnesium deficiency is a yellow spot that
begins at a leaf's base and gradually
spreads over most of its surface.

26. Zinc Deficiency
Symptoms Figure 8. Zinc deficiency
 Early stages appear as small
blotches of yellow between
green veins on the leaf. With
severe deficiency, leaves may
become increasingly yellow
except for the green veinal
areas (Fig. 8). Under severe
deficiency conditions, leaves
will also be small with narrow
pointed tips on terminal growth.
Foliar fertilizer applications are
usually recommended for
correcting zinc deficiency.
Trees with citrus blight will also
show leaf symptoms of zinc
deficiency.

27. Iron Deficiency
Symptoms Figure 9. Iron deficiency
 In mild cases, leaf veins are slightly
darker green than interveinal areas with
symptoms appearing first on new
foliage (Fig. 9). In severe cases,
interveinal areas become increasingly
yellow with entire area eventually
becoming ivory in color with emerging
foliage, which is smaller. Trees may
become partially defoliated with
eventual twig and canopy dieback. Iron
deficiency is usually an indication of
calcareous soil condition and is more
likely to be expressed on high pH-
sensitive rootstocks like Swingle
citrumelo. An early expression of
flooding damage to roots and of copper
toxicity may be iron deficiency
symptoms.

28. Copper Deficiency
Symptoms
Figure 10. Copper deficiency
(ammoniation)
 Mild copper deficiency is usually
associated with large, dark green
leaves on long soft angular shoots.
Young shoots may develop into
branches which appear curved or “S-
shaped," referred to as “ammoniation”
usually resulting from excessive
nitrogen fertilization (Fig. 10). Twigs
can develop blister-like pockets of clear
gum at nodes (Fig. 11). As twigs
mature, reddish brown eruptions may
occur in the outer portion of the wood.
Severely affected twigs commonly die
back from the tip with new growth
appearing as multiple buds or “witches
broom”. Necrotic-corky areas on the
fruit surface may sometimes occur in
extreme situations. Copper deficiency
is more likely to occur in new plantings
on previously uncropped soils, which
are usually deficient or totally lacking in
copper

29. Boron Deficiency
Symptoms Figure 12. Boron deficiency
 Fruit symptoms most indicative
of boron deficiency include
darkish-colored spots in the
white albedo of fruit and
sometimes in the central core
(Fig. 12). Fruit may be
somewhat misshapen with a
lumpy surface. Unlike other
micronutrient deficiencies,
boron can impact fruit quality
and should therefore not be
allowed to occur. Slight excess
can cause toxicity, so
maintenance or correctional
applications should involve
ground or foliage applications,
but not both.

30. Molybdenum Deficiency
Symptoms
Figure 14. Molybdenum
deficiency
 Rarely observed, it can
occur under acidic soil
conditions. The most
characteristic field
symptoms are large
yellow spots on the leaves
that appear first as less
defined water-soaked
areas in spring (Fig. 14),
later developing into
distinct larger interveinal
yellow spots.

31. Phytotoxicity from diuron
Identification tip:
When citrus roots take up too much
diuron, major leaf veins turn yellow
 Leaf veins can turn yellow or
white (vein clearing) after
herbicide application due to
citrus root uptake of bromacil or
diuron. After simazine
exposure, leaves yellow
between veins with the
chlorosis increasing in severity
in proportion to the amount of
herbicide exposure.

32. Phytotoxicity from simazine
Identification tip:
Range of damage from
simazine on citrus
 Pale blotches develop in leaves
after exposure to simazine
herbicide. Interveinal chlorosis
can range from relatively mild
to severe depending on the
amount of herbicide absorbed.

33. Mesophyll collapse
Identification tip:
Mesophyll collapse of leaves
caused by water stress.
 Soft tissue between leaf
veins becomes sunken
and translucent or pale
due to moisture stress
when trees are unable
to provide leaves with
enough water; affected
leaf tissue then
becomes tan-colored or
necrotic.

34. Salt Injury
Symptoms Figure 16. Salt injury
 Many salinity-induced symptoms are similar
to drought stress symptoms, including
reduced root growth, decreased flowering,
smaller leaf size, and impaired shoot growth.
These can occur prior to more easily
observed ion toxicity symptoms on foliage.
Chloride toxicity, consisting of burned
necrotic or dry appearing edges of leaves, is
one of the most common visible salt injury
symptoms. Actual sodium toxicity symptoms
can seldom be identified, but may be
associated with the overall leaf “bronzing”
(Fig. 16) and leaf drop characteristic of salt
injury. Slightly different symptomology may
occur depending on whether injury is due to
root uptake or foliage contact. Excessive
fertilizer applications, highly saline irrigation
water, and storm-driven ocean sprays can all
result in salinity-induced phytotoxic
symptoms.