Tangerine Physiological Disorders A Lecture By Allah Dad Khan To FFS Trainee

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

4. Frost
Identification tip:
• 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.
Frost dieback

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

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

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
• 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
Figure 4. Phosphorus deficiency
[Click thumbnail to enlarge.]

21. Potassium Deficiency
Symptoms
• 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.
Figure 5. Potassium deficiency (3 levels of K
deficiency with the smallest fruit being the most
deficient.)

22. Manganese Deficiency
Symptoms
• 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
Figure 7. 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
• 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.
Figure 8. Zinc deficiency

27. Iron Deficiency
Symptoms
• 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.
Figure 9. Iron deficiency

28. Copper Deficiency
Symptoms
• 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
Figure 10. Copper deficiency
(ammoniation)

29. Boron Deficiency
Symptoms
• 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.
Figure 12. Boron deficiency

30. Molybdenum Deficiency
Symptoms
• 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.
Figure 14. Molybdenum deficiency

31. Phytotoxicity from diuron
Identification tip:
• 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.
When citrus roots take up too much
diuron, major leaf veins turn yellow

32. Phytotoxicity from simazine
Identification tip:
• 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.
Range of damage from simazine
on citrus

33. Mesophyll collapse
Identification tip:
• 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.
Mesophyll collapse of leaves
caused by water stress.

34. Salt Injury
Symptoms
• 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.
Figure 16. Salt injury