4. Symptoms
The pathogen affects the leaves,twigs and
furits.
Infection may cause distortion on citrus .
Light brown,raised,circular scabs appear on
young stems .
Pathogen effect young fruits.
Scab effects color of fruits pink to light brown.
Sometimes light brown pustules or scab visible
on lower surfaces of leaves.
5. Symptoms
Symptoms of citrus
scab disease on a
orange fruit. When
the pathogen
infects young fruits,
light brown, raised,
rounded, warty
scabs appear on
the rind
surface in large
numbers.
8. Epidemiology
The optimum temperatures for spore
formation, germination, and infection are 75-82°F
(24-28°C). However, infection can still occur at
temperatures below 75°F (24°C) if wetting
periods are long.
9. Disease Cycle
Dispersal. Spores are produced in scab
pustules on diseased fruits, leaves and twigs and
spread to other tissues
by splashing rain or irrigation water.
Infection. Approximately 3 to 4 hours of surface
wetness on susceptible plant tissues is required
for infection
to occur.
10. Disease Cycle
Pathogen survival. The pathogen survives
on diseased leaves, twigs, and fruits within
the tree canopy
and in citrus plant debris.
Symptom development. Fruits remain
susceptible to
infection and disease development until
about 3 months after petal fall. Growing
leaves are the most susceptible
and become resistant just before reaching full
size
12. Control
Culture Control
1)-Before planting:
Establish nurseries for production of rootstocks
and budwood at distance from commercial
orchards where the disease may be present.
2)-During growth:
Prune trees regularly to keep the canopy open
and free of deadwood; this is to remove sources
of spores and to improve air movement.
13. Chemical Control
Fungicides should be applied to plants
in nurseries at the beginning of leaf
flush to prevent infection leading to
stunted bushy plants that are difficult
to bud. Copper (copper oxychloride) or
chlorothalonil are suitable choices.
Treating mature lemon trees is not
recommended.
14. Fungicide applications
Three Fungicide applications per
season may be required.
First Spray Before Flowering .
Second Spray When Petal fall .
Third Spray during fruits Formation .
