Introduction
The common diseases in turmeric are
Disease
|
Causal agent
|
Stage infected
|
Rhizome and root rot |
Pythium aphanidermatum
P. graminicolum |
All stages of crop |
Leaf blotch or Taphrina
leaf spot |
Taphrina maculans |
2-3 months after planting |
Colletotrichum leaf spot |
Colletotrichum capsici |
2-4 months after planting |
Dry rot |
Rhizoctonia batalicola |
Rhizome maturation stage |
Brown rot (Nematode - fungal
complex) |
Pratylenchus sp. & Fusarium
sp. |
All stages of crop |
Leaf spot |
Cercospora curcumae |
All stages of crop |
Leaf blight |
Rhizoctonia solani |
All stages of crop |
- Turmeric is mainly infected by three rhizome diseases
viz., rhizome and root rot, dry rot and brown rot and
four foliar diseases viz., leaf blotch, Colletotrichum
leaf spot, Cercospora leaf spot and leaf blight.
- Rhizome and root rot and foliar diseases of turmeric
are very important because they affect the yield of
rhizomes considerably.
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Rhizome and
root rot
Pythium aphanidermatum
P. graminicolum
P. myriotylum
Association of Pythium sp. and Fusarium sp.
- This is an important disease prevalent in all turmeric
growing areas.
- Both C. domestica and C. aromatica
are affected by rhizome and root rot disease.
- The disease was first reported from South India viz.,
Krishna district of Andhra Pradesh, Tiruchirappalli
and Coimbatore of Tamil Nadu .
Crop losses
- Losses to the tune of 50 per cent and above have
been reported in some parts of Telengana and farmers
resort to distress harvest to salvage the remaining
crop once the disease starts appearing.
Symptoms
- The infected plants show yellowing of leaves starting
from lower leaves which gradually spread to the upper
regions of the plant.
- The margins of the yellowing leaves turn necrotic
and start drying from the margins inwards resulting
in partial or complete blighting of leaves.
- Water soaked dark brown lesions appear on the pseudostems
at the base which enlarge rapidly resulting in drying
up.
- The affected pseudostems break away with a pull and
the affected tillers topple off.
- The affected plants show varying degrees of rot.
- The infection spreads from roots to rhizome causing
soft rot (affected rhizome becoming soft to touch).
- Infection is also noticed from tips of rhizomes spreading
inwards.
- The affected rhizomes show varying degrees of brown
shades in contrast to the bright orange yellow colour
of healthy turmeric.
- In advanced stages, the rotten rhizomes emit foul
smell.
Epidemiology
- Turmeric is grown as pure and also as an intercrop
along with maize, redgram and chillies
- The disease is soil borne and seed borne, and occurs
at random and spreads contiguously to adjacent clumps
- Irrigation water from diseased fields also helps in
the spread of the disease
- In artificial inoculation studies, P. graminicolum
could induce root rot in a week and death of two months
old plants within 18 days
- The fungus has been found to grow over wide range
of pH (3.0 to 9.0) and the best growth is obtained between
pH 7.0 and 8.0. Oospores production is maximum between
pH 6.0 and 9.0
- The fungus was also found to be pathogenic to seedlings
of sorghum, maize, barley, oats, arrow root and cotton
and could not infect ginger
- Where it is intercropped with maize, the symptom expression
would be sudden immediately after the maize harvest.
Role of associated organisms
- Association of maggots of M. coeruleifrons
with disease affected rhizomes was noticed to varying
degrees.
- Root knot infestation (M. incognita) in turmeric was
noticed where rhizome and root rot incidence is severe.
Management
- Selection of healthy seed from disease free gardens.
- In endemic areas, rotation of crops using non-host
crops.
- Removal and burning of the infected clumps from the
field.
- The survival of the fungus was affected by application
of urea (5 kg/ha) to the infested soil. Urea did have
depressive effect on the fungal growth.
- The turmeric varieties viz., PCT 13 and PCT 14 were
free from the disease.
- Seed dip in metalaxyl 8 + mancozeb 72 (Ridomil MZ)
at 2.5 g lit for 40 minutes and soil drenching (0.1
g/lit) not only controlled rhizome rot disease but also
increased the rhizome yield
- In the field immediately after seeing the initial
symptoms of the disease. drenching the soil in root
region with any one of the following has to be taken
up.
1.Mancozeb (75 WP) - 1500 g/ha
2.Captan (50 WP) - 1000 g/ha
3.Copper oxychloride (50 WP) - 1250 g/ha
4.Bordeaux mixture - 5000 g/ha
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Dry rot
Causal organism : Rhizoctonia bataticola.
Symptoms
- The disease causes root rot and rhizome rot resulting
in typical dry rot of rhizomes from October onwards.
- The affected rhizomes appear soft and shrunken to
start with, later dry up and become hard.
- Foliar yellowing and drying up of foliage which are
the normal symptoms of maturity of the crop during October
- November would be indistinguishable from the symptoms
of the disease affected clumps.
- When infected rhizomes are cut open, the infected
zones typically appear as dull brown and dark.
- The disease is becoming increasingly important in
Kerala.
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Foliar diseases
- Next to rhizome rot, foliar diseases are economically
important, since the loss of active photosynthetic area
of the leaves affects the rhizome yield considerably.
Leaf blight
Causal organism : Rhizoctonia solani (Syn: Thanatephorus
cucumeris)
- It is wide spread and appears every year in North
Eastern States of India.
Symptoms
- The disease manifests itself as water soaked spots
of varying size and shape on the lower leaves and these
gradually increase in size during warm and humid climate,
as a result of which, a large leaf portion or the entire
leaf may get blighted.
- The blighted leaf area is divided into well developed
sectors, a characteristic symptom by which the disease
can be diagnosed easily.
- In moist weather, the fungal growth appears on the
undersurface of the leaves on water soaked diseased
portions.
- The disease ultimately leads to death of the affected
plants.
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Collectotrichum leaf
spot
Causal organism : Colletotrichum capsici
Syn: Vermicularia curcumae
V. capsici
C. curcumae
- The disease is more destructive and prevalent in majority
of turmeric growing areas of Tamil Nadu viz., Coimbatore,
Vellore, Thiruvannamalai, Salem and Trichy districts.
- This was first recorded in Coimbatore district of
east while Madras State in 1917.
Crop losses
- When the infection is severe resulting in drying up
of the whole foliage, losses would exceed 50 per cent.
- Reduction in the dry rhizome weight by 62.7 per cent
was also reported due to foliar infection.
Symptoms
- Infection is confined usually to leaf blades and occasionally
extends to leaf sheath also.
- Leaf spots elliptic to oblong of various sizes enlarge
into 4-5 cm and 3 cm wide occupying the major portion
of leaves.
- The mature spot appears greyish white at centre with
a brown margin surrounded by a yellowish halo, which
is responsible for the production of toxin.
- Endotoxin produced has been found to play a definite
role in symptom expression.
- The whitish centre with dark acervuli often becomes
papery and gets torn off.
- Sometimes spots are found on leaf sheaths.
- The rhizomes are also affected and black stroma appears
on the scales covering the rhizomes.
Epidemiology
- The disease spreads by air borne conidia. The pathogen
persists through infected rhizomes and other plant debris
left in the soil.
- The disease generally appears in August - September
when the crop is about 4-5 months old.
- Infection is evident when the humid condition prevails
continuously.
- The disease starts in the younger leaves and spreads
to the other leaves.
- The younger leaves were more susceptible than older
leaves, which was attributed to loss of carbohydrates
and phenol and more of total nitrogen in younger leaves
compared to older leaves.
- The time of planting influenced the onset and severity
of the disease. The crop sown between 12th June and
17th July under Coimbatore condition showed severe disease
incidence.
- Late planting during July-August also recorded severe
disease incidence.
- Weather factors in relation to disease incidence showed
a positive correlation of total rainfall to disease
incidence at 90 days crop growth phase.
- At 120 days, there was positive correlation between
relative humidity and disease incidence.
- The fungus could infect Aristolochia bracteata,
seedlings of Gossypium herbaceum, chick pea,
pigeon pea, cluster beans, jowar, ginger, papaya, brinjal
fruit, chillies and Whitiana sominifera
- The disease spread is mainly during wet weather.
- C. curcumae was found to survive in the field
and laboratory for about 9 and 12 months respectively,
which could be potential source of primary inoculum.
Management
- The variety, Sugantham was found to be highly resistant.
- Potash application reduced the disease incidence.
Higher dose of potash at 70 and 120 kg/ha reduced the
disease, the disease incidence was 21.8 and 18.6 per
cent, respectively compared to 46.3 per cent in control.
- Incidence is less if the rhizomes are planted in May
- June.
- Spraying the crop with Bordeaux mixture (5 kg/ha)
during August and Mancozeb (1 kg/ha) at monthly intervals
during September - December checked the disease.
- Edifenphos (1 ml/lit) with 5 rounds of spray at 15
days intervals starting from 15th June to 15th September
reduced the disease caused by C.curcumae effectively.
- Spraying twice at initiation and 15 days later with
Carbendazim (500 g/ha) or copper oxychloride (1250 g/ha)
controlled the leaf spot.
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Leaf blotch (Taphrina
leaf spot)
Causal organism - Taphrina maculans
- The disease is widely distributed in the Southern
States and the Gangetic Plains in Uttar Pradesh and
Bihar.
- This disease was first reported from Gujarat, Saharanpur
(UP) and Rangpur (East Pakistan) in 1911.
Crop losses
- The foliar destruction, it causes, would reduce the
yields considerably especially when the disease starts
in its early stages of crop growth.
Symptoms
- The disease starts as small scattered oily looking
translucent spots on the lower leaves when the plants
are in 3 to 4 leaf stage.
- The leaf spots later turn dirty yellow and deepen
to the colour of gold and sometimes to hay shade.
- The adjacent individual leaf spots of 1-2 mm in diameter
coalesce forming reddish brown blotches leading to varying
degrees of leaf blight.
- Owing to excessive spotting and destruction of chloroplasts,
the functional laminal surface is considerably reduced
resulting in indirect bad effect on the productivity
of the plant.
Epidemiology
- The pathogen infects most of the leaves leaving 2-3
leaves at the top.
- The disease incidence is influenced by soil borne
inoculum and prevailing weather condition.
- The dried leaves having spots and lying in the field
may function as chief source of primary inoculum.
- Moist cloudy weather with temperature of 25-30oC during
August - September was found condusive for the disease
initiation.
- The primary infection occurs on the lower leaves during
October - November when the temperature of 21 - 23oC
and relative humidity of 80 per cent prevail.
- Young leaves, two weeks after unfurling remain susceptible
for about a month and susceptibility gradually decreases
with age.
- They remain susceptible considerably for a longer
period irrespective of their age provided environmental
conditions and inoculum are at optimum level.
- The secondary infection is by ascospores discharged
from successively maturing asci which grow into octosporous
microcolonies and infect fresh leaves without any dormancy.
- The primary infections are less harmful than the secondary
infection inciting profuse spotting covering a large
foliage.
- The disease perpetuates from one season to other through
viable ascogenous cells borne on the infected leaf debris
in the fields after harvest as well as through desiccated
ascospores and blastospores ejected from mature asci
during the crop season and over-summaring in the soil
and leaf trash.
- T. maculans has been reported to infect
1. C. amada
2. C. angustifolia
3. Zingiber cassumunuar
4. Z. zerumbet and
5. Hedychium sp
Management
- Field sanitation should be practiced.
- Crop rotation becomes important to reduce the inoculum
build up.
- Aureofungin, antifungal antibiotic at 2.5 g/ml was
highly inhibitory to the growth of T. maculans.
- To reduce the spread of the disease, spray at 20 days
interval with any one of the following.
1. Bordeaux mixture 5000 g/ha
2. Copper oxychloride (50 WP) 1250 g/ha
3. Zineb (75 WP) 500 g/ha
4. Mancozeb (75 WP) 1000 g/ha
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Storage rots
- The storage rot of turmeric is caused by
-
Sclerotium rolfsii
-
Aspergillus flavus
-
A. niger
-
A. tamari
-
Cladosporium cladosporiods
-
Cephalosporium acremonium
-
Dlreschlera tetramera
-
Fusarium culmorum
-
F. nivale
-
F. oxysporum
-
Macrophomina phaseolina
- Rhizoctonia bataticola
- Seed treatment with Emison (1 g/lit) checked the rot of seed rhizomes and ensured better germination.
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Brown rot
- It is a complex disease caused by the nematode, Pratylenchus sp. associated with a fungus, Fusarium sp.
- This was first reported from Kerala in C. aromatica and was noticed in freshly harvested rhizomes indicating its natural occurrence during the crop season.
Symptoms
- The disease affected plants were stunted with poor root development.
- The infected rhizomes appear dull coloured, later become deep grey to dark brown, less turgid, light and wrinkled exhibiting dry rot symptoms.
- The necrotic lesions in the rhizome start from margins and progress inwards involving a major portion of rhizome.
- Infection is initiated in the fields during harvest and later leads to spoilage in storage.
- The fungus is able to penetrate and establish infection through intact host tissues.
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