The common diseases in turmeric are

• 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.

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

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.

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.

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.

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 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

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.

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.

Nematode Management

Root knot nematode, Meloidogyne incognita

• The earliest record of nematode infestation on turmeric was that of root gall nematode by Ayyar (1926) in South India.

Symptoms

• Affected plants show stunted growth, yellowing, marginal and tip drying of leaves, reduced tillering and galling and rotting on roots.
• High densities of M. incognita cause yellowing and severe stunting and withering in large patches.
• Plants die prematurely leaving a poor crop stand at harvest.
• Infested rhizomes tend to lose their bright yellow colour.

Crop loss

• An initial inoculum level of 1,00,000 nematodes/plant caused 76.6 per cent reduction in rhizome weight under pot conditions.
• Avoidable yield loss under field conditions was 45.3 per cent.

Management

• Use of resistant turmeric varieties like Kodur, Cheyapasupu, Armoor, Duggirala, Guntur 1, Guntur 9, Rajampet, Sugandham and Appalapadu.
• Soil application of Aldicarb 10 G (10 kg/ha) two times at 3rd and 5th months after planting followed by irrigation.
• Aldicarb 10 G (10 kg/ha) and Carbofuran 3 G (33.3 kg/ha) effectively controlled the root knot nematodes and increased the yield by 71 and 68 per cent respectively.

Burrowing nematode, Radopholus similis

Symptoms

• The infested plants show a tendency to ageing and dry faster than healthy plants.
• Infested rhizomes are of yolk yellow colour compared with the golden yellow colour of healthy rhizomes and have shallow water soaked brownish areas on the surface.
• Roots show rotting and most of the decayed roots are devoid of cortex and stelar portion.
• The scale leaves of rhizomes harbour R. similis.

Crop loss

• An initial inoculum level of 10 nematodes/plant can cause a reduction of 35 per cent of rhizome weight after four months and 46 per cent at the end of the season.
• With 1,00,000 nematodes, the extent of reduction in rhizome weight is 65 and 76 per cent after 4 and 8 months respectively.

Management

• Application of Aldicarb 10 G (10 kg/ha) or Carbufuran 3 G (33.3 kg/ha) controls the nematode infestation.
• Lesion nematode, Pratylenchus coffeae

Symptoms

• It causes discolouration and rotting of rhizomes of C. aromatica.
• In advanced stages of infection, the rhizomes become deep red to dark brown in colour, less turgid, and wrinkled with dry rot symptoms.
• The fingers are more severely affected than the mother rhizomes, internally the affected rhizomes show dark brown necrotic lesions.

Nematode Management

• Among the many species of plant parasitic nematodes reported on turmeric, Meloidogyne spp., Radopholus similis and Pratylenchus coffeae are of economic importance.
• Survey of turmeric fields in Coimbatore and Erode districts revealed the presence of following plant parasic nematodes associated with the crop.
  1. Medoidogyne incognita
  2. Longidorus elongatus
  3. Xiphinema elongatum
  4. Hoplolaimus seinharstii
  5. Helicotylenchus multicinctus
  6. Tylenchorhynchus martini
  7. Pratylenchus delaltrei
  8. Radopholus similis
  9. Rotylenchulus renifornis
• Under Vellore conditions, CO 1 turmeric grown after banana or solanaceous vegetables was affected severely by nematodes. So, planting turmeric after banana or solanaceous vegetables should be avoided.