DISEASES OF GROUND NUT – Agricultural study materials

1. TIKKA LEAF SPOT

Symptoms

a. Tikka early leaf spot – Cercospora arachidicola

The leaf spot appear 3-4 weeks after sowing. Circular to irregular reddish brown to dark brown spots appear on the upper surface with a light yellow, circular halo. On the lower surface, the lesions are light brown in colour. Later, the colour of the lesion on the upper surface turns to reddish brown to black colour.

b. Tikka late leaf spot – Phaeoisariopsis personata

The late leaf spot disease appears 5-7 weeks after sowing. Circular and darker colour spots appear on the lower surface without halo. The colour of the lesion in upper surface turns to brown to black colour. Late leaf spot attack in usually coincides with rust disease.

Mode of spread and survival 

The pathogen spread through air borne conidia and survive in the infected plant debris 

Epidemiology 

Prolonged high RH, low temperature with dew and rain splash encourage the disease development

Management 

• Field sanitation
• Seed treatment with thiram or carbendazim @ 2 g/kg of seed
• Spray mancozeb @1kg/ha or carbendazim @250 g/ha or chlorothalonil @ 1 kg/ha
• Grow resistant varieties.

Early leaf spot – PI 109839, 162857, NC 5, 3033

Late leaf spot – PI 261893, 262090, 371521, ALR 1

For both the leaf spot – PI 259747 and NCAC 3139

COMPARISON OF EARLY AND LATE LEAF SPOT

2. RUST – Puccinia arachidis

Rust is now considered as an economically important disease in almost all groundnut growing areas of the world 

Symptoms

Orange coloured pustules (uredosori) appear on the lower surface of the leaves and ruptures, release masses of reddish brown uredospores. Severe infection leads to production of small and shriveled seeds. Only uredial and telial stages were known to occur.

Mode of spread 

    Air borne uredospores spread the disease

Survival 

The pathogen survives in the volunteer groundnut plants and infected plant debris

Epidemiology 

High RH, optimum temperature (20⁰ -30⁰ C) and heavy rainfall favour the disease development

Management

• Volunteer groundnut plants and ground keepers should be eradicated
• Spray chlorothalonil @ 1 kg/ha or tridemorph @ 500 ml/ha or mancozeb @ 1 kg/ha
• Grow resistant ICRSAT-bred lines ICG(FDRS) 4, 10 and Tifrust 12, 13

3. CROWN ROT/COLLAR ROT –Aspergillus niger and A. flavus

Symptoms

The infected areas become water-soaked and turn light brown and are soon covered with black fungal spores [sooty like appearance]. The fungus sporulate on the surface of mature pods resulting in patches of black sooty spores. A.flavus causing seedling disease produces ‘’Aflatoxin’’

Mode of spread and survival 

    The pathogen is seed and soil borne and survives in the infected seeds and plant debris

Epidemiology 

    High RH, temperature of 30⁰ -35⁰ C encourages the disease development

Management

• Avoiding mechanical damage to the pods and kernels  
• Harvested pods should be dried promptly
• Deep ploughing and crop rotation with chick pea and wheat
• Seed treatment with thiram or captan or carbendazim @ 3 g/kg
• Grow resistant genotypes – EC 21115

4. DRY ROOT ROT – Macrophomina phaseolina

Symptoms

Initially reddish brown water – soaked lesions on the stem appear. Later, these lesions change in to light brown in colour. The infected roots become black, rott and the tap roots shreds. The fungal hyphae spread to form a white mat of mycelium over the kernels and turn grey and eventually turn black

Mode of spread 

The pathogen is soil borne

Survival 

The pathogen survives as sclerotia in the soil and infected plant debris

Epidemiology 

Low soil moisture and a temperature of 29⁰ -35⁰ C favour the development

Management

• Field sanitation
• Seed treatment with thiram or carbendazim at 2 g/kg or T.viride at 4 g/kg of seed
• Crop rotation with non-host crops

5.  STEM AND POD ROT – Sclerotoum rolfsii

Symptoms

The first symptom of stem rot are yellowing and wilting of branches near the base of the plant. Sheets of white mycelium develop at or near the soil line around the affected areas of the stem which become shredded. Diseased pods are completely covered with a white mycelial mat and show a characteristic bluish – grey discolouration of the testa, known as ‘’blue damage’’  

Mode of spread and survival 

    The pathogen is seed borne and survives as sclerotia in soil

Epidemiology 

    High temperature and high soil moisture help the disease development

Management

• Field sanitation
• Crop rotation with cotton or wheat or onion
• Application of triazoles like propiconazole through irrigation water
• Grow resistant genotypes like ICGV 86416, 87359, NC 9 and GAT 141.

6. ANTHRACNOSE – Colletotrichum dematium

Symptoms

Small, water-soaked yellowish spots appear on the lower leaves which later turn in to circular brown lesions with yellow margin

Mode of spread and survival

The pathogen spreads through wind borne conidia and survives in the infected tissues

Epidemiology 

Cloudy weather encourages the disease

Management

• Spray with mancozeb 0.2% or copper oxy chloride 0.25 % or Bordeaux mixture 0.4%

7. BACTERIAL WILT – Pseudomonas solanacearum

Symptoms

Infection of young plants results in rapid wilting of stem and foliage. Infection of mature plants results in loss of turgidity and leaves become light green, chlorotic and curl at the tips. The characteristic symptom are dark brown discolouration in the xylem and pith and the streaming of ‘’bacterial ooze’’ from the cut ends of infected root and stem.

Mode of spread 

Seed borne inoculum spreads the disease

Survival 

Long term survival of the pathogen is favoured by continuous cropping of susceptible host. 

Epidemiology 

High soil moisture and wet soil favour the disease development

Management

• Field sanitation
• Crop rotation with wheat or sorghum or cotton or rice or sugar cane
• Use disease free seeds
• Soil application of urea, mineral ash and organic manure
• Applying chloropicrin @ 30 kg/ha 10 days before sowing
• Grow resistant varieties like Anoa, Rusa, Tupai and  Banteng

8. BUD NECROSIS –Tomato spotted wilt virus [TSWV] 

It is also called as Ring mosaic, groundnut mosaic, bunchy top, chlorosis, ring mottle and bud blight. 

Symptoms

Initial symptoms appear on young leaflets as chlorotic spots. Terminal bud necrosis occurs when temperature is high. Early infection results in stunting and proliferation of axillary shoots. The seeds produced by the infected plants are small, shriveled and mottled.

Vector

    Thrips – Thrips tabaci and Frankliniella sp. transmits the disease

Management

Remove and destroy the infected plants up to 6 weeks after sowing and Inter cropping with sorghum or pearl millet reduces the incidence. Spray monocrotophos @ 500 ml/ha or spraying with antiviral principles [AVP] from sorghum or coconut leaves either alone or in combination.

– Grow resistant cultivars – ICGV 86030, 86031, 86032, 86033, and 86538.

9. ROSETTE VIRUS – Ground nut rosette virus [GRV]

Symptoms

The infected plants appear as dense clump and produce dwarf shoots with tuft of small leaves. The infected plants exhibit chlorosis and mosaic mottling. The infected plants remain stunted and produce few flowers but none bear seed.

Vector

    Aphid – Aphis craccivora transmits the disease in a persistent manner

Management

• Use heavy seed rate and rogue out periodically the infected plants.
• Spray monocrotophos or methyl dematon @ 500 ml/ha to control vector population.
• Grow resistant cultivars like  RMP 12, 91.