Collar rot of Groundnut
Collar rot of Groundnut:
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C.O.: Aspergillus niger

Symptoms:

• The fungus causes both seed and seedling rot and drastically reduces plant stand.
• The diagnostic symptoms are Pre-emergence rotting of seedling, roting of hypocotyls.
• In moist soil, seeds may be attacked and killed due to rotting.
• Seeds removed from soil show black sooty cover.
• Post -emergence
• At this stage, the hypocotyl and tissiues of the cotyledonary node are particularly rotted.
• As the infection spreads, the whole collar region becomes shredded and dark brown .
• The infected areas of seedlings are covered with black fungal spores
• The dead dried branches are easily detached from the disintegrated collar region.
• The dead and dried branches are easily detached from the collar region.
• The dead and dried branches are easily detached from the collar region

Management:

• Remove and destroy the previous season’s infested host debris,
• Seed treatment with Thiram, or Captan, or Difolitan at 2.5 g/kg seed gives good control
• Recently a bunch variety J 11 has been reported to be resistant to collar rot. In endemic areas, J 11 variety could be grown.
• Deep planting of seed should be avoided as etiolated hypocotyl is prone to infection.
• Avoiding mechanical damage, destroying plant debris, deep ploughing and rotation of groundnut with gram and wheat are useful in reducing the collar rot disease incidence.
• Seed treatment with tetramethyl thirum disulphide (thiram, TMTD) 75% WP @ 3-5 g/kg seed or Captan 80% WP 3 g/kg seed or Carbendazim (Bavistin) 50% WP @ 2 g/kg seed will control borne infection.
• Spray mancozeb 3gm/lit of water immediately when the disease is noticed


Stem rot/ Sclerotial rot
Stem rot/ Sclerotial rot
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C.O.: Sclerotium rolfsii
Symptoms:

• Development of white fungal threads over affected plant tissue particularly on stem.
• Base of the plant turns yellow and then wilts down.
• Sheaths of white mycelium develop around the affected areas of the stem near the soil due to this the stem becomes shredded.
• White sclerotia of mustard seed size are produced in the infected tissues which later turn to brown colour.
• Seeds in the infected pods show a characteristic bluish-grey discolouration

Management :

1. Crop rotation long time – maize ,wheat, cotton and Sorghum.
2. Crop sanitation – burning of crop residues, deep ploughing.
3. Control of leaf spot : Prevent leaf drop & hence availability of leaf for growth of S. rolfsii will be reduced.
4. Bio-control agents : Bacillus subtilis. In Gujarat pl. che application of T. harzianum mixed either with well decomposed FYM or castor cake @ 1.5 kg in 300 kg can applied in furrow just before sowing.
5. Chemical seed treatment will alone not work but soil application of penta chloronitrobenzene (PCNB) just before planting or after planting.
6. Control moisture : Practices that reduce moisture retention in the canopy Irrigation should be managed maximum in dry period.


Leaf spot (Tikka / Early & Late ) diseases Early leaf spot

Leaf spot (Tikka / Early & Late ) diseases Early leaf spot
Leaf spot (Tikka / Early & Late ) diseases Early leaf spot :
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C.O : Cercospora arachidicola

Symptoms :
• The early leaf spots caused by C. arachidicola are small circular to irregular in out line, 1-10 mm in diameter but larger than late leaf spot.
• They are surrounded by yellow halo from the very beginning. On the upper surface, the necrotic area is reddish brown to black while on the lower surface it is light brown.
• The yellow halo is indistinct or not present on lower leaf surface. The fungus do not produced haustoria. The spores are produced mostly on the leaf.
• This spots are generally occurs early in the season i.e. 10 to 18 days after emergence.

Late leaf spot :

C.O : Phaeoisariopsis personata (Cercosporidium personutum )

Symptoms:

• C. personatum produces smaller, more circular spots which are 1-6 mm in diameter and dark brown to black in color.
• These brown spots are not surrounded by yellow halo in early stages. The lower surface of the spots is carbon black in colour.
• Pathogen produced conidia are restricted to the lower surface and cushions of conidiophores can be seen in concentric rings. They occur mostly on leaf but may occur also on the petiole and stem. Severely infected leaves may drop off prematurely.
• This disease comes late in season. Minimum after 1 month of sowing and becomes severe in between flowering & harvesting stage under favorable climatic condition. Late spot develop 2-4 weeks later than the early spots.
• This disease is more damaging causing spots and spread faster and cause early defoliation.

Management :

• Cultural practices promote vigorous growth which help to minimize infection.
• Plant debris from the previous crop should be burnt to avoid soil borne primary inoculum.
• Rotation and deep burying of the debris may also help to destroy the soil borne inoculum.
• Seed treatment is essential to eliminate seed borne inoculum. Treatment of seed with thiram or captan @ 3 to 4 g kg seed.
• Alteration in the date of sowing can help in avoiding the damage by the disease.

• Early maturing varieties usually escape the losses caused by the disease.
• Select rersistent variety.
• In chemical control- spraying of carbendazim 0.05 % twice or Chlorothalonil 0.2 % (Kavach) + Mancozeb 0.2 % controlling both the rust and leaf spots.


Rust
Rust :
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C.O. : Puccinia arachidis

Symptoms :

• The disease is usually found when the plants are over 6 weeks old. Small brown to chestnut browns dusty pustules occur on the lower surface of leaves.
• The epidermis ruptures and expose a powdery mass of uredospores. Corresponding to the sori, small, brown, necrotic spots appear on the upper surface of leaves.
• The pustules are 0.3 to 2.0 mm in diameter and usually surrounded by a yellow halo. In severe infection lower leaves wither and drop prematurely.
• The kernels formed in the affected plants are shriveled and small.

Management :

• Three spray (40, 55 and 70 days of germination) of Tridemorph @ 0.04 % (Calixin) or Mancozeb @ 0.2 %
• For the control of Rust & Tikka (both mix infection) 3 spraying of mixture of carbendazim 0.025 % and Mancozeb 0.2 % at 30, 42 & 54 days after sowing. Or Alternative spraying of 0.2 % Mancozeb 3 spray or 0.2 % Chlorothalonil at 30, 50 and 70 days after germination.Removal of volunteer groundnut plants/ ground keepers
• Removal of volunteer groundnut plants/ ground keepers

Viral Diseases of Groundnut
Viral Diseases of Groundnut Bud necrosis :
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C.O.: Tomato Spotted Wilt Virus (TSWV)

Symptoms :

• The first sign of infection appears as chlorotic speckling of ring spot on the terminal leaf (about 30-40 days after planting) followed by necrosis of the terminal but.
• Later the vascular tissue of the shoot just below the growing tip becomes necrotic and the shoot bud is killed ,which later dries and becomes brown. The necrosis may proceed down ward and the whole branch may become blighted.
• Necrosis may also be seem on the petioles and along the stem and on terminal bud. Proliferation of axillary shoots takes place but the leaves of such shoots remain smaller than normal and show a wide range of symptoms, including distoration, mosaic, mottling and general chlorosis.
• Affected plants remain stunted because of the reduction in the length of internodes and the whole plants may show bushy appearance.

Management :

• Bud necrosis of groundnut is primarily associated with infestation by thrips during the month of August, September, January & February, adjustment of sowing dates should be expected to reduce disease incidence & crop loss.
• Intercropping groundnut with pearl millet shows lesser incidence of disease.
• Control the alternative weed host.
• Application of the insecticides to control the thrips.
• Plants population per unit area should be increased.

Root Knot
Root Knot :
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C.O.: Meloidogyne

Symptoms :

• Above ground plant parts do not show distinct symptoms except that affected plants remain stunted & leave become yellow & scorched along their margins.
• The stunting of the plants result as the nematode larvae feed in the vasculur system of the plant, causing formation of giant cells which disrupt the vascular system.
• Affected plant, when uprooted, show the presence of galls on pods and roots. The feeding roots are deformed.
• The galls on the roots usually are similar in size and shape to the nodules formed by nitrogen fixing bacteria on pods & pegs the galls are corky & variable in shape.
• The galls produced due to infection of M.hapla remain small. Proliferation of pegs, excessive brunching of lateral roots, and poor nodulation are some other symptom produced by M.hapla.

Management :

• If nematode infestation is light control can usually be accomplished by rotation such crop as Cotton, Maize, Oats, Wheat and grain Sorghum are less susceptible & the root knot.
• Fallowing is the practice of keeping the land free of all vegetation for a specific period by occasional ploughing of soil, especially during hot summer months. It kills the nematodes by starvation and by desiccation or by exposure to high temp, during summer.
• Flooding: Submergence of land under water can be a part of fallow (flood fallow) in which the crop free land is submerged in water for specific period.
• Chemical control : For medium & high income crops this is the best method. Systemic or non fumigant nematicides such as carbofuran (Furadon), Phenamiphos (Nemacur), Phorate (Thimet)@ 1 to 2 kg ai/ha etc. are use for chemical control. Application can be made by spot treatment at the time of planting in field or by row treatment.

Chlorosis (Iron deficiency)
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Symptoms:

• Young leaves turn yellow & then white, and the plants become dwarf.
• Under such induced iron – deficiency, chlorotic symptom appear more rapidly under low light intensity.

Management:

1. A solution of 100 g ferrous sulphate and 10 g. citric acid in 10 litre of water sprayed at 10 days interval for 2-3 times.
2. Chelated iron 2 % sprayed at 10 days interval for 2-3 times.