ONION Neck Rot - Botrytis allii Neck Rot - Botrytis allii Blue Mould Rot - Penicillium spp Blue...

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ONION ONION Neck Rot - Neck Rot - Botrytis allii Botrytis allii Blue Mould Rot - Blue Mould Rot - Penicillium spp Penicillium spp White rot - White rot - Sclerotium cepivorum Sclerotium cepivorum Bulb rot/ basal rot - Bulb rot/ basal rot - Fusarium oxysporum Fusarium oxysporum f.sp f.sp . cepae . cepae Macrophomina rot - Macrophomina rot - Macrophomina phaseoli Macrophomina phaseoli Purple blotch - Purple blotch - Alternaria porri Alternaria porri Black stalk rot - Black stalk rot - Stemphylium botryosum Stemphylium botryosum Black mould - Black mould - Aspergillus niger Aspergillus niger

Transcript of ONION Neck Rot - Botrytis allii Neck Rot - Botrytis allii Blue Mould Rot - Penicillium spp Blue...

Page 1: ONION Neck Rot - Botrytis allii Neck Rot - Botrytis allii Blue Mould Rot - Penicillium spp Blue Mould Rot - Penicillium spp White rot - Sclerotium cepivorum.

ONIONONION

Neck Rot - Neck Rot - Botrytis allii Botrytis allii Blue Mould Rot - Blue Mould Rot - Penicillium spp Penicillium spp White rot - White rot - Sclerotium cepivorumSclerotium cepivorum Bulb rot/ basal rot - Bulb rot/ basal rot - Fusarium oxysporum Fusarium oxysporum f.spf.sp. cepae. cepae Macrophomina rot - Macrophomina rot - Macrophomina phaseoliMacrophomina phaseoli Purple blotch - Purple blotch - Alternaria porriAlternaria porri Black stalk rot -Black stalk rot -Stemphylium botryosum Stemphylium botryosum Black mould - Black mould - Aspergillus nigerAspergillus niger

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Neck Rot - Neck Rot - Botrytis allii Botrytis allii

Latent disease - although infection takes place in the fieldLatent disease - although infection takes place in the field

Softening of scales which take on a water soaked appearanceSoftening of scales which take on a water soaked appearance

Under moist conditions - greyish sporulating mycelial mat develops Under moist conditions - greyish sporulating mycelial mat develops on the surface of the scales on the surface of the scales

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Mode of spread and survivalMode of spread and survival

Fungus persists saprophytically on dead onion tissue, on humus in Fungus persists saprophytically on dead onion tissue, on humus in soil and as soil and as sclerotiasclerotia near the surface of previous onion crop cells near the surface of previous onion crop cells

Sclerotia germinate in moist weather and produce conidia that are Sclerotia germinate in moist weather and produce conidia that are disseminated by air currentsdisseminated by air currents

When conidia land on the onion necks that are cut or wounded they When conidia land on the onion necks that are cut or wounded they can geminate, penetrate and kill onion tissue can geminate, penetrate and kill onion tissue

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ControlControl

Dusting the seed with benomyl at 1g/kg of seed Dusting the seed with benomyl at 1g/kg of seed

Avoid excessive and late (after mid-July) applications of nitrogenAvoid excessive and late (after mid-July) applications of nitrogen

Rapid and thorough drying directly after harvest Rapid and thorough drying directly after harvest

Provide good ventilation for curing onions before storageProvide good ventilation for curing onions before storage

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Blue Mould Rot - Blue Mould Rot - Penicillium spp.Penicillium spp. Initial symptoms - water soaked areas on the outer surface of scalesInitial symptoms - water soaked areas on the outer surface of scales

Later, a green to blue green, powdery mould may develop on the surface of the lesionsLater, a green to blue green, powdery mould may develop on the surface of the lesions

Infected areas of fleshy scales are tan or grey when cut Infected areas of fleshy scales are tan or grey when cut

In advanced stages, infected bulbs may disintegrate into a watery rot In advanced stages, infected bulbs may disintegrate into a watery rot

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Penicillium digitatum, P. oxalicum, P. expansum, P. luteumPenicillium digitatum, P. oxalicum, P. expansum, P. luteum

Produces enormous number of spores on a Produces enormous number of spores on a broom like conidiophorebroom like conidiophore

Saprophytes on plant debris and senescent plant tissueSaprophytes on plant debris and senescent plant tissue

Invasion - through wounds, bruises, or uncured neck tissueInvasion - through wounds, bruises, or uncured neck tissue

Optimum conditions include moderate temperatures (21° to 25°C) Optimum conditions include moderate temperatures (21° to 25°C) and high relative humidityand high relative humidity

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ManagementManagement Avoid wounds and insect damage to bulbsAvoid wounds and insect damage to bulbs

Harvest and handle onion bulbs with a minimum of bruising or Harvest and handle onion bulbs with a minimum of bruising or wounding wounding

Cure the bulbs so the necks are dry Cure the bulbs so the necks are dry

Store bulbs at temperatures of 41°F (5°C) or less with low relative Store bulbs at temperatures of 41°F (5°C) or less with low relative humidityhumidity

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White rot / mouldy nose/ Dry rotWhite rot / mouldy nose/ Dry rot((Sclerotium cepivorumSclerotium cepivorum))

Leaves - yellow and diebackLeaves - yellow and dieback

Roots - rotten & base of the bulb covered with a watery or grey fungal growthRoots - rotten & base of the bulb covered with a watery or grey fungal growth

Numerous small black spherical sclerotia are producedNumerous small black spherical sclerotia are produced

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Mode of spread and survivalMode of spread and survival Sclerotia persists in soil for eight yearsSclerotia persists in soil for eight years

Pathogen has no direct sporulation stage and it is not air bornePathogen has no direct sporulation stage and it is not air borne

Sclerotia are transported from field to field by flood waterSclerotia are transported from field to field by flood water

ManagementManagement Long rotation of 8 to 10 yrsLong rotation of 8 to 10 yrs Good drainageGood drainage Use of healthy planting materialsUse of healthy planting materials Destruction of wild onion and leeks Destruction of wild onion and leeks Seed dressings-benomyl/carbendazimSeed dressings-benomyl/carbendazim

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Bulb rot/ basal rot Bulb rot/ basal rot ( (Fusarium oxysporum Fusarium oxysporum f.spf.sp. cepae. cepae))

Occur in patchesOccur in patches

Leaves - turn yellow and then dry up slowlyLeaves - turn yellow and then dry up slowly

Entire plant shows complete drying of the foliageEntire plant shows complete drying of the foliage

Bulb - shows soft rotting and the roots get rottedBulb - shows soft rotting and the roots get rotted

Whitish mould growth on the scaleWhitish mould growth on the scale

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FungusFungus Produces many chlamydospores which are thick walled resting Produces many chlamydospores which are thick walled resting

spores spores Microconidia – one celled and thin walledMicroconidia – one celled and thin walled

Mode of spread and survivalMode of spread and survival Soil borneSoil borne Infection occurs through root, either directly or through woundsInfection occurs through root, either directly or through wounds Soil insects are common carriersSoil insects are common carriers

MacroconidiaFusarium sp

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Epidemiology Epidemiology High temp and low level of soil moisture - favourable for high disease High temp and low level of soil moisture - favourable for high disease

incidenceincidence

Temp- 28 to 32Temp- 28 to 32oocc

ManagementManagement Field sanitation - destruction of infected plant debrisField sanitation - destruction of infected plant debris

Soil drenching - COC-0.25%Soil drenching - COC-0.25%

Pre planting treatment of bulbs - benomyl 15%+ mancozeb 60%Pre planting treatment of bulbs - benomyl 15%+ mancozeb 60%

Local Bellary, Poona Red Globe, Patna Red, White Large - resistant varietiesLocal Bellary, Poona Red Globe, Patna Red, White Large - resistant varieties

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Black stalk rot (Black stalk rot (Stemphylium botryosumStemphylium botryosum))

Affects garlic and leekAffects garlic and leek

Attacks only diseased, injured bulbs and aging tissue Attacks only diseased, injured bulbs and aging tissue

Damage by weakening the seed stalks when they are almost ripe Damage by weakening the seed stalks when they are almost ripe causing them to break overcausing them to break over

Spoil the appearance of the bulb with a sooty mould before they are Spoil the appearance of the bulb with a sooty mould before they are marketedmarketed

The fungus Stemphylium botryosum growing and sporulating on top of a downy mildew lesion

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Fungus Fungus Producing short clavate to cylindrical asci in brown pseudotheciaProducing short clavate to cylindrical asci in brown pseudothecia

Ascospores yellow to yellowish brown, oval to ellipsoid, 26-50 x 10-Ascospores yellow to yellowish brown, oval to ellipsoid, 26-50 x 10-20 um with 1-5 vertical and 7 transverse septa20 um with 1-5 vertical and 7 transverse septa

ControlControl Harvest without causing any bruisesHarvest without causing any bruises

Bulbs should be dried properly before storageBulbs should be dried properly before storage

Conidia - Stemphylium botryosum

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Purple blotchPurple blotch/scald disease/scald diseaseAlternaria porriAlternaria porri

Leaves - whitish minute dots on leaves with irregular chlorotic areas on tip portionLeaves - whitish minute dots on leaves with irregular chlorotic areas on tip portion

Circular to oblong concentric black velvety rings appear in chlorotic areaCircular to oblong concentric black velvety rings appear in chlorotic area

Lesions develop towards the base of the leavesLesions develop towards the base of the leaves

Leaves die from the tip downwards, break at the point of infection and hang downLeaves die from the tip downwards, break at the point of infection and hang down

Bulbs – semi watery rot, shrinkage of the fleshy bulb scales and desiccation followed by these scales becoming dry and paperyBulbs – semi watery rot, shrinkage of the fleshy bulb scales and desiccation followed by these scales becoming dry and papery

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FungusFungus Mycelium - branched, coloured and septateMycelium - branched, coloured and septate Conidiophores - singly or in groups, septate, pale to mid brownConidiophores - singly or in groups, septate, pale to mid brown Conidia - solitary, straight or curvedConidia - solitary, straight or curved

Mode of spread and survivalMode of spread and survival Carried through seed bulbs collected from infected fieldCarried through seed bulbs collected from infected field Spreads mainly through air borne sporesSpreads mainly through air borne spores Pathogen enters through stomata or woundsPathogen enters through stomata or wounds Survives in plant debris for 8 monthsSurvives in plant debris for 8 months

Conidia Conidium

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EpidemiologyEpidemiology Temp - 21 to 30Temp - 21 to 30oocc RH - 90 %RH - 90 %

ManagementManagement Seed treatment - thiram @ 2.5g/kg of seedSeed treatment - thiram @ 2.5g/kg of seed

Three sprays of, Three sprays of,

• Copper oxychloride - 0.25%Copper oxychloride - 0.25%

• Chlorothalanil - 0.2%Chlorothalanil - 0.2%

• Zineb - 0.2%Zineb - 0.2%

• Mancozeb - 0.2%Mancozeb - 0.2%

Varieties - New Selection, Red Creole - resistantVarieties - New Selection, Red Creole - resistant

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Black mould - Black mould - Aspergillus nigerAspergillus niger

Masses of black powdery spores on both exterior and between the Masses of black powdery spores on both exterior and between the scales of the bulbsscales of the bulbs

Especially along the vascular strands of the veinsEspecially along the vascular strands of the veins

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FungusFungus Mycelium - branched, septate thick walled foot cells differentiate and Mycelium - branched, septate thick walled foot cells differentiate and

give rise to a single conidiophoregive rise to a single conidiophore

Conidiophore - globose on which brown sterigmata are formedConidiophore - globose on which brown sterigmata are formed

Vesicle, sterigmata, conidia make up the black head - characteristic Vesicle, sterigmata, conidia make up the black head - characteristic of the fungusof the fungus

ControlControl Rapid and thorough curing Rapid and thorough curing Storage - good ventilation Storage - good ventilation Temp - just above 0Temp - just above 0oocc

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Macrophomina rotMacrophomina rotMacrophomina phaseoliMacrophomina phaseoli

Rotting of onion in storageRotting of onion in storage Diseased bulbs become ashyDiseased bulbs become ashy Close examination shows – dark charcoal coloured blemishes on one or two scales below the outer papery scaleClose examination shows – dark charcoal coloured blemishes on one or two scales below the outer papery scale Many pin head size sclerotia- embedded in affected tissuesMany pin head size sclerotia- embedded in affected tissues

ControlControl Dipping bulbs in formalin 0.03% or boric acid 2.0%Dipping bulbs in formalin 0.03% or boric acid 2.0%