ONION Neck Rot - Botrytis allii Neck Rot - Botrytis allii Blue Mould Rot - Penicillium spp Blue...
-
Upload
lyric-bare -
Category
Documents
-
view
232 -
download
2
Transcript of ONION Neck Rot - Botrytis allii Neck Rot - Botrytis allii Blue Mould Rot - Penicillium spp Blue...
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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%