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

2. Neck Rot - Botrytis allii
Latent disease - although infection takes place in the field
Softening of scales which take on a water soaked appearance
Under moist conditions - greyish sporulating mycelial mat develops on the surface of the scales

3. Mode of spread and survival
Fungus persists saprophytically on dead onion tissue, on humus in soil and as sclerotia near the surface of previous onion crop cells
Sclerotia germinate in moist weather and produce conidia that are disseminated by air currents
When conidia land on the onion necks that are cut or wounded they can geminate, penetrate and kill onion tissue

4. Control Dusting the seed with benomyl at 1g/kg of seed
Avoid excessive and late (after mid-July) applications of nitrogen
Rapid and thorough drying directly after harvest
Provide good ventilation for curing onions before storage

5. Blue Mould Rot - Penicillium spp.
Initial 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 lesions
Infected areas of fleshy scales are tan or grey when cut
In advanced stages, infected bulbs may disintegrate into a watery rot

6. Penicillium digitatum, P. oxalicum, P. expansum, P. luteum
Produces enormous number of spores on a broom like conidiophore
Saprophytes on plant debris and senescent plant tissue
Invasion - through wounds, bruises, or uncured neck tissue
Optimum conditions include moderate temperatures (21° to 25°C) and high relative humidity

7. Management
Avoid wounds and insect damage to bulbs
Harvest and handle onion bulbs with a minimum of bruising or wounding
Cure the bulbs so the necks are dry
Store bulbs at temperatures of 41°F (5°C) or less with low relative humidity

8. White rot / mouldy nose/ Dry rot (Sclerotium cepivorum)
Leaves - yellow and dieback
Roots - rotten & base of the bulb covered with a watery or grey fungal growth
Numerous small black spherical sclerotia are produced

9. Mode of spread and survival
Sclerotia persists in soil for eight years
Pathogen has no direct sporulation stage and it is not air borne
Sclerotia are transported from field to field by flood water
Management
Long rotation of 8 to 10 yrs
Good drainage
Use of healthy planting materials
Destruction of wild onion and leeks
Seed dressings-benomyl/carbendazim

10. Bulb rot/ basal rot (Fusarium oxysporum f.sp. cepae)
Occur in patches
Leaves - turn yellow and then dry up slowly
Entire plant shows complete drying of the foliage
Bulb - shows soft rotting and the roots get rotted
Whitish mould growth on the scale

11. Fungus
Produces many chlamydospores which are thick walled resting spores
Microconidia – one celled and thin walled
Mode of spread and survival
Soil borne
Infection occurs through root, either directly or through wounds
Soil insects are common carriers
Macroconidia
Fusarium sp

12. Epidemiology
High temp and low level of soil moisture - favourable for high disease incidence
Temp- 28 to 32oc
Management
Field sanitation - destruction of infected plant debris
Soil drenching - COC-0.25%
Pre planting treatment of bulbs - benomyl 15%+ mancozeb 60%
Local Bellary, Poona Red Globe, Patna Red, White Large - resistant varieties

13. Black stalk rot (Stemphylium botryosum)
Affects garlic and leek
Attacks only diseased, injured bulbs and aging tissue
Damage by weakening the seed stalks when they are almost ripe causing them to break over
Spoil the appearance of the bulb with a sooty mould before they are marketed
The fungus Stemphylium botryosum growing and sporulating on top of a downy mildew lesion

14. Producing short clavate to cylindrical asci in brown pseudothecia
Fungus
Producing short clavate to cylindrical asci in brown pseudothecia
Ascospores yellow to yellowish brown, oval to ellipsoid, x um with 1-5 vertical and 7 transverse septa
Control
Harvest without causing any bruises
Bulbs should be dried properly before storage
Conidia - Stemphylium botryosum

15. Purple blotch/scald disease Alternaria porri
Leaves - whitish minute dots on leaves with irregular chlorotic areas on tip portion
Circular to oblong concentric black velvety rings appear in chlorotic area
Lesions develop towards the base of the leaves
Leaves 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 papery

16. Fungus
Mycelium - branched, coloured and septate
Conidiophores - singly or in groups, septate, pale to mid brown
Conidia - solitary, straight or curved
Mode of spread and survival
Carried through seed bulbs collected from infected field
Spreads mainly through air borne spores
Pathogen enters through stomata or wounds
Survives in plant debris for 8 months
Conidium
Conidia

17. Epidemiology
Temp - 21 to 30oc
RH - 90 %
Management
Seed treatment - 2.5g/kg of seed
Three sprays of,
Copper oxychloride %
Chlorothalanil - 0.2%
Zineb - 0.2%
Mancozeb - 0.2%
Varieties - New Selection, Red Creole - resistant

18. Black mould - Aspergillus niger
Masses of black powdery spores on both exterior and between the scales of the bulbs
Especially along the vascular strands of the veins

19. Fungus
Mycelium - branched, septate thick walled foot cells differentiate and give rise to a single conidiophore
Conidiophore - globose on which brown sterigmata are formed
Vesicle, sterigmata, conidia make up the black head - characteristic of the fungus
Control
Rapid and thorough curing
Storage - good ventilation
Temp - just above 0oc

20. Macrophomina rot Macrophomina phaseoli
Rotting of onion in storage
Diseased bulbs become ashy
Close examination shows – dark charcoal coloured blemishes on one or two scales below the outer papery scale
Many pin head size sclerotia- embedded in affected tissues
Control
Dipping bulbs in formalin 0.03% or boric acid 2.0%