1. Post harvest diseases of garlic
White rot - Sclerotium cepivorum
Blue mold rot - Penicillium spp.
Black mould - Aspergillus niger
Pink rot - Pyrenochaeta terrestis
Internal bulb rot - Macrophomina phaseolina
Basal rot - Fusarium oxysporum f. sp. garlic
Neck rot - Botrytis allii

2. White rot - Sclerotium cepivorum, s. rolfsii
Leaves decay at the base, turn yellow, wilt, and topple over
Roots and bulbs - covered with a fluffy white mycelium
Affected bulbs may become watery, and the outer scales crack as the bulb dries and shrinks
Small black sclerotia form on and in affected bulb parts

3. Mode of spread and survival
Cool weather - needed for germination of sclerotia and hyphal growth
Mycelium - encounters a host root, the fungus will form appresoria
Mycelium can grow outwards from the roots of one plant to the roots of a adjacent plant
Control
Rotating out of Allium crops for ten years
Destroying infected tissue
Planting disease - free seed stock
Seed dressing with benomyl or carbendazim( g/kg of seed)
Micro sclerotia of the White Rot fungus S.cepivorum developing on an infected garlic bulb

4. Basal rot - Fusarium oxysporum f. sp. garlic
Plants - show reduced emergence, yellowing and/or browning (necrosis) of leaves beginning at tips
Reduced bulb size, bulb decay, and brown, poorly developed root systems
In storage - bulbs show spongy, sunken, yellow brown rotting lesions

5. In early stages - infected bulbs are softened, brown and watery when cut open
White, light pink or reddish fungal growth covering the cloves or in rot cavities
Deep cracks form in the cloves, followed by break down of the tissue, which will eventually dry down to a portion of its original size, the cloves becoming crinkled and small

6. Disease Cycle
Soil borne fungus and can persist for long periods in the soil
Transmission - infested soil on tools or equipment, infected debris, infected seed, or run-off water
Pathogen enters the plant through wounded tissue
Disease develops from the base of the bulb and progresses towards the tips of the cloves
Favored by higher RH and temperatures(20-30oC)

7. Management
Avoid rotations with Allium spp.(e.g. onions and leeks) and cereals
Store bulbs at cool temperatures and low humidity with good ventilation
Avoid storing damaged bulbs

8. Blue mold rot - Penicillium spp.
A blue-green color powdery mould is observed on cloves in soil and in storage, thus its common name, “Blue Mold”
Air-borne spores spread the disease
Infection first occurs on wounds sustained when cloves are separated from the parent bulb
CONTROL
Bulbs are harvested carefully to avoid wounds and bruising, then promptly dried or cured

9. Black mould (Aspergillus niger and A. alliaceous)
Whole tissue become black powdery mass
Individual bulbs shrivel and become light in weight
Under high humid condition the inner tissues become moderately soft
Infected bulbs lose their pungency and smell
Rotten garlic cloves show black, brown, pink or white coloured rotting

10. 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

11. Pink rot Pyrenochaeta terrestis
Roots are affected and they turn pink or reddish and sometimes darken to a red or purple colour
Black spores form on the diseased roots which eventually shrivel and die
Pathogen - Soil borne and infection is mostly from mycelia in the soil
Temp oc

12. Internal bulb rot - Macrophomina phaseolina
No external symptom can be observed unless the outer scales are removed
Black pin head microsclerotia develop over the fleshy scales which are light in weight, brown, mostly shrivelled
Do not lose their pungency
Control
Dipping of bulbs in formalin 0.03%
Boric acid-2.0%
After harvest to minimize
storage rot

13. Neck rot - Botrytis allii
Found upon the bulbs at the time of harvest
Affected scale tissue become soft
Dense layer of grey mould appear at the neck
Infection progresses most rapidly down the scales which have been originally infected
Garlic with neck rot

14. Mode of spread and survival
Survive as sclerotia
Requires cool and moist weather
Temp -15 to 20oc
Control
Promoting rapid drying at harvest and good aeration in storage is best for managing Botrytis on bulbs
Additionally, cooler storage temperatures may help control the disease