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Post harvest diseases of garlic

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Presentation on theme: "Post harvest diseases of garlic"— Presentation transcript:

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

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