EPWS 310 - PLANT PATHOLOGY

LECTURE 16 ASCOMYCETES

White Mold

Postharvest Diseases

General Blights - Botrytis and Sclerotinia.

Postharvest Diseases Study on your own

Pages 510-514, 546-550, 553-561

General Blights.

Gray Mold - Botrytis cinerea

The most common foliar disease of greenhouse crops throughout the world. The disease is serious under cool, humid conditions particularly when there is no drying period during the day (ie greenhouses).

The disease is characterized by a gray felty mycelial growth over all herbaceous parts of the plant. It affects pine seedlings, strawberry (in the field), all vegetables, flowers etc.

It is also a storage rot if present in stored vegetables stored at too high humidity.

Can also cause damping-off.

DISEASE CYCLE - Figure 11-97

Overseasons as sclerotia and mycelia and on weeds (near greenhouses). The conidia are abundant and can infect directly as well as through wounds. It is a necrotroph.

Can be spread by seed contamination and by contaminated potting mix.

Control?

Botrytis usually has no perfect stage but if present it is Sclerotinia.

WHITE MOLD - Sclerotinia

This fungus causes white mold and blight diseases of many vegetables and ornamentals. Very wide host range. All herbaceous parts of the plant are affected and under humid conditions white cottony mycelium develops on all parts of the plant. It is a soil invader.

Can cause a soft rot on tubers or corms and will spread by mycelial growth on the soil surface if humid enough.

If you ever find a white cottony mycelium on your green beans after a few weeks in the fridge this is it!

DISEASE CYCLE Figure 11-123.

Survives as sclerotia and is very aggressive.

Control?

POSTHARVEST DISEASES

Not a major part of this course just need to know the main pathogens.

Rhizopus - Mucorales: Zygomycete

Alternaria - Ascomycete anamorph

Fusarium - Ascomycete anamorph

Geotrichum - Ascomycete anamorph

Penicillium - Ascomycete anamorph

Aspergillus - Ascomycete anamorph

Sclerotinia - Ascomycete anamorph

Control?

Mycotoxins!!!

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