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Aphanomyces Root Rot

Aphanomyces spp.

Aphanomyces Root Rot, Common Root Rot, Root Rot, Black Root, Black Root Disease

Common Root Rot is a plant disease caused by oomycete fungi. It's a type of water mould which thrives in wet and poorly drained soils. Aphanomyces spp. specialises on infecting Legumes, such as Peas, Beans and Lentils. Some species are known to attack Sugarbeets, Radishes and Spinach. Symptoms may vary depending on the species of Aphanomyces, but, some general signs of infection include honey brown/ black roots and wilting, yellow foliage.
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Roots soften and die back - usually associated with a foul smell. Plants begin to wilt. Stunted growth. Black/ brown roots.

Growth factors

Wet or over-watered soils.


Wilting, yellow or sparse foliage
Golden brown roots
Poor, slow growth
Poor nodulation in legumes
Leaves may appear scorched
Tap roots may be destroyed completely

Biological treatment

Improving soil drainage can greatly reduce the risk of plants succumbing to the disease. Where the disease is new or localised in the garden, affected plants should be destroyed and the soil from the root-run replaced with fresh topsoil. Replanting should be done with less susceptible species. Depending on the severity, plants may recover. Remove the affected roots and lightly clean those which are still healthy. Make sure tools to remove the infected roots have been sterilised before use. Replant with fresh topsoil. Replanting will only work if plants with root rot are caught early enough. Any plant pots used should be cleaned and sterile.

Chemical treatment

Sterilise water in hydroponics/soil in pot plants.


Only water plants when the soil is bone dry. Always provide good drainage when planting.

Affected plants


Medicago sativa

Sugar Beet

Beta vulgaris 'Sugar Beet'


Spinacia oleracea

Swiss Chard

Beta vulgaris (Cicla Group)


Pisum sativum

Common Bean

Phaseolus vulgaris

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