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Pythium Root Rot


Pythium Root Rot

Usually appear in

All Year

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Caused By:-     Various Species of the Pythium Genus


Pythium disease on Cowpea Picture by Howard F. Schwartz, Colorado State University,
Pythium Root Rot is a common plant disease caused by a genus of organisms called Pythium of the Pythiaceae family. They are closely related to Phytophthora species which causes many serious crop damage including Potato Late Blight.
They use to be classified as fungi, but are now classified as Oomycetes of the Eukaryotic organisms. They are often called Water Moulds, because most are dependant water for their spread. They are therefore most prevalent in wet poorly drained soils.
These Oomycetes survive as both saprophytic and pathogenic organisms and can live in soils for many years even with crop rotation. It is also common for other fungi to be involved in a root disease so an accurate diagnosis require laboratory culturing to determine the cause of the root rot.
Symptoms of Pythium root on individual plants are the crowns, roots, rhizomes, and/or stolons will appear dark and greasy. The amount of roots will be drastically reduced. The plants will wilt and the leaves turn yellow and eventually the whole plant will die. Seedlings are particularly susceptible as are lawns with short cropped grass and in wet areas.
Pythium is easily spread in water based systems like hydroponics as the Oomycetes are free swimming organisms.
See also Damping Off, Pansy Sickness.


Remove infected plants as soon as possible along with the soil around the plant.
If possible water the soil with soil sterilants.
Ensure good drainage and apply potassium in late summer and early fall for those areas that are routinely affected by Pythium root rot.
If the plant is important it might be saved with foliar feeding until the roots recover.
Some fungicides will kill Oomycetes if applied to the soil.

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