A water mould which attacks the roots of nearly all types of plants. Potted plants being the most likely to be attacked because of poor drainage and over-watering which leads to overly moist soil conditions.
Root rot is also cause by starving the roots of oxygen due to over-watering or improperly aerated soil. The symptoms are virtually the same as the mold infection.
Symptoms and Damage:
Symptoms of rot often appear suddenly and without any real warning but there may subtle clues that can be an early indicator. Things like abnormal yellowing of the leaves and stunted growth. The plant may wilt and seem to be under-watered though the soil is damp to the touch. At this stage you should check the root system of the plant. If the roots are observed to be black, soft and mushy. have a strange smell or fall right off the plant you have root rot.
Stem rot is caused by similiar conditions (overly moist) and will characterized by brown or black mushy spots on the stem or branches. Growth above these points will be compromised and the plant will ultimately die if left untreated.
Rot requires moisture to take hold, whether its caused by the fungus or not. The best action to take against rot is to prevent it. A proper watering schedule and regular inspections of all your plants can help to save a ton of trouble.
Control and Prevention of Root Rot
There are many benefits to avoiding chemicals when dealing with plant diseases. The harsh chemicals in some fungicides may cause more harm to an already injured plant not to mention the possible harmful effects to you or your loved ones.
✔– First choices for attempting disease control.
✔– Used when green don't solve the issue.
✔– Only use when blue options have failed and the plant cannot be discarded.
Prevention✔– Be sure to follow proper watering techniques and requirements based on your plants. As always maintenance and hygiene are very important. Remove dead and decaying matter from the soil as soon as possible and preform regular inspections on your plants.
Manual✔- The plant may be removed from the soil and the rotted roots manually removed, wash the remaining healthy roots and repot in clean sterile compost or soil. For stem rot the affected sections may be cut away if possible.
Organic✔– None available to the home gardener.
Biological✔- The only biological controls currently in use are only really suitable for green house applications.
Chemical✔– Chemical controls are ineffective after the above soil symptoms are present making prevention the number one priority. Some fungicides will help to prevent the spread of root rot but will rarely, if ever cure a plant of it.
More information on Root Rot:
Treating Root Rot - http://www.gardeningknowhow.com/treating-root-rot.htm
Root Rot - http://en.wikipedia.org/wiki/Root_rot
Royal Horticultural Society - http://apps.rhs.org.uk/advicesearch/profile.aspx?pid=542