Plant roots are highly susceptible to disease. When attacked, they are prevented absorption of nutrients and water from the soil, lowering a plant's productivity and potentially causing death. Root rot is a major issue for plants, in which plant roots are subjected to unfavorable moisture conditions and fungal spores.
Root rot is caused by over-watering the plant, creating moist conditions that slowly drowns the plant roots. This also creates the conditions where fungi grow. Fungi attack the roots of the plant. Water-logging itself is sometimes enough to cause root rot, says the Ohio State University Extension's website, and sometimes fungi is not present.
Plants will first exhibit a light foliage color and may turn yellow and wilt, says the Ohio State University Extension service. Symptoms may appear immediately, or might take months to develop properly. Examination of the plant roots will show brown or black roots that are mushy to the touch. The outer portion of the root may slide of when pulled or touched. Fungi-caused root rot may be visible at the stem for some soft-stemmed plants--the stem at the soil line appear brown or black and is soft to the touch.
Prevention When Planting
Proper planting may prevent the formation of root rot in plants. Proper soil drainage is integral to prevent the disease. A hole dug to twice the size of the plant's root ball when a once-potted plant is being inserted into the garden, otherwise the hole requires enough space to hold the roots without crowding. When planting in a pot, the University of Minnesota's website recommends using a pasteurized, disease-free soil to prevent rot. Evaluate water drainage by pouring water in the hole dug for the plant, and check to see whether the water drains after 24 to 48 hours.
Treating the Disease
Some plants are not treatable once root rot develops. When foliar conditions are visible, says the University of Minnesota, then the roots need examining. Pots replanted in new soil when there is a small amount of damage may rejuvenate the plant. Pruning decaying roots and dipping the remaining roots in a diluted bleach solution (one part bleach to nine parts water) for a half-hour will kill any fungi. Replanting requires finding a new spot to plant; the soil in the original area is contaminated. New plants that are not root rot resistant should not be planted in the area.
Fungicide treatment is possible to control spread of fungi in the soil and potential stop root damage. Fungicides specifically for root rot include thiophanate-methyl and other phosphorous-based fungicides. Applications of fungicide should be rotated to prevent the development of fungicide resistant strains of fungi, says the University of Florida Extension website.