Defining and Preventing Root Rot in your Hydroponic Garden

Root rot is a common yet unwelcome pest in any hydroponic garden. This fungus-like organism Pythium has many species. The three most common species of this organism are Pythium irregulare, Pythium aphanidermatum, and Pythium ultimum. These species of Pythium can be found in water sources as well as in soil. Pythium aphanidermatum is most commonly found in Poinsettia plants and few other plants.

Pythium aphanidermatum and Pythium irregulare cause the most damage in ebb and flow systems because the organism has a swimming spore stage that can attack your plants quickly. Pythium ultimum is most closely associated with soil and sand though it is not as prevalent as the other species of this organism.

The Pythium organism is found in pond and stream water as well as the sediment from these sources. The organism can also be found in soil and sand as well as in the dead roots of plants. Pythium can also be introduced to your plants through dirty gardening tools, can be carried by pets walking into your growing room and by being carried by the fungus gnat and shorefly.

Symptoms of root rot include stunted plant growth, plants that turn yellow and die, wilted plants that recover at night, root tips that are brown and brown tissue on the outer portion of the root that can be pulled away exposing plant tissue.

Treating the disease is harder than preventing it. Prevention methods include treating pond or other untreated water before you use it to irrigate your plants. It is especially important to filter untreated water to avoid getting sediment into your irrigation system. Slow sand filtration systems have been shown effective in controlling this organism. Other water treatment plans include heating the water, the use of ultraviolet light, ozonation or chlorination, all of which can stop the organism before it attacks your plants.

It is important to keep all things within a grow room clean to prevent infection from this organism. Benches, tools, equipment, reservoirs and floors should all be cleaned periodically to avoid contamination. Keep pets out of your grow room to prevent contamination as they can track the organism in on their paws and leave it on your floors and benches where it can be carried to other items in your grow room.

Biological agents may be applied to containers prior to planting in grow rooms and green houses that have a history of the Pythium organism invading the water supply. Biological agents and fungicides will have to be applied more than once to contain this organism. Common chemicals that can help treat this organism include etridiazole, etridiazole + thiophanate methyl, fosetyl-Al, mefenoxam, metalaxyl and propamocarb. Biological agents that can help control this organism include Gliocladium, Trichoderma, Bacillus and Streptomyces.

Many hydroponic gardeners never have to deal with root rot in their grow rooms or greenhouses, especially if the water to their plants is already chlorinated. Those gardeners that collect water from other sources or have untreated well water should have their water checked or treat it themselves before they use it to irrigate their plants. Many plants will be lost if they are infected through an irrigation system.

After a greenhouse or grow room has been infected, the plants will need to be destroyed. Affected plants cannot be composted because the organism lives within the roots of the dead plants. Greenhouses and grow rooms will have to be treated chemically to remove any traces of the organism, especially in all areas that the water came in contact with. Garden tools can be cleaned with alcohol. Before any new plants are introduced to your treated hydroponic garden, the water treatment plan should be changed accordingly to a system that will prevent the organism from entering the irritation system at any time in the future.