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Tips on Treating and Preventing Root Rot

Root rot is the archnemesis of the hydroponic gardener. If left untreated, root rot (pythium) can spread like wildfire and quickly disrupt natural patterns of growth. At the extreme, rot even has the potential to devastate a crop and leave nothing but the withered and maimed structure of once happily growing plants. But how do we treat root rot? Or better yet, how can we avoid it? Like most problems in the garden, root rot can be avoided by following a routine of care and consistency; however, when problems do arise, there are tools and techniques widely available to help remedy issues like root rot. Read the following passages for tips on treating, preventing and managing root rot: 

What is Root Rot? 

Root rot, or pythium, is a fungal root disease that can be induced and identified in a variety of indoor, outdoor, greenhouse and hydroponic crops. While the pythium pathogen can be transferred by pests like fungus gnats, the most likely cause of root rot is a lack of drainage, oxygen, or the unmitigated presence of moisture in soil/soilless containers. Roots exposed to rot will cease to expand, become dark, and in the most extreme cases, develop a reddish-brown sludge that will quickly consume the root ball.

Reddish-Brown Sludge
Dark & No Longer Expanding

Plants outside of soil are also susceptible to root disease, especially if they are all sharing the same water. For example, most hydroponic systems have a central reservoir that is responsible for expelling and recirculating water back and forth from containers, buckets or net pots. If a single plant becomes contaminated, then the likelihood of pythium exposure to the rest of the garden is exponentially increased. If left to rot, root disease in hydroponic systems can be the most devastating of all issues.

Avoiding and Preventing Root Rot

In Soil/Soilless Mediums 

Among other causes, root rot in soil systems is most likely caused by bad drainage, damp soil, overwatering or a poorly functioning root system. So, to avoid root rot in soil gardens, invest in a porous medium or inert compound that loosens dense or muddy soils: peat moss, coco, perlite, volcanic pebbles and vermiculite are all good examples of highly porous mediums. Also, allow these medium sufficient time to dry out – approximate the weight of a completely saturated plant and compare this weight with a plant in need of water. Root rot can be easily prevented in mediums like peat moss and coco by giving your plants a sufficient amount of time between irrigations. These tips, along with regularly supplying your plants with root enhancing additives are a sure way to keep root disease at bay. 

Peat Moss // Coco // Perlite // Volcanic Pebbles // Vermiculite
These highly porous mediums will help improve drainage.

In Hydroponic Systems

Unlike soil systems, water-based gardens are more highly susceptible to root rot, especially if the nutrient solution is shared between plants or water temperatures are left unmitigated. Hydroponic systems like deep-water culture (DWC), flood and drain (ebb & flow) and aeroponic are the most high risk for developing rampant root disease – it only takes a single plant to become contaminated to put the entire crop at risk. 

Pythium in hydroponics is usually induced by high, or unstable water temperatures. Oxygen levels are extremely low in water temperatures above 72 degrees Fahrenheit (22C), and when mixed with acidic plant food, a hydroponic system can quickly become the perfect breeding ground for plant disease. To prevent root rot in hydroponic systems, manage and monitor the temperature of your nutrient solution. To ensure your plants maintain regular periods of growth, attempt to stabilize your water temperature around 65 degrees Fahrenheit (18C).

 The ideal water temp is around 18-22C

Identifying Root Rot

Identifying root rot can be challenging, especially since the root zone is not visible to gardeners. So, rely on your plant’s foliage as an indicator for potential root disease. Here are some of the foliar characteristics of a plant with root rot: withered or drooping leaves, discolouration, mutated growth and decreased water and food consumption. 

Upon noticing a massive decrease in water and food consumption, growers can monitor the daily drinking habits of their plants. This can be done in both hydroponic and soil-based systems. To monitor the water consumption of plants in hydroponic systems, measure the water level of your reservoir on a daily basis. If your crop’s water consumption does not increase over time, it’s likely that root disease has affected the health of your plants. In soil-based systems, approximate the amount of time it takes for your plants to completely dry out. If the time between waterings regularly decreases, it’s possible that root disease has begun to negatively affect your plant’s metabolism. 

David “The Garden Sage” Robinson explains how to identify plants affected by root disease.

Treating Root Disease

After identifying the characteristics and causes of root rot, it’s time to treat the problem at the source. For plants in hydroponic systems, consider implementing an emergency reservoir maintenance program. This process will involve stripping the roots of disease with high-strength hydrogen peroxide, followed by stimulating root growth with a quality source of microbes. David Robinson describes this maintenance program in the book, The Grower’s Handbook: Teachings of the Garden Sage. Follow the chart below for tips on treating root disease: 

Root Disease Emergency Reservoir Maintenance Program

STRIP ROOTS GROW ROOTS FEED

DUMP
RESERVOIR
H202 or 35% food grade hydrogen peroxide at 3ml per gallon
DUMP RESERVOIR
300 – 400 PPM food and root stimulating product
DUMP
RESERVOIR
700 – 800 PPM food and root stimulating product
12 – 24 hours 1 – 2 days 2 – 4 days
(Robinson, 2012, p. 96)

The program above will likely cause some stress, however, it’s best to deal with the problem directly, rather than limping your crop through the final weeks of harvest. After the final stage of the program, the root zone will have returned to its original size, your plants will have resumed their regular feeding routines, and the previously destructive root disease will have vanished. This program can also be used in drain-to-waste systems for plants in potting soil, coco and rockwool. For a quality source of beneficial bacteria, use GreenPlanet Nutrients Root Builder. 

The best way to treat root rot is to completely avoid it. So remember, quality controls like resistant genetics, stable systems, care and consistency all play an important role in treating and preventing root rot. Need support in the garden? GreenPlanet is here to help! For more information on the products or information mentioned in this article, contact your GreenPlanet representative directly, or your local garden supply store. 

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