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Disease Guide – Root Rot

May 7, 2020
Fungi & Other Diseases

How to Recognize, Treat, and Prevent Root Rot in Marijuana Plants

Pythium, commonly referred to as root rot, is a type of fungus that can attack the roots of your i49 marijuana plants grown from even the best quality USA premium seeds. The roots of a plant are critical for its health. Without roots, the plant cannot take in water and nutrients effectively, and it will eventually die. This fungus is an opportunistic one, and it typically attacks plants that have already become weakened due to nutritional deficiencies and other types of damage.

What Should You Know About Root Rot?

Root rot is a type of fungus with microscopic spores that are quickly spread. It typically attacks the most vulnerable of plants, feeding off young and tender seedlings and causing great destruction to marijuana plants that are already under stress.

Pythium is a fungus that can attack all types of plants. While it does not always lead to a complete crop loss, it can if the signs are not recognized and treatment is not carried out right away.

The development of this disease is contingent on environmental factors. There are multiple species of Pythium, and some prefer warm, moist conditions, while others grow prolifically in cold temperatures.

One of the biggest problems in treating root rot is being able to recognize the signs. Because soil-grown plants have their root systems covered, it can sometimes be difficult for growers to notice damage is being done to their plants until it becomes extensive.

Signs of Root Rot

Unfortunately, the symptoms of root rot are often challenging to detect because this plant disease travels through the soil and begins to cause catastrophic damage at the root level before any signs occur in the parts of the plant above the soil level.

The outward signs of Pythium include the following:

Wilting leaves

Yellowing leaves

Edge browning on the leaves

Burning in the leaves

White colorations in the leaves

Dropping leaves


Signs of Pythium in the roots include the following:

Pale roots

Root disintegration

Soft roots

Loss of root branches (begins to resemble a rat’s tail)

Watery roots

As this fungal disease progresses, eventually, the outer protective layers of the root will dissolve, and you will see the fibrous inside. Once this happens, the affected sour diesel or weeding cake strain plant is in great danger of dying because its root system will completely dissolve, preventing it from taking in vital nutrients. If you are an i 49 seed grower who prefers to use a hydroponic system, it is quite simple to see when root problems begin to occur. Those who grow in soil should gently dig into the soil around the root system and check it periodically for any signs of problems. If the roots seem unhealthy, it is time to act quickly.

Understanding Healthy Root Systems

Marijuana plants need a healthy and robust root system to stay alive and thrive. Once the roots become infected with a disease, the plant will start to die quickly.

A healthy root system of a marijuana plant is always going to be white and creamy in color. The roots should have many branches, and they should be firm and glossy. If you notice the roots browning or developing a rotten odor, it is likely the plant is suffering from root rot. Do not wait until the plants start wilting to check the root systems. A weekly peek at the roots can make a big difference in how quickly you can respond when the beginning signs of root rot start to occur.

How to Treat Root Rot

Knowing how to treat root rot efficiently could mean the difference between your plants surviving or all being lost. It takes a concerted effort to treat root rot, but it can be done.

The first step to take when root rot is present is remove the plant from the soil and start rinsing the root system with water. Try to wash away as much dirt as possible and carefully remove any diseased shoots from the root system.

If a lot of the roots are damaged, you may have to cut away much of the root system. When removing a large portion of the roots, try to trim your marijuana plant by at least 1/3. Doing so will give the plant a better chance of putting most of its energy into creating a new and healthy root system.

You should also make sure to dispose of the soil the marijuana is being grown in and sanitize the container. If you put the plant back in the same soil and an unsanitized container, root rot will continue.

It is important to dip the trimmed root in a fungicide to kill the Pythium. There are different fungicides on the market, so it is vital to choose one that is made specifically for marijuana plants. You do not want to select a fungicide that will be too harsh on your plants.

Never treat your purple kush weed or white widow feminized plants with fertilizer directly after removing portions of the diseased root. Doing so can put stress on your marijuana plants and cause damage.

Taking Care of Marijuana Grown in Soil

Prevention is vital when it comes to taking care of root rot. It is much easier to prevent this fungal disease than try to treat it. Too much moisture in the soil is a prime breeding ground for Pythium. You should not water every day. Water just when the soil is starting to lose moisture. If you are growing in containers, make sure there are plenty of drainage holes so the water can flow through after the soil has absorbed all it can.

Consistently well-drained soil that’s full of beneficial nutrients is going to discourage Pythium from growing. If the soil is too wet and the plant is under stress from a lack of nutrients, this will end up producing a prime breeding ground for Pythium to start growing in abundance.

Like all types of fungi, Pythium thrives best in warm, humid conditions. While warmth and moisture are both necessary for healthy marijuana plant growth, you must be careful to monitor the humidity level, so the soil does not become a breeding ground for fungus to thrive.

Root rot can be prevented, but it takes a careful effort. If you are actively monitoring your plants and watching for problems with moisture, Pythium should become less of a risk.

Another source of prevention for root rot is pest management. There are some species of insects that carry fungi and can infect your plants. The fungus gnat is one of them. To keep insects away, make sure you wait to water until the soil is dry one inch deep. Watering too often attracts tiny insects, such as gnats, and makes it more likely Pythium can begin to grow.

Taking Care of Marijuana Grown in a Hydroponic System

The preventative measures needed for hydroponic systems are slightly different than those for soil. One of the biggest concerns for hydroponic systems is making sure they are as clean as possible.

One of the ways to keep your hydroponic system from developing Pythium is to utilize good bacteria. Adding good bacteria to the system will help to keep harmful bacteria in check. Although some medical cannabis seed growers add hydrogen peroxide to their systems to keep bacteria away, putting in some good bacteria seems to work best for the prevention of Pythium.

Unfortunately, hydrogen peroxide kills all bacteria, even the good. Once you strip the hydroponic system of good bacteria, the harmful types can easily take over and cause diseases to set in.

It is also critical you lower the temperature in your grow room, thereby reducing the water temperature in the hydroponic system. Lowering the water temperature helps to increase the oxygen in the water. Oxygen helps to combat parasitic fungi like Pythium. By simply working to keep the water temperature at 72 or below, you will find the chances of the plants developing root rot is significantly reduced.

Preventative Measures Will Help Protect Your Plants

In addition to the above, it is also possible to purchase root control products, and some of these specifically target the Pythium fungi. Carefully research the options and learn as much as possible about the benefits and disadvantages of each one. If the root control product does not explicitly target root rot, it would be best to find one that does.

You can also use natural essential oils, such as coriander and sesame. Many growers successfully protect their marijuana plants by using copper-infused sprays.

The Bottom Line

Root rot is a serious threat to cannabis seed growers, whether you are growing in soil or a hydroponic system. As with all plant diseases, prevention is better than trying to treat.

Although marijuana is undoubtedly a hearty plant, it can fall victim to fungal infections such as those caused by Pythium. By taking care of a few maintenance chores for prevention, you can help to keep this fungus at bay, so it does not begin to attack your plants and cause great destruction. Taking time to address this issue now will ensure your plants maintain healthy root systems that end up leading to bountiful buds.

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