What Does Mold Look Like on Weed?


Table of contents

  1. What Causes Mold on Cannabis?
  2. How to Identify Mold
  3. Is Mold on Weed Harmful?
  4. 12 Ways to Prevent Mold on Weed

Mold is a fungus that grows from multicellular filaments called hyphae. Discolored spots and white fuzz are the telltale signs of mold. Mold can also be green or black. Bud rot is also a mold that develops in the dense cores of cannabis buds. Root rot is a mold that grows on the roots of the cannabis plant.

Mildew is a type of powdery mold and can appear as thin black or white spots on the leaves and buds of cannabis plants. If the buds have a fuzzy white, brown, black, or gray growth, do not use them.

Just like any other plant, cannabis has a shelf life.

What Causes Mold on Cannabis?

Exposing cannabis to light, humidity, oxygen, and the wrong temperature can promote mold growth. Injuries to the plant can increase the chances of mold growing on the weed. If the temperatures are too low, exposure to moisture can result in mold. Overwatering or leaving your plant in overly humid conditions can also contribute to mold growth. Improper curing and storage of cannabis can also cause mold.

In nature, mold helps the recycling process of plants by breaking them down and making the nutrients available in the soil. However, mold is very undesirable for humans requiring the plant for medication. It can increase the likelihood of other plants in your grow space being infected by mold, pathogens, and pests.

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How to Identify Mold

Mold on cannabis often presents as white, fuzzy hairs but can also be fuzzy brown, black or gray growth. These darker colors may also signify bud rot, as they could be a type of mold called “botrytis.”

fungi on cannabis plant
Fungi on the cannabis plant. Photo Credit: PLG/iStockPhoto
closeup of white mold on cannabis plant leaves
White mold on cannabis plant leaves. Photo Credit: OlegMalyshev/iStockPhoto
moldy cannabis flower with bud rot
Moldy cannabis flower with bud rot. Photo Credit: Pong Pong/Shutterstock
closeup of cannabis flower with mold and bud rot
Closeup of cannabis flower with mold and bud rot. Photo Credit: Pong Pong/Shutterstock

Is Mold on Weed Harmful?

Yes, moldy cannabis can be harmful, especially if inhaled into the lungs, as it can cause a lung infection or an allergic reaction. This is especially dangerous for immunocompromised patients. Ingesting any expired food, including cannabis, may cause nausea and vomiting.

12 Ways to Prevent Mold on Weed

The best ways to prevent moldy weed include:

  • Proper drying and curing.
  • Appropriate storing.
  • Adequate airflow and grow room filtration systems.
  • Avoid over-watering during the final stages of flowering.
  • Botrytis is a type of mold spread through wind and rainwater. It tends to attack injured plants, so stress training can be a vulnerable time for a plant, even if it can increase yield and strengthen the plant in the long term. You can prevent the start of the bud rot cycle by providing a warm, dry and airy environment for the plant to recover.
  • Controlling humidity levels and reducing them to less than 50%.
  • Propolis or bee glue can be spread or sprayed on plants to kill mold.
  • Bordo mix is an organic fungicide mix made up of copper, sulfate, and slaked lime and used as a spray.
  • Horsetail tea: 1 ounce of powder makes a gallon of ready-to-spray solution.
  • Essential oils of thyme, rosemary, eucalyptus, black caraway, and lemongrass can be used as diffusers to help prevent mold spores from settling.
  • Silica in the soil can help strengthen stems and act as an alkaline adjustor.
  • Removing the infected parts of the plant or removing the plant entirely and disposing of it if the mold is too severe.

Moldy plants are more susceptible to diseases and pest infestations, which can harm other plants in the vicinity. Treating mold growth before it becomes a further problem is of utmost importance to prevent a great crop from becoming a disaster. In some cases, you may need to dispose of the plant. Appropriate drying, curing, and storing of buds are required to prevent mold.

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