The most common cannabis diseases

Content

• Mold and fungal diseases
• Bacterial infections and root rot
• Pests: insects and parasites

Growing cannabis is not only about caring for the plant, but also protecting it from a host of diseases and pests that can significantly affect the quality and quantity of the harvest. Regardless of the type of cannabis, whether sativa, indica or feminized varieties, each species requires special attention and conditions for healthy growth.

Cannabis diseases are often caused by environmental conditions such as high humidity, inadequate ventilation and improper watering. Mildew, bacterial infections and pest infestations can seriously damage even the most resistant varieties, affecting their yield and quality. It is important to remember that certain diseases are more likely to affect certain varieties. For example, the thick and dense inflorescences of indica are more susceptible to fungal infections, while the thin leaves of sativa can be affected by pests such as spider mites.

Mold and fungal diseases

Mildew and fungal infections are one of the most common and dangerous problems in cannabis grooving, especially under conditions of high humidity and inadequate ventilation. These diseases can affect any part of the plant, from the leaves to the inflorescences. Cannabis varieties with denser buds are particularly susceptible to fungal infections due to poor air circulation within the flowers. The most common types of fungi that can threaten cannabis plants are powdery mildew and gray rot (botrytis).

Powdery mildew

The powdery mildew manifests itself as a white powdery plaque, which can first be seen on the lower leaves and stems. As the disease progresses, the plaque spreads to cover more and more of the plant. This plaque resembles a fine layer of dust and is easily washed off, but soon reappears, causing considerable stress to the plant.

The main factors contributing to powdery mildew are high humidity (above 60%), temperature fluctuations and poor ventilation. If there are infected plants near cannabis, the risk of infection also increases.

Control methods:

• Prevention: maintain optimum humidity levels (40-50%) and ensure good ventilation.
• Plant care: remove affected parts of the plant to prevent further spread of the fungus.
• Use of organic fungicides: using natural preparations such as neem oil and a solution of baking soda and water can help prevent and treat powdery mildew. You can also use a milk solution (1 part milk to 9 parts water) to spray on plants.

Gray rot (botrytis)

Gray rot, or botrytis, manifests as brown, soft spots on the inflorescences that eventually turn gray and fuzzy. This fungal disease spreads especially quickly in high humidity, making it dangerous to dense indica flowers. If the disease is not stopped, it can destroy buds and lead to a complete loss of the crop.

High humidity, poor air circulation and warm climates are ideal conditions for gray rot to develop. The disease usually begins in the mid to late flowering stage, when dense inflorescences retain moisture and create a favorable environment for the fungus.

Control methods:

• Keeping humidity low: during the flowering period, humidity should be around 40% or lower.
• Pruning and cleaning: regularly trimming the lower leaves and ensuring sufficient space between plants promotes good air circulation.
• Use of fungicides: special antifungal preparations designed for cannabis plants can effectively prevent the spread of gray rot. However, they should only be used as a last resort and according to instructions to avoid harming the plant.

Bacterial infections and root rot

Bacterial infections and root rot are serious threats to cannabis, especially when grooving in high humidity and overwatered soil conditions. These problems are often caused by improper watering and lack of drainage, leading to rotting roots and weakening the plant's immune system. All cannabis varieties, including sativa and indica, can be susceptible to these diseases if basic care rules are not followed.

Root rot

Root rot most commonly affects the roots of the plant, turning them into a soft, brown mass with a characteristic putrid odor. External signs of root rot may include wilting and yellowing of leaves, stunted growth and loss of leaf turgor (elasticity). The plant becomes weak because the damaged roots cannot absorb water and nutrients.

The main causes of root rot include overwatering, lack of good drainage and lack of oxygen in the soil or hydroponic system. In conditions of too much moisture, the bacteria and fungi that cause rot begin to actively multiply and damage the root system.

Control methods:

• Moisture and drainage control: use a good quality, well-drained soil mixture to prevent water from stagnating around the roots. For hydroponic systems, it is important to maintain optimum oxygen levels in the water by using aerators.
• Moderate watering: Water only when the top layer of soil is 2-3 cm dry. Avoid over-watering, especially for plants that have just passed the germination stage.
• Use of biopreparations: some natural preparations such as mycorrhizal fungi and beneficial bacteria promote root health and help prevent the growth of pathogens.

Bacterial infections

Bacterial infections can affect various parts of the plant, including roots, stems and leaves. Symptoms vary depending on the type of infection, but often include leaf spotting, wilting, deformity and discoloration of tissue. Young plants and seedlings that have not yet developed full immunity are most vulnerable.

The main causes of bacterial infections are contaminated soil, contaminated planting material and the use of untreated tools. Bacteria can spread rapidly in warm and humid environments, so improper storage and handling conditions can contribute to infection.

Control methods:

• Sterile conditions: pots, working tools and surfaces are thoroughly disinfected before grovelling to reduce the risk of spreading bacteria. Use sterile substrates and make sure the soil is pathogen-free.
• Removal of affected areas: at the first sign of infection, remove affected leaves and stems to prevent the spread of bacteria to healthy tissue.
• Use of biological preparations: natural biopreparations containing beneficial bacteria and microorganisms that compete with pathogens and prevent their reproduction can be used to control bacterial infections. Preparations based on beneficial bacteria such as Bacillus subtilis can protect the plant by creating a protective barrier on its surface.

Pests: insects and parasites

Pests are one of the main problems for cannabis grooving and can cause damage to the leaves, roots and even the inflorescence, reducing yields and degrading the quality of the plant. There are different types of pests that can attack cannabis, including aphids, spider mites, whiteflies, and fungus mites. Some pests are particularly active in certain climates and can more quickly affect varieties with thin leaves, such as sativa, as well as weakened plants, such as feminized and indica varieties, if not properly cared for.

Cobweb mites

Description and symptoms: Spider mites are tiny insects that attack the underside of leaves and feed on their juices. One of the first signs of their presence is the appearance of small white spots on the leaves, and later a thin web covering the plant. If the infestation is severe, the leaves turn yellow, dry and fall off, which weakens the plant.

Spider mites are especially active in dry and warm conditions, which makes them common in greenhouses and indoors. They spread easily, so an infestation can quickly spread to neighboring plants.

Control methods:

• Moisture control: Keep humidity high, as spider mites do not tolerate damp conditions. Regular spraying of the leaves with water can reduce the risk of infestation.
• Insecticide application: biological insecticides such as neem oil or pyrethrum-based products can effectively kill mites without harming the plant.
• Natural predators: releasing predatory insects such as Phytoseiulus persimilis, which feed on spider mites, is an environmentally friendly control method.

Aphids

Aphids are small insects, usually green or black in color, that form colonies on the stems and underside of leaves. These insects suck the sap out of the plant, which causes the leaves to curl and discolor, weakening the plant. Aphids also secrete a sweet secretion that attracts ants and promotes fungal infections.

Aphids can enter the plants from outside, especially if the cannabis is grown outdoors. Infestation can also occur through infected plants in the vicinity.

Control methods:

• Manual removal: In the initial stages of infestation, aphids can be removed manually by wiping the leaves with a soft cloth or washing off the pests with a stream of water.
• Application of insecticidal soap solutions: treating the plant with a mild solution of insecticidal soap helps to remove aphids without harming the plant.
• Natural enemies: releasing ladybugs and lacewings that eat aphids is an effective biological control method.

Whitefly

Whiteflies are small white flies that live on the underside of leaves and feed on plant juices. Their presence can be detected by flying white insects around the plant when touched. Infested leaves may turn yellow and fall off, and the whitefly produces sweet secretions that promote mold development.

The whitefly breeds actively in warm, humid conditions, especially in greenhouses. It quickly spreads to nearby plants, so it is important to monitor and detect their presence in a timely manner.

Methods of control:

• Yellow sticky traps: Placing sticky traps helps to control whitefly populations by attracting and trapping them.
• Use of biopreparations: preparations based on the bacterium Bacillus thuringiensis or predatory insects such as Encarsia formosa can be effective in controlling whiteflies.
• Regular airing and keeping clean: airing and maintaining moderate humidity reduces the attractiveness of conditions for whiteflies.

Mushroom gnats

Mushroom gnats are small black midges that lay their eggs in the soil. Their larvae feed on the roots, especially in young plants, which can stunt cannabis growth and cause wilting. The mosquitoes often live in soil that is too wet and indicate overwatering.

Overwatering and stagnant water in the soil create breeding conditions for fungal mosquitoes. If plants are near other infested plants, the risk of infection increases.

Control methods:

• Watering control: avoid overwatering the soil to reduce the risk of mosquitoes. Allow topsoil to dry out between waterings.
• Yellow sticky traps: these traps help control adult insect populations.
• Biopreparations: the use of beneficial nematodes such as Steinernema feltiae helps control fungus mosquito larvae by killing them in the soil.

Related articles:

• Ways to protect cannabis plants from insects
• Optimal conditions for growing hemp
• Why experienced grovers use a microscope
• How to determine the sex of cannabis?

Caution! Errors Seeds does not encourage you to grow cannabis and does not contribute to this in any way. Growing is prohibited by Ukrainian law. The article is of purely scientific and informational interest.