Organic fungicides and How to Apply them to Cannabis

Cannabis growers have long relied on fungicides to stave off the threat of fungal infections. However, a growing awareness of the environmental and health-related consequences of chemical fungicides has led to a resurgence of interest in organic alternatives, fungicides derived from natural sources that offer a sustainable and effective approach to disease control without the harmful effects associated with their conventional counterparts.

With thousands of fungal species around the world, cannabis is under constant threat from microscopic spores floating in the air, just waiting to take over our plants. Under the right growing conditions, these spores can cause mold, root rot, wilting, and other diseases that stunt growth and drastically reduce yields, or even kill crops. Therefore, it is first essential to understand approaches to the treatment of fungal diseases to keep crops safe from these silent enemies.

How to combat fungal diseases

There are several methods to prevent and treat fungal diseases in cannabis plants, and each of them is based on different approaches:

• Controlling environmental variables: the most important factor is to control the cultivation parameters that make plants vulnerable to fungal diseases. This includes temperature, irrigation frequency, moisture, soil pH, and mineral content. Applying best practices to these factors can prevent the spread of fungal spores throughout the area where crops are planted.
• Cleaning and disinfection: by far the best way to deal with fungal diseases is to prevent them in the first place. Controlling temperature, humidity and irrigation is a good start, but it’s important to be able to neutralize the spores once they are present. This is why many indoor growers invest in air purification systems that ensure you never have to worry about mold.
• Chemical fungicides: After noticing signs of fungal infection in plants, it’s important to take immediate action. Many growers opt for non-organic solutions, such as conventional fungicides. These chemicals can be an effective way to kill fungi on cannabis plants, but they can be harmful to both plants and the environment, and make their consumption problematic.
• Organic fungicides: today many consumers are looking for cannabis grown in a pesticide-free environments, making organic fungicides a very attractive option. For example, potassium bicarbonate is a natural fungicide that can reduce the spread of powdery mildew and other fungi. Hydrogen peroxide is another compound that features antifungal and antibacterial properties. Similarly, copper sulfate has been used to control fungi on vines for centuries. Unfortunately, it can harm marijuana plants, but adding lime can partially attenuate this effect.

Reasons to opt for organic fungicides

The choice between organic and chemical fungicides extends beyond the realm of crop protection; it is a decision that impacts the environment, human health, and the sustainability of agricultural practices. Organic fungicides offer an attractive array of benefits, including reduced environmental impact, increased food security, improved soil health, and decreased resistance to these pathogens. As we strive for a more sustainable and ecologically harmonious future, adopting organic fungicides emerges as a clear choice that can lead to healthier harvests and a cleaner planet. Let’s take a look at the options available.

Organic products to increase biological competition

Within organic fungicides, an effective approach is to use strains of bacteria that fight fungal diseases such as downy mildew and botrytis without affecting plants. The most common biological sprays include species such as Bacillus pumilis, Bacilus subtilis, and Streptomyces lydicus. These species can be used to populate the surfaces of leaves, providing strong competition against many pathogenic fungi.

While these products can work very effectively, a less expensive option would be to apply to your leaves compost extracts or teas with a high content of a broad spectrum of beneficial microorganisms. This is a less specific but more holistic and economical approach when disease pressure is relatively low.

Beneficial microbes are more of a prevention strategy than a treatment for fungal diseases, but they can certainly bolster treatment efforts, as well as trigger the plants’ natural systemic resistance. And, when applied in the soil, they can even physically cover the plants’ roots to prevent fungi such as Fusarium, Pythium and Rhizoctonia from penetrating their skin and infecting crops, causing wilting.

Organic products to reduce fungal populations

To attack fungal infections directly there are several compounds that reduce their populations before they get out of control. These products have different modes of action:

• Sulfur: Sulfur-based products have long been the material of choice for two main reasons: they are economical and effective. In addition, despite 150 years of use, little resistance to them has been developed. The main sulfur products to consider are wettable sulfur, lime sulfur, and lime powder, although it’s necessary to apply them with caution, especially lime sulfur, which is caustic.
• Sterilizing products: Products like ZeroTol (a combination of hydrogen peroxide and peroxyacetic acid), pure hydrogen peroxide (about 3% is best), potassium bicarbonate, and potassium silicate will kill fungi like downy mildew or powdery mildew quickly and aggressively. Their modes of action are different, but they are all designed to kill, instantly. In fact, ZeroTol should be considered a great weapon when things get out of hand.
• Vegetable oils: In general, vegetable oils are effective at reducing fungal populations, probably by reducing spore germination. One study found that when tomato leaves were sprayed with 0.1% emulsified canola oil, corn oil, grapeseed oil, peanut oil, safflower oil, soybean oil, or sunflower oil, the activity of Oidium neolycopersici was significantly reduced. Among the edible oils tested, sunflower oil was the most effective. Vegetable oils emulsified with egg yolk have also been found to be a very good option. Products such as Thyme Guard offer a broad spectrum of suppression, using thyme oil, while Cinnerate offers suppression using cinnamon oil. Several products, including Trilogy, also use neem oil to reduce colonization.
• Mineral oils: Products such as SuffOil-X have been used successfully to reduce infections, as it keeps the pathogen from attaching to hosts, acting as a suffocant.
• Plant and food extracts: Some studies suggest that comfrey extract can markedly decrease infections in plants with mildew. This is due to both protective action and photosynthetic activation within the plant. Quillaja extracts are also a very effective product. A solution made with garlic extract is another natural remedy, as garlic contains sulfur. Finally, apple cider vinegar diluted in water is another readily available ingredient that can become a natural remedy against fungal diseases.

The power of ultraviolet light as a final solution

Finally, the use of ultraviolet light is a relatively new crop protection strategy, sterilizing the entire room. These bulbs generate 254-nanometer (nm) light, a specific wavelength range of UVC energy known to kill fungi, bacteria, and viruses. However, these may not be the most suitable options for all growers, as they are usually expensive. So, if you’re a small producer with a small budget, this may not be for you. Another disadvantage of using UV light is that prolonged exposure to it can put users at risk for retinal burns and cataracts. However, as an organic fungicide it is, undoubtedly, unbeatable. After all, who wouldn’t want to stop a fungal infection without putting a finger, or any kind of product, on their marijuana plants?