Preventing Powdery Mildew in Cannabis

Zac Ricciardi

National Cannabis Specialist 

Powdery mildew (PM) is a scourge that every experienced grower encounters at one time or another. There are a multitude of scenarios where powdery mildew establishes itself, through ventilation, worker transportation, transplants etc., but once it finds its way in growers struggle to get their gardens back to a sanitary state. From contaminated genetics to power failures to unbalanced environments, there are many reasons a powdery mildew outbreak can occur. Both preventative and curative measures can be taken to counter the infestation and overcome the situation. It is imperative that growers understand the disease triangle; three things must be in proper alignment for pests to cause a problem.

  1. A susceptible host
  2. A conducive environment
  3. A virulent pest or pathogen

Note: Powdery mildew is NOT systemic. It can affect localized areas with topical spores and spreading mycelium but does not translocate through the xylem or phloem.

A susceptible host can be any plant that encounters some sort of stressor. That stressor causes pathogens or disease pressure to present itself in the form of an outbreak. Once a plant is compromised it becomes a liability to the rest of the garden and the potential for the outbreak to spread goes up exponentially. When the worst-case scenario presents itself what do you do? Spray the plants? Ditch them and start over hoping the issue doesn’t replicate itself? Nothing at all? BioSafe Systems wants to help you figure out the process for curing and preventing PM outbreaks.

When you find powdery mildew in the garden you want to react immediately and address the issue as soon as possible. To treat powdery mildew effectively, you must understand the physiology behind it. Powdery mildew’s network of root-like structures is known as mycelium, and they imbed in the cellular tissue of the plant leaf and cannot be removed with just a topical fungicide. We treat powdery mildew like a dandelion; kill the roots to get rid of the plant. Once you see the mycelium spread out like thin white threads on the leaves, you’ll know the infection has been established for some time. That’s where BioSafe Systems’ OxiPhos® and ZeroTol® 2.0 combo come into play. The tank mixture of these two gives the grower a strong disinfestant, the 

Powdery mildew on cannabis

ZeroTol® 2.0’s 27% hydrogen peroxide, and the OxiPhos 27% phosphite elicits the plant’s ISR (Induced Systemic Response), which allows the plant’s defense system to help mitigate the spread of embedded mycelium. The plant’s systemic defense response is triggered by the potassium phosphite (mono and dipotassium salts of phosphoric acid) in OxiPhos. The plant cannot regulate the uptake of the phosphite molecule and because it cannot, the stress response initiates systemic control for a period of up to 21 days. Stimulating the plant’s three-week active stress response gives the grower the ability to time out applications easily and have a crop consistently defending itself during propagation through till harvest. The ZeroTol 2.0 can be used during that 21-day period as a standalone for spot treatments when needed.

Properly controlling your environment is essential to upsetting the disease triangle and preventing powdery mildew. Air quality, air movement, temperature, moisture, and sanitation all contribute to outbreaks and need to be monitored to safeguard the grow. Stagnant air plays a big role in outbreaks, but fans circulating the air means optimized heat distribution, promotes strong transpiration, which enhances uniform development. Humidity is another factor, maintaining consistent levels of moisture in the air helps growers control swings in dampness and keeps plants healthy; too much moisture and you can risk fungus and algae growing rampant, not enough moisture and the plants can dry out. Utilizing SaniDate® 5.0 on hard, non-porous surfaces during the grow and in between runs means their facility is thoroughly disinfected and prevents old issues from recurring, and new issues from materializing. Proper sanitation supports all the other aspects of a balanced environment, which is key to preventing re-infection.

Growers need to be preventative rather than curative with PM because it is a lot easier to keep things clean than to get them clean after an outbreak. One way to spot the problem in advance is for managers and growers to do frequent scouting for indications of an infestation and removing infected plants to help stop the spread. For growers bringing in new genetics, there are tissue tests available that identify contaminated genetics. Otherwise, quarantine new clones and follow proper IPM (Integrated Pest Management) procedures until clean genetics can be verified. Some growers find an inhibitor like OxiPhos aids in suppressing powdery mildew where variables can’t always be controlled by inducing the stress response and keeping the plant constantly “on guard”. In addition, utilizing a microbial stimulant, like TerraGrow® or TerraGrow® Liquid, can boost plant health.

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BioSafe Systems, LLC is a company leading innovations since 1998 for environmentally sustainable practices and products that protect crops, water, and people. Our success hinges on a commitment to customer service, quality research, regulatory compliance, and the willingness to adapt. BioSafe Systems is a family-owned and operated company certified by NQA to ISO 9001:2015, 14001:2015, and 45001:2018, and our products are manufactured proudly in the United States. More about BioSafe Systems

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