Prevention of Powdery Mildew in Cannabis Plants

Pest and pathogens come with the territory, and most commercial growers are no strangers to powdery mildew. Because indoor and greenhouse environments are especially susceptible to powdery mildew, growers who adopt proactive measures against the disease are more likely to be set up for success than those who only react to outbreaks. In this article, we’ll discuss steps growers can take toward preventing powdery mildew in their cannabis plants.

Pre- & Post-Harvest Prevention

It takes just two weeks for a cannabis plant infected with powdery mildew to lose water, nutrition, and cell functionality and begin to show the appearance of white powder on its surfaces. The disease can ultimately impair photosynthesis, causing discoloration, abnormal growth, and trichome damage – reducing quality and yields in the process. 

Powdery mildew needs a living host to survive. Since the industry relies upon the use of mother plants, clones, and cuttings for propagation, the potential for an outbreak remains high for commercial cultivations. The use of resistant strains is one way to help the entire garden stay healthy, so keep an eye out for those during pheno hunts. If an outbreak occurs, removing infected plants and their debris is the surefire way to eliminate the source of the fungal disease which, if left unchecked, can cause crop loss and continue to spread even post-harvest. Growers may elect to use fungicides to treat powdery mildew, but for the utmost consumer safety must adhere to local and state requirements when choosing a solution and the ideal time in a plant’s cycle to apply it.

When factoring in the humidity and temperature fluctuations typical to indoor and greenhouse facilities, it’s clear that growers who take a proactive approach toward managing powdery mildew will be better equipped in the long run to manage the disease. Conducting regular plant inspections helps the cultivation team ensure the health of existing crops and new cuttings, while also giving growers the chance to apply mitigating measures well before the infection gets out of hand. 

But proper plant nutrition is about more than making sure cuttings and mothers are pathogen-free prior to propagation; growers must also make sure their cultivation practices aren’t contributing to the problem. Proper plant spacing facilitates airflow between plants and helps to eliminate the potential for spores to spread due to overcrowding, while good pruning techniques can help minimize damage to the flowers and trichomes during post-harvest processing. As an alternative to fungicides, growers may instead apply certain biological controls at key times prior to harvest which may succeed in killing the pathogen without raising regulatory red flags. 

Facility Maintenance & Sanitation

Between high humidity and moderate temperatures creating the ideal conditions for powdery mildew to bloom, and wind and fans further facilitating the pathogen’s spread over long distances, it’s no wonder outbreaks are so common in indoor and greenhouse facilities. Growers who adopt an overall integrated pest management(IPM) strategy that prioritizes sanitation and facility maintenance may find themselves better prepared to handle powdery mildew.

For growers to create an indoor or greenhouse environment in which plants thrive and pathogens don’t, a facility needs dehumidifiers and other equipment to maintain proper humidity control throughout all stages of plant growth all the way to post-harvest drying and curing. Air filtration systems help cultivators ensure proper air circulation while also limiting the ability of airborne contaminants to survive in the facility. Because CO2 loss can result from stagnant, humid air in poorly ventilated environments, growers may consider adding CO2 enrichment to their environment to foster plant growth. And by managing proper temperature control with air conditioning and other means, cultivators will be able to avoid temperature fluctuations that can facilitate a powdery mildew infection. 

But the best equipment in the world won’t make a difference if the environment is dirty and disorganized. Staying vigilant about sanitation practices is crucial for warding off powdery mildew and other pests and pathogens. Taking the time to disinfect everything from fresh seeds to new equipment before bringing them into a facility; regularly cleaning and sanitizing air filters, trimmers, dehumidifiers, and other tools; and requiring team members to wear gloves, hair and beard nets, and follow decontamination protocols when going from room-to-room can all help minimize the potential spread of powdery mildew. Honing in on an effective IPM strategy and using what works to create standard operating procedures can go a long way toward minimizing the instance and impact of this and other pathogens that may crop up in the garden.

Powdery mildew isn’t going anywhere. The reality of commercial cultivation in fact all but guarantees that cannabis growers will someday have to face this and other potentially harmful fungal diseases. But rather than being an ongoing source of stress and frustration, this pathogen’s resilience is a great reminder that there are always ways to dial in processes and make improvements that ensure outbreaks are few and far between.