Powdery mildew on cannabis (PM) is a common growing problem. There are many methods to treat powdery mildew on cannabis. However, time is ultimately the most relevant. In addition, cleanliness, thoughtful environmental design and attention to detail are central to solving this growing common problem.
Fortunately, there's no need to panic if powdery mildew on cannabis starts to appear. Here's why:
What is mildew?
Powdery mildew is a common fungal disease affecting cannabis plants. Two unique species of PM are capable of infecting cannabis: Taurica and p.macilans. Scientists classify these types of particles as "obligate biotrophs", which means that they require a host to spread.
PMs thrive in the warmer, more humid climates of places like Hawaii, Florida and many southern US states.
Again, be aware that this is a common and treatable disease for cannabis plants. However, it is more difficult for a mature plant to bounce back from this widespread attack. Younger plants have a better chance against this dusty assault on cannabis leaves.
How does it harm the plants? By weakening the leaves and slowing growth. Not ideal if high yield is the goal. In addition, the particles that develop as the cannabis plant flowers can contaminate the buds, rendering them useless. As such, you should control powdery mildew on cannabis as soon as possible.
How to identify powdery mildew
Powdery mildew appears as a grey or white dust on cannabis leaves. Unfortunately, outdoor growers often mistake it for bird droppings until it is too late.
Although you can remove powdery mildew from cannabis, you must do so with caution. Touching the unwanted dust could spread it and infect more plants. If you don't know if you have a particle problem, ask yourself if the plant is having trouble growing.
Healthy cannabis has a solid chance against PM. However, if the plants lack adequate nutrition and are infected, the risk of disease is higher. This is similar to the human immune system facing the flu or the current pandemic.
The environment in which the plants are growing can cause a powdery mildew problem in these ways:
- Moist conditions
- Stagnant water
- Stagnant air / poor ventilation
- Low light greenhouse or indoor growing
- Dead or mouldy vegetation
- Pest infestations
- Hot / dry weather
- Lack of environmental sanitation (more on this in prevention)
As such, it is essential to have a keen eye for detail. Even in a well maintained environment, there is always the possibility of PM. This is because it can happen at any time, sometimes without prior warning. Moreover, PM grows in the same conditions as healthy cannabis plants.
Fortunately, there are preventive methods to avoid this problem. If powdery mildew on cannabis is a current problem, you need to tackle the problem now before it gets out of hand.
Treating mildew on cannabis plants
The mildew treatment is most effective on young plants. It is almost impossible to recover mature plants, so time is of the essence. Fortunately, there are a variety of solutions available; those shown are organic.
Ideally, you should stay away from chemical solutions. As the plants are intended for human consumption, it is vital to solve the problem without causing further problems for the plant or the consumer.
As this is an urgent matter, start treatment at first sight. This process requires patience and possibly several applications.
To start, remove any PM-infected leaves that you cannot treat directly. Use clean gardening tools to trim and discard the leaves - DO NOT compost them! Then apply an organic fungicide or make your own solution using diluted milk and a spray bottle. Simply mix 1 part milk with 9 parts water in a spray bottle. Using direct sunlight, spray directly onto PM.
Organic fungicide options are numerous and include many items you probably already have around the house. For example, hydrogen peroxide or apple cider vinegar work well to treat powdery mildew on cannabis. Other products include potassium bicarbonate, Bacillus Subtilis, Streptomyces Iydicus, Green Cure, and mixtures of vegetable sulphur oil and garlic oil, cottonseed oil or corn oil.
Powdery mildew prevention methods
Prevention of powdery mildew on cannabis plants starts with these crucial factors:
- Indoor cultivation or greenhouse arrangement
- Clear and repeatable procedures
- Macro-level pest management systems
At the heart of it all is the need for cleanliness. This applies to the environment, as well as to anyone interacting with the growing area. This means washing your hands regularly and possibly changing your clothes when entering and leaving the greenhouse or indoor facility.
You should also regularly sweep up dead leaves, plant material and pollen, and never leave standing water. Properly dispose of any infected plant material (again, do not compost problematic plants!). Use bleach to clean all walls and surfaces where fungi (and other problems) can survive.
This article from Cannabis Business Times lists 11 key preventative measures against powdery mildew. These steps include:
- Only add clean genetics from reliable sources
- Only add clean genetics from reliable sources
- Sterilise plants before quarantining
- Create positive air pressure environments
- Establish good airflow controlled by temperature and humidity
- Sterilise the air circulating in the crop/greenhouse
- Clean ALL equipment regularly with hydrogen peroxide
- Prioritise cleanliness at all times (be obsessive to the limit)
- Control humidity
- Develop a decontamination procedure for all staff
- Establish a method for maintaining temperature differential
- Find the "sweet spot" of the growing area for the vapour pressure deficit
Final thoughts on mildew on cannabis
Regardless of the grower's level of experience, keep this information on file and watch for any future problems.
For quality hemp seeds, check out the Silent Seeds shop [silent-seeds/home] and add mould resistant varieties like Stardawg to your crop. Contact us if you have any questions.
Have you had an encounter with this vile dusty fungus? What treatments have worked (or not)? Comment below and share your experience with other fans of our Swiss seed bank.
The Silent Seeds team would like to point out that all seeds sold on their website are forbidden to germinate. They are for collection purposes only. We do not encourage our customers to disregard the law and are not responsible for their use.