Powdery Mildew: Identify, Prevent and Treat White Powdery Mildew on Cannabis: Part 2 – Prevention of PM

Prevention of powdery mildew

this is part 2 of a series on Powdery Mildew. If you have not yet read it, please continue to:
Part 1 – Identification of Powdery Mildew

Preventing powdery mildew in the cannabis grow room really comes down to 3 main things. Controlling the environment completely, genetics, and plant nutrition! Yes, the correct environment, a quality source of genetics, and proper nutrition are the 3 biggest controllable factors you have to deal with.

While you can’t control issues outside of your grow room that might lead to getting powdery mildew, you can control what goes on inside your grow room so let’s talk about sourcing genetics first.

There is no doubt in my mind that the single largest contributing factor of contracting powdery mildew, especially in an indoor-grow, is the exchange of contaminated cuttings and clones throughout the cannabis community.

Powdery mildew is often easily overlooked in the beginning stages, and since we are dealing with literally thousands and thousands of microscopic spores, it is almost impossible to tell if they are present until they begin to take life and spread throughout your precious marijuana garden in the form of white powdery mildew that you can see with the naked eye.

Since powdery mildew is spread by microscopic spores, and literally 1 spore can and will infect a plant, it is very easy to contract powdery mildew by bringing in plants from another source. Even the cleanest-looking, otherwise healthiest plants – can have the spores present and lying dormant.

Many times, if the conditions for spores to germinate are not optimal, the microscopic powdery mildew spores will lie-in-wait. This means they can exist, but show no visible signs or growth.

If you bring a plant into your grow room which contains spores and fail to control the environment the next thing you know – outbreak.

Starting your cannabis crop from seed, is the first line of defense…

in not contracting powdery mildew in your indoor cannabis garden. Simply put – the less things you bring into your grow room the less chance of spores coming along for the ride!

There are also strains that are less susceptible to powdery mildew than others. Selecting a good, hearty, known to be resistant strain can go a long way, especially if you fail to properly control your environment.

Just like some people are more susceptible to disease than others, the same goes for plants. Choosing a good “blood-line” if you will, can go a long way. I have personally seen grow rooms that had 1 strain go unaffected while the others were overtaken by powdery mildew. They were grown under identical conditions, side-by-side and one strain was just able to keep itself protected, “somehow”.

Do your research when choosing the right cannabis strain for your grow and try to pick varieties known to be pest and disease resistant. Buy your seeds from quality dealers that provide information on a strains resistance.

Environmental control is the second defense in preventing powdery mildew attacks.

Since powdery mildew spores need a certain habitat to germinate and reproduce, controlling your environment is vital. The real key is to take away the environment for powdery mildew to live – while also providing the correct setting for cannabis to thrive. This makes it a fine line and a frustrating one to walk for many cannabis growers.

“Powdery mildew is favored by temperatures between 68° and 77° F and humidity of 40% or more.” Source: Powdery Mildew of Hemp | Kentucky Pest News

So what are some things that will help take away the environment for powdery mildew, while still allowing your cannabis to thrive?

Airflow: Proper airflow will reduce the chances of powdery mildew. If the air is constantly blowing around your plants, it makes it extremely difficult for the tiny spores to land and latch on. Good airflow is also great for your cannabis plants in many ways, so get those fans blowing and keep it breezy.

Exhaust: When you properly ventilate, or exhaust, your cannabis grow room – you are letting out stale air and bringing in new fresh-air. This helps to keep humidity under control along with the constantly moving air from the fans.

Proper temperature: If you keep your temperature at the best optimum range for cannabis and allow proper airflow, you should significantly reduce your chances of getting powdery mildew infections in your marijuana grow room.

Consistency: Keeping an ideal climate is very helpful and rapid or extreme swings in temperature and or humidity should be avoided. The more stable and consistent you can be with the environmental control, the better!

If you do a quick search or follow this Amazon link for “Grow Room Controllers” you will find many environmental controllers that work with the several different fans, filters, and other grow room equipment that will help you provide the proper environment for you cannabis plants while minimizing the chances of getting powdery mildew.

Plant Nutrition and Strength

Plant Nutrition: Proper plant nutrition is a great way to help prevent powdery mildew in your cannabis grow. Just think about the basics. A healthier plant will be able to defend itself better against attacks. This is no different than people. When you let yourself go, don’t eat right, maybe have too many stress factors going – you get sick easier!

Keeping your plants strong is a great preventative measure against getting powdery mildew.

Many growers are starting to turn to nutrients that have added silica to help strengthen their plants overall and to help thicken the cell walls of the leaves making it harder for the powdery mildew spores to latch on and penetrate the leaf’s surface to feed.

To order Plant nutrients with silica from Amazon Click Here

Silica, when added to a plants feeding schedule, is said to increased resistance to pathogens and pests in the cannabis garden. It also has added benefits of helping make the cell-walls stronger, and stems and stalks larger, making the plant itself a powerhouse of efficiency when it comes to growth.

Cleanliness is next to…

So we all know the saying. Well let’s apply it here too.

By keeping all of your work areas in the grow room clean, you will help eliminate the chances of getting powdery mildew.

This means keep EVERYTHING clean.

A simple solution of peroxide and water is a good overall cleaning agent that should be used to clean all work areas and is safe at many dilution levels to spray on plants themselves.

Rubbing alcohol is another great tool for cleaning surfaces and tools like scissors and blades you might use for taking clones, but you must be very careful to never spray it on your plants.

If you make it a regular habit to clean all your tools, pick up and discard all plant debris immediately, and wipe down all surfaces regularly, you will greatly reduce your chances of a powdery mildew outbreak. Bottom line, the more you clean and discard from your grow room, the less likely it is that spores are hiding in the corners.

To sum it up

Prevention of powdery mildew is going to come down to some basic routines in how you garden, where you get your genetics and how you control your environment. Add these things with proper plant nutrition and you shouldn’t have too many issues with powdery mildew in the future.

If you do find yourself dealing with a powdery mildew outbreak, please have no fear. We will have part 3 coming soon where we will talk about several methods of treating a powdery mildew outbreak. In the meantime, for a great reference book on treating many diseases and pests that are common in cannabis gardens – be sure to pick up a copy of:  “Marijuana Pest and Disease Control: How to Protect Your Plants and Win Back Your Garden by: Ed Rosenthal” it’s been a great addition to my marijuana bookshelf!


For more reading material on preventing powdery mildew in the cannabis grow room – visit the sources below:

“When a plant is fed a soluble form of silica, the plant accumulates the silica around the infected site forming selectively fortified areas that can fend off fungal infections such as rust, pythium and powdery mildew. As a resistance measure, the plant uses the silica to build up an additional mineral barrier, essentially lining the cells, making it more difficult for diseases and plant pathogens to make their way inside the plant.”

Source: Why Your Plants Need More Silica

“Under ideal conditions (moderate temperatures and high humidity), an infection site of just one square centimeter can produce an average of 300,000 spores each day.  Within 5 to 10 days after infection, diseased plant tissue becomes a source for new spores, and the cycle continues.  Under greenhouse conditions, this repeating cycle is continuous.”

Source: Powdery Mildew of Hemp

“Powdery mildew spores can be transported to your plants on the wind, through air ventilation systems, from pets, and any other living thing that moves (including yourself). Until the surrounding environment is ideal, the spores from mildew will stay dormant, biding their time.”

Source: Stop Powdery Mildew On Marijuana Plants Now!

“This fungus is one of the most common to affect marijuana plants, it needs high humidity and a minimum temperature of 20ºC to be able to grow and sudden changes in temperature benefit its appearance..”

Source: The most common fungi that can attack your marijuana plant

© CannabisChris.com 2016
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