White Powdery Mildew, WPM or PM for short, can destroy an entire crop if not caught and treated in time. Here I’ll tell you what you can do to prevent, recognize, and lastly treat this menace of growers across the world.

As a wise person once said “An ounce of prevention is worth a pound of cure”. I could not agree with this more and in my opinion the best step to take is to make your grow room a place that PM does not want to live. The four major factors I’ve found that will put your room in danger:

  • Cool night time temperatures
  • Stagnant or non-circulating air
  • Generally wet/humid conditions
  • Heavy contact between leaves

Removing these factors will greatly reduce the chance of your plants contracting PM in the first place. Although these are what I would consider the major risk factors, there are a few other good practices in avoiding PM. One thing that can be done is asking your staff to change into a uniform or a Tyvek-type suit when entering the grow room. This will prevent any staff from accidentally carrying in mold spores or any other contaminants. Also installing a UVC light can be beneficial as it can kill airborne spores. By implementing some or all of these preventative measures you will hopefully be saving yourself a headache further down the road.

The second key factor in protecting your plants from Powdery Mildew is going to be identification. The earlier, the better being the most important part of identification. PM can be had to spot in its earliest manifestations so a personal recommendation is to get yourself a jeweler’s loupe or some other type of portable magnifying device in order to be able to see the Mildew much sooner than with the naked eye. Although PM is invasive, it is not particularly hard to recognize. With the eye alone, PM looks like small dots or patches of flour and should not be hard to recognize. In earlier stages the patches will simply be much fainter and under magnification look like bright white or greyish strands. These white strands should be highly distinguishable from trichomes. Once you’ve made a positive diagnosis and had a good cry, then it’s time to move onto treatment.

So you’ve established that you have Powdery Mildew. Now what? Generally there are two routes to go when ridding your grow of PM. The first being home remedies, which can be very effective for some, whereas others will choose the second route, products designed to treat PM.

Here are a few home remedies that a large number of growers swear by:

  • Milk (1:9 ratio of milk to water)
  • Baking soda (2 tablespoons per gallon of water)
  • Neem Oil (4 teaspoons per gallon of water)
  • Hydrogen Peroxide (1 teaspoon of 35% H202 per gallon of water)
  • SM-90 (1:5 ratio of SM-90 to water)

If you choose to go the pesticide route here are some products that have proven to be useful:

  • Bergman’s Plant Protector
  • Lost Coast Plant Therapy
  • GrowSafe
  • Bush Doctor

Armed with this knowledge, it is my hope that you are all now a little more prepared in your grow room venture or gardening adventure. Powdery Mildew is a pest that master growers and beginners alike have to be wary of. However it is not necessarily a death sentence for your plants. I hope you found this helpful in answering any questions you may have had regarding this issue and I wish you all a happy harvest!

Thank you Billy for the lowdown on PM – as with most garden related issues an ounce of prevention is worth a pound of cure, so maintain good ventilation, watch nighttime temperatures, keep your plants well defoliated, and appropriate humidity.