How to Use SM-90 for Growing Cannabis

by Nebula Haze

Important Note (12/22/18): SM-90 is no longer being sold. See this article for details or our All Natural Pesticides article for replacements.


Not long after I first started growing cannabis, I noticed some white powder on some of my leaves and learned I had a type of mold called White Powdery Mildew. A fellow grower told me to get something called SM-90 from Nutrilife to treat (at 1 part SM-90 to 5 parts water) as a foliar spray. I thought it was weird because the label doesn’t say anything about mold, but after using it the mold was gone overnight and I never saw WPM again!

SM-90 Can Treat and Prevent WPM. It Is Safe To Use on Cannabis Until Just Before Harvest.


I learned the trigger for WPM is hot, humid, stagnant air and bushy plants with leaves laying on top of each other. Once I fixed the environmental problems, I didn’t need SM-90 again for years and almost forgot about it.

Then when we started our growing forum, there started to be several posts about various ways that growers have been using SM-90 for their growing marijuana plants. I was amazed at how effective it is for so many different applications. Here is some quick info about it.

  • Safe for humans and animals
  • The main ingredients are coriander oil, canola oil and triethanolamine (an organic compound)
  • Can be used on cannabis plants up until the day before harvest, though you should avoid getting it on buds if possible to avoid affecting the taste or odor
  • Pleasant smell that reminds me of citrus

SM-90 is Surprisingly Useful in the Cannabis Grow Room!

SM90 kills White Powdery Mold AND smells great!

What is Nutrilife SM-90 Good For?

  • Wetting Agent – this is the only use actually listed on the label. From what I understand there is some legal reason they can’t list other applications on the bottle. A wetting agent is used to make foliar sprays more effective because it helps spread the water more evenly over the plant surface. It also helps moisture penetrate into the soil more quickly and evenly
  • General Root Health – Seems to generally help plant roots and some growers regularly add it to their water. I use it whenever watering my outdoor plants, especially if they get heat stressed.
  • Root Rot – There is some evidence from hydroponic growers that SM-90 can help protect roots against root rot, and additionally won’t hurt the good bacteria contained in many root rot prevention products like Hydroguard and Great White. Root rot can be caused by more than one type of pathogen, and no one solution works all the time, but SM-90 does appear to be effective for some people with some types of root rot.
  • White Powdery Mildew – SM-90 as a foliar spray is very effective at treating and preventing WPM.
  • Bugs – SM-90 is not the best choice for all bugs, but it does seem to be somewhat effective against aphids, spider mites, thrips and whiteflies when used as a foliar spray. Additionally, some growers have had good luck reducing their number of fungus gnats by adding this before watering their plants. I think SM-90 can be a good first line of defense if you want a one-product-does-everything to get rid of a few bugs before there is an infestation, and it can also be used alongside other pesticides. In fact, as a wetting agent, it can also help make other pesticides more effective!

How to Use as a Foliar Spray

  • 1 part SM-90 to 5 parts water
  • Always use a sprayer to mist all your leaves evenly and thoroughly, making sure to get under the leaves
  • Use once every three days for up to three applications in a row. If still experiencing mold or bugs, consider trying something else in addition. Often you will get the best results by combining more than one treatment.

How to Use for Watering and Hydroponic Applications

  • 1 tsp SM-90/gallon when added to a reservoir or to water before giving to your plant
  • Be aware it does change the pH so add SM-90 first before pHing your water!
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