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Auto Warrior
Jun 23, 2015
Hi everybody. Well, we’re heading into summer, and most of you who’ve got a few grows under your belt know what that means. BUGS!!! :cuss:

Though there are myriad types of beastly bugs out there, two types, fungus gnats and spider mites, are the ones I’ve developed a sincere hatred of. I’m always on the look out for tips and tricks that will help me keep them away from my plants. So here’s a few simple tricks that you may not know about PREVENTING these critters from attacking your grow.


  1. It’s far easier to keep fungus gnats away if you use fabric pots. If you are using regular plastic pots or air pots it’s harder to keep gnats away because they can get into your soil or coco through the drainage holes and air holes, as well as enter your soil from the top of the pot. With fabric pots the fix is simple. Just top your soil or coco off with about a half inch of well-washed sand and fungus gnats have no way to enter your soil layers.

  1. If you are using regular plastic pots, you can also put a half inch layer of sand about a half inch above the drain hole openings, then fill as usual with soil or coco and lastly, top the pot off with another layer of sand. With air pots, lovely as they are, there are just too many holes so sand won’t help. But you air pot growers could try the following trick.

  1. Fungus gnats hate the smell of cedar and avoid areas that smell of cedar. There is a product called “Cedar Magic” (you can find it on Amazon and Ebay) which is a solid, hanging air freshener made to keep your closets smelling fresh and clean like cedar. If you hang one or more of these air fresheners in your grow area down low by your pots, you’ll stand a much better chance of keeping fungus gnats at bay.


  1. Spider mites detest the smell of Chives! Commercial greenhouse growers regularly introduce pots of growing chives among their bedding plants in order to keep spider mites out. They’re using the time honored trick of “companion planting” to keep the bugs away. Chives are small, easy to maintain members of the onion family that you can grow on in a small 6” pot. You’ll find 4” pots of chive starts at your local garden center. Some grocery stores also have potted chives for sale in their produce departments. It’s a very small thing to tuck a few pots of chives among your autoflowers and if it keeps spider mites out of your grow, why not do it?

  1. Spider mites avoid areas where Cilantro grows. Now cilantro can grow up to 2 feet tall, so it isn’t a good candidate for companion planting in your grow rooms, but if you are growing outside, put a few cilantro plants among your girls to deter mites.

Additionally, cilantro seeds, which are the spice known as “Coriander” has the same effect on spider mites! They HATE the smell of it! Coriander is a popular spice that is used in baking and the seeds are also pressed to make essential oils for perfumes and room deodorizers. (Yes, coriander smells that good!) If you get yourself a small bottle of Coriander Essential Oil, you’ll have a lot of options for preventing spider mite attacks.

You can cut up small strips of cardboard coat them with coriander oil and hang them from fishing line in your grow as DIY bug strips. Or you can coat pipe cleaners with coriander essential oil and loosely hang them on your girls.

Or you can spend an afternoon making this simple recipe for DIY air freshener gel using nothing more than water, unflavored Knox gelatin and coriander essential oil.

Make a few of these air fresheners in old baby food jars and then put ‘em in your grow room knowing that if some nasty spider mite invades your lovely girls, those mites are going to turn around and leave your grow room because they can’t stand the smell!

These are simple, cost effective ways for keeping bugs out of your grow and in the long run, PREVENTION is a much better cure for spider mites and fungus gnats than having to resort to some sort of insecticide to kill them! Just remember folks, if you have to resort to neem oil it may kill the bugs, but Neem will do nothing for the taste of your bud. :yoinks:

Here’s wishing you all good summer growing! Let’s keep those damn bugs away! :vibe:


Just some lurker dude
Apr 17, 2015
This may be more getting rid of then prevention, but I found these two on a site regarding gnats and wonder what anyone's take and/or experiences are with 'em. The vinegar one in particular I'm curious about as cider vinegar is common in BBQ so I usually have a jug on hand. :chef:

1): Gnats are attracted to the color yellow:
  1. go to your local garden store and buy yellow sticky cards or tapes to use it as traps
  2. put some of these cards on the infected plants
  3. After a few days, yellow cards will exterminate many of these creatures

2): Gnats are attracted to the smell of apple cider vinegar:

  1. Mix tablespoon or two of Vinegar with a little liquid dish soap to make this method more effective
  2. Pour this soap/vinegar mixture into unused jar, bowl, cup, or container.
  3. Place Vinegar bowl under infected plants
  4. Gnats will get trapped while flying into the bowl of vinegar and will not be able to escape.


Auto Warrior
Jun 23, 2015
Yep, I've read that peppermint and rosemary oil are great deterrents too. Knowing which essential oils keeps away which bugs is a pretty important step in good grow room practices. Essential oils are not often thought about by most cannabis growers, but understanding how to use them to keep pests out of our grows is probably one of the smartest and easiest things we can do to keep our grows pest free. There's lots of info out there about what to use to kill them, but it's a whole lot smarter to just keep the bugs away in the first place.

It's just a fact that certain bugs hate certain smells and that makes essential oils our grow room friends.


Auto Warrior
Jun 23, 2015
Great informative thread @Nuggz
I have also read that Fungus Gnats hate cinnamon. So if you sprinkle some on the top layer of your pot it should deter them.
Well, that's a simple fix! Thanks for the tip! We're developing a good list here, and a whole lot of the fixes simply require stuff that many of us already have in our kitchens. How cool is that?

If anybody else knows a good bug begone trick, please share 'cuz bug season is a comin'!


Stark Raving Sane
May 22, 2016
Great informative thread @Nuggz
I have also read that Fungus Gnats hate cinnamon. So if you sprinkle some on the top layer of your pot it should deter them.
Its anti fungal properties kill the fungus the adults eat. I've read it's also used to cure the fungal infection that causes damping off. The cinnamon you can steap 2 TBS in a gallon of warm water and actually water your plants with it. Don't get it on the plants leaves though. It'll cause little bleach spots. and it had be the Ceylon cinnamon. Not cassia. Chamomile tea is supposed to work also in much the same way.
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Apr 4, 2016
somewhere under the rainbow
Good info Nuggz. I wonder would cilantro (I call it coriander) be considered a companion plant to cannabis?
I think I will try it!!!
as for damn fungus gnats, I had 3 months of the little shits on what should have been a top shelf grow (NL5Xhaze); it became my worst grow ever!
the reason I got them in the first place was because I included organic (supposedly) manure in my mix.
fungus gnats thrive on organic matter. everyday I was squashing the little ****ards,
yellow sticky cards were of little use; what I needed was entire yellow walls smeared with Vaseline.
I had to redecorate the room afterwards there was that many black spots all over the place.
then it got worse I ended up with aphids for the next 3 months; I thought fungus gnats were bad!
if I am not mistaken, some people refer to aphids as "the borg"; I can tell resistance was futile!
after 6 months I had to pull the plug on the whole show because I was loosing,
they were sapping the life out of my immature buds; it was going nowhere.
lesson learned???
Never, grow indoors over winter when you have no recourse to natural predators;
never put organic matter into your mix if its an indoor only show.
I am sure I learned a few more "nevers" but it was a few years ago.
I am also sure others regularly grow successfully during winter, but I don't use poisons, so no more winter growing for me,
and organic matter is great...outdoors.


Auto Warrior
Jun 23, 2015
I think Cilantro is a very good companion plant IF YOU ARE GROWING OUTSIDE. But inside? You must remember, Cilantro can get up to 2' tall and can be a rather leggy plant. It's one that at maturity, would take up considerable space in a grow room. If you've got the space (and the time) you could give it a try, but I think trying coriander essential oil might be a more reasonable solution.

Also, many growers use a product called SM 90 which uses Coriander oil as one of its primary ingredients. A fellow on one of the Mephisto threads who had a terrible fungas gnat infestation just tried it and reported that it's done a great job killing the gnats. SM 90 is made from safe, food grade ingredients and can be used even in the seedling stage. It can also be sprayed on the foliage and buds to prevent or stop bud rot and mildews, as well as stopping spider mites.

If you've already got a bad gnat problem, then you are way past the "prevention stage."

Personally, I'd try SM 90. You can find it on Ebay and Amazon, and most hydro stores also carry the product.

Hope it works for you!