Suddenly have an insect infestation after using potting soils? Tiny little gnats flying out of the soil in pots and your garden? Yeah, me too. I found out that they’re called fungus gnats, and they are certainly annoying!
I was so ecstatic to have put together my first raised bed for a vegetable garden. It’s nearly full with mushroom compost received from a neighbor, who got a huge haul at a local mushroom farm. The final touch was to add some garden soil to the top of the bed and plant some seeds.
Tiny Fungus Gnats in New Potting Soil
A special sale at a major home improvement store meant that organic Miracle-Gro soil was just $5 a bag – a pretty good deal. I got two and immediately added it to my bed.
(While this is my experience with this brand, I also tried EcoScraps potting soil and had the same fungus gnat problem. And plenty other people – see the many comments below – have also had issues with other brands, too.)
The next day, I went out to check on my raised bed and noticed the soil teeming with tiny little flies with white wings.
These insects were NOT in the compost before I added I the soil, yet appeared in droves within 24 hours of dumping the bag of soil into my raised bed.
I checked the mound of mushroom compost that I still had in another garden bed that was delivered the same day. Nope, the insects weren’t in there. I asked my neighbor if he had any problems with the tiny flies in his piles of compost. It was the same compost from the same delivery. That was a negative, too.
So I determined that the organic soil that I bought to complete my vegetable garden actually caused a HUGE problem that now I have to deal with.
Potting Soil Killing Plants
Maybe it was the compost, or just a coincidence, you might say?
Nope. I bought Miracle-Gro soil (the conventional kind) last year. I had three healthy houseplants that I had bought from the store and kept in pots for a few weeks that were fine. When I decided to finally repot them I bought one bag of soil. All three plants were planted in this same soil, and then placed indoors and outdoors in different locations.
ALL of the plants started developing problems and were infested with gnats. I lost $30 of plants, tons of time in taking care of them, and time spent to return the stuff to Home Depot where the cashier looked at me dubiously as to how my soil could have caused this.
Problems with Fungus Gnats and Potting Soil
Now, fast forward another year, and I’m researching gnat insect infestations online (I have SO much time in my life to do this, by the way) and finding out that this is a very common problem with Miracle-Gro, as evidenced in this stream of negative reviews on their website.
*Since the time I originally wrote this post, a string of positive reviews has flooded in. Check carefully and you’ll see that many of them are from sweepstakes entries (check in the description box). For non-sweepstakes reviews about gnat problems, filter the review search to one star reviews.
This is such an issue that the first comment for these gnat bait traps on Amazon speaks directly about using the baits to kill gnats on houseplants brought in due to Miracle Gro soil. Apparently these will work, but I haven’t tried them out.
Scotts response to past complaints is that it’s a natural product and not sterilized. True, I agree.
Their other solution in review comments is that there is a money back guarantee. How do I put soil back into a bag ripped in half in order to get the soil out? How do I return this nasty stuff to the store without getting it everywhere all over my car?!? Most importantly, what about MY time??? The time spent in researching this problem, in tending to plants at risk, to monitoring insect populations and in applying remedies to problems that Miracle-Gro acknowledges? Isn’t my time more valuable than the $5 that I spent on their bag of soil??
Check out my course on easy to grow, hard to kill houseplants to add to your home right now! These gorgeous plants will start detoxing your indoor air immediately:
Best Houseplants to Detox Your Home
How to Kill Fungus Gnats
Scotts response to all of the fungus gnat infestation comments and complaints on the review page has been that the gnats are not a problem to humans. And they cause little damage to plants.
Notice “little.” (Rolling my eyes…..)
The University of California Integrated Pest Management says differently. They state that a large infestation can kill seedlings or young plants.
The company’s response is also that adding 1/2 inch or more of sand to the top of your pots will help control the fungus gnats.
Which is good news for those of you who were wanting the look of houseplants planted at the beach or love the feel of the Sahara desert in your garden bed.
P.S. If you don’t mind the look of sand or rocks on your houseplants, here’s a recipe for how to get rid of fungus gnats using sand.
Also great for those of you who want to spend more money on unnecessary products when all you really wanted was a simple bag of potting soil and to be done.
But hey, now you get to go back to a garden center and buy sand and plant sprays and plant amendments. YAY!!!!!!
I had tried soaking my garden bed with insecticidal soap, which apparently doesn’t work on killing fungus gnats.
Adding sand to my garden beds was not an option for me. I was not going to buy a bag of sand, nor did I want to mess with this issue any more.
I basically just lost the entire garden bed and never went back to try again.
Related Posts:
- How to Get Rid of Gnats
- How to Keep Your Plants Alive While on Vacation
- Four Colorful Carefree Plants for Your Garden
Potting Plants in Compost
After this experience, I don’t buy potting soil at all anymore.
I use straight mushroom compost to pot my plants. I buy mine at Lowe’s, where the price is comparable to a bag of potting soil, but you can buy mushroom compost online here).
Everyone says never to plant your plants directly in compost. Maybe that’s for rich compost straight from the backyard. Or only cow compost. I don’t know. But what I do know is that I’ve never had problems planting any plant in mushroom compost or worm casings. It costs a little more, but I don’t have to buy soil amendments, fertilizers, insect sprays from bringing in gnats in potting soil, etc.
If you don’t want to avoid potting soil and use compost, then I suggest you don’t try to pinch pennies like I was. Go to your local garden center and get your potting soil from them.
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Where do you get your soil? Have you ever had an insect infestation with any other brand?
I am devastated that I’m going to have to throw out all my houseplants! I thought I was being proactive by repotting all my plants with miracle grow (first and only time). Now the gnats have taken over my entire house! I tried soap/vinegar and hydrogen peroxide! Nothing at all helped. I currently have my plants tented in clear plastic bags until I come up with a solution. My next move is the garbage! Any other suggestions????!!!! I really don’t want to throw away these plants I’ve had for 6+ years.
Tania, I’m sorry to hear this. I don’t have any other suggestions other than putting them outside and hoping the gnats die while using gnat-killing biological controls. Hopefully you might find some help in the comments.
Well, wish I had know before using the Organic soil. Going to try nematodes, luckily it’s just one pot… unluckily it’s my wasabi plant, hard enough to keep alive without the parasites. Can’t believe it still seems to be an issue. 🙁
Years later here we are with the same problem……. So mad I wish I would seen this blog before I bought Miracle grow for Raised beds Gnats everywhere Know!!!!! I am out hundreds……………..
Ugh, Tammie! Were they new plants or existing ones?
Beneficial Nematodes will take care of fungus gnats. Buy them from Amazon and mix in when you water. It’ll take about 2 weeks but the reviews are consistently positive! Also mosquito dunks or mosquito bits work. It uses a bacteria that eats the larva. I dont think you can use both at the same time, just one or the other.
Thanks, Jessica! These sound great. I’ve been using the mosquito dunks, but found these beneficial nematodes that specifically say to kill fungus gnats and might give these a try: https://amzn.to/2IQ9StJ
Sadly for me the gnats were caused by over watering. It was horrible and nothing I tried worked.
The simplest solution was to throw out all the infested plants. I did manage to save my bird of paradise by washing the roots thoroughly and using new soil. Horticultural sand layered over the top is the best gnat deterrent for me. The down side is I am dependent on a water meter to know when the soil is dry. I love the look of the sand. My plants are all potted so it is easy to top off the soil with a dusting of sand. I stick a plastic tube into the soil and water using a funnel. A lot of faffel but it works for me.
Thanks for sharing! Great tips!
Hi Bruce! So glad to see one of my favorite farmers reads this type of thing! It saddens me that we have to deal with “bad dirt”. Pests will always be among us, but paying good money to have them infest your home and garden, that is a shame.
Tanya (the viilinist)
Wenatchee
Billy,
Don’t bother, they crawl up into the sand and walk around in the top of it like they’re on Waikiki Beach.
I tried the sticks, the powder, dishes of vinegar and soap all over the house, sticky paper all over the house, I even tented my plants with cheesecloth to prevent them from getting into the soil. Little did I know they we’re coming from the soil. At one point I even would get woken up by them flying on my face. I thought it was always because I lived in a humid climate but that wasn’t the case at all apparently.
This thread has taught me so much.
Good luck to you.
Grace
I dont know if anyone’s mentioned it yet – but I start all my seedlings indoors and cannot stand fungus gnats. I learned from one of the gardening gurus online to pour boiling water into ANY soil I use in my house – cover it for a few minutes and then any larvae will be DEAD! Works like a charm!
Wow!! It’s been four years of hell for me. Every time I repot my plant (which is a 39 year old Christmas cactus) I have this issue. Sometimes it’s right away and sometimes it takes a few weeks. My plant has gone from literally having a tree stalk to being about three little sprigs.
I never thought of it being the soil except for one time that i bought a bag that I thought was infested. I had called miracle grow and they suggested the sand, which I tried, which was a living hell. They also told me to use apple cider vinegar and water to water the plants but never once offered me a coupon to replace the bag. Tomorrow I am going to buy new soil because, last weeks brand new soil is already invested
Thank you for answering so many questions!! Now hopefully i will stop finding these dead bugs all over my house and floors
Ugh! Best of luck to you!
I have purchased several different brands of potting soil and sadley each of them have been full of gnats. This last bag of Grow Well was from a local bursary not Lowes or Home Depot but I had the same horrible experience as with Omni Soil and Miracle Grow. I am just grateful that I had not potted anything before noticing they literally flewcout of the bag. Takes the joy out of the experience for sure.
Hi, I had the same problem. I had to literally bake soil that I bought (I bought Black Gold potting soil/ organic). Very time consuming and smelly to bake it. I had to do half a bag one day, and the other half of the bag the next day. I also had to buy vegetable fertilizer that I sprinkled into it after it was done and cooled. My seedlings are now about 3 inches tall and there are no bugs. Since I have them indoors (it’s March), I’m grateful that I don’t have the bugs flying all over my house like I did last year. It drove my crazy. We were literally infested. My seedlings were destroyed by them.
My question is, WHY isn’t there a company out there that can do the baking of soil for us in one of their huge warehouses and package it in sealed bags to be sold to us all ready to go. Why do WE- the busy consumer- have to do this in our homes? My kitchen smelled like very strongly cooked sweet potatoes for days after the baking process. Took me two solid days of sterilizing soil in my little oven. Then cooling the soil outside and rebagging it.
I’d gladly pay anything to just buy a bag of sterilized soil right off the shelf. But not one company does it. Why? Seems there would be a pretty big market for it, especially for people who start their gardens indoors in winter.
Donna, I totally agree! I just had to buy potting soil to repot new plants. I never know what to buy. And where I’m living now doesn’t give me any other choices than Miracle Gro in all of the stores. I even thought about ordering soil online but it was too expensive. And I opened the bag and sure enough gnats came out. I don’t know why this has to be a problem.
I have to say I heard good results of a mosquito bait that can also be used for fungus gnat control. You add it to the soil and water it in. It’s a biological mosquito control and works on fungus gnat larvae, too. I’ve just started trying it. I added it to my Amazon storefront if you want to check it out: https://www.amazon.com/shop/kimberlybutton
I just had the exact same thing happen but it wasn’t Miracle Gro – it was Just Natural with worm castings. I have a total mess on my hands with gnats and Christmas Cactus I used it with. Grrr! 😡
Grrrrrrrrr! I’ve had it happen with EcoScraps, which is a natural brand. So I’ve found it happens more frequently than I’d like now. I just discovered this easy product that you can water in to plants and it kills larvae over the course of three weeks. It’s not perfect all at once, but it can ease the pest problem. Check out my Amazon store where I have it listed: https://www.amazon.com/shop/kimberlybutton