Gnats in Potting Soil
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 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 another organic brand of 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
I bought the conventional kind of soil from the same brand 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 and finding out that this is a very common problem with bagged soils.
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 bagged potting soil.
Apparently these will work, but I haven’t tried them out.
How to Kill Fungus Gnats
Responses to fungus gnat infestation complaints generally say that the gnats are not a problem to humans. And they cause little damage to plants.
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 ½ 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:
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.
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.
I’m having a gnat infestation problem only I had bough Black Gold which I was told is top of the line. So… it’s not just Miracle Gro. I’m going to sterilize any potting soil before I use it inside going forward.
True, that! It’s not just Miracle Gro. It’s definitely a lot of bagged soils and potting mediums. You just never know how long a bag has been sitting around and in what conditions it has been stored in.
There are two products, bacterial that will eradicate fungus gnats overnight. Met 52 and bio war. Is them both with excellent results
Bruce Spencer
Spencer Farm
UGH!!! Wish i would have seen this sooner!! Purchased 5 Scarlet Trumpet Vines for about $100 along with 5 bags of you guessed it, Miracle Grow Potting Soil. The morning after I spent hours carefully planting my vines the are was infested with gnat type bugs. I have tried several organic pesticides as I purchased the vines for my hummingbirds. The plants look horrible and I am still battling the bugs. I will try the peroxide since digging the plants and returning them at this point will take more time then I have. So angry!!
I’ve been there, too! SO frustrating! Your time and energy is worth so much. It’s not the money spent on the soil (though, it is…) but it’s the effort and emotion put into planting the plants, and then having to do all of this research to find an answer. Good luck! We love hummingbirds and understand your desire to use organic pesticides to not hurt the hummers!
Hi, I normally use pro-mix for all my plants indoor and outdoor but silly me thought organic soils should be fine since it’s organic. I tried every brand and they all yield the same results…fungus gnats. Having the little bugger’s in your house is just irritating not to mention gross. Definitely going back to using pro-mix! Also, if you’re in the habit of taking your indoor plants outdoors when the weather is nice, you may want to try a systemic bug killer before bringing your plants back in. Love your post BTW.
Adrienne, thank you so much! I appreciate it! And, yes, those fungus gnats are SOO annoying!
I have just tried chatting with a “Live” Miracle Gro rep from the Help Center – tried twice as a matter of fact. No info given from either except to say “I will be glad to answer your question”, “Give me a minute”, and both times my chat was ended by MG rep. Tried calling the 1-888-295-6902 and was told a rep would be with me shortly. That never happened. I had no idea until I read all the complaints about Miracle Gro potting soil mix this morning that my black gnat problems could be attributed to the “higher priced and preferred” potting soil mix. Needless to say I will not support them any longer. However, would love for Miracle Gro vendor to step up and tell us what scientific test show about their mix after sitting in their warehouse for 6 months or so, how do they treat the soil to prevent infestations of these insects from entering our homes, how can we rid our homes of them once we have them. I have tried the sticky things, I have repotted the plants 3 times, I have had a professional exterminator treat our house, I have used numerous home treatments along with the purchased bowls which contain apple cider vinegar which are to lure the bugs in there and they drown…nothing has worked well. I am sure we have eaten some of them in our food as well. UGH – No help, no concern, no service from Miracle Gro.
I am so sorry to hear about this experience. It is horrible. Especially when you’re treated horribly by customer service. There are so many complaints out there about gnats and the soil. Thank you for sharing your story, too.
I don’t have a yard. I have a small balcony and I grow tomatoes. I actually grew 120 plants and game all but 6 of them away. I watched my plants one by one die after adding a bit of miracle grow soil to already growing plants. The sticky traps would could not catch them all. Shame on you miracle grow.
Oh, that’s so sad when you’re trying to give homegrown food away. So sorry to hear this. Would love to see how you grow that many plants on a balcony 🙂
I bought some organic Miracle Gro indoor soil and I am deal with small flies, I think are gnats. There are tiny worms in my soil. Years ago potting soil companies use to heat the soil at high temperatures to kill such. I guess they don’t do this anymore. I would have been better off using the soil from my yard. We use potting soil to avoid bugs, but looks like Miracle Gro is selling nasty infected dirt.
Jackie,
I agree. It would be easier – and cheaper – to just use the stuff in your yard. Though it wouldn’t have as much nutrition. That’s why I just plant in straight compost now. I could always add in some dirt from my yard to the mix. Then I don’t have to pay or worry about buying bagged dirt which only brings on more headaches, I feel.
I just tried the peroxide solution that was suggested in the thread….lol, what a mess. I did it in my kitchen sink and the dirt bubbled over like a volcano. I suggest that this sterilization method is done outside. Two weeks ago I did a solution of neem oil and Dawn Dishwashing liquid. they went away and came back this week. I am guessing that the neem oil and Dawn does not kill the eggs, but will kill the maggots and gnats. This is such a headache. I left a post on Miracle Gro’s wall….will be interesting to see their response.
Oh, boy. What a hassle! All for dirt. Seriously. Wishing you the very best of luck in getting control of these gnats. I just left them be and walked away. I don’t have as much resolve as you do!
I will not buy that brand again. One reason why I purchased indoor potting soil was to avoid insects and such. They are supposed to heat it to kill any insects and eggs. Well, that is how they use to treat packaged dirt. I had a lot of big pots with plants, so it was a job treating all of them. Thankfully, I had several bottles of peroxide being I stockpile from Costco sales. Will do it again next week and then the next. I hope by then they will all be dead bugs! The gnats were all over our house before we realized they were coming from the freshly repotted plants. I don’t know if all of the treatments are good for the plants.
Ugh! Yes, I don’t know if the treatments are good for the plants either!
Just always remember and NEVER forget that any company can print that their products are “organic” or “natural” but that does NOT mean that they are. If you are looking for “organic” products – look for products with the OMRI designation. I find it useful because OMRI is an independent, non-for-profit organization (and no, they didn’t pay me to say this!) You can learn more about them here- http://www.omri.org/
Personally, I would NEVER expect Miracle-Gro or Scott’s to put out any product that I could safely use in my garden. Just my $.02
Agreed!!!!!!! There is no certification for the words organic or natural, except for USDA Certified Organic foods. Good points made!
At Costco, I saw some of the Miracle Gro state that the dirt came from landfills, like that is a good thing. I did not buy that dirt, because all sorts of toxic items go into landfills, I can’t imagine the dirt being safe, However, the Miracle Gro I purchased was organic, but did not have any mention about it being harvest from a landfill. I don’t think dirt should come from a landfill….it’s my understanding that a landfill must sit 100 years after it is c
osed before one can build on the land, so this being said, how can their dirt be safe???
Yeah, how can landfill dirt be something that you want to grow plants in? A place where people throw toxic substances that won’t decompose isn’t the kind of basis I want for my dirt!
It is not just the gnats for a year and a half 5 antibiotics the sore on his face will not go away. We have always used MG , he had his gloves on and just wiped the sweat off his face and soon blusters came up, we called MG same BS . Now the doctors want to cut his face open !!! And the gnats are driving our dogs and us crazy ! So fed up !!
Kimberly, can you share any brand names that you have found to be more reliable? I’ve had this problem many times, and not just with Miracle Gro, unfortunately.
Missy,
I know your frustration. I’ve tried EcoScraps from Target and had mold issues in some bags. What I’ve done from this experience, and also trying other brands, is to just use straight mushroom compost. For me, cow manure compost always has issues and is to hard and cakey. I buy Lowes’ brand of mushroom compost ~ about $3 a bag ~ and use that as potting soil. My plants have never looked healthier! I’ve done flowers, as well as veggies, and haven’t had a problem. I don’t mix it with any soil whatsoever! Hope this helps!
~Kim
I needed to repot all my house plants since it had been years and they were root bound. Now I also have a problem with fungus gnats and mold because I tried miracle grow potting soil. Very frustrated because of all the time it took to repot and the cost of the bags of miracle grow soil.
Thanks for the tip on hydrogen peroxide I have a website here with more information on it and an article from that website.
http://hubpages.com/living/Hydrogen-Peroxide-for-Plants
Application –
Soil Pest and Root Rot Treatment –
Mix one part of additive-free 35% Hydrogen Peroxide with ten parts water.
Water infected plants thoroughly. The soil will bubble as the oxygen is released.
For Pests – Water with the mixture twice a week, allowing the top 2 inches of soil to dry between watering. Root pests should reside within a week.
For Root Rot – Water plants very thoroughly, then allow the soil to dry. The top 2-3 inches of soil should be completely dry before returning to a regular water regimen. If the process is done correctly, root rot can easily be treated with only one watering of peroxide.
Foliage Pesticide Spray –
Mix equal parts 3% Hydrogen Peroxide and distilled water.
Use a spray bottle to thoroughly soak the infected plants. Make sure to get the undersides of the leaves.
Spray once a week or after it rains. Hydrogen peroxide both treats and further prevents pest infestation.
This weaker solution will prevent damage to the leaves but is effective as a general insecticide. I’ve found that the hydrogen peroxide is effective against a variety of mites and aphids. Because hydrogen peroxide also has fungicidal properties, one may find it as a possible solution to mildew and fungus outbreaks.
Water Treatment –
For a general water treatment and dechlorinator, mix one tablespoon hydrogen peroxide for every gallon of water used. The hydrogen peroxide acts instantly to drive out chlorine, excess iron and sulfates.
This soil is horrible I will never use miracle grow again!!! I had a brand new raised bed I filled it with 8 bags of their soil. The gnats were everywhere I also had several pots with the soil. I had never encountered this before and had my kids helping so by the time the gnats were noticed it was too late. I tried to spray with soap and wait a few days but couldn’t lick the problem and within 2 weeks mushrooms were everywhere. This was a huge amount of money and time and I could not afford to start all over again at this time. I can not believe they continue to sell this product! I now realize there are negative comments all over the internet. Apparently MG doesn’t care about satisfied customers just making profits!!!
Bettylou,
I agree. It’s amazing how many people have had this problem – and that’s just the few who have left comments on this blog. I wish more people would leave their comments on having a problem, too, so that we can make sure to tell everyone that this is a REAL problem and it causes you so much grief when all you want to do is grow healthy plants.
It’s not a big help, but after I posted my complaint on their website they answered me and asked me to contact their customer service. I spoke to someone and was able to at least get a refund for the soil I purchased. over $100. It didn’t do much for the cost of the initial soil their soil ruined (far more than $100) but at least I got something back. I suggest anyone seeing the problem review the product on their website – maybe if enough people complain they will have to change their ways!?
Agreed, thanks Vicki!
I’m glad you got the money back. We all know your time and effort were worth more, but at least you got something back. Hoping more people will call and get their refunds, too!