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 have 4 raised vegetable garden beds in my yard and 15-20 potted basil plant that I had kept in my house under lights to avoid getting basil powder mildew.. My raised beds were started last year with Bumper Crop, vermiculite, peat moss, and several types of organic good quality compost. I needed to supplement my raised beds this year with dirt and compost so I chose Miracle Gro organic compost and raised bed soil, that was all I added to the raised beds. I used Miracle Gro orgainc potting mix for the inside basil plants. The raised beds this year have been infested with gnats, squash bugs and cucumber beetles – NONE OF WHICH I have ever had before adding the Miracle Gro soil to the beds. The basil plants were INFESTED with fungus gnats – so badly that the pot I had given to my mom for Mother’s Day had infested her apartment and she had to return it to me. I wanted to be sure it was the dirt I had used, so I bought more Miracle Gro organic potting mix, sterilized all the basil pots and repotted each plant using ONLY Miracle Gro potting mix. 3 days later the plants were swarming with gnats and eventually a few plants actually died because the larvae had eaten the plant’s roots – I could see the larvae in the pot – there were SO MANY!! I immediately moved them outside and was swarmed by the gnats in the process. Because of this I have spent countless hours and dollars – mostly trying to salvage my raised beds. The cucumber beetles killed my cucmber plants and have wreaked havoc on my squash and zucchini plants. I have tried Nematodes, Captain Jacks spray, hand picking the pests and their offspring….and am really concerned about next year and what the larvae they have left in my beds will do then. I can not afford to start all over again – hundreds of dollars for the vermiculite, peat moss and organic compost for four 4x4x18″ beds. Miracle Gro is – OR WAS – a trusted name – shame on you Miracle Gro – SHAME ON YOU!! What recorse do I have??
I’m in the same boat with big bags from Costco. I am livid and feel I need to dump all the soil before planting anything in the fall. Someone needs to refund the purchase cost….
I posted a review on the Miracle Gro potting soil website with my story and their answer was such B..S…they didnt even reply with the facts I presented – it was like they did not even read what I wrote. The plants that died due to the gnat larvae eating the roots Miracle Gro said something about ‘root rot’ which was totally irrelevant. They also said something about insects getting into the bag of soil after it sits open which I clearly said their bag did not and that the plants and dirt were in my house – indoors!!!
I wonder how many customers out there truly have found issues with their soils and if there is anything as a group that can be done??
Thank you for this useful post! I recently repotted a dying plant in my office with some Miracle Gro Potting Soil. A few days later, there were little gnats all over the entire office, not just my area. I went to water the plant today, and I noticed a few gnats fly off the dirt. I never thought this could be the issue until today. I did some research and ended up here. Now I wonder if I sentenced that plant to death by repotting in in Miracle Gro!
Ohhhh… I also experienced this problem. First, let me say I have always grown houseplants for years, in different apartments, never having had a problem, taking joy in growing them, re-potting as they grew. WELL, a couple of years back, I got a few new plants and soil, which were from Home Depot. I went to lot of trouble to gently separate sections from larger plants, potting in different sized pots, also re-potting others I had, as I had always done.
Not long afterward, I began noticing gnats. I would see them landing on my computer, iPad or TV screen, flying around lamps, also getting the cat pretty worked up. I did get sticky paper and though I kept trying some solutions on the plants, I think I lost my patience and felt I needed to get the plants out of here, which was upsetting. I think I even tried another plant, later – having same problem. I wondered if it was due to the soil in new plants or from the bag of soil. Unfortunately, I don’t recall if it was from M. G. or not and had even wondered if it was the fault of Home Depot’s nursery – and having gotten rid of gnats, I resigned myself to go without plants for a while.
So, what did I do? Yesterday, I walked by plants at the Home Depot and could not resist. I picked one up and saw an insert stating “This plant has been protected from problematic aphids, white flies, beetles, mealy bugs and others”, treated with Neonicotinoids. Thinking “Hmmm”… I decided to get a few, however, I don’t know how that will protect added soil, bringing me to doing research and feel relief finding resolve here. Now, I need to consider carefully what soil to buy. Just to mention, in previous years I had even purchased healthy looking plants and bags of soil from the “99 Cents store”, never having had this problem prior, no matter where I bought plants and soil. Thanks for all the info and good luck to everyone!
Ugh, you know it’s bad when even the cat is worked up! 😉 Sorry this happened to you, too. I’m pretty concerned when soil has to start being treated with neonicotinoids just to stay bug free. When starting from a healthy base, it’s easy to stay insect-free, as you know and experienced for years. Wondering why soils are having to be treated now in big box garden centers? Good luck to you!!
Thanks.. it has been over a month and so far, no gnats, so something is good. The problem I am having is trying to maintain the right indoor growing conditions, keeping the heat out yet having proper light… poor plants. (Glad to have confirmed the problem here about the potting soil).
This just happened to me with Miracle-Gro soil. Plants that I had for years and had recently repotted are teaming with fungus gnats. They are all sitting outside while I try to figure out what to do. May just throw them all out. Not happy!!!
I had one bag of their organic soil that I used and the plants got infested. We put them outside and they died. I thought it must just be the plants. Maybe a problem at the greenhouse. Yesterday I opened the second bag and got a face full of gnats. I chatted with Miracle Gro. The person was rude and told me there were definitely not bugs at the time of bagging. They must have gotten in through the “various” holes in the bag during storage. I called Miracle Gro and has told that they are fungus gnats. They recommended putting sand on the soil and putting it outside to dry “or your house will be full of them”. Definitely no more Miracle Gro. It’s in the trash.
I had the problem with their organic care potting soil. What a mess! I think I’m taking your stance and avoiding Miracle Gro, too. Just awful!
CJ,
Yes, I’m definitely more choosy as to what potting soil I buy nowadays!
Hi.
I NEVER WRITE ANYTHING in a comment section but I must say… I am so, gosh I don’t even know how I feel right now.
Here’s My story….
I was 17. My grandfather & I sat on his front porch often for chats but hadn’t ever talked about plants before. I was close to leaving for college & I was struggling to imagine life without regularly seeing him. I decided that I could take something with me to remind me of him until I could get back home however, my grandfather “Papa” was a very financially poor man. I knew he could spare nothing and I would never had wanted him to.
As he and I sat and talked about the coming freshman orientation for me
(I did most of the talking, Papa had a 3rd grade education, & retired from being a logger, sharp as a tack though.) I mentioned to him that I knew he had never seen an ocean & I wanted to take him on my first spring break. The next words from his mouth blew me away…
He said “I think we just need to find something for you to take with you”
Than he got out of his rocking chair, asked me to come with him.
We walked two feet. That’s when he showed me what a Devil’s Ivy plant is.
He said he knew that I had no experience with plants but that this would never die.
He gave me a small, one stemmed plant with two leaves inside a pot no more than 5 inches. If that.
That fall I left.
I came home at every opportunity. I couldn’t ever seem to talk Papa into riding to the beach but I did humor him with my stories about my “flower”. He’d joke, and laugh and say “what flower “. In other words I thought he was saying it was probably a goner. After four falls of saying goodbye to my family I finally graduated. Everyone came to see me walk the stage and take my diploma.
After that it was time to pack up and move back home. My dad had a small U-haul ready for everything but, what no one knew is that I had already shipped most of it to my new apartment. When my Dad went with me to my room I surprised him and my Mom with my job offer and plans.
When they all calmed my Dad turned and said Ok well let’s head home (the room appears empty of my things.)
There was one thing left I wanted to take myself back home, my 4x repotted Devils Ivy (Pothos Plant). It sat tall, never ending, & the deepest shades of green I’d ever seen. I carried the 12 inch pot with all of its luscious green vines piled on top and wrapped over my shoulder all the way to the car.
Before I could sneak up on him, Papa turned and his crooked smile played stage to our traditional wink. So excited I had to ask him, “so what do you think now!?!” To which he replied, “Told you, what flower haha! Now, THAT is a plant!
That was what seems like a lifetime ago. I am now 29.
Two years ago I read my handwritten eulogy to my Papa at his funeral. The most tragic, unexpected, heartbreak of my life.
Recently I had slightly neglected my Devils Ivy from traveling for my work so last month when I got home with time off the first thing on my mind was breathing fresh life back into it.
I went to Lowe’s and after a $60 trip I had all I needed to revamp my Papa’s gift to me.
I used Miracle Grow Soil. Two days after I gave it all that attention I woke up to find the top of it covered in white mold and white mushrooms growing all over it.
I had no idea what was happening. I cleaned off the mold etc. Than waited.
As it kept getting worse my small dog suddenly became sick. She was having horrible breathing issues. Since I put it all together and figured out what her problem was coming from I have had my “flower” out in a room blocked off and alone. It’s dying because I used miracle grow.
I had done no other harm. I am certain of this now from Reading your post.
What should I do? Please help
Oh, Sarah. Your story is so eloquently written and so emotional. We want you to get your plant, and your memories, back ASAP.
I’m not a horticulturist or veterinarian, so these are my guesses. You obviously know you need to get your plant into new potting soil. I would go to a nursery and ask for the appropriate kind (nothing too fancy). Pothos is pretty hardy, as you know. I’m not sure what your plant looks like, and, again, this in only a guess. Could you cut back the plant pretty heavily, taking off the affected parts, and repot in brand new soil? Perhaps that will allow it to bounce back with a new vigor. I’ve used insecticidal soaps with great success, but never on anything with mold. You might want to find an organic garden disease control spray.
Because this is a sentimental plant, I’d fight for it. Hopefully with a lot of TLC, it will be strong again soon. We’re thinking of you and praying for the best!
Let me tell you what happened to me. I had soil from last year in my garage. I bought a plant and repotted it and put it on my desk in my home office I work from. In a week I feel this odd crawling on my skin. After research I find out its mites from the potting solid and now it’s like an infestation in my house and they are in my hair and on my body. I’ve tried every bath, spray ointment for a whole week. It’s only slightly getting better. I’m researching where to get the soil tested and keeping my receipts from over $400 in products/creams I’ve had to buy and have even put organic pesticide on my legs and arms to see if it kills them. I have to change clothes 3 times a day and immediately launder them to try and get some control over this. I can’t even tell you how pissed I am and how disgusting this is. I live in a very nice house and I now have bugs on me and in my house. I can’t have people over or go anywhere because I’m scared to carry it to their house. After I solve this in my house I will be consulting a lawyer.
Barbara,
Yikes! I hope those bugs are taken care of quickly and you find your health restored soon!
I had mites in my apartment a few years back. You can’t see them, but you know they’re there. They were actually biting me in my sleep, and were infested in the carpet and in the couch. After trying to fight these things to no avail, I came across Enzymedica brand Digest Gold while doing research on an unrelated topic. These enzyme capsules, found in health food stores, contain the 4 enzymes that are in a mite killing solution, Kleen Free, which had great reviews on Amazon.
I didn’t try the Kleen Free. I just went straight for the enzyme capsules, figuring that I would make myself repellent to them. It worked for me.
Please try this product! I know what it’s like to have the crawling sensation all over your skin. I now think that they are in a lot of places–stores, homes– and either most people don’t feel them, or the mites don’t bother with them.
On another note, I too have just finished a frustrating bout of gnats in my houseplants’ soil. Nature’s Care brand organic soil is also fertile with these little pests. As someone else stated, a flypaper collected an obscene amount of the critters.
Done a bit of information gathering since my post in Dec. about gnats. I started a small nursery business and talked to the person that checks out new businesses. He’s from the agricultural dept. He suggested GNATROL and I found it on Amazon. It works much better than the peroxide in a shorter amount of time. Last thing I wanted was to have an infestation in the greenhouse. And sure enough, they showed up. If you use Gnatrol 3 weeks straight, once a week they are gone. Ag. Man said they just show up, can be in any potting soil because it’s not sterilized and any decomposing soil more than likely will have them especially if it sits around, but Miracle Grow is horrible. Interestingly, I bagged up moist leaves from last year to compost. I also grow worms and decided to feed them some of the leaves. Well…I opened the bag inside the house and out flew a swarm of gnats. The Ag Man said more than likely there were larvae in the leaves when I bagged them. I am using the gnatrol on the houseplants again. After the first week of using it in the greenhouse they were almost gone and was able to completely get rid of them by the third week. You can read about how it works on the internet. I found it is much better than the peroxide. Happy planting!
Patty,
Thanks so much for this information! It’s great to share how to control this problem.
I’ve had this junk burn starter plants…I think it carries fusarium wilt as well and is mostly peat moss, which is unsustainably mined in Canada and releases a lot of methane into the atmosphere. Don’t cheap out by using this awful product.
Same thing here. I bought miracle gro potting soil and replanted my 6 year old banana plant which was a gift from a dear friend, two money trees which my husband and I bought 5 years ago when we got married, and a big ficus lyrata. I had no gnats problem at all before and now they are all over the place.the plants and my house is infested. Miracle Gro potting soil wasted my time. At first I thought it’s only the ficus so I replanted it, but no I was wrong, gnats were and still are all over the place. I added sand on top of the plants and It’s not working. The gnats are still there. I tried to do everything, bought Fungicide 3 spray and have been spraying for almost 2 months and still nothing. miracle Growpotting soil, you destroyed my plants and made my life miserable. Please, never buy Miracle Gro ever again.
Jane,
I agree! My one experience wasted my time so much, that I have no desire to ever try it again.
I am in the same boat. I decided to Google to see if there were others. I only made the connection to soil when I potted plants in my office. I have sprayed the plants with pesticide but to no avail. I’ll try the peroxide.
I love the idea of the peroxide in the plant water and I will be trying that at next watering since I have tried everything else except the layer of sand. I have sworn off Miracle Grow potting mixes of any line and now will try anything that makes sense to rid these knats. I have too many plants to just throw them out and I am hesitant to try another potting soil. I also thought about putting the soil in the oven at 200 degrees and sterilizing it, but don’t have the patience for that nor do I want the smell. Thanks for the great info.
Thanks, Sharon! I appreciate your kind words!
My sister use to make her own potting soil by using the dirt from her yard and heating it….but she had an outdoor oven. Potting soil use to be sterilized by heat, it appears companies have stopped doing this. I tried heating my own and had a serious allergy attack. I would not recommend heating it unless you have an outdoor oven
.
Do you think the heat of a compost pile would kill the flies or the larvae?
I’m not sure the compost pile would ever get really hot enough to kill all of the larvae.