Gnats are tiny insects that can pester you beyond belief. Unfortunately, even with the best care practices, you’ll likely run into a gnat infestation in your plants sooner or later. For when you do, it’s best to be prepared to take them out before they can multiply and spread to other plants.
Get rid of gnats in plants by making an insecticide mix with dish soap. Apply the mixture to gnat-infested plants using a spray bottle. Keep up treatment until no gnats remain—this can take a few weekly sessions. Cleaning your houseplants regularly will lower the odds of a future infestation.
This article will be a comprehensive step-by-step guide on using dish soap and a few other common household items to deal with gnats. I’ll also tell you how to safeguard your plants against future gnat infestations.
1. Prepare Your Insecticide Mix Using Dish Soap
Insecticide is your first line of defense when staving off an assault by all sorts of tiny bugs and critters. It’s readily available, effective, and does what it’s supposed to do quickly.
That said, it’s not the best idea to use full-strength, commercial-grade insecticide as soon as you get the chance. As great as it is at killing insects, it has the potential to cause serious damage to sensitive plants as well.
If your gnat infestation is still in its initial stages, you can deal with it without bringing out the heavy weaponry. Instead, go for options that are gentle on your plants, such as using a homemade insecticide made with dish soap.
This solution has the benefit of being super-convenient as well. Why run out to the store to buy expensive insecticides when you can simply make do with the ingredients you have at home?
I do need to stress, though, that you should not rely on the dish soap solution to treat large-scale infestations that span across multiple plants.
If an infestation gets that bad, it’s honestly best to use concentrated insecticide. Sure, it will hurt your plants, but the only alternative is to discard pest-ridden plants to prevent a further spread.
With that out of the way, let’s find out how we can make dish-soap insecticide at home.
The items you’ll need are:
- A cup of water
- 2-3 drops of liquid dish soap
- A tablespoon of vinegar
Mix the above ingredients, and pour the final mixture into a standard spray bottle. Simple enough, right?
Note that the vinegar is somewhat optional. It improves the insecticide’s efficacy, but it’s not absolutely necessary. Simply up the dosage of the dish soap by 1-2 drops if you do not have any vinegar to use for this mixture.
You can now use this handy spray to kill off the gnats plaguing your precious houseplants.
The best part is that a solution as dilute as this won’t do any meaningful damage to your plants, but it still will effectively rid them of gnats. You can also use the spray to kill off any individual gnats you may encounter around the house.
2. Spray Gnat Infested Plants
Now that your gnat-killing spray is ready, it’s time to test it. Yes, I did say that it won’t hurt your plants, but it’s better to see how your plants react to it before going all in. Better safe than sorry.
You should spray a leaf of a clean plant and wait for at least 24 hours before checking for results. If you don’t notice any bleaching, loss of color, wilt, or other signs of distress, you’re good to go.
If you do notice the above-mentioned distress signals, you may have added too much dish soap, or the target plant may have been particularly sensitive to insecticide.
Nevertheless, you can’t delay for too long, as a gnat infestation is best stomped early on. Gnats can multiply in population in mere weeks. Dilute the solution further by adding 1/2-1 cup (125-250 ml) of water.
Spray gnat-infested plants all over thoroughly. Make sure to get all the foliage, including the underbelly of the leaves—this is where most pests tend to hide.
Use a generous amount of spray mix. It’s okay if some of it seeps into the soil, as it won’t cause any toxicity.
3. Spray Regularly Until No Gnats Remain
Okay, so you’ve just finished curing the last of your pest-ridden plants with insecticide. What now? Well, the good news is that you’ve probably caused significant damage to any and all gnats that happened to be caught in the line of fire.
The residual insecticide will remain on the plant body for another few hours and kill off any gnats that weren’t caught in the initial spray.
The bad news is, and I hate to break it to you, one treatment session likely won’t resolve your gnat problem.
There is a chance that you got them all and won’t have to deal with the bugs until the next time they wander onto your residence if the gnats were few and had barely any time to establish and reproduce.
However, it’s much more likely that there are survivors. Gnat larvae can reside up to an inch deep (2.5 cm) in the soil. A dilute spray like the one we just used likely won’t be able to kill off these larvae completely.
So, how do we eliminate the gnats once and for all?
It will have to be through regular treatment. You should check up on the target plant every few days and give it another spray if you spot any gnats on it.
It can take several treatment sessions before all the gnats are gone for good.
4. Add Soap to Your Regular Watering
Even if you get rid of the visible adult gnats with dish soap spray, you likely won’t be able to kill off the larvae. This is a major problem because unless you can kill the larvae hiding underneath the soil, the gnats will keep returning to bother you and your plants.
To attack the larvae in the soil directly, add dish soap and vinegar to your regular watering.
You’ll need to be a bit more generous with the amount of the solution in this case because, unlike adult gnats, larvae are protected by the soil.
Mix one tablespoon of vinegar and one tablespoon of dish soap with one gallon (3.8 liters) of water. This amount should be enough to water a regular-sized plant in a 2-gallon (7.6 l) or 8-inch (20 cm) pot.
Water thoroughly until you see water exit from the bottom of the drainage hole.
Resume the treatment for every watering until you’ve gotten rid of the gnats. I would even recommend keeping it going for another one or two weeks to guarantee the death of any remaining larvae.
Truth be told, the most effective way of getting rid of gnat larvae in the soil is by using a soil drench of 1% hydrogen peroxide solution.
Don’t get me wrong; our dish soap solution will work. It’s just less effective and will take longer to get rid of the larvae.
Hydrogen peroxide diluted to the above concentration won’t hurt your plants, but it will kill off any and all gnats in the soil with a thorough application.
It also kills off fungi by causing their cell walls to break open, meaning it’s particularly effective against fungus gnats because it kills off their food source.
We’ll talk more about fungus gnats in a later section.
5. Complement Your Efforts With a Gnat Trap
It’s time to get creative and engage in some DIY. We can construct a specialized gnat trap to lure the unsuspecting critters to their sudden demise!
This isn’t a substitute for the regular spray routine I’ve detailed above. However, it is a great addition. A gnat trap will allow you to catch and kill any stray adult gnats wandering around your house. It’s great for keeping your indoors gnat-free while you’re handling an infestation.
Here’s how to build this trap:
- Get an empty bowl. Any similar container will also work.
- Add a few tablespoons of apple cider vinegar to the bowl.
- Add an equal amount of liquid dish soap.
- Add a teaspoon of sugar to the mixture for better results.
You can be flexible with the quantity of apple cider vinegar and dish soap you add to the bowl. The only thing to keep in mind is to add both liquids in equal parts.
The apple cider vinegar has a sweet, fruity smell irresistible to gnats. Nearby gnats will be lured into the mixture, only to be trapped inside by the sticky, dense dish soap we’ve added. The trapped gnats will be unable to escape and will drown in the mixture.
You can use red wine as an alternative to apple cider vinegar and it will do the job just as well. The sugar increases the attractiveness of the trap, and while it’s not necessary, it does help.
In the end, we get a compact, portable gnat trap that you can place near gnat-infested plants to cull their population. One trap per plant should be enough. You can make multiple traps to deal with infestations spread across multiple plants.
Often, when you spot gnats on your plants, you’ll spot them in other hotspots around your house as well. Kitchens, for example, are places where gnats tend to congregate to feed on leftovers and scraps. You should place one of these traps in your kitchen as well.
Once the trap catches enough gnats, you can dispose of everything inside the bowl into a garbage bag and prepare a new mixture if necessary. You can expect to have to do this once every couple of days.
6. Soak the Entire Plant in Diluted Soap
I only advise doing this in extreme cases, like when you can’t get a handle on the infestation despite your best efforts.
Soaking the entire plant, pot included, in water will cause the gnats infesting it to drown. Now, you can use only water for this because it will work to get the adult gnats off your plant’s foliage.
However, water with dish soap has the additional benefit of killing off gnats in the soil. Completely submerging your pot in soapy water for 5-10 minutes should be enough to saturate the soil and wet the leaves.
You should not submerge your plant in water if it’s in a container with no drainage hole. Doing so will almost certainly lead to overwatering, which can be devastating.
After you’ve completely soaked your plant in water with dish soap, leave it on a drip tray until all the excess water has finished flowing out of the drainage holes.
7. Water Your Plants Less to Prevent Future Infestations
The lack of a drainage hole might be the underlying problem causing or at least contributing to your gnat problem. Plants grown in containers that don’t have drainage holes are easily overwatered. Any water in excess stays in the soil with no way to escape (other than naturally, through evaporation).
Overwatered soils are conducive to fungal growth. This soil-based fungus then attracts fungus gnats.
Fungus gnats are named so because their larvae feed on fungi in the soil. Therefore, they typically only inhabit soils that have fungus growing in them, mostly due to overwatering.
Not only does overwatering lead to gnat infestations, but it also has several direct, severely damaging consequences for the affected plant.
The most notable is root rot. As you may already know, plant roots need oxygen to survive and function normally. When there’s too much water in the soil, their access to oxygen is cut off, and they begin suffocating.
The oxygen-deprived roots die, leaving behind a plant incapable of fending for itself. If enough roots die, the plant eventually succumbs to starvation.
It may sound scary. Unfortunately, it is. Overwatering is the leading cause of death in indoor houseplants. We tend to grossly overestimate how much water most plants need, so it’s something important to consider.
Here’s how to avoid overwatering your plants:
Water Less Frequently
With most houseplants, you should aim to let the soil or growing medium dry out a bit between waterings. This is a great way to stave off overwatering. Letting the soil dry out guarantees that your plant roots aren’t always standing in water.
Go With Deep Waterings
Watering the soil deeply, all the way through, is much better than simply wetting the top layer. Thorough watering encourages plants to grow their roots deeper into the soil. You can also bottom water your plants to keep the soil surface from becoming wet.
Learn more about how to deep water your plants from the bottom in my article here: How to Water Plants from the Bottom (Beginner’s Guide)
Use Pots With Drainage Holes
Simply put, not using a pot with drainage holes is just asking for trouble. You can still use pots without drainage holes as cachepots to fulfill your decorative desires.
Use a Well-Draining Potting Mix
You can increase the water-draining ability of your soil by mixing in organic matter, such as compost. However, I don’t recommend doing this until you’ve properly handled the gnat infestation. Gnats feed on decomposing organic matter in the soil, so they will feed on the compost and multiply.
Move the Plant to a Room With Lower Humidity
You may also want to move gnat-infested plants to a less humid environment for the time being. Most plants prefer high humidity, but unfortunately, so do gnats. By lowering the humidity, you can make environmental conditions unfavorable for pests.
However, avoid moving your plant to a very dry room that can compromise its health. If your plant thrives in 30-50% humidity, you can move it to a room that has 30% humidity but never lower.
8. Clean the Affected Plant Regularly
This is just a solid plant-care guideline in general. Whether you’re an avid outdoor gardener or someone who values houseplants for their decorative capacity, you should regularly inspect and clean your plants.
Doing so will help keep your collection free from pests, insects, and diseases. A clean plant is also better able to absorb sunlight and oxygen, although the difference is marginal.
You can clean your plants with a standard spray bottle and cloth. Make sure to get all the foliage. Leaf undersides are hiding spots for pests, so they’re worth paying special attention to.
Remove any decomposing organic matter above the soil as it attracts gnats.
Plant cleaning doesn’t have to be another chore on your list. You can do it once or twice monthly and it will still provide great benefits.
9. Check for and Eliminate Items That May Be Attracting Gnats
By now, we’ve taken several steps to deal with the gnat infestation head-on with dish-soap-based insecticide. We’ve also discussed how we can make environmental conditions unfavorable for these bugs by adjusting water, humidity, and hygiene.
Now, let’s tackle the problem at its root cause and get rid of the things that may be attracting gnats to your home. This will help prevent the gnats from returning in the future.
Here are the items you want to identify and eliminate from your surroundings:
- Leftovers and food scraps, especially fruits
- Uncovered garbage containers
- Spills of sweet liquids, such as honey
- Dirty drains
- Stagnant water
- Decomposing organic matter (mulch and compost are usually fine, but you should refrain from applying either during an infestation)
10. Seek Professional Help if Necessary
If the infestation becomes widespread and takes over multiple plants, you may want to seek professional help.
The problem is that gnats multiply rapidly. Larger infestations are exponentially harder to deal with. Your best bet to stop one is to act in its early stages and prevent it from ever establishing a foothold on one of your plants, where it can easily spread to the rest.
To get rid of gnats in plants using dish soap:
- Spray the affected areas with dish-soap-based insecticide.
- Add dish soap and vinegar to each watering to kill the larvae.
- Built a gnat trap to catch and eliminate stragglers.
- Soak the entire plant in water with dish soap, if necessary.
- Let the soil dry out between waterings.
- Check up on and clean your houseplants regularly.
- Eliminate any gnat-attracting items.
- If all else fails, seek professional help.
That about sums up our guide. I hope you learned something useful and wish you all the best in dealing with your gnat problem.
If you would like to explore more options to get rid of gnats in your soil, check out my other article: How to Deal With Fungus Gnats in Your Soil