Fantastic pests and how to fight them

If you have house plants and never, ever had a pest problem - congratulations, you're a very lucky person and I envy you. Having pests in a garden is a whole different issue, but having them in your own home can also be incredibly frustrating. For me, the only big problem so far were Sciaridae, also known as Fungus Gnats. Since I've found the way to deal with this problem, I'd like to share my experience in a hope that one day it'll help someone who is as desperate as I was fighting off these foul creatures. So without further ado,

What are Fungus Gnats and why are they so bad?

Fungus gnats, or Sciaridae, are tiny little flies usually found in plant and flower pots. You can get them from the store-bought potting soil, or from a plant you brought with you from outside. They may go unnoticed as most likely it won't be the adult flies you'll see but rather their eggs or larvae hiding in the soil. However, if you have brought them inside somehow and no upfront measures were taken to prevent the infestation, you'll notice these pesky little guys very soon, and before you know it other plants will be infected as well.

Besides being incredibly annoying, adult gnats are completely harmless to humans, pets and plants. Their larvae, however, pose a significant threat to your plants, especially seedlings and stressed, overwatered greenery. They feed off the plant's root system, causing it to fade, weaken and even die completely in some cases. Young plants and those weakened by stress suffer the most, not least because using insecticides on them isn't recommended until they develop and/or acclimate. And the worst thing is - fungus gnats reproduce like crazy, which is why it's very important to not only deal with them as soon as possible but also make sure all of your plants are healthy and thriving.

Preventive Measures

With pests like fungus gnats, it's often better and easier to prevent the issue rather than wait until there's no choice but to fight off the invasion. There are a few steps you can follow to minimize the possibility of even getting the sneaky flies in the first place:

• Make sure to never overwater your plants! 

This might be difficult if you have plants that adore moisture. I own a couple tropical greenlings myself, and I know the last thing they want is for the soil to go dry. They also love being misted often and take showers, which only adds to the problem. However, I found a few hacks that might help even with those types of plants. First, start watering them from the bottom! Instead of watering the soil, pour water into the tray (or a plate, or wherever the water is usually draining to). This way, you will always keep the top layer of the soil (also known as the home for fungus gnat larvae) dry, which would discourage the gnats from laying eggs in there. Don't let the pot soak in that water, though - pour it out after a short while to keep the tray dry and gnat-free. Misting the plants, in this case, won't do much harm as it's not enough to soak the top layer; if the plants like to shower, simply cover the soil with a plastic bag to prevent it from soaking. If you still happen to overwater for some reason, just let the top layer dry before adding any more water to be safe.

• Consider adding sand to the top layer of the soil!                                                                           

As I've explained above, keeping the top layer of the soil as dry as possible is key for preventing gnats from laying eggs in the pot. Sand dries faster than soil and serves as an additional protective layer for your plant. The only difficulty is that when you water the plant from the top, you'd always wash some sand down or around the pot. So in order to make this work to its full potential, consider watering from the bottom at all times - most likely, you'll never see any gnats if you combine these two steps. 

• Remove the foliage!

Gnat larvae mostly feed off fungus and decaying matter, so all of those fallen leaves or organic debris that you forget to remove from the pots (and the trays!) are very attractive to gnats and thousands of their babies. Keeping the pots and trays clean is another way to discourage gnats from even considering your house garden as their home. 

• Mind your plants' food! 

I know a lot of people prefer to feed their plants with... leftovers. Cooking water, tea and coffee left after you drank them, milk and broth - you name it. We think if it's good for us, it's probably good for our plants. Well, not exactly. While it's debatable if our food is good for our green friends, one thing is certain: it attracts all kinds of unwanted bacteria that doesn't really go away fast enough to keep the soil clean. Outdoor gardens might be much more forgiving of household waste fertilizer, however potted plants are very limited in the amount of soil they get - and if the mold or unwanted bacteria gets in, getting it out might prove difficult. If you still wish to keep feeding your plants "off your own table", make sure to drench them well afterwards and use fungicides to be on the safe side. 

• Quarantine new plants!

As you may already know, repotting a new plant isn't recommended until it's fully acclimated to a new environment (and some plants can stay in their store/nursery pots for a while!), so there's a good chance that if the store-bought plant is infected, the gnats may spread, and if they do - it'll happen fast. Even if you haven't noticed any visible signs of gnat presence, it's best to keep a new plant away from others until you repot it. 

• Sterilize your soil! 

Even if you're buying good quality soil, there's always a chance that it might already contain pest eggs. You won't notice it until it's too late, so it's important to always sterilize your soil, whatever it is. There are several methods you can find online, and they're all pretty much equally effective, so it's completely up to you. The most popular methods are baking the soil, freezing it, microwaving it, or soaking in boiling water. Don't be afraid to kill the "good" things - you'll be fertilizing your plants regularly anyway, so even if the soil is "sterile", it's still good for plants! 

And that's about it for preventive measures (please comment below if I forgot something!). Now, to the dirty work: 

How to get rid of fungus gnats

Now there are plenty of things that people use all around the world to kill gnats. While trying to get rid of them for the past few weeks, I've researched and read about so many methods and opinions that it'd take another blog to list them all. Even though I prefer all-natural pesticides and fertilizers 99% of the time, I still had plenty of options to try out. None of them really worked for me until I did two things, so that's what I'm going to talk about below. 

First thing I did was soaking and spraying all my plants, pots and trays in hydrogen peroxide solution. Hydrogen peroxide is generally used in gardening for many reasons, from helping the seeds germinate to fighting root rot and aerating the soil. There's plenty of info out there on how exactly HP works in the soil - what matters is that it does work if you do it right. The solution I made was about 50 ml (~1.7oz) of 3% hydrogen peroxide per about 450ml (~15 fl. ounces) of tap water. Give it a good shake and then water the plant thoroughly until it starts dripping out of the draining holes in the bottom. Repeat if necessary and leave for the water to run out as much as possible. You'll hear it hissing for a few minutes - that's peroxide releasing oxygen, which is good for the soil and for the roots. Mist the plants with the same solution, clean the trays with it too, and return the plants to their spots. Leave them overnight and I promise you'll see fewer gnats flying around the next morning. Peroxide fights off the mold and fungus, helps with root rot, aerates the soil and helps the plants. While you shouldn't be overdoing it (less is more in this case!), the amount of positive effects from using it is absolutely amazing. However, I found that's not enough to completely kill off the pests. I didn't want to use a stronger solution, so I moved to the next step: soapy water. 

This might sound odd, but soapy water is a great way of getting rid of pests such as gnats. Essentially what it does is prevent soft-bodied insects from breathing, causing them to die a quick and painless death. When mixed correctly, it's equally effective on larvae, eggs and even adult pests. 

There are insecticidal soaps made specifically for use on plants. If you have any at hand or have access to a store that sells it - by all means, get it and use it to fight off the pests! Don't be discouraged if that's not an option - you can still make your own soapy solution that will be as effective. I wouldn't recommend using cosmetic soaps or dish detergents that contain lots of additional elements you wouldn't want to spray on your plants or soil - especially if you're planning to use it on herbs! What you'll need to make your Gnat Killer solution is a simple old-fashioned laundry soap bar. The main thing to remember here is that the fewer additions (such as perfume, coloring and such) the soap has, the safer it is to use. The best soap to use for this task, if you have access to it, is tar soap. Not only it is eco-friendly, but also tar can help with tiny cracks or injuries on the stems and leaves. So if you have this option - it's really the best one! Now regardless of the soap you choose, proportions are the most important part. You do not want to use too much soap, even the least toxic one - it can still burn the plant if used in high concentration. I used about half a bar of tar soap per 5l (or about 1.3 gallons) of tap water. Two things to keep in mind: grating the soap bar on a cheese grater makes mixing it with water a very easy task; however soap dust is not the most pleasant thing to breathe in, so it's better to either grate it outside, or cover your nose and mouth with a cloth (or a breathing mask, if you have one) while you're doing it. 

Shake the mix well, pour into a smaller bottle with a spraying hose, and get to work! Now the gnat larvae mostly hang out in the top layer (about half an inch) of the soil. Before applying the soapy water onto the soil, loosen that top layer carefully with a spoon or your gardening tool of choice - this will disturb the larvae and allow the water in, killing off as many as possible. Spray the soil thoroughly until it soaks, and then spray the plant's stem and leaves. Even if there are no insects on the leaves by the time you do it, a layer of soap on the surface will prevent adult gnats from sitting on them. If you see any adult gnats flying around - spray the solution on them as well! The more flies you spare, the more chances that they'll have time to lay more eggs before they die off naturally, so as harsh as it sounds, you do need to kill as many as possible - and soapy water is a natural and effective way to do just that. If you're worried that it may harm the friendly insects - don't be, since nice guys like bees, bumblebees and ladybugs aren't really affected by this solution (as long as it's weak enough to only work on soft-bodied pests!) and will most likely survive even if some gets on them. 

Note that you may need to repeat the soapy water part again if you see any flies on the next day, so keep the remaining solution at hand for a little while just in case. Remember those very young seedlings may be too weak to survive this kind of procedure (and you can't loosen the soil around them without harming them), so it's best to hold off on planting new greens until you're done with gnats. One day after I've done both steps (hydrogen peroxide and soapy water), a spinach seedling from the seeds I've planted a few days earlier poked out. Other seeds, however, weren't showing any signs of life. I will update this part later on when there's more info to share - but for now, I'd just say use the methods at your own risk, if you're feeling confident, but hold off on planting new greens if that's an option.


As far as the results go, the next day after soapy water treatment, there were no more flies or larvae/pups to be found both in the herb garden and houseplants. Since I've been basically pouring insane amounts of water down the pots for two days straight, best thing to do is leaving the soil to dry as much as possible, following general recommendations for each plant. You can check the moisture level easily by sticking a chopstick (or just a sharp wood stick) into the soil gently. If you know how much it takes approximately for the soil to dry in your houseplant pots - just give them enough time to do that before watering again. Start following the preventive steps (at least some of them) to ensure your plants are protected from any future issues. If you have any tips, or questions, or advice on the matter - please comment below! I am by no means a specialist, and I'm learning all of this slowly just like any other beginner plant person out there, so if you have any words of wisdom to share - please do.