Fungus Gnats Versus Gem

So you're plagued with fungus gnats! Or are you here just to do a bit of research for your botany class? If the latter, Sciara thomae is its Latin name. Hope that helps! My guess though is the former and you have come to the right place.

Fungus gnats closeup picture

These little critters are not as harmless as some folks make out. Not only do they persistently try and fly up your nose, they breed like wildfire when they invade your house and the larvae suck the life juice out of your seedling roots.

drawing image of a fungus gnat

The close-up photo above is of one of the last remaining fugitives that I pursued all about the house with camera in hand.

I compared it to some illustrations I have of common garden insects and posted the one that fits the profile. Yeah, it's the fungus gnat alright!

Some people mistake it for the fruit fly, but it's rather large in comparison plus fruit flies don't fly around your nose and mouth all the time attracted to the carbon dioxide on your breath.

Don't get me wrong! I am a firm believer in live and let live. These wee bugs have a right to be on this planet as much as I have. But enough is enough when they cross the line, invade my space and destroy my prized windowsill herb garden, then you'll hear the war cry,"Let's do battle!"

Just like you, I was searching the internet for ways to deal with the enemy and came across plenty of tips and tactics on how to rid fungus gnats. Some of them sounded feasible, others down right ridiculous, but after so many failed attempts even the ridiculous became believable.

I eventually found out what did work and even employed some successful ideas of my own. To this day I'm still using them.

Let's talk about the pretty bad tips and tricks some well meaning people advised which turned out disastrous for my plants.

How Not to Get Rid of Fungus Gnats

bottle of hydrogen peroxide to rid fungus gnats


That`s is a no-no for me period! Especially when growing food.

Hydrogen Peroxide 3% Food Grade

Just watching this fizzing down into the roots of my pepper plant made me cringe and regret using it. Apparently when diluted, hydrogen peroxide should kill fungus gnat larvae with periodical use. As the larvae emerge you apply another dose until all have gone.

But after a while it dawns on you, all you're doing is soaking the compost including the surface layer which just leads to more fungus and gnats. By the time it takes for the extra moisture to dry out the little beasties have had a feast, laid their eggs and before you know it you're outnumbered.

Yellow sticky pads

Not a good war strategy! I watched as the little gremlins ran around the rim of the pot and completely avoiding these "deceptive landing pads". I still gave the strategy the benefit of the doubt and kept them there for several days. Not a chance. My enemy was too clever to say the least!

Grit and sand

Doing this was a messy business. Then there was the question, "What to do when the plant needs re-potting?" I would need to wash off the roots and start again.What!

Wash off roots and change to fresh compost

This is shock treatment to the plant. It was the last straw for the chilli pepper. It just shriveled up and died.

OK. Back to the drawing board. How did I save the rest of my plants after witnessing the death of my oregano too? This is a list of the good tips that worked and why.

How to Rid Fungus Gnats Successfully

graveled house plant

Use gravel as a mulch indoors and outdoors

If you pour at least a 2 to 3cm layer of gravel around your plants indoors and out the gnats are fooled and will not find the compost. I mulched all my herbs including all my other house plants.

They love it, especially outdoors. It helps retain moisture in summer and retain warmth in winter and it looks pretty into the bargain.

Use a closed compost maker

Open compost heaps kept in the shade are a breeding ground for fungus gnats. Winston, my hubby has one in a plastic container in our garden. They eventually make their way into our house especially when the cooler weather comes.

Your home is a warm haven helping to extend their breeding period so check the methods you use for making compost. A closed compost maker keeps a lot out so avoiding clouds of them. I'm trying to convince Winston!

Water from the bottom when watering pot plants

Keep the compost dry on top. Not so easy if you're in the habit of watering from the top. Pea-sized gravel is a good material to cover the top soil in case you`re prone to forgetting. Yet another reason why using gravel works.

Buy Formulated compost for House plants

The enemy can enter your home via potting compost bags. If the larvae are present they will soon emerge, so treated potting compost is safer. Look for pasteurised potting soil or solarize compost yourself by exposing it in the sun in a clear plastic bag for several weeks before using.

My Own Discoveries That Work

...and now for my own solutions and preventative measures. 

Use a vacuum cleaner and suck them up

No kidding! It works! The little critters are hard to swat. The vacuum cleaner makes light work of it. Just be careful not to go too near the herbs and compost or “thunk!!!” No more problem!

Homemade mini plant tentGive your seedlings a good start with a mini cloch

Protect the seedlings

Make mini tents (cloches) for seedlings that are just emerging and need to come from under the nursery cover. They are far too small to be mulched with gravel but still need the compost to be fairly damp which in turn will attract the gnats.

Mini tents are a great preventative method that I am using for all my indoor sowing. You can cut up an old net curtain or use garden fleece. They`re easy enough to make.

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