Last Updated on December 16, 2019 by Yuvika Iyer
Bugged by small gnats buzzing near your houseplants?
Here is a cheat sheet on how to get rid of gnats in houseplants that you can put to use right away.
How to Control Gnats in Houseplants
Have you been recently bugged by small flying insects that appear the moment your houseplants have damp soil?
These insects are known as gnats; most of them are “fungus gnats.”
Are you wondering ‘how to control gnats in houseplants’?
In this blog, I am sharing simple and effective techniques to get rid of these pesky insects.
The wet soil of your houseplants is a safe haven for gnats as they prefer excess moisture to lay eggs.
They feed their larvae with the organic compounds present in your potting soil.
Such a rapid multiplication of gnats can not only be annoying but cause grave damage to your beautiful and air purifying houseplants.
Read on to know the strategies you can adapt to stop these sneaky insects.
What are Fungus Gnats in Houseplants
These flies can be clearly recognized by their light grey colored wings, narrow shaped legs and distinct antennae bigger than their heads.
They can’t be easily located because of their minuscule size. Their adults grow in length only around 1/16 to 1/18 inch.
Though fungus gnats have flying abilities, they prefer to stay close to the source of food.
They thrive on the fungus on your potting soil and other organic compounds, including the fertilizers, composts, and manure present in it.
The gnats lay eggs inside the damp soil, and the growing larvae feed on the root hair of your houseplants and organic matters in the soil.
The larvae have a distinct gray or white form with a ¼ inch of length and glossy black heads.
Initially, you may not be able to locate them because of their miniature size, but once they start trailing like slugs or snails, it’s time to plug them out.
Why to Get Rid of Gnats in Houseplants
Well, the only respite is that fungus gnats don’t bite pets or humans.
The grown-up gnats don’t directly harm your plants.
They are more of slow killers.
It munches away the small feeder roots of your plants, limiting its growth by sucking up all their nutrients.
The problem is seen more in local nurseries where tiny saplings are grown in damp soil.
The problem arises when you buy those little plants from the nursery and keep them with other houseplants.
These tiny monsters can fly and replicate in the soil of other houseplants after you water them.
They cause irreparable root damage by feeding its larvae with root hairs. The moment root stops growing, your plant will slowly wilt and die.
By now, you must have understood that gnat’s larvae and not the adult ones are the main culprits.
Knowing it’s lifecycle helps how to get rid of gnats in houseplants.
In the humid and moist condition, the tiny eggs hatch faster within 3 days into larvae and remain in that form for about 10 more days, after which they transform into pupae.
Around 4 days from this transformation, pupae grow into adults and start the breeding cycle again.
These tiny insects are capable of producing a whole new lot of fungus gnat in 3 weeks or less.
You can only stop this vicious cycle if you catch and eliminate them early.
Look for any drooping sign in your houseplants, if you find any, go for the gnat-hunt right away.
How to Control Gnat Infestations in Houseplants
If you can locate the existence of fungus gnats, immediately quarantine the infected pots away from their healthy companions.
Your prompt action will ensure that healthy plants are not affected.
The majority of the fungus gnat’s lifecycle and the damage they cause is limited to the soil.
The gnat damage does not spread any beyond it.
If you see any trace of these deadly fungi on your potting soil, target them right away.
One of the proven techniques is to keep the soil dry for many days before pouring water on it.
The eggs and larvae won’t be able to survive for long in dry soil. If your planters have any self-draining saucers, remove them immediately to avoid extra water accumulation.
I would recommend another easy technique of using a sterile potting mix as it contains less organic compounds for the young larvae to feed on and survive.
Laying a Trap to Catch the Houseplant Gnats
You can lure the existing larvae of fungus gnats with a few pieces of raw potato.
Put the fleshy sides of potato pieces down under the soil and check for larvae in every alternate day.
If you find them sticking on the potato, remove it immediately, kill the gnats and put new pieces of potato.
Target the adults as they have a short life. If you can eliminate their population, you can stall the breeding cycle.
I would recommend using yellow sticky straps to control the germination process and reduce the adult fungus gnats.
Yellow sticky traps are nothing but the adhesive on the yellow paper sheets. You can visit your nearest garden center and get these sticky papers.
Yellow color attracts the gnats and the moment they draw themselves towards the trap and get stuck.
When your trap is full of fungus gnats, replace it with a new one. Using this technique, you can destroy most of the existing adult gnats in a non-toxic and simple way.
Once you put up a sticky trap, my suggestion would be to check it periodically and see its effect on the fungus gnats.
Using Biological Controls to Control Gnats in Houseplants
You can also find multiple ways to control fungus gnats biologically.
These methods are primarily applied in nurseries and greenhouses to prevent gnats’ impact on mass propagation.
Well, if you feel that most of your houseplants are severely impacted by gnats that you can’t save them without the dose of biological control.
I would suggest against spending so many dollars on biological control, instead, get rid of the gnat affected plant and add a new plant in your collection.
(Don’t forget check for larvae and safeguard the new plant).
However, if you want to try your hands on biological control, the tried and tested measure would be Bti (Bacillus thuringiensis subspecies israelensis).
It is widely used to control the germination of mosquitoes in ponds. These are good bacteria and ideal for controlling gnats but risk-free to pets and humans.
Ask for “Bt” as granules or mosquito dunks in the pond supplies or pest control section of your nearest garden center.
To eradicate the root cause you may have to apply the same solution more than once by following the instruction written in the product label.
You can also try nematodes to eliminate fungus gnat larvae.
These you can order online and get it delivered at home from a plant pest control provider.
But if the delivery is taking a long time, you should go for quicker remedies and get your gnat-affected plant back on shape.