The gnats will now crawl through the small holes in the cling film, but will be unable to escape and will drown in the vinegar
They are drawn to moist conditions and, as their name suggests, feed on fungus and other organic matter. In their larval form they eat plant roots, which can make them a potentially lethal infestation for young or vulnerable plants. In their adult form they can be identified by their long legs, squat body and their semblance to tiny mosquitos. In their larval form they are white or translucent and around 5mm long, with a distinctive black head.
Andy: Fungus gnats are those annoying, tiny little black flies that you find wafting around your pot plants. They are notoriously difficult to get rid of and I never know how to advise gardeners on this one. I was particularly interested to hear from Geoff Hanbury who has researched all the possible solutions:
Did it Work?
Diatomaceous earth (DE) is made from microscopic fossil shards and shreds the larvae and the gnats upon contact.
It did reduce the number of larvae wriggling about underneath the soil, but it didn’t come close to eliminating the problem completely. Because many plants can’t be chronically under-watered for a long time, it means that once you resume normal watering, the gnats will just multiply again.
- Till the first inch or so of soil
- Sprinkle ground cinnamon all over the surface of the soil
- Set up vinegar traps around the plant and change them daily
- Insert slices of potato daily
- Do not water the plant until the top layer of soil is totally dry
- When top soil is dry, thoroughly drench the soil with the hydrogen peroxide solution
- Once the hydrogen peroxide solution has stopped fizzing, repeat step 1 onwards
Want To Know How To Control Fungus Gnats On House Plants? In Our Weapons of Gnat Destruction Article We Will Show You The Ultimate Guide to Killing Fungus Gnats.
Fungus gnats reproduce by laying eggs in the top couple inches of damp soil. The eggs hatch into larvae, the larvae feed on organic matter within the soil for 2 weeks, and then they pupate. A couple of days later, the adult flies emerge and start buzzing around. You’ll commonly see fungus gnats hanging out on the soil surface, edge of the pot, or maybe around the drainage holes of the pot. They most often only fly in short bursts, and otherwise crawl around.
At the first sign of a fungus gnat issue, this should be the initial step. Allow the top few inches of the plant’s soil to dry out. This will make the soil unattractive to adult flies, preventing them from laying more eggs. If you’re lucky, this can kill a lot of the eggs and larvae too! Furthermore, eliminate standing water. This includes in the pot drainage tray, or even from other sources nearby – such as leaky pipes, condensate puddles, and so on.
Read along to learn how to kill fungus gnats in your house plants. These tips can also be applied to other plants and soil too, such as in potted plants in a greenhouse, or even outdoors. When it comes to fungus gnats, prevention is key! Therefore, we’ll go over a few ways to prevent fungus gnats first, so maybe no intervention will be needed at all. Yet when you already have an infestation on your hands, there are several organic methods you can use to get rid of fungus gnats.
To apply Bti, follow the instructions for a “soil drench” on the product that you purchase. It is usually recommended to water the plant with the solution, since only spraying the surface of the soil may not penetrate deep enough to kill all of the fungus gnat larvae. Repeat as needed, following the instructions. One popular option is this Gnatrol brand. Get it? Natural gnat control…
Let’s go over each of these options! But first…
As we’ve already established, fungus gnats love moist soil – and need it to breed! Therefore, overwatering your plants can easily lead to a fungus gnat problem. To prevent and battle fungus gnats, avoid overwatering your plants in the first place. Only provide water when the top couple inches of soil has dried out. Remember, that top shallow soil is where the fungus gnats are drawn to!
When you bring home a new houseplant, look for the presence of fungus gnats. Unfortunately, only the flies will be obvious since the larvae or eggs are very difficult to detect. It is a good idea to keep new plants away from your other houseplants for several days to monitor, especially if you have suspicions that they may be infected. Remember, fungus gnats don’t typically fly long distances unless they have to!
Another good indicator of moisture control is the drainage tray or trough at the bottom of the pot. This should be dry within a day of watering the houseplant, and not have standing water. If it does, you may be overwatering! A quick-filling drainage tray could also be a sign that the plant’s soil has poor water retention, is root-bound, or that water may be running around the sides of the root ball and soil – rather than seeping through. To read more about houseplant care tips for watering, soil, fertilizing and more, check out this article – “Houseplant Care 101: The Ultimate Guide to Happy & Healthy Indoor Plants”.
Another non-toxic way to treat fungus gnats is to use biological controls, such as Bacillus Thuringiensis. Specifically the subspecies israelensis, also known as Bti. Bti is a naturally-occurring bacterium that is found in soil. According to the EPA, Bti contains spores that produce toxins that specifically target and only affect the larvae of the mosquitoes, blackfly and fungus gnats. Meaning, it is not harmful to other organisms.
Read along to learn 5 easy and non-toxic ways to get rid of fungus gnats in your houseplants, plus a few tips on how to prevent them in the first place!