Which Plants Are At Risk Of Fungus Gnat Damage
Vegetable plants, herbs, fruit plants, flowers, tree saplings, and houseplants are all subject to an attack from fungus gnats. The younger and more tender the plant is, like vegetable saplings started from seeds in the early spring, the more susceptible it is to a fungus gnat infestation.
These young plants typically have fresh, loose growing mediums that are easy for the fungus gnats to deposit their eggs into. The fresh growing medium is filled with the fungi and decomposing matter that the larvae need to feed upon. The looseness of the growing medium makes it easy for the larvae to wiggle around.
Females lay tiny eggs in moist growing mediums or organic debris so their larvae will have a rich food source as soon as the eggs hatch. Plants being grown in outdoor soil are rarely bothered by fungus gnats. Its primarily the plants being grown in containers indoors at risk.
Can Fungus Gnats Cause Damage
Adult fungus gnats dont bite or feed, so they arent a threat to people or plants. However, they can become an annoyance if they arent controlled and are left to reproduce in large numbers. The larvae of fungus gnats pose a small threat to young plants. Larvae feed on organic matter in the soil and will sometimes feed on the roots of indoor plants. Seedlings and other less-established houseplants are most at risk for damage since their roots are delicate.
Apply Organic Pest Control Products
Pour or spray an organic insecticidal soap or a neem oil mixture into the top of the soil to kill gnats in potted plants.
I make my own insecticidal soap by mixing using 1 tsp Dr. Bronners Baby-mild Liquid Soap to one liter of water.
Neem oil works great to kill houseplant pests, and has a residual effect that helps with prevention. You can buy neem oil here.
These natural gnat pesticide treatments should be effective after a few applications, just take care not to overwater your plants.
Soapy water will kill gnats in potted plants
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How To Get Rid Of Gnats Outdoors
As an alternative to saturating outdoor plants with a Bti drench, you can drop a mosquito dunk labeled as safe for use around pets and wildlife in a watering can or bucket. Let it sit overnight or long enough for the dunk to soften and release its insect-killing bacteria into the water. Then remove the dunk, save it for later use and pour the water over the soil in your outdoor plants. Do this for several weeks to ensure any gnat larvae in the soil are killed.
Electric pest traps arent recommended for gnats, because they often kill beneficial insects along with real pests. Traps that use ultraviolet lights to attract gnats can work, but they only trap the adults, so any larvae that remain can grow into adults and reproduce, starting the cycle over again.
Some gnats like to swarm around porch lights or other outdoor lights and sneak inside to fly around your TV or lamps. To discourage them, switch to yellow “bug lights” or low voltage bulbs, or keep lights near doors and windows turned off. Some pest control manufacturers add a pheromone that attracts gnats to their light traps and report this can help when used as part of a larger gnat management effort.
Overwatering: A Classic Mistake
Overwatering is the cause number two, after infested soil, for fungus gnats in potted plants .
This is particularly true in autumn/winter. Indeed, what I noticed chatting with gardeners, is that overwatering is caused by lack of any seasonality in the watering pattern. Indeed, in cold and cloudy weather, when not much photosynthesis is going on, not much water is needed. Moreover, the low temperature also reduces the water that naturally evaporates from the growing medium. Hence, during winter, you should water way less your plants.
People forget that, and they end up constantly dumping the plant-soil in the cold season. This is the perfect environment for fungus gnats to lay their eggs.
How to avoid overwatering?
First, to avoid overwatering, it is important to test the soil before applying water. Just stick your finger in the potting mix Is the soil moist? If so, then its enough, no more water is needed. This simple truth is applicable to the vast majority of houseplants and especially herbs. Remember, it is quite often easier to recover a plant from lack of water than too much water.
Second, avoid letting stagnant water sit for too long in trays and saucer beneath pots. Indeed, that water might be closer than you think to the plant roots. Moreover, if dry, the soil will suck water from the bottom, making the situation worse .
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How To Get Rid Of Fungus Gnats In Houseplants
If you’re annoyed by tiny flying insects that seem to appear every time you water your houseplants, you’re probably dealing with gnatsmore specifically, fungus gnats. These pests are attracted to the damp soil of potted houseplants. They need the moist soil as a haven to lay their eggs, and the organic matter in the soil feeds their larvae. Besides being annoying, this feeding behavior can damage your plants.
Although they look a lot like tiny mosquitoes, fungus gnats are small flies of the Orfelia and Bradysia species. They can be identified by their narrow legs, light gray or clear wings, and segmented antennae that are larger than their heads. These are fairly tiny insects. The adults grow to about 1/16 to 1/8 inch long.
The good news is that fungus gnats do not bite people or pets. The adult gnats dont do much damage to plants, either rather, its the larvae that will munch on your plant’s tiny feeder roots, limiting the plant’s ability to take up nutrients and stunting its growth. This is more of a problem in nurseries, where susceptible young seedlings are grown in damp conditions. While you may not be growing your plants in a nursery or greenhouse setting, with a large enough population, they can pose a threat to common houseplants, too. If you notice these gnats flitting about and your plants seem to wilt for no reason, it could be root damage being caused by the feeding larvae.
Allow The Potting Soil To Dry Out To Get Rid Of Fungus Gnats
As fungus gnats are attracted to damp environments, it is important to ensure that your house plants potting medium is not always wet or damp. It is tempting to water house plants frequently, but you might not be doing your plants any favors if your watering frequency is attracting insects.
If your plants are constantly watered, the environment becomes prime real estate for mold and algae to grow. And by now you already know that mold and algae are two things fungus gnats love.
Before you water your house plants, feel the surface layer of the plant. If it is wet or damp, do not water. If it is dry, you can water. Female fungus gnats specifically seek out soil that is consistently wet. Drying soil deters eggs from hatching into larvae.
Giving your indoor plants the right amount of water is the most important thing you can do to keep your houseplants healthy. It seems like such a simple thing to do, but its a skill that you need to develop. Ive written several articles to help you get this right. Read about ways to tell when to water your houseplants and how often to water your houseplants for more information
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Castile Soap Essential Oil Solution
If you see large numbers of fungus gnats, then one organic insecticide to try is a castile soap solution. For those of you who do not know, this is not a generic soap. Castile soap was made in the Mediterranean area before its use spread to Europe. Traditionally, castile soap was made of olive oil. It gets its name from the Castile region of Spain.
Castile soap is produced based only on vegetables with no animal fat or synthetic ingredients. This is a 100% organic soap that will not damage the environment when it ends up in the drain. It is not toxic, and it is usually sold both in liquid and solid form. These days, the soap is also made with coconut, castor, or hemp oils. Sometimes its made with avocado, walnut, and almond oils as well.
Castile soap is not meant to be used as an insecticide but mainly as a body cleaning product due to its lathering, moisturizing, and cleansing properties. However, there are more than 20 uses of this soap, from deodorant, dish soap, shampoo, body wash, and plant spray for bugs.
In case you want to use this soap as a fungus gnats killer, here what to do:
How To Identify A Fungus Gnat
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Size: Adult fungus gnats are tiny. Their size ranges from about 1/16 to of an inch in length , which is about the same size as a fruit fly. Fungus gnat larvae may be up to of an inch in length.
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Appearance: Adult fungus gnats are a grayish-black color and have gray or see-through wings. Their long legs and long antennae give them a mosquito-like appearance, though they are much, much smaller in size. Compared to a fruit fly, fungus gnats have a thinner body with longer legs and antennae.Larvae have a small, black head and a thin, white or see-through body.
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Activity: Fungus gnats tend to spend most of their time on the soil surface of potted plants, but they may be seen flying around the outer edge of the pot or near drainage holes as well. They are not strong fliers, so they have a tendency to walk along the soil and fly only in short bursts. Their flight is erratic and they are much slower than fruit flies, acting more like mosquitoes while flying.Annoyingly, fungus gnats have a tendency to fly into peoples faces and drinks, though they are completely harmless and a few well-placed swats will show them whats what.
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Soil Drench To Kill Fungus Gnats
A soil drench is a chemical pesticide that saturates the soil and kills pathogens and insects like the fungus gnat. Bacillus thuringiensis are a naturally occurring soil bacterium, and according to the Colorado State University Extension, it is the only microbial insecticide that is available for everyday use .
Different strains of the microbial insecticide kill different insect species. To kill fungus gnats, you need to use bacillus variance israelensis , also called H-14 strain.
When you apply a Bti soil drench to your plants, it saturates the soil, harmlessly coating the roots of the plant while providing a toxic snack for the fungus gnat larvae.
Controlling Fungus Gnats In The Home
The best option for the home gardener is to control watering. Keep plants drier and you will eliminated most issues with fungus gnats. Be aware that it will take weeks to clear up a problem with any method you use, so dont give up on it.
A second option is Bti. It is effective if placed in each pot and its readily available. It is not a quick fix since it only kills the larvae.
Nematodes do work but are tricky to use and not easily available to home gardeners. The other options listed above either do not work, or there is no scientific evidence to support them.
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Home Remedies For Fungus Gnats
Yellow Sticky Trap paperis a great first solution as supposedly theses flies are attracted to the color yellow.
These fungus gnat traps are perfect cheap first defense.
Just place theses traps around your infected plants and watch them stick and die!
Apple cider vinegar smell also attracts the fungus gnats.
Mix in a jar or cup or bowl, the apple cider vinegar about two tablespoons or more with some dish soap and water. Then place it around your plants.
Hydrogen Peroxide can be used if the fungus gnats have infected the soil and you suspect larvae are growing.
One of the ways to get rid of the fungus gnats in larvae stage is hydrogen peroxide.
- But beware it can harm the roots if used to much.
Make sure you dry out the soil, then mix 1 part hydrogen peroxide to 4 parts water and then water your infected cannabis plants.
If it starts to foam, it is killing the larvae.
Preventive Measures
Sand this another significant step that can be done when transplanting.
Place and inch on the bottom and top of your pots. It acts like shredded glass, and they cannot get inside it impenetrable.
The growing trend in the growing community is the use of living organisms and bacteria to help fight pests and insects in the garden.
One of them is nematodes,
Beneficial Nematodes are microscopic roundworms that seek out and kill 200 different insects in soil or growing medium.
Thats 200!. No wondering it is starting to be a trend.
Here is short video about using nematodes
Overwatering Can Attract Fungus Gnats
If you remember nothing else from this article, hang onto this tip: “Let the soil dry out between watering!”
Why? Gnat larvae love warm, wet environments so your overwatered indoor plant is like a little paradise for them.
Letting a finger-length of top soil dry out before you water again will help prevent or slow an infestation.
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Do Fungus Gnats Harm Plants
This seems like it should be a simple question, but its not very clear how much damage they cause. The term fungus gnats is used for a number of species that are very difficult to identify. Some species seem to harm plant roots, while others live just on decaying organic matter. It is quite possible that your gnats are doing very little harm to the plants.
Types Of Fungus Gnat Larvae
There are six different families of insects which make up the broader category of fungus gnats. These six families include the Sciaridae, Mycetophilidae, Ditomyiidae, Bolitophilidae, Diadocidiidae, and Keroplatidae.
Most fungus gnat species are not harmful to our gardens, but the dangerous ones are in the Sciaridae family.
While adults dont cause any lasting damage, the fungus gnat larvae of that family will move on to plant roots once their preferred foodstuff is gone. The larvae will chew holes in the roots and can cause yellowing, wilting, and even plant death in large numbers.
Not only do they damage roots, but the Sciaridae can spread disease. Since their preferred food is fungal growth, they can easily pick up spores from infected plants or soil and spread leaf spots, scabs, cankers, rot, and more.
Fungus gnat adults are often confused with mosquitos as they look similar in shape, but are much smaller. These tiny black gnats rarely get any larger than an eighth of an inch long.
The larvae themselves grow a bit larger than the adult gnats. Fungus gnat larvae have a black, shiny head with a white to clear body that can reach almost a quarter inch in length. Theyre hard to locate because they tend to remain under the soils surface, out of view.
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How To Really Truly Finally Get Rid Of Fungus Gnats For Good: We Asked The Pros
I accidentally brought a plague upon my house.
In November, I perched a newly purchased pinstripe calathea on the dresser in my bedroom.
I have plants in every room of the house and plenty outdoors too. My collection ranges from thumb-size succulents to a dracaena taller than I am. I’m on and off my two balconies a lot to water and fuss over them. So the first few times I swatted a little fly getting up in my face, I assumed one had followed me back inside.
Wrong.
The calathea started to struggle right away. I fretted over it, brought in a humidifier, moved the plant closer to and then farther from the window. Then the ‘Marble Queen’ pothos hanging in the window started struggling. The philodendron ‘Brasil’ began to droop. I took them down to get a look at the soil and was met with a face full of fungus gnats.
That was in early December. It was already too late.
Since then I have been playing whack-a-gnat.
A lot of us became plant parents in quarantine. My collection expanded from a handful of cute little cactuses picked up on a whim at Trader Joe’s to a sweeping collection of more than three dozen posed in corners and on countertops in every room of my house. But as parents of all kinds know, even the cutest little additions to the family come with potentially unpleasant corollaries.
With plants, it’s bugs.
I am still subject to the scourge.
Three 48-packs of sticky traps: $44
Landscaping sand: $15
Bag of cedar shavings: $10
Mosquito bits: $19
Do Fungus Gnats Die In Winter
Fungus gnats’ bodies contain what are called antifreeze proteins which make them especially hardy when it comes to cold temperatures. The larvae can survive freezing, though may suffer some tissue damage in their heads and “tails.”
Otherwise, they continue their normal life cycle of birth to death in 3 to 4 weeks.
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