Fungus gnats and their young (the fungus gnats larvae) are among the most frustrating pests found in most indoor gardens. These little pests can destroy your entire vegetable or plant garden if you are not vigilant. Not only that, they can as well do it very quickly.

One common way by which fungus gnats can affect your garden is through their larvae. How? They tend to lay their eggs in your growing medium. Once they begin to hatch, the larvae will attach to your plants’ roots and drain them of their nutrients in the process.

Although the larvae carry out the foremost destructive duty, the adult fungus gnats are also disease carriers, especially fungal diseases. Adult fungus gnats can be very deadly on their own. They tend to lay thousands of eggs at a fast rate, which, in the end, destroys your plants.

Therefore, you must stop these pests before they destroy your plants, whether indoors or outdoors. As it is, I’m sure that the last thing you need is for your plants to get killed as a result of these pests.

In this section of the article, I’ll give you ways to overcome or prevent fungus gnats from infesting your plants. But first, you need to have a little knowledge of fungus gnats and their larvae and how to destroy them before they ruin your garden.

Fungus gnats: Life cycle

The fungus gnat’s life cycle consists of four stages: the egg stage, the larvae stage, the pupae stage, and finally, the adult stage.

According to research, the egg stage: the adult fungus gnat can lay roughly 300 eggs in its short lifespan. They live for only about one week as adults, which is likely why they make the most of their time (reproducing). Fungus gnats tend to lay their eggs in soils that are richly endowed with nutrients and very fertile. Hence, they go for moist soil at the base of plants.

The larvae stage: After about 4 to 6 days after the eggs are laid, the larvae emerge, the second stage. Now, these larvae tend to be too tiny at first. During the two week period in which fungus gnat larvae are growing, they increase rapidly by only eating enough organic matter in the soil.

The pupae stage: This stage occurs the Laval has achieved maximum larval growth. The pupal stage lasts for about 3 to 4 days, during which the pupae will be hidden under the soil’s surface, and when the adult emerges, this cycle begins again.

The adult stage: Many generations of fungus gnats can be reproduced quickly because of the pest’s life cycle. Not only that, more than one set of the life cycle can occur at any given time. Therefore, not only do you need to get rid of the pest, but you also need to find a way to eradicate the larvae and sterilize the eggs.

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Fungus gnats: Common habitats

Fungus gnats take refuge in moist and highly nutritious soils. They take refuge in grounds that are a bit overly damp as this is considered perfect for their rapid growth. Planting varieties of crops that contain coconut coir or a large amount of peat moss will encourage them to move to a different location.

Not only that, but you should also avoid overwatering your plants, most especially during spring months or cooler winter. This is so because too much moisture in the soil will speed up their growth and cause roots to decay, making it a perfect food source.

Also, greenhouses are usually warmer during winter than the outside garden. This makes them the perfect abode for fungus gnats to stay over winter. It becomes worse when the greenhouse has richer soils regularly watered and well taken care of, making it the perfect place for fungus gnats.

Finally, it is easy for people who have houseplants to find fungus gnats trying to invade the houseplants during winter. I’m more than sure that this is something that you want to put an end to as soon as possible.

How do you know when fungus gnats have attacked your garden?

Fungus gnat problems are most likely to occur around the fall. The cooler the weather gets, the more desperate they get to search for warmer weather temperatures. This, therefore, makes the greenhouse of your house the primary target. Once fungus gnats manage to get to your soil and lay eggs, they can infest your plants very quickly.

Should in case you notice any unusual growth or damage in your plants, there’s a possibility that it could be the work of a fungus gnat. It would be best if you were on the lookout for yellow leaves that may otherwise appear normal or extremely slow growth.

Both are symptoms of the fungus gnat infestation in the soil.

If you pay close attention and notice any of these symptoms, or perhaps you see adult flies buzzing around your garden, this could also indicate that fungus gnats have infested your garden.

To eradicate it, you are advised to treat all the plants and not just the affected ones. This is so because it is quite difficult to tell if larvae are on plants that look okay. Therefore you should cover your bases and treat them all. Prevention is better than cure.

It is important to note that your plants may have recovered from fungus gnats infestation does not mean that it can never be infected again. Fungus gnat larvae can spread fungus spores that are dropped by adult gnats to your plant’s roots, thereby further causing several common plant diseases.

Therefore, to be on the safer side, you are advised to threaten all affected parts and those around the area in which the pest has infested one day or a maximum of 2 days after the pesticide has been applied. This is done to ensure that the plants do not contract diseases if they have contact with disease spores.

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It is more advisable to use a root drench rather than spraying the plant’s foliage, which could cause damage to the plant.

How to get rid of fungus gnats outside

If you can correctly carry out these preventive measures, you may never have to face the wrath of fungus gnats or their larvae.

(i) The use of organic fungus gnat control like hydrogen peroxide, neem oil, pyrethrin, and AzaMax.

Hydrogen peroxide: One of the top items I’ll recommend for controlling fungus gnats is hydrogen peroxide. Mix one-part peroxide with four parts water, and then pour it through the soil at the root zone until it begins to come out of the base of the pot. The peroxide kills fungus gnat larvae once it comes in contact with it.

Neem oil: Neem oil is yet another top item that can control pests like fungus gnats. Neem oil is beneficial when it comes to drenching soil to fight against fungus gnat larvae. All you need to do is dilute the oil with water (strictly follow the manufacturer’s guidelines on how to do that) and then directly drench the soil at the plant’s roots. You can as well spray the upper parts of the plant to keep the adult gnats from infesting.

Pryethryn: Pryethryn sprays are very effective against fungus gnats as well as their larvae. To use pyrethrin, lightly mist all plant surfaces and the top of the soil. A thin mist will be enough since we don’t want the plants dripping wet. If there happen to be fungus gnat larvae in the ground, spray them directly to moisten the soil’s top. Avoid watering afterward until the soil has dried to at least a 2″ depth.

AzaMax: AzaMax is safe for use in greenhouses, gardens, and indoors. All you need to do is follow the manufacturer’s guidelines on using it the same way you would use neem oil.

(ii) The use of environmental fungus gnat control

This is yet another effective way to get rid of fungus gnats. There’s a particular form of bacteria that helps to destroy fungus gnats. This bacteria is known as Bacillus thurigiensis var. israelensis.

Although it is not in most commercial BT sprays, it is available as part of a product called Microbe-Lift BMC Fertilizer. If you use this to fertilize, you will notice a decline in the fungus gnats infestation in your garden.

You can as well get this bacteria in your soil by simply spraying mosquito bits all over the surface of your ground and then watering them thoroughly.

This method can be applied both inside and outside.

They are essential for eradicating fungus gnats and not just mosquitoes.

As they break down, they tend to release Bacillus thurigiensis var. israelensis into your soil. The bacteria then helps to eradicate the fungus gnat larvae.

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Nematodes can also play a vital role in getting rid of fungus gnats and fungus gnat larvae. They are usually very tiny. Hence you might not be able to see them with your naked eyes, but they will help to eradicate the fungus gnat along with thousands of other soil-dwelling pests.

For indoor plants, you can add these nematodes to your soil with Nema-Globe Pot Poppers. For more extensive gardens, you can use Dr. Pye’s Scanmask.

It helps to disperse the nematodes evenly with water.

Finally, it is essential to know that you cannot use beneficial nematodes together with your hydrogen peroxide, as this will kill the nematodes. You are to wait for a couple of weeks after the infestation before adding the nematodes back to the soil.

(iii) Preventive method

It is essential that you thoroughly inspect plants before you purchase them. Do this by thoroughly checking the plant’s base to see if you will find signs of transparent whitish fungus gnat larvae. Avoid any plants with visible adult fungus gnats around them.

To be overly sure that the new plants have not been infested, I advise that you quarantine them for at least 2 to 3 weeks. Doing this will provide you with more than enough time to notice any new adults and establish control methods before they get the chance to spread.

You must avoid overwatering your plants. This is because fungus gnats tend to make moisturized soils their home. If you have already noticed that your plant has been infested, avoid watering it until the soil has dried up at least 2″ deep.

Make sure to use sticky traps to catch adult gnats. Since you are already aware that it only takes one gnat to produce thousands of eggs, I’m sure you’ll want to keep the adult gnats away from your plants.

You can use butterfly-shaped sticky stakes for indoor plants as they work well and are smaller in size, although they still look kind of big when they’re next to smaller plants. For Outdoor plants, you can use these double-sided sticky traps.

Finally, mulching also has a good effect against fungus gnat infestation, as the mulch keeps the adults away from the soil. This helps in preventing them from laying their eggs.

You are free to use a thick layer of a stone chip mulch over your soil, or perhaps you can go for a product such as GnatNix.

GnatNix is a product that is made from recycled glass. It prevents emerging adults from getting out of the soil. Not only that, but it also keeps adult fungus gnats from laying their eggs in the first place!

In all, the best possible solution for fungus gnats is prevention. Prevention is better than cure. But there are many other options you can take if they catch you unexpectedly.


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