Fungus Gnats

Fungus Gnats

One of the most common and annoying pests that a gardener may experience is the fungus gnat also known as dark winged fungus gnats (Sciaridae). Fungus gnats are a resilient insect capable of surviving harsh elements such as cold temperatures due to their antifreeze protein. These little insects can be annoying in many ways. They are quite prolific and therefore their numbers can spread rapidly. Although fungus gnats do not bite, they can be annoying because they are attracted to Co2 which explains why they fly in people’s faces. These tiny creatures can also inflict tremendous amounts of damage to a growers plants. The adults are known to carry many diseases that attack plants including Phytophthora cinnamomi which causes root rot. The larva provide a threat to plants because of their ability to eat beneficial fungi to the plant as well as the root hairs on the plant itself.


Fungus Gnat Remedies/Control

Because of the prolific nature of the fungus gnat many horticulturists and growers reside themselves to living with them. However this is a bad idea as these pests should be dealt with for the sake of increasing production and yields from your crops. Along with that fungus gnats can cause exceptional damage to a young seedling causing damping off.  There are many ways of dealing with fungus gnats however many remedies you come across may work to a degree, but may not entirely rid your crops of them. Either that or they may contaminate your crops rendering them harmful for human consumption. Some remedies may work but keep in mind anything you put in your soil can affect the plants Ph which will cause it produce lower outcomes.   


Sticky Traps: One of the best ways to control the numbers of these insects are with yellow sticky traps. Fungus gnats are attracted to the yellow color and will fly, leap, or run on the yellow sticky traps. The best method is to stick the traps straight up to catch flyers and to place some flat down across the pot to catch leaping and running gnats. These are relatively cheap for the amount you can get however keep in mind that these traps will not entirely rid you of these bugs and will add up in money over time. These traps are best used to control outbreaks with large numbers or to control them from getting to that point.


Sand/Pebbles: Sand and or pebbles have been shown to help deter fungus gnats from landing and laying their eggs in the plant’s soil. Fungus gnats typically lay their eggs in the soil about ¼ to ½ of an inch deep. Sand drains quickly which can confuse the adult gnats into thinking the soil is dry thus seeming unappealing to the insect. Pebbles can work because they are simply too heavy for the weak insect to move therefor they cannot get under it to lay eggs in the soil. However keep in mind these insects are very prolific and adaptive. Fungus gnats can still get into the soil by climbing into the drain holes in your flower pots. Preventive measures should be used to attempt to keep them from entering in at the draining hole location.


Soil drying: One way of controlling even sometimes effectively exterminating gnats is simply by letting your soil dry. Fungus gnats are are attracted to wet, typically over watered plants where fungus is thriving. Letting the soil dry will kill the fungus that the gnats need in order to survive. Along with that adult fungus gnats cannot reproduce in dry soil and this will thin out their numbers. Be sure to avoid over watering plants as fungus gnats are attracted to wet moist areas.


Cinnamomum Verum: Cinnamon can prove to be useful in your efforts of removing fungus gnats. Cinnamon wil destroy the fungus that the larvae consume thus severely reducing numbers and making it difficult for them to breed. Keep in mind Cinnamon will kill beneficial fungus for the plant as well which could affect aspects of growing.


Mosquito bits: Mosquito bits are quite effective in neutralizing mosquitos as well as fungus gnats. Mosquito bits contain an ingredient called BTI (Bacillus thuringiensis subspecies israelensis) which is a larvicide. This ingredient is a natural bacterium that is highly lethal to fungus gnats. BTI is recommended by GoGrow as well as many other  growers when it comes to dealing with fungus gnats.


Predatory Nematodes:  Used to control many pest that can be found in soil predatory nematodes (Steinernema feltiae) are effective when it comes to fungus gnat removal. These parasitic nematodes actively seek out fungus gnat larvae and enters through the gnats natural openings. The nematode then releases a bacterium that rapidly kills the insect. Many growers have found success with using these parasites.


Peroxide: Using a 3% hydrogen peroxide mix can rid a plant of fungus gnats and other pests. Hydrogen peroxide will kill the larvae of the gnat on contact. However be sure to not make the solution too strong as it could be very hard on a plant. Using too much peroxide will not only kill gnats and other pests, but can be harmful to the plant as well. A 3% solution will be enough to kill gnats, and plants typically react well to that dosage. It is recommend that you wait until your soil is dry before applying for best results. Be sure to monitor the plant the next few days and use other preventive measures if needed to help ensure the eradication of the gnats.


Pesticides/Insecticides: Not recommended if you are planning on consuming the plant in anyway as many pesticides/insecticides can prove to be harmful for human consumption. However if you are not planning on consuming the plant and are looking for a guaranteed solution to extermination fungus gnats pesticides/insecticides will do the job effectively and quickly.


Pyrethrin: A somewhat relatively safe and organic way of killing gnats and still allowing consumption is the use of pyrethrin. This will kill adult fungus gnats on contact however pyrethrin is not as effective on larvae and can be hazardous if a lot is inhaled. It is not the most recommended method as it can be absorbed by plants as well and repetitive use and consumption could potentially be harmful to a degree. Although relatively safe and typically okay for consumption it is not recommended for repetitive use and consumption.


Preventive Measures

Fungus gnats are annoying pests that can prove to be quite the headache for growers. They can come from many places such as plants bought from stores, soil from stores and from a cracked window or an opening. There are preventive measure an indoor grower can use to help make sure fungus gnats are not picked up. First off when purchasing soil from a store it would be wise to take precautions as this is one of the top ways gnats are acquired. One way to neutralize these insects is to sterilize your soil or bake it in an oven to kill any gnats beforehand. Purchasing plants or clones from places can also be another way to get fungus gnats. It is wise to inspect the plant your are getting and it would be recommend to try to pick the one with the driest soil. Remember fungus gnats are attracted to moist areas. Over watered plants from stores have the potential to have these pest in them. Along with that be sure to not over water plants as that can attract gnats from various areas.
By Jory Rayton