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The first thing we have to talk about when we want to find ways to get rid of gnats is actually “What are gnats?”
You will probably say that everyone knows what gnats are. You would be wrong. Everyone thinks they know what gnats are, but the scientific world, and especially entomologists (people who study insects) have varying descriptions of what constitutes a gnat.
The word ’gnat’, when applied to insects is actually a very loose descriptive category and can be any member of many species of extremely small flying insect. The actual definition varies depending on who you speak to. The following describes just a few of the definitions and who defines them:
University of Kentucky. Entomologists from this establishment describe gnats to be “non-biting flies”.
University of Nebraska. The Institute of Agriculture and Natural Resources, based in this university, defines any non-biting flies as well as fungus gnats as ‘gnats’.
University of Georgia. This university describes a black, biting type of gnat called a buffalo gnat.
North Carolina State University. This university says that the bloodsucking biting midge belongs to the gnat species. Biting midges are known by various names; Biting gnats, sand flies, punkies and ‘no-see-ums’.
Smithsonian Institute. The definition from here is that gnats are non-biting flies attracted to the moisture secreted by eyes. They further describe them as “no bigger than a few grains of salt”.
It seems to me that the available definitions are extremely vague and can describe any tiny fly that either doesn’t bite or does bite and may or may not fly in swarms of a few or many insects!
We now know what constitutes a gnat (well, approximately anyway).
Next, we want to know a bit about their lifecycle. Like most, if not all, flying insects their first stage of life is as an egg, which subsequently turns into a larva (a type of tiny worm or maggot). The habits of the larvae are as varied as the adult insects.
Some are aquatic and some are not.
Some are vegetarian and some are carnivorous.
Gnats are attracted to moisture and any organic material. Some species prefer decomposing food debris, some prefer manure, and some prefer soil. They are to be found in garbage disposals, on over-ripe fruit, around farm livestock, gardens, garbage tips and ponds. You often see hazy clouds of many tiny flies hovering over one of their favourite locations. If you have any fruit trees in your garden you will see them hovering and landing on over-ripe fruit when harvest time has arrived, ready to lay their eggs.
The lifecycle of each type of gnat depends on the type, but in general, the cycle follows the same as any other insect.
The eggs are extremely small and cannot be seen except with the aid of a microscope or good hand lens.
The following list discusses the habits of common, female gnats.
Fruit Flies. Female fruit flies lay eggs either under the skin or on the surface of ripe and decomposing fruit and vegetables. They also use places where moist organic detritus accumulates. There is a duration of about thirty hours from when the egg is laid until the lava starts to develop. Apart from fruit and vegetables, typical egg laying sites include:
Fungus gnats. These are found in areas of high humidity. Females lay their eggs in soil or damp decaying plant matter, a ready-made food source for their larvae. The eggs subsequently hatch into larvae. The larvae of some species feed on the fungus found in over-watered soil. Other larvae infest plant roots and obtain their nutrients from them. When feeding on root systems, the larvae cause stunted growth and bad health in plants which attracts more larvae to the site. The larvae carry plant parasites and diseases which attack the already weakened plant.
Biting midges, also known as punkies, no-see-ums, sand gnats and flying teeth, are normally grey in colour but turn red after a feed. They like to feed in the early morning and in the evening, but may be found on days without wind and with cloud cover. If you have weather like this it is best to stay indoors and avoid the areas frequented by these midges. Because they fly in swarms it is generally the case that a person will have many bites rather than just one or two.
Sand Flies are a golden, brown or grey colour and have long thin legs. Only the females have mouthparts able to suck blood. They do not like windy conditions and bites are much less common in this weather. Sand fly bites produce irritation, redness and swelling and can transmit sand fly fever as well as other viral and bacterial diseases. Thankfully these diseases are not usually found in the U.S. or other temperate zones.
Black flies, also known as black gnats, buffalo gnats or turkey flies, are also biters. Once again it is the females that feed on blood while the males feed on nectar. The bites from these gnats are initially painless but they bleed copiously from bite sites. Typical symptoms include itching, skin lesions, fever and blood spots where the females bite. The Black fly bites warm blooded animal such as humans, dogs, cats, livestock in general, wild mammals and birds. Although there are no records of diseases being transmitted to humans in the U.S., River Blindness is transmitted in tropical areas of the world.
Fungus gnats are not biters. They deposit their eggs around over-watered plants. The hatched larvae then feed on the root system. They affect many common useful plants that will be listed later.
Like all insects, they come in search of a place to lay their eggs and which also supplies food for themselves and their larvae. Usually gnats stay outdoors where there are many dark and damp corners and lots of decaying vegetable matter, but if you have any damp or unsanitary conditions in the home, or any food lying around, you run the risk of attracting them indoors as well.
Once they come inside they will take advantage of the food sources and favourable living conditions and start to reproduce. Before you know it you will have a thriving colony of either vegetarian, bloodsucking or carnivorous (or all three) larvae and adult flies. If you live near the coast you will have a problem with flies attracted by the abundant rotting marine debris found at low tide. If you have a pond or a lake in or near to your property, the gnats will be attracted by the stagnant water, in which some species breed.
Gnats do not do any harm to your house and are more of a nuisance than anything else. They can however spread parasites and bacteria from their favourite unsanitary outside haunt. Fruit flies are attracted to the smell and moisture of ripening fruit and lay their eggs in the fruit flesh. Not only do the larvae feed on fruit and vegetables but the adults also contaminate the area as well.
Fungus gnats can harm indoor house plants and bloodsucking gnats may cause irritation and carry parasites and infection to humans, livestock and pets.
It is usually the females of the biting species that feed on blood and many successful health programs have been designed and established around the world, to try to eradicate gnats and the diseases they carry.
Biting gnats can be distinguished by having two large and prominent wings and have extremely small bodies. Female biting gnats feed on blood while the males feed on plant nectar and do not bite.
Gnat bites can occur on any exposed skin and will most likely occur on the:
Gnat bite symptoms are generally itchiness, redness and swelling at the location of the bite. If the bites are scratched too much, they can become an open sore which may result in a bacterial infection gaining hold. Sometimes, especially in tropical countries, the bite can transfer infectious diseases from person to person. In some parts of the U.S. bluetongue virus is transmitted among sheep and cattle by biting gnats.
Fungus gnats are not biters but they are still a nuisance as their larvae prefer to feed on the roots of many plants especially these common and useful plants:
The Hessian fly larva (also a gnat) causes a swelling growth, known as a gall similar to a wart in humans, to be produced on the host plant in the roots, stems and leaves.
Some types of fungus gnats cause problems with mushrooms and indoor potted plants.
Some gnats actually pollinate some plants. There is a species of South American orchid which has such a tiny flower that only gnats can enter to pollinate.
First of all, how do you know you have a gnat problem? Simple, you will see them flying in a swarm, sometimes above water or soil, but often just flying in your garden as a swarm over nothing in particular.
The best way to get rid of gnats is to stop them from feeding and breeding. You can do this by eliminating the unclean sites in and around your home. Obviously you will have no control over the environment in which you live, such as a nearby farm, garbage tip, lake or beach but you can do a lot to clean up your own property.
Ponds. If you have a garden pond, you will always have gnats, so it is better to site this as far away from the house as possible. As gnats prefer stagnant water, consider connecting an electric pump to try to get the water moving.
Compost heaps. Likewise compost heaps should be built at the other end of the l, not just because of the potential smell problems but also because you want to keep the gnats as far away from the house as possible. If you can use a container with a lid for your compost, rather than an open mound, you will reduce the number of gnats flying freely around.
Saturated soil. Fungus gnats love wet soil. If you allow the soil around the plants to dry out completely, you will kill the larvae already in the ground and stop any new adults from emerging. Any existing adults can be removed from around the plants and from window sills using a household, tube style vacuum cleaner. Fungus gnats, sometimes called black gnats (although not all dark coloured gnats are fungus gnats), breed in fungus. The commonest source of fungus indoors is in overwatered house plants.
In small numbers fungus gnats do not harm houseplants but large numbers can cause problems with the root systems. They are not directly harmful to humans but tend to be a nuisance around the face and land in food and drinks.
Fruit and vegetables. Trying to remove their food supplies will help with reducing most types of gnat. Storing fruit and vegetables in the refrigerator and not in the open air, will not only keep them away from the gnats but will also keep the food fresher for longer. As soon as fruit and vegetables start to become over-ripe, dispose of them to your composting container or garbage bin.
Dirty dishes. Once again we say that all species of gnats are attracted to decomposing food products. One of the best sources of gnat food is to be found on dirty dishes. Ensure you wash all dirty dishes and cutlery as soon as the meal is over or load them into the dishwasher. If using a dishwasher, run the rinse cycle after every meal and run a complete wash cycle when full or at least once a day.
Kitchen waste bins. Not all households have mechanised garbage disposal systems, some just have a pedal bin in the kitchen for food waste. Make sure this is emptied regularly and the empty bin washed and disinfected.
Mops & brooms. If cleaning utensils such as mops and brooms are not cleaned after use, they will collect decaying organic matter which is very attractive to the gnat and their larvae. Always clean these tools thoroughly after use with bleach or disinfectant.
Nooks and crannies. We all try to keep our kitchens hygienic but sometimes it is just not possible to clean everywhere. Because gnats and their larvae are so tiny they are able to crawl into the smallest hole or gap where decomposing organic matter has built up. The corners between walls and floors are very difficult to clean as are the grout lines in kitchen tiles. Both these places will contain decomposing food and will be a prime attraction for the gnat.
Drains. Often we have a drain or drain gulley near the front or rear doors of our house. The purpose of these is to collect rainwater and divert away from the house. Unfortunately they also collect leaves and other organic detritus that has been washed in with the rain water. This organic matter becomes clogged and starts to decompose within the gulley. Make sure you regularly clean your outside drains, not only by physically removing organic material but also by rinsing through with diluted household bleach or disinfectant.
Damp areas in the home. Gnats are attracted to damp and humid areas. Look around the house especially in the bathroom or kitchen and see if you can identify any damp areas. If you find some then try to find the cause and fix them.
Pot soil. Indoor plants are kept in pots and often deplete the soil of nutrients. The indoor gnats are almost certainly coming from there. Change the soil for top quality without weeds or pests. Not only will you be getting rid of gnat eggs and larvae, you will also be giving the plants a boost of fresh food too.
A messy garden. Regularly remove rotting piles of leaves and other waste material from your garden. If you use mulch to cover the soil, try to choose one that does not decompose. If you have no option but to use decomposing mulch then turn your mulch layer occasionally to allow the bottom, sodden layers time to dry out.
Soil drainage. As gnats are attracted to over-watered soil, it would be a good idea to improve the drainage throughout the garden. Dig coarse sand or gravel into the soil to help damp and soggy areas drain properly.
Watering time. Water your garden plants in the morning to avoid fungal growth overnight.
Standing water. Get rid of any standing water in drains, gutters or low spots.
Water features. Birdbaths and water features need to be kept clean from fungal and mossy growths.
The most common non-biting ‘gnats’ are generally not attracted to light, but a description of their behaviour may be useful for an understanding of the differences between them:
Fruit flies. Not attracted to light.
Phorid flies. Dislike the light.
Moth fly. Males are attracted to light but not the females. Usually found at windows and doors.
Fungus gnat. Both male and female are strongly attracted to light. Indoors fungus gnats often hang around doors, windows, televisions and interior lights. Outdoors they are attracted to porch lights and street lighting. This fondness for light can be used to augment other methods of control and gnat control products can be found which incorporates gnat pheromone to help attract the insects.
Although lights and light traps are useful in ridding your house of the individual adults of some species, something more is needed when dealing with whole swarms.
As with every problem in the house and garden, it is no good treating the symptoms if you don’t know the cause. This applies to getting rid of gnats and fruit flies as well. As long as the insects are attracted by something, you will be for ever treating the symptoms.
Before using these DIY methods to get rid of the insects, you need to know specifically where they are coming from and congregating. For example if you are treating drain flies then put the remedy near to the drain. Always remember that these home remedies will not always work. Your success will depend a lot on the severity of the infestation and how complex the situation is. These remedies are still worth trying before phoning for a pest control contractor. You never know you may have just saved yourself quite a few dollars.
Many home improvement stores and hardware stores as well as online retailers stock gnat traps. Only buy one manufactured by a reputable supplier and always follow the instructions supplied. Some traps contain toxic chemicals and it is vitally important to buy one from a manufacturer you can trust. Many are designed solely for use against fungus gnats (although they may be successful against other types) and work by trapping them as soon as they emerge from the soil.
You can buy other traps which attract flying insects using ultraviolet light and then when they come close to the source, they are either caught on a sticky surface or are electrocuted. Although these work well with gnats and other flying nuisance insects, they can also kill many flying insects commonly regarded as beneficial, such as those who hunt other damaging insects and those who are pollinators. The traps are very good at ridding your house of individual adult gnats but if you have an infestation of larvae or many adults then it is best to consult a pest control expert for advice.
This is a common trap used by many people. The gnats are attracted to the vinegar and sugar and fall in the water. The detergent has removed any surface tension from the water so the insects cannot stay above the surface. They submerge and drown. It might be worth preparing a few containers with the mix and distributing them around the house. By counting the number of flies in each bowl, it will give you an idea of where they are coming from. The recipe is as follows:
This may or may not be successful, depending on where the flies are breeding. If the gnats are breeding deep within the drainage system then this method will not necessarily work. Don’t forget to dilute the bleach first and wear eye, nose and mouth protection along with protective gloves. Do not inhale the fumes and try to use the bleach where there is plenty of ventilation.
Use the same method as if you were using bleach. It is very important not to mix ammonia with bleach as the resulting mixture gives off very aggressive toxic fumes.
Pour a couple of tablespoons of baking soda into your kitchen sink drain. Add a cup of white vinegar and wait for the few hours after the mixture has finished fizzing. Then rinse the drain with running water.
Close off the entrance to your sink drain by inserting the drain stopper into the drain hole, when it is not in use.
This is similar to the vinegar method. The idea is to attract the gnats and then drown them. Gnats do not mind whether the wine is an expensive vintage or some cheap stuff. Mix with sugar and detergent and place in a container. Cover the container with kitchen plastic wrap (cling film or similar) and punch a few holes through with a pencil. Set up the container where the gnats can get to it and leave it overnight.
Gnat swarms do not like smoke. You can buy many types of fogging products from hardware stores as well as camping supply stores. If you can’t manage to find any then try lighting a barbeque with some green sticks or light a garden bonfire. The only problem is that you will have to then endure the smoke.
This is a similar method to the red wine trick. Put a piece of over-ripe or rotten fruit into a bowl and cover with plastic wrap. Punch a few small holes through the wrap and then sit back and watch the gnats crawl into the trap.
Vanilla oil, pine oil, lavender oil, eucalyptus oil and citronella are very effective gnat repellents. The advantage of these is that they can be applied harmlessly to the skin and carried around with you. We will talk more about plants repelling gnats later on.
If you can keep a fan on your porch or patio to keep the air moving, you will effectively discourage gnats from being near you and will discourage hovering gnat swarms.
Any insecticide spray designed for flying insects will prove effective against gnats. They are, however, only a reaction to the symptom. Sprays will not prevent gnat swarms from returning.
Keep all doors and windows closed as much as possible. If you must keep them open then use a tight mesh fly screen to keep flying insect outside.
You can make a home-made gnat spray by mixing a couple of squirts of household dishwashing detergent in water and spraying the mix onto your house plants. Use the lemon scented variety and liberally soak the leaves, stem and soil with the spray. Leave for a couple of hours and spray with clean water to rinse. This is also a good way to get rid of greenfly on your plants.
A good way to be rid of gnats is by the use of natural parasites of their larvae as they do not respond well to insecticides. These parasites can be bought from some gardening websites. The most common gnat larvae parasites are:
Bacillus Thuringiensis v israelensis (known as BTi). This bacterium is sometimes known as Gnatrol. It kills gnat larvae. It is most efficiently used if you can identify and apply to the specific place where the gnat larvae are hatching and feeding.
Nematodes. Beneficial nematodes and predatory insects, once they are established in your garden, can provide long term control over gnat larvae.
Not only are there specific gnat larvae predators, there are also common plants that will help prevent gnats and other harmful pests from invading your garden and house.
Marigolds. Plant marigolds in pots and place near doors, windows and on your patio or porch. They are also good for preventing insects from preying on your tomato plants. You can either grow them from seed or buy a ready grown plant from a nursery.
Citronella. This plant has such a strong smell that it completely masks other gnat and mosquito attractants. Plant them in pots or in the garden. They can grow to up to five or six feet high and do best in full sun and with good draining soil.
Catnip. This plant is related to mint and is very easy to grow. Once again this also repels mosquitoes as well as other flying insects but will probably attract every cat in the neighbourhood.
Lavender. The scent from this plant aids relaxation and promotes a good night’s sleep. The scent also repels gnats, mosquitoes, moths and other species of fly, so plant in pots and keep by the doors, windows, on the patio and other entertainment places. As well as the fresh plant you can harvest the flowers and either make lavender bags or hang bunches of dried lavender indoors to repel the insects. Lavender will also attract pollinating insects such as butterflies and bees.
Basil. As well as being a favourite herb in Italian cooking, basil will keep gnats and mosquitoes away. You don’t have to crush the leaves either. Just plant in pots and move to the required location. For best results use, lemon basil and cinnamon basil.
Lemon Balm. Lemon balm repels mosquitoes and biting gnats but attracts pollinators like bees and butterflies. It is very fast growing and will re-seed itself.
You can also buy a registered insect skin application or clothing repellent. Cover as much skin as possible and avoid areas where gnats are feeding and swarming.
As stated earlier, if you can get rid of a gnat’s food supply or breeding ground without any outside help then the job will be done and you shouldn’t have many more infestations. If you have tried all the DIY tips mentioned so far in this article and you still have a problem with gnats and other tiny flies, the cause of the problem is probably beyond your control. You may live near the coast, near a farm with livestock, near a pond or near a lake. If this is the case then your only option will be to call a contractor who will come and first of all make sure all the possible causes have been eliminated and secondly he or she will treat your home and garden with chemicals designed especially for your application. Alternatively you can always relocate to an area without gnat breeding grounds!
Bearing in mind that gnats fly and are attracted to damp, rotting vegetation, drains and garbage, any contractor will never be able to permanently remove the flies from your property in one visit. We all have gardens which contain soil, we all produce garbage and we all have drains that catch rainwater. The best that you can expect from any pest control operative is to remove your present infestation until the next time.
Pest control contractors will provide two different services; One–time eradication and contract eradication. With gnats I would advise you to have both. You have a really bad gnat infestation and need them dealt with immediately. You also would like the contractor to return regularly during the breeding season and deal with them before they get to nuisance stage.
The cost of each service depends on factors such as frequency of visit, size of the home and property, and which type of gnat you want to be rid of. Remember too that the price will vary depending on where in the country you live, the time of year, the level of accessibility of the gnat breeding grounds and type of common flies and gnats found in your area.
The cost of a one-time visit will be higher than subsequent visits because of the extra work involved;
After the initial visit, it is then wise to enter into a contract with the operative for regular visits to keep the problem at bay. The agreement will stipulate when the visits will take place and usually includes free of charge treatment if you have an infestation between scheduled visits.
The figures below are for gnat and other fly infestations for a ‘one-time’ visit as well as for a contract of initial visit followed by either monthly, bi monthly or quarterly visits. The figures are for a typical house of approximately 1,500 sq. ft floor area. Some pest controllers charge an extra $25 per 1000 sq. ft over the normal 1,500 sq. ft.
|One –time visit.||$200 + (small)||$400 + (medium)||$600 + (large)|
|Contract, initial visit.||$200 to $250|
|Contract, periodic visit||$50 per month||$60 per bi-monthly||$300 per quarter|
The quarterly cost is so much larger than expected because there is likely to be a large build-up of pests during the interval between visits.
The figures will also vary depending on the size of the infestation and the steps needed to eradicate the pests.
Remember too that if you have an infestation of gnats because of an over-ripe drainage system, you may also have other pests such as rats. It is worthwhile asking the pest control contractor to check for the presence of other pests, but try to get a second opinion as well to stop any dis-reputable contractors from ‘suddenly finding all manner of pests which need treatment’.
Infestations of gnats will need treatment just like any other infestation of flies or other flying insects. Luckily there are many simple and effective methods of treating the infestation as well as many ways of preventing the infestation in the first place. All these methods we have talked about today and you can do all of them yourself. It is when the infestation is particularly invasive or large and when the insects have really gained a foothold into your property that these methods fail. It is then that you should call in a contractor.
A normal pest control operative is the person to contact and he or she will come armed with all the most effective tools and elimination methods. They will have the training to eradicate your specific pest, in this case the gnat, but also they will be able to specifically identify the species of gnat and note the presence of any other pest. Some pests may like similar breeding and feeding conditions as the gnat and these will be readily identified.
The main advantages of doing the job yourself are:
Convenience. You can use the simple home-made remedies whenever the gnats are noticed.
Non-toxic. The majority of DIY methods are simple to use and harmless to humans and animals if used as instructed. Those substances which are toxic such as bleach and ammonia are present in most households and people are familiar with their use.
Cost. Doing the job yourself will cost the price of the materials used and your time.
The advantages of hiring a pest control technician to do the job include:
Speciality. The pest control contractor has the required skills and training to handle the pests and chemicals needed to do the job. Their specialised knowledge allows them to diagnose your complete problem and propose an effective solution. They can tell if you have any other pests besides the obvious ones.
Training. They are trained in the use of speciality chemicals needed to exterminate the pests. They have the training necessary to know the best time and place to lay the bait.
Poison. Professional pest control contractors are licensed to use poisons in the forms of trap bait, spray and fumigation.
Regular inspections. No matter how diligent we are, there is always something else which wants to use up our spare time and re-organise our priorities. If you have arranged with a contractor to come at regular intervals, then they will come and do the job.
Infestations. If your locality has an infestation of any type of pest, you may find that a pest control operative cannot come to do your job immediately. If you already have a contract with the local pest exterminator, you may find that you get preferential treatment.
Licensed. In many states, pest control contractors must be licensed. Find out if this applies in your area. The contractor’s license may be to work with some pesticides or all pesticides, ask to see the license before hiring.
Insurance. A licensed contractor will have insurance to cover the company and employees from damage caused to property or people.
Work plan. A licensed contractor will design and develop a specific plan to identify and control the specific pests present on your property. The plan will also state the best methods to control the infestation and the ways to reduce the chance s of infestation in the future.
Green and humane. The qualified exterminator will have access to more diverse methods of removing the pests than you will.
Diatomaceous earth is a compound made from the remains of certain algae. The substance kills insects by interfering with their waxy skin.
Biological control agents such as parasites, bacteria and predators such as nematodes and mites can be released into the environment to eliminate the gnat or their larvae.
Advice on other methods such as window and door screens, weather-strips and other methods of blocking holes where insects can gain entrance. The contractor will educate the customer on ways to prevent the pests from entering the home in the first place.
Advice on habitat modification is a good way to remove the feeding and breeding sites needed by the pest to reproduce. Regular cleaning in the house and removal of debris from the garden will help prevent the pest from gaining a foothold.
Today we have looked at what people generally call a gnat and found that they can in fact be many different types of tiny fly. Some of the species bite humans and animals and suck their blood, some species prey on other insects and some feed entirely on plants. We have found that they all like to lay eggs in damp places with plenty of rotting organic matter on which their larvae can feed.
There are many methods to attract and trap gnats, usually by means of their attraction to sugar and rotting vegetation. Once you have them trapped, it is an easy job to drown them in soapy water. There are also various plants that emit a strong odour, which will repel gnats, mosquitoes, houseflies and certain other flying insects. We have talked about the ways to disrupt a gnat’s favourite habitat and by ensuring the house is clean and free from damp.
If all these DIY methods fail or your infestation is too great for you to handle yourself, we talked about calling in a pest control specialist, their costs and the advantages of using one.
Finally we have learned a lot about gnats, their larvae and their lifestyle and how to prevent them from coming into the house and being a nuisance.
I hope you have fun in your garden this summer and don’t suffer too much from the swarming clouds of hovering gnats.