How to get rid of Wood Wasps

The terms “wood wasp” and “horntail” are actually used to describe various species of insects that belong to the family Siricidae of the order Hymenoptera and that inhabit wood structures. They are called a wasp because of their resemblance to a wasp, but actually don’t sting. Most of the times, though, people will use them to refer to the greatest cause of concern, which are the large wasps that are normally attracted to the dead or dying conifer trees.
The main problem with wood wasps is that wood, infested with eggs and larvae, can be processed into infested lumber, which can then lead to adult wasps emerging in recently completed buildings. This can happen easily, seeing as wood wasp larvae often go unnoticed. Due to the same reason, wood wasps can also be brought inside homes through firewood.

Between a year and three years after infested lumber was used in construction, wood wasps will emerge, and chew a 6-7 mm hole through anything covering it, including drywall, linoleum, carpeting, non-ceramic floor tiles or hardwood. Once they emerge from the wood, no treatment is needed since they don’t reinfest structures. Even if male and female wood wasps had the opportunity to mate in the building, the females would not be stimulated to lay eggs in dry, finished lumber, as they will search for untreated one.
Wood wasps are also a problem outdoors, seeing as the tunnelling of larvae can weaken wood, making it prone to further disease or damage. Adults also help with wood decomposition by introducing yeasts, bacteria, and wood-rotting fungi. If the damage caused by them is severe, replacement of the affected wood will be needed, for safety purposes.

Signs of infestation

The most obvious signs of infestation are the galleries that larvae dig beneath the bark, together with the fine dust this process leaves behind. Wood wasps’ larvae are recognisable by the spine they have on the end of their bodies, and their colour is white. The adults also leave round, clean-cut holes when they emerge from the wood, so the sight of such holes is also a sign of infestation.
Since woodpeckers and other types of birds can “hear” the larvae as they work inside infested wood, it is not uncommon to see such birds start pecking away at the wood or any part of a structure which is harbouring horntails larvae. If you see such behaviour from the birds found in the trees or lumber in your yard, you can take it as a sign of wood wasps presence. They can be found anywhere, from siding, overhangs, soffits, decks, to door frames, window frames, attics, basements, crawl spaces or porches.

Seeing as wood wasps only target unhealthy trees, you can try to prevent an infestation by:

• maintaining trees healthy;
• preventing attacks on recently dead or cut trees.
• removing, treating and processing wood as quickly as possible.

Otherwise, store logs in a safe area, and if you are using firewood, you should store it outside the house, and only bring it inside when you plan to use it.

Getting rid of Wood Wasps

The number of wasps per individual nest is relatively small, as wood wasps don’t normally live in a colony. This is good, because if timber infested with wood wasps is to be used in your home, even after they emerge from the wood, the wasps will be quite small in number.

Although they are extremely annoying due to the low buzzing noise they make when flying, these insects are not harmful to humans or to the wooden structures they have infested. The little damage they manage to do is only cosmetic (especially unsightly in wood that has been painted or stained), and the actual number of wood wasps that emerge in any building as a result of infested lumber is small. Wood wasps are also unable to bite or sting; the females’ ovipositors are used strictly to lay eggs. Wood wasps are otherwise only attracted to untreated wood, not the one used in buildings or to furniture; as such, they will not re-infest the structures, as females are not being stimulated to lay eggs in dry, processed lumber. They prefer weakened, dying, and recently cut trees, and can also attack freshly cut timber before it is dried, or fire-damaged trees. Due to this, the best methods of control management are to prevent attacks on dead or fallen trees. Removing and processing wood quickly is the best way to prevent damage. Proper handling methods of wood that might be attacked by wasps includes milling or debarking susceptible logs prior to the attack period and storing them in an area safe from attack.

They also do not build nests in the ground or attached to higher terraces, so dealing with removing a nest will not be the case here. They will only use decaying, weakened tree trunks or timber, to inject their eggs directly into the wood, which will then be eaten from the inside, once the larvae hatch. Considering this, the best course of action is to wait for them to complete their life cycle and then to repair the cosmetic damage they have inflicted upon the wood.
Kiln drying or vacuum fumigation of lumber are the only effective ways to kill wood wasp larvae, but this sort of treatment is costly, and timber is usually not considered valuable enough to be treated. Finding a wood wasp nest can also be very challenging.

Spraying concentrated insecticides for Wood Wasps control:

Concentrated insecticides are the most common used products in fighting insect infestations. They provide the safety that any insect coming into contact with the treated surfaces dies shortly.

Sprayers used for Wood Wasps control:

The equipment needed for a professional Pest Control Operator depends on the type of pest the treatment is made against, and if the treated surface is indoors or outdoors. Sprayers help in applying products meant to reach difficult places, as well as guaranteeing an economic control of the treatment application.

You can use products that will be able to penetrate the infested wood, such as borate based ones. These act as stomach poison to any wood eating insects, affecting wood borers and wood lice as well. As borate base products are normally odourless, you can easily apply them with the help of a low-pressure pump, spraying the wood you have, both inside and outside your home. Treating all the exposed wood will serve as a method of long term control, as it will protect the deck, door frame or window sill from fungi, molds and mildews as well.

Fogging concentrated insecticides for Wood Wasps control:

Fogging insecticides involve using a fine spray (aerosol) which is directed by a blower. This makes the application of the treatment easier, as it helps dispersing the product in places hard to reach.

Foggers for Wood Wasps control:

Cold foggers use cold spraying methods, which in most cases is using a high air pressure to spray out the fogging liquid into tiny particles. They are also known as ULV fogger, and as opposed to thermal foggers, they do not use heat to vaporize the fogging liquid.

You can also choose to apply treatments directly to the exit holes found in the wood. Drione dust, which is based on pyrethrin, can be used. It is a light dust that can easily penetrate the holes made by the wasps, and it will affect the pests by dehydrating them. This will ensure that no wasps will enter that hole again, giving you the opportunity to find a way of sealing them with wood fillers or silicone sealant. It will also kill any eggs or larvae found in the wood galleries, ensuring they will not make their way out through a different tunnel.
To apply such powdered solutions, you can use hand dusters, but if you choose to use sprays, you can use aerosol insecticides. These will have a quick and powerful blast, making sure to fill the gallery created, and kill anything in its way. Even if eggs manage to hatch, the larvae will then come in contact with a lethal dose of insecticide, as it will be absorbed throughout the wood.

Fumer insecticides for Wood Wasps control:

Fumer insecticides are mostly used together with a contact based one. While the fumer irritates the pests and makes them come out of hiding, they come in contact with the sprayed solution, which then eliminates them.

Cypermethrin based products can also be used, as they act as insecticides and repellents for a number of insects. They are considered a broad-spectrum insecticide, killing beneficial insects as well as the targeted insects. Exposure to sunlight, water and oxygen will accelerate their decomposition, so reapplying it from time to time might be needed.

As an alternative method of removal for the wood wasps you see flying, you can use a hand-held zapper, or another type of electrical zappers placed on your deck. However, they will not solve the problem of your infested wood, as will only remove the flying adults that might escape the holes in the wood.

Once the horntails begin emerging, no treatments are needed as this process will soon be over. Pieces of wood that have been badly infested may require replacement or cosmetic repairs (to exit holes), but the wasps cannot reinfest the seasoned wood in homes and buildings. However, it is best to try and prevent such infestations from taking place. Make sure you only use fry, treated wood, and when dealing with firewood, make sure not to store it inside your house.