Last Updated on 2 May 2021
You approach your roof timber, floorboard or beautiful piece of solid wood furniture. You look closely, and there it is. Tiny little holes bored into the surface, the dreaded woodworm signs! You brace yourself, and turn to the internet and type: ‘How to treat woodworm’.
Thankfully then this guide pops up and you relax, because I’m here to tell you exactly what to do to get woodworm-free.
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What is Woodworm?
The term ‘Woodworm’ actually refers to the larvae of wood-boring beetles.
In the UK, there are several different species of woodworm, but as the name suggests, the most common offender is the Common Furniture beetle.
When it comes to the level of damage inflicted on your poor home, the Longhorn Beetle is the worst offender.
The larvae of wood-boring beetles usually have a white creamy colour with curved bodies. It’s very unlikely you’ll ever see the larvae because they stay hidden within the timber, feeding on the wood until they’re full-grown adults.
Adult beetles have various appearances, depending on their species. For example, the Common Furniture beetle is a brown winged beetle, normally about 3-4 mm in length.
The four key stages of the woodworm life-cycle are listed below in chronological order. As you’ll see, the life-cycle begins with an egg and ends with a fully grown adult beetle munching away at your timber!
- Adult beetle
Female wood boring beetles typically lay their eggs on the surface of the timber, inside cracks, crevices and pores.
Safely tucked inside the timber, larvae cause damage by feeding on the timber for several years before they pupate and hatch as adult beetles.
Once they’re grown up, the latest generation of wood-boring beetles leaves the safety of their timber homes to breed. Females find a suitable surface on which to lay their eggs, and the life cycle/damage continues…
How Serious is Woodworm Infestation?
The extent of woodworm damage depends on the size of the infestation, the species, and what parts of the home have been infested.
Not all woodworm are harmful. However, if left untreated, woodworm can weaken timber, causing severe structural damage.
The Longhorn Beetle is known as the most damaging species, but any major infestation should be checked by a qualified professional.
What Environment Attracts Woodworm?
This depends on the species, as different types of wood-boring beetles are attracted to different types of timber.
Some prefer hardwoods like mahogany, oak and ash, whereas others prefer softwoods like cedar, pine and spruce. Remember, they all love damp wood because it’s easier to digest. Therefore, damp-proofing is a must, especially if you’ve suffered from damp in the past.
Common furniture beetles are happy in both hardwoods and softwoods. Although they can be found all over wooden objects, they typically prefer damp floorboards and worn furniture with no varnish.
Female wood-boring beetles like hardwoods with around 30% or more moisture content. This environment provides their larvae with the highest probability of pupating into fully grown adults.
Having said that, you can find wood-boring beetles living in wood with around 10% moisture content. Remember, the dryer the timber, the harder it becomes for them to eat and grow.
It’s worth noting that the larvae only eat the sapwood/outer section of a tree because it’s toxin-free and has more nutrients, as opposed to the heartwood/inner section of timbers like oak and pine.
Therefore, if you have furniture made of high-quality heartwood, there’s a much lower risk of getting a nasty woodworm infestation.
Pro Tip: Sapwood is typically lighter than heartwood. Knowing this helps you identify where the risky areas are
Tools & Materials
- Bucket (if mixing insecticide powder with water)
- Drill (if dealing with Deathwatch beetle)
- Sprayer (for liquid solution)
- Brush (for gel solution)
- Applicator gun (for paste solution)
- A second brush for paint or varnish
- Insecticide; either boron (in powder, gel or paste form) or permethrin
How to Treat Woodworm – Step-by-Step Instructions
IMPORTANT: Follow steps 1 to 4 regardless of what infestation you have. For step 5, only follow the instructions for the type of woodworm you have (i.e. Common Furniture Beetle, Deathwatch Beetle or Longhorn Beetle).
1. Signs of Woodworm
First of all, woodworm isn’t a worm, it’s a beetle. Small exit holes in the wood and crumbly edges made by larvae actually mean that the woodworm beetles are advanced, as the larvae have already turned into emerging adult beetles.
The beetle flies out of the hole but returns to lay more eggs, that turn into larvae. Keep watch for frass, which looks like sawdust, as this is evidence the larvae are active and are clear signs of woodworm beetles emerging.
Pro Tip: Peter Cox suggests hanging fly strips in roof rafters to catch adult beetles and kill them.
2. Identify Woodworm
Now you know you have woodworm, check which type it is, as the woodworm treatment methods are different.
The common furniture beetle is, unsurprisingly, the most common type, the deathwatch beetle sounds scary but is reasonably easy to treat, while the longhorn beetle requires a professional bug killer.
Exit holes about 1-2mm across, surrounded by fine sawdust (actually a waste product called ‘frass;) indicate the furniture beetle, while larger exit holes and large pellets mean you’ve got the deathwatch beetle (not as scary as it sounds). Tiny exit holes and sticky frass suggest the longhorn beetle.
3. Choose Your Insecticide
For common furniture and deathwatch beetles, I recommend Boron instead of Permethrin, as the latter is a man-made chemical that is harmful to the environment and can kill animals as well as insects. Do not use Permethrin in a house with pets. I
f you have Longhorn Beetles, contact a professional (see below for more details).
4. Protect Yourself
Insecticides are dangerous, so put on a mask and goggles to prevent irritation.
5. Apply Treatment
Only follow the steps below for the type of infestation you have. I.e. Common Furniture Beetle, Deathwatch Beetle or Longhorn Beetle. Ignore all steps that do NOT match your type of infestation.
Common Furniture Beetle
Indicated by exit holes 1-2mm across. Frass will be very fine.
I. Dilute Powder
If using a boron-based solution, dilute according to the manufacturer’s instructions. This is likely to be 1 kg of boron powder to 25 litres of water. You can buy a ready-made solution.
II. Apply First Coat
Spray the solution onto wood, giving a thorough coating. Pre-made solutions often come with a sprayer attachment. Leave to dry.
III. Apply Second Coat
Spray a second coating when first is dry, usually after a couple of hours, but check the manufacturer’s instructions to be sure.
IV. Apply Gel
For heavy patches of infestation, apply the boron solution in a pre-mixed gel. 1 litre of gel provides coverage for 4 square metres.
Indicated by exit holes 3mm across or larger and pellets of frass.
I. Locate the Woodworm Infestation
Tap the infected wood to see which areas sound hollow, this is where the woodworm infestation is.
II. Drill test Holes
Drill holes around the edge of the infested areas to accurately work out how big a patch you are dealing with.
III. Drill More Holes
Drill holes in a diagonal polka dot pattern across the area that are 10mm wide. Drill down until 15mm from the other side of the wood.
IV. Fill Holes
Fill holes to the top with boron paste using an applicator gun.
Pro Tip: The DIY Doctor recommends attaching a small length of plastic tubing over the nozzle of the paste container for greater accuracy.
V. Insert Dowels
Push dowel inserts into filled holes to trap boron paste. Use a cloth to wipe away excess.
VI. Apply Gel
Coat the outside of the wood with boron gel, allow to dry and apply a second coat.
Indicated by very small exit holes and frass that appears sticky (as though it has been mixed with wood sap).
I. Check Hole Size
Commonly found in roof timbers, longhorn beetle exit holes are larger than the 1-2mm made by the furniture beetle.
II. Do Your Research
Check the Building Research Establishment (BRE) to see if longhorn activity has been reported in your area.
III. Contact A Professional
If you think you have longhorn infestation, then you need to contact a professional for removal. The chemicals involved are not safe for a DIY job and will result in a lot of dead beetles!
Preventing Woodworm from Returning
Having gotten rid of woodworm, you don’t want it coming back, so here are a few tips to help you stay woodworm free:
- Keep your house well-ventilated and invest in damp proofing to fight rising damp. Woodworm loves the damp, so keep a close eye on any timber that is in a damp environment.
- Adding to the point above, basements are notorious damp hot spots, especially basements without cavity walls (a cavity wall is crucial is damp defence). Therefore, basement waterproofing and condensation control is a must. Remember, when fighting damp, along with dry rot and wet rot, property care is your most powerful weapon.
- It is easier for beetles to bore into timber that doesn’t have paint or varnish on it, so maintain these items regularly and follow basic rot treatment guidelines.
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Hopefully, you are now on your way to being woodworm-free using the woodworm treatment methods laid out in this article. Woodworm isn’t difficult to tackle, and it doesn’t need to be the end of your home or furniture.
Being infected once doesn’t mean you will have a second infestation, especially if you take the proper property care precautions like damp proofing your property.
Do you have any family or friends that have spotted the signs of woodworm? If so, please send them this woodworm treatment guide so they too can be free of woodworm infestation.