How to Get Rid of Woodworms to Protect Your Outdoor Furniture

Woodworms can destroy valuable outdoor furniture. Fortunately, woodworm treatment and prevention may be easier than you think.
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Woodworms are one of those common household pests that many have heard of, but most people know little about. In fact, woodworms aren’t just one pest but several, and although small, woodworms can ruin untreated indoor and outdoor furniture. In extreme cases, they can even damage the structure of your home.

Prevention can save you a fortune, and treating woodworm isn’t difficult if you know the right steps. We’ve got all the information you need to know in order to protect and treat your home, so continue reading to learn more.

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What are Woodworms?

Woodworms are beetle larvae, little whitish grubs that eat wood. However, a harder-to-answer question is what does a woodworm look like? This is because you’re more likely to see woodworm damage than woodworms themselves, as they spend most of their lives burrowing beneath the surface of wood.

Woodworms in furniture live anywhere from 2 to 5 years. A single grub can do a lot of damage to your home in that time. The female typically lays 30 to 70 eggs, and an infestation like that can ruin anything made from wood. Eventually the larvae pupate, and emerge from the wood to become fully grown adults. Although these only live a few days, they soon mate. Then, the female will look for somewhere to lay her eggs. Wood that has already been infested is a prime target, and the cycle begins again.

Termites also attack wood, but the two creatures are very different, as is their treatment. If you think you have a termite infestation rather than a woodworm problem, be sure to take proper termite prevention and treatment measures.

The most common woodworm beetle types include common furniture beetles, longhorn beetles, powderpost beetles, and deathwatch beetles.

Common Furniture Beetle

Also called the common house borer, the common furniture beetle is about 1/8-inch to 3/16-inch long and is a dark reddish brown. It has a preference for softwoods over hardwoods, though it can be found in hardwoods, too. Not only are furniture beetles difficult to spot because they are small, but with a diameter of just 1/16-inch, the exit holes are also hard to see.

Longhorn Beetle

This is a much larger insect at anywhere from 5/16-inch to 3/4-inch long. The longhorn beetle creates large tunnels and huge exit holes of up to 2 inches across. As a result, it can cause severe damage to structural softwoods. Its body is dark brown or black, and it has long antennae that are pulled back. Because of this feature, longhorn beetles are sometimes mistaken for cockroaches.

Powderpost Beetle

This is a medium-sized woodworm beetle about 5/16-inch long and a bright reddish brown in color. The head of a powderpost beetle takes up about a third of its body, while the name comes from the way that the insect chews wood into powdery dust. Powderpost beetles prefer oak and European hardwoods. Their exit holes are difficult to see, usually no larger than 1/8 inch in diameter.

Deathwatch Beetle

This dark-brown wood boring beetle is similar in size to the powderpost beetle, and it also leaves relatively small exit holes. The deathwatch beetle is particularly fond of oak, and it can often be found in the frames of old buildings. The males and females bang their heads against wooden beams in order to locate each other; this makes a tapping sound at night, a clear sign of infestation. Deathwatch beetles live a long time, with a life cycle of up to 10 years.

Signs of Woodworm

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One of the biggest challenges in identifying a woodworm infestation is that the larvae are rarely seen on the surface of wood. The appearance of exit holes (also known as pinholes) means the woodworm has left and the damage has already been done. Often the wood can be saved in the method described further below.

First, though, there are a couple of obvious signs of woodworm you can look out for:

  • Look closely for the beetles themselves, as well as dead beetles. Not all beetles found near wood are harmful but it’s a good idea to investigate. Catching an infestation early can prevent severe damage.
  • Frass (basically woodworm poo) varies in texture and color but generally looks like coarse dust. If found on or under furniture it is a sure sign of a problem.

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Ways to Prevent a Woodworm Infestation

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The good news is that woodworms seldom attack dry, healthy timber. Problems typically begin when outdoor furniture is left on a damp lawn, for example, and the wood absorbs moisture. It then starts to soften, and provides an ideal place for the female to lay her eggs.

Woodworms can easily travel from one piece of damp furniture to another, but they don’t normally spread from bad wood to healthy timber. So care and protection are key factors in preventing woodworm infestations.

  • Once a month, check outdoor furniture for cracked or peeling finishes, and especially for soft spots where it rests on the ground. Repair if necessary. A solid, undamaged layer of varnish or paint often protects against woodworm attack.
  • Avoid leaving wooden outdoor furniture on lawns overnight or in places where water pools underneath.
  • Check that furniture is thoroughly dry before storing for the winter. Try to keep furniture somewhere where there is good ventilation to prevent dampness.

How to Get Rid of Woodworms

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If you have found holes or noticed frass, it is important to act quickly to stop further damage. While these steps on how to get rid of furniture beetles take a little time, they fortunately aren’t difficult to follow and the necessary products are widely available.

Note that the following is for treating indoor and outdoor furniture. If you believe you have woodworm in roof beams or other structural timbers, call a registered pest control expert immediately.

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Project Overview

Working Time: 2 to 5 hours
Total Time: 2 or 3 days
Skill Level: Beginner
Estimated Cost: $40 to $100

STEP 1: Strip the furniture’s existing finish.

Existing finishes will prevent proper penetration of woodworm killer into wood furniture, so they need to be removed. Modern water-based paint and varnish strippers are easy to use, but you should still wear gloves and eye protection and work in a well-ventilated area.

This is likely to be the longest part of the job, but it’s important to be thorough. When the furniture has been stripped, run a vacuum cleaner over any visible holes. Sometimes they are blocked by frass, which can absorb woodworm killer and reduce its effectiveness.

STEP 2: Apply woodworm killer to the wood.

Applying a 1:1 mix of white vinegar and water to the wood surface will clear woodworm infections. While they find it unpleasant, it does not kill them. However, permethrin (which usually comes as a concentrare) kills woodworms at all life stages. Permethrin-based insecticides are toxic, so you should carefully follow the safety instructions. Mix it as instructed, then apply it liberally to the surface of the furniture using a cloth or spray bottle.

STEP 3: Fill holes and repair damaged areas.

Once the woodworm treatment has been absorbed and the furniture is dry, any visible damage can be repaired. Tiny pin holes in indoor furniture can often be disguised with beeswax or similar wood care products.

For larger patches, we suggest wood putty rather than wood filler since wood putty is plasticized. Even though it takes longer to set, it is more resilient and flexible, making it particularly appropriate for repairing outdoor furniture.

STEP 4: Refinish and protect the wood surface.

A couple of coats of your preferred paint or varnish don’t just make your furniture look attractive, it also protects the wood. It provides an effective barrier against further woodworm infestation.