How to Spot Piano Woodworm in Your Instrument

A few small holes in the timber beneath a piano can be unsettling, particularly when the instrument has been in the family for years. Knowing how to spot piano woodworm properly helps you avoid two costly mistakes: overlooking active infestation, or assuming that every old hole means the piano is currently under attack.

Woodworm is a common name for the larvae of several wood-boring beetles. The visible holes are made when adult beetles emerge, often long after the larvae have been feeding inside the timber. A piano may therefore show evidence of woodworm without having an active problem. The distinction matters, because a piano is not simply a piece of furniture. Its timber structure supports the action, casework, keyboard and, in an upright piano, the considerable forces held within the frame.

Where to look for piano woodworm

Begin with a good torch, a clean sheet of paper or light-coloured card, and time to inspect without moving parts unnecessarily. Do not dismantle the action or remove structural fittings unless you are confident in doing so. A piano contains delicate regulation components and, in older instruments especially, fragile felt, leather and timber parts.

On an upright piano, inspect the lower back, underside of the keybed, base, rear feet and the internal timber framework visible from the back. Look closely at unfinished or less polished wood, where small holes are easier to see. The lower areas deserve particular attention because they may have experienced cooler, damper conditions or contact with an external wall.

For a grand piano, examine the underside of the rim, the legs, lyre, pedal supports, keybed and any exposed wooden braces. The internal case should be viewed with care, but avoid resting objects on the soundboard or touching its ribs. The soundboard is a thin, acoustically vital piece of spruce and is not a surface to test by pressing or poking.

Pay attention to timber parts that are hidden in ordinary use. Beetles favour wood, not polish, so immaculate exterior casework does not rule out activity in concealed structural sections. A piano stored in a garage, outbuilding, basement room or against a persistently cold wall may warrant a more thorough inspection.

The signs of active woodworm in a piano

Small round exit holes are the most familiar sign. In many domestic cases, common furniture beetle holes are roughly 1 to 2 mm across. They can resemble pinpricks, often appearing in scattered clusters. However, holes alone cannot tell you whether the infestation is current.

The strongest indication of activity is fresh frass - the fine, pale, powdery debris pushed out by larvae or left around newly opened exit holes. Place clean paper beneath the affected area and check it periodically, especially in late spring and summer, when adult beetles are more likely to emerge. Fresh dust directly below holes can be significant, although ordinary household dust and debris from a deteriorating finish can be misleading.

Look for crisp, clean-looking holes with pale exposed wood at their edges. By contrast, older holes are often darkened by age, polish or accumulated grime. New holes appearing over time are more persuasive evidence than a single inspection, which is why photographs taken in good light can be useful for comparison.

Other warning signs include timber that feels unusually brittle, a weakened edge around a fixing, or a cluster of holes in a component carrying weight. Do not test this by forcing joints or applying pressure. If a leg block, pedal support, base rail or keybed appears compromised, keep the piano in place and arrange a professional inspection before it is moved or played heavily.

Woodworm is not always the cause

Pianos often acquire marks, holes and dust for reasons unrelated to beetles. Old pinholes may be from historic cabinet work, previous fittings or long-completed infestation. A dusty floor beneath an upright may simply reflect loose material from a worn back panel, while a musty smell may point to damp conditions rather than active woodworm.

It is also possible for an instrument to have been treated successfully many years ago. In that case, the exit holes remain as part of the piano's history, but there may be no living insects and no continuing damage. This is especially common in older pianos that have changed homes several times.

Why woodworm can matter more in a piano

Not all affected timber has the same importance. A few historic holes in a non-structural back panel may have little bearing on the piano's musical life. Activity in the keybed, action rails, leg supports or internal framework deserves more careful assessment.

The real concern is cumulative loss of strength. If larvae have tunnelled extensively through a supporting component, screws and glue joints may no longer hold as intended. In a piano, this can lead to instability, unwanted movement, noisy pedals, action alignment problems or difficulty maintaining accurate regulation. It may also make the instrument unsafe to move.

There is a further practical consideration. Wood-boring beetles are encouraged by suitable conditions, particularly damp timber and poor ventilation. A piano that has been exposed to prolonged humidity changes may have other issues alongside woodworm, such as loose glue joints, rusty strings, mould, sticking keys or a distorted soundboard. The beetle holes may be the visible clue to a wider environmental problem.

What to do if you suspect piano woodworm

First, avoid applying a household woodworm treatment directly to the piano. Many products are designed for general joinery or furniture, not for an instrument containing sensitive finishes, felts, leather, adhesives and precision mechanisms. Liquid treatment can stain casework, affect glue joints, leave lingering odours and create problems within the action if used indiscriminately.

Instead, make a careful record of what you have seen. Photograph the holes with a coin or ruler nearby for scale, note the location, and place paper below the area if fresh frass is suspected. This gives a technician or timber specialist useful evidence and reduces the temptation to disturb the piano in search of an answer.

Next, consider the room itself. Keep the piano in a stable, well-ventilated environment, away from persistent damp, radiators, open fires and external walls that run cold in winter. The aim is not to make the room hot or dry, but to avoid severe fluctuations. A piano benefits from steadiness far more than extremes.

If the signs appear active, or if they are concentrated around structural parts, seek an in-person assessment. A piano technician can identify which timbers are involved, judge whether damage affects the instrument's function or safe handling, and advise when a conservation-minded pest-treatment specialist is required. In some cases, treatment is straightforward; in others, a damaged component may need sensitive repair or replacement.

Before buying, renting or accepting a used piano

Woodworm checks are particularly worthwhile when considering an older piano. Do not be reassured solely by an attractive cabinet or a recent tuning. Ask to view the back and underside, and inspect the feet, base and keybed in good light. If access is restricted, that is a reason to be cautious rather than to assume all is well.

A carefully selected older piano can offer tremendous character and musical value, but it should be assessed as an instrument, not merely as a decorative object. Evidence of historic woodworm is not automatically a reason to reject it. Active infestation, extensive tunnelling or weakened supporting timber may be a different matter.

For owners in Surrey and the surrounding South East, Runnymede Pianos can assess the piano-related implications of suspected woodworm as part of expert care for the instrument. The priority is always to establish what is genuinely happening, protect the piano's musical integrity and avoid unnecessary intervention.

A calm inspection, a little patience and the right specialist advice will usually tell you far more than a row of old holes ever could.