Have the woodworms returned? There are little piles of sawdust on the lovely mahagony cabinet and tiny holes on the frame of the painting above it. It wasn’t a cheap frame. The little creatures who destroyed an entire row of kitchen storage cabinets some years ago seem to have returned. A few signs of infestation [...]

The Sunday Times Sri Lanka

Under attack: The enemies of your wood

Daleena Samara tackles household pests in our new series ‘De-bug’

Have the woodworms returned? There are little piles of sawdust on the lovely mahagony cabinet and tiny holes on the frame of the painting above it. It wasn’t a cheap frame. The little creatures who destroyed an entire row of kitchen storage cabinets some years ago seem to have returned.

A few signs of infestation aren’t necessarily cause for panic, says Raja Mahendran, agro and urban pest control expert and consultant to global pest control organisations. The cause is probably either wood borers or dry wood termites. If there is fine powder then it’s generally beetles. If the wood is hollow, then it’s drywood termites.

Wood borers belong to the powderpost beetle group that comprise several different species and families whose larval or adult forms live on wood. The larva are commonly known as woodworm in the West.

Not all termites need mud

Drywood termites on the other hand are social creatures and live in colonies. They look like their ground-dwelling cousins, the subterranean termites. Unlike the latter, however, drywood termites prefer wood and dry conditions and they don’t need to be at ground level, and the work is not done by worker termites but by the young before adulthood. They look similar to soil-dwelling termites, but have a lighter, more delicate appearance.

The miniature mountains of sand-coloured grains are actually their fecal pellets, called frass. If you were to examine them closely, you’d find the grains are about a millimetre long and hexagonal, and that most pellets are the same size. Pest controllers check them by rolling them between the fingers to identify the culprit.Wood borers leave behind a fine powder that’s wood and not fecal pellets.

Together the wood borer and drywood termite can wreak havoc on your wooden furniture and fittings. Of the two, it’s the drywood termite that causes the most serious structural damage by constructing feeding galleries in the heart of the wooden structures like support beams, and nibbling at them from inside out upto just below the surface, so that only a thin facade of wood remains intact under the polished or painted surface.

Occasionally, there would be a blister or two on the surface.Some frass is left in the feeding gallery, some cemented together and used to seal up exits, and others discarded. That may be the pile of ‘sawdust’ on my mahagony table. Because they are out of sight, the extent of the damage they have caused would not be known until perhaps the frame snaps in my hand.

Borer beetles invade wood

The wood borers on the other hand lay eggs on the wood, usually in wedges or cracks of raw woods, i.e. wood that is unvarnished or untreated.These are usually too small to spot with the naked eye, but the larva soon become visible as they munch on your wood. Some types of borers, like the Anobiid species, are attracted to both hardwoods and softwoods, others only to softwoods.

The little cavities that appear on furniture are “flight holes”, evidence that the eggs have hatched, larva has tunnelled deep into the wood, pupated and emerged to the surface to fly away. The larva can remain in the wood,boring a network of tunnels inside, for months or even years, depending on the species of beetle, seriously weakening it. Badly damaged wood has a honeycombed appearance.One species, The Old House Borer (hylotrupesbajulus) larva, for example, lives for many years, chewing away at the wood. Their hard jaws are said to make a rasping sound so loud it’s audible to humans a few feet away. Yet, they won’t be detected until they emerge from their nest, leaving behind an oval opening. Pest controllers sometimes listen hard to detect them.

The Deathwatch Beetle

In medieval UK, occupants in medieval sick rooms keeping watch over the diseased heard a certain woodborer making a ticking sound when chewing on wood and named it The Deathwatch Beetle.

What’s to be done about these wood-eating pests?

-  Prevention is always better than cure, so make sure you get good quality seasoned and treated wood. When purchasing wood, check carefully for borer exit holes and cavities. Tap it to make sure it isn’t hollow, and make sure it has been stored properly.

- Finely sand wood to ensure there are no crevices that will attract borers to lay eggs.

-  Termites, both drywood and soil-dwelling, arrive in swarms on rainy days, shed their wings and start colonies. Shut them out of your home.

-Address signs of infestation immediately. Serious infestations, for example, wooden flooring, would require fumigation, an expensive option, and less serious ones can be treated with special pesticides.

“In Sri Lanka, pest controllers usually inject affected timber with chemicals (fipronil) and do regular inspections on annual contract. Only Licensed Fumigators and not (just) any Pest controller can fumigate furniture. In America they cover the entire house and gas fumigate,” says Mahendran.

There seem to be non-toxic solutions: The active compound d-limonene contained in orange oil is said to be particularly deadly for drywood termites. Colonies have been exterminated by spraying the substance. Neem oil has had similar results when ingested by drywood termites. Extreme heat and cold treatments have also been found to be effective. If you are consulting a pest control agent, inquire about these options. The US has also found a way to electrocute them with an electric gun!

“While it cannot be guaranteed that wood pests will not attack hard woods it is best to use hardwoods like teak to minimize damage. Also do not place furniture in dark damp areas, and ensure ventilation. Do not forget to inspect your furniture with a bright flashlight and lift up any paper that may be on shelves to see for any frass or powder droppings, says Raja Mahendran

Four anti-termite woods

We all know that termites and wood borers eat wood, but did you know that there are four types of wood these creatures won’t touch, asks Mahendran?

-    Pressure Treated:Wood treated using cycles of both extreme pressure and vacuum. During the process, a preservative is embedded into the pores of the timber, creating a chemical barrier that is not only termite resistant but which also slows the decay process. Two main chemical preservatives are used during pressure treatment: alkaline copper quaternary (ACQ) and copper boron azole (CBA).

-   Naturally resistant woods: While termites will bite into almost every type of wood, there are a few tree types that are naturally resistant: heartwood, the older harder non-living central wood in trees. This part is usually darker, denser, less permeable, and more durable than the surrounding sapwood of some tree species, e.g.the Redwood and Alaskan cedars (Pacific Coast yellow cedars). A University of Hawaii study found Alaskan cedars performed better than the redwood in resistance tests. The Laotian teak and tallow wood were also found to be resistant to subterranean termites in the same study.

-    Toxic woods:The same study found the heartwood of a group of Malaysian and Hawaiian woods such as tualang, sentang, casuarinas, pine and the kempas are toxic to Formosan subterranean termites.

-   Composite materials: New manmade materials that include wood in their ingredients, specially designed to be termite resistant. They are made with waste wood fibre and plastic and are totally impervious to termites. They also do not warp like natural woods.

 Next week: Subterranean termites


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