Life in an old Japanese house VOL.11: Termites in Japanese Homes

One thing many individuals concern themselves with when living in old Japanese homes is termites. They typically inhabit areas between tropical and temperate climates and are not usually found in cold areas. That said, due to climate change there are incidents of termites in Northern Japan including Hokkaido. This is why old wooden homes across Japan are continually under risk of termite damage.

Although termites are feared by homeowners for their propensity to devour wood, termites are in fact very weak creatures that are low on the food chain, and will die from extended exposure to the sun. They also serve the planet well since termites' natural behavior helps dead and weak trees return back to the earth.

Two species of termites chiefly found in Japan are the Japanese termite and the Formosan termite a.k.a. the ‘Super-termite’. Outside of parts of Hokkaido, Japanese termites are seen throughout the country and the Formosan termite are primarily seen in Western Japan and warm areas near the  Pacific Ocean. Besides these two species, other termites are only found in very specific areas of Japan. The Japanese subterranean termite, or kanmon termite, is seen only around the Kanmon Straits, the body of water separating the islands of Honshu and Kyushu. The daikoku termite is found only in Okinawa and the western drywood termite is known to have come to Japan from the United States inside imported lumber.

Japanese termites nest inside damp and soft wood which they prefer. The kanmon termite looks and acts similar to a Japanese termite, but they eat dry wood in addition to damp wood and the season when the swarmer termites set up new colonies is known to vary.

The super-termite nests underground and invades by forming paths from the dirt and expanding up by eating through the wood. They will carry water to the nest site to moisten dry wood and therefore can cause greater harm to one’s home and are even known to reach a home’s ceiling and beams.   

The daikoku termite and western drywood termite both eat dry wood and will nest inside timber and furniture leaving their granulated feces around outside the nest.  

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A cross-section of wood destroyed by termites. They prefer eating the moist portions.

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A termite trail rising up from underground.

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Worker Formosan Termites

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The soldier formosan termite shown here is peeping outside from a broken termite trail

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Mating of swarmer termites. Mating season varies depending on the species but they are most often seen between early Spring and early Fall. 

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A formosan swarmer termite. Their wings fall out upon landing. When you spot a pair of wings, they are certain to be nesting in the damp ground nearby.

It’s not uncommon when starting to renovate a newly purchased old house to discover that there is termite damage within the walls and floors. What might have been intended as a small DIY project can turn into a major project involving completely redoing the floors, replacing the pillars or reinforcing the structure. Although homes typically will not suddenly collapse from termite damage alone, the weakened wood may collapse during an earthquake. Damaged pillars may buckle causing the home to lean. Also since a home’s floor is near the ground, it is also likely to sustain damage and if left unrepaired may also collapse.

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Pillar buckling caused by termite damage.

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A beam broken by termite damage.

When doing home repair if you discover termites inside the home’s wood, it is not wise to leave the wood as is since termites can spread into other pieces of wood around the house. Therefore either burn the wood or spray termite pesticide in the affected area. For large pieces of wood that are hard to replace such as pillars, since simply spraying the affected area will cause them to flee to other parts of the house and thereby cause the termites to spread, it is necessary to have the whole house and underground treated for termites.

If you find wood that has sustained termite damage without a current trace of termites, then protectant pesticide should be sprayed and the damaged wood should be replaced or reinforced. Although non-professionals could repair termite damage to the floor, it may be wise to consult a professional to reinforce or replace key structural elements such pillars and beams.  

When replacing or reinforcing wood, it is best to avoid using untreated cedar and pine since soft wood is preferred by termites. Therefore you should buy treated wood or you can coat it with a wood preservative yourself. Unfortunately, protectant pesticides and wood treatments alike do not last forever, you can expect them to be effective for around 5 years. If you want a longer lasting protection from termites it will cost you extra, but you should consider replacing damaged wood with hardwoods like elm and cypress. Or you could even purchase ironwood, the dense type of wood that termites are known to not like.  

Termites may look like a type of ant but in fact evolved from the cockroach family. Therefore, boric acid is an effective way of exterminating them both. Boric acid is a popular pesticide in recent years since it is low in risk to human health. Although all pesticides are getting to be safer for humans and mammals and have less of an impact on us, it is always worth considering pesticides impact on aquatic life toxicity and the overall environment.


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