Posted: 05/05/2014 at 10:10
There's no cure as such. Pre-treated wood will last longer but will eventually succumb to one of the thousands of types of fungi (only a laboratory could definitely ID which one.) However, it could last another 5 years before falling apart completely. The only real solution is replacement - pre-treated wood can last 15 years but if in permanent contact with wet soil it can be much less. That's why railway sleepers used to be soaked in boiling tar, which makes them last for decades. Unfortunately, it was found to be rather toxic and carcinogenic, so you can't generally find them for domestic use any longer.