Abstract
Large preservative-treated timbers and poles can develop internal and external decay as they age in service. Arresting this damage can pose a challenge, especially internal decay. Boron plays an important role in helping arrest fungal attack in a variety of applications. This paper discusses the use of borates as a component in pastes for limiting external decay and the use of boron solutions or rods for arresting internal decay. Long-term field trials show that boron movement is initially slow, but boron was found in Douglas-fir poles almost 30 years after application. The results illustrate the value of boron as a remedial treatment for limiting fungal attack in timber in service.