Natural durability of the Iranian domestic bamboo (Phyllostachys vivax) against fungal decay and its chemical protection with propiconazole

Abstract

Bamboo culms are unique building materials for various kinds of structures. A wider acceptance of bamboo for structural uses, however, is often hindered by its propensity to biological degradation. The preservation of bamboo structures against biological hazards is an important requirement for utilizing this valuable lignocellulose resource. In this research, first, the chemical composition of bamboo tissue and its extractives, natural durability and the process of bamboo decay were investigated using two species of white rot fungi, i.e. Trametes versicolor and Xylaria polymorpha, two brown rot fungi, i.e. Coniophora puteana and Oligoporus placenta, and the soft rot fungus, Xylaria longipes. The samples were subjected to 4, 8, 12, and 16 weeks of exposure to fungi according to EN 113, and their weight loss (WL) and moisture content (MC) were studied. Secondly, aqueous suspension of 1% propiconazole was used as a fungicide to protect bamboo against different rotting fungi. The bamboo species Phyllostachys vivax was highly vulnerable to soft and white rots but showed a relatively higher durability against brown-rot fungi. However, it was not durable enough to be used without preservation and its biological resistance improved after treatment. Surprisingly, WL of bamboos decreased after leaching procedure, which could be related to the extraction of non-structural carbohydrates during leaching with water. A light microscopic study showed that different fungi preferably degrade different cells; white and soft rots mostly invaded ground parenchyma, while in brown rots, deterioration of phloem cells was more severe. In brief, bamboo needs to be treated before indoor and outdoor applications, and propiconazole as a cheap and environmentally friendly preservative can safely protect it against different fungal decay.