Durability of timber from exotic species against termite attack in Indian conditions

IRG/WP 07-10629

O K Remadevi, R Muthukrishnan

Exotic trees species, Acacia mangium Willd. and A. auriculiformis A. Cunn. ex Benth. and their hybrid are widely grown in India for multiple uses including use as timber. It is essential to know the natural durability of timbers against termites for predicting the service life of the timber and deciding on the application of preservatives to enhance the durability. Studies were conducted to test their durability against termites with and without chemical treatments and in comparison to the natural durability of Rubberwood, which is a highly perishable wood. Test panels (30.5 x 3.8 x 3.8 cm) were prepared from pure heartwood and treated with CCA (Copper-Chrome-Arsenic), Permethrin and Cashew Nut Shell liquid (CSNL) formulation by pressure impregnation. They were buried half their length in the termite test yard along with untreated stakes and rubber wood stakes and tested as per Indian standards (IS 4833-1968). Bimonthly observations on termite infestation were recorded for a period of 5 years. A. auriculiformis, A. mangium and the hybrid were found to be more durable as compared to Rubberwood, which was fully damaged within 6 months of field exposure. The hybrid was highly resistant to termite attack and both treated and untreated stakes were found undamaged or with negligible damage upto 5 years. A. auriculiformis was slightly less durable than hybrid showing 10% damage by 5 years. The damage in A. mangium was 10% by one year, more than 30% by 2 years and by 5 years the damage was 100%. Pressure treatment with CCA (4%) and Permethrin (1%) gave 100% protection to all stakes against termite attack in the field. CNSL (30%) treatment was also effective to a great extent. The comparative performance of different timbers on field exposure to subterranean termites is discussed in the paper.

Keywords: exotic species, durability, Acacia, Copper-Chrome- Arsenic, Permethrin, CNSL

Conference: 07-10-29/11-02 Taipei, Taiwan

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