In order to investigate the effect of phenol-formaldehyde (PF) modified boron compounds on termite resistance of two main plantation-grown wood species, namely, Masson pine (Pinus massoniana Lamb.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), laboratory termite tests and field tests were carried out according to AWPA standard E1-97 and AWPC protocols/2007. Different concentrations of boric acid (BA), borax (BX), and disodium octaborate tetrahydrate (DOT) mixed with 20% aqueous solution of PF were used to impregnate the sapwood of both wood species. Formosan termite (Coptotermes formosanus Shiraki.) was used as the test termite in laboratory termite tests, while the field tests were carried out in Guangzhou, China. The results showed that the compound treatments of boron compounds with PF could efficiently improve the termite resistance of both wood species, especially the treatments by using BX. According to the laboratory termite tests, the untreated Masson pine and Chinese fir sapwood rated 5 and 4 (seriously attacked) with average weight losses of 29.3% and 43.7%. After treated with PF modified boron compounds with concentrations of 0.5, 1.0, 1.5, and 2.0%, the average weight losses were reduced to lower than 5.9, 5.1, 2.3, 1.2% for Masson pine and 7.6, 5.0, 1.8, 1.1% for Chinese fir, respectively. The performance of Masson pine in field test was much worse than Chinese fir by showing complete digestion by the termites. BX-PF treatment showed the best results in field test by reducing the average weight loss of Masson pine samples from 100% to lower than 6.1% or Chinese fir from 25.6% to lower than 8.6% at a BX concentration lower than 1.0%.

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