The candidate wood species used in this study were Acacia mangium, Paraserianthes falcataria, Hevea brasiliensis and Pinus merkusii. All four species are rated as durability classes III and IV (based SNI 01.7207-2006 [2]. Cryptomeria japonica was selected as the comparative reference control species as it is used as such in the Japanese Standard JIS K1571-2004 [3]. All five wood species were subjected to bioassay against termites according to the test methods described in SNI 01.7207-2006 and Japanese Standard JIS K1571-2004 (recently revised as JIS K1571-2010).

This standard describes a 4-week, no choice laboratory test using 200 g of sand matrix, 50 mL of distilled water and 200 workers of Coptotermes formosanus Shiraki. Test specimens (25 × 25 × 5 mm) were placed upright position within a glass jar one of the 25 mm edges resting on the inside wall of the jar. We performed this research in five replicates. Full details of the test method are given in SNI 01.7207-2006 and [4]. A diagram of the test method according to SNI 01.7207-2006 is provided in Figure 1.

This laboratory test method is similar to that described in the Indonesian standard. The Japanese method is also a no-choice test. Sugi (Cryptomeria japonica) sapwood specimens are used as the untreated reference wood species (control). This is implied by the no-choice description (Figure 2). The test specimen is placed on a plastic net to avoid direct contact with the moistened layer of Plaster of Paris on the base of a cylindrical acrylic container. C full. formosanus (150 workers and 15 soldiers) were added to each test container. Full details of the test method are given in JIS K1571-2004. A diagram of the test method according to JIS K1571-2004 is provided in Figure 2. Test containers containing termites were maintained at 28 ± 2 °C and 80% RH for three weeks in the dark.

Percent mass loss of the individual wood specimen is calculated by the difference between the before and after weights according to the following equation:

     Percent mass loss = (W₁ − W₂)/W₁ × 100

where W₁ = weight of oven-dried wood specimen before test (g), W₂ = weight of oven-dried wood specimen after test (g). When the mean percent mass loss of five untreated wood specimens is <15%, the test is not valid and should be repeated.

In addition to the percent mass loss, termite mortality was calculated according to the following equations:

  Termite mortality (%) for SNI = (number of dead workers)/200 × 100

  Termite mortality (%) for JIS = (number of dead workers)/150 × 100

The feeding (wood consumption) rates are most useful for comparing test results obtained with wood species of different densities. In order to calculate the feeding rate, an assumption is made that termites die linearly with time. This statement was also confirmed by Su and LaFarge 1984 [5].

On the basis of the above assumption, feeding rates were calculated according to the following equation:

Feeding rate (mg/termite/week) = (weight of wood eaten by termites)/termites × test period (weeks).

Data on mean mass loss, mean termite mortality and wood consumption obtained from the laboratory test conducted according to the Indonesian Standard (SNI) are presented in Table 1.

Mean mass losses ranged from 11.6% (A. mangium) to 42.1% (C. japonica). One of the requirements of the Japanese standard method of test is that the untreated control shall sustain a mean mass loss of more than 15% for the test to be considered valid. If this occurs, the test is deemed valid. Given the Japanese requirement, the results of the Indonesian SNI test suggest that H. brasiliensis, P. falcataria and P. merkusii (mean mass losses of 21.0%, 24.5%, and 25.4%, respectively) could be suitable candidates for reference controls. A. mangium with a mean mass loss of 11.6% failed to qualify as a suitable reference control. It appears that under the conditions of the SNI test, A. mangium displayed some resistance to attack by C. formosanus, probably due to its inherent extractive content.

Data on mean mass loss (%), mean mortality (%) and wood consumption obtained from the laboratory test conducted according to the Japanese Standard (JIS) are presented in Table 2. The mortality results obtained from the JIS and SNI termite tests both had similar trends.

Mean wood consumption per termite per day ranged from 55 µg (A. mangium) to 129 µg (H. brasiliensis). Mean wood consumption per termite per day for P. falcataria, P. merkusii and C. japonica was 66 µg, 95 µg and 98 µg, respectively. Like the SNI results, mean wood consumption of P. merkusii was also quite high (95 µg).