Sub-kingdom : Tracheobionta
Order : Gentianales
Family : Apocynaceae
Subfamily : Apocynoideae
Genus : Dyera Hook.f.
Species : Dyera costulata (Miq.) Hook. f.
General Characteristics of jelutong's wood:
Peninsular Thailand, Peninsular Malaysia, Singapore, Sumatra, Borneo and intervening islands (Lemmens, Soerianegara and Wong, 1995).
The species occurs in primary evergreen lowland or hill forest, in well-drained locations up to 300 m (Lemmens, Soerianegara and Wong, 1995).
Jelutong has a scattered natural distibution and has declined as a result of tapping for latex and felling for timber. The risk of extinction was recognised 60 years ago. In Peninsular Malaysia the species has been reported to be threatened (Ng et al 1984). Jelutong does, however, regenerate readily in logged-over forest. It is also planted commercially for timber.
Exploitation for latex, felling for timber, conversion of lowland forests to agriculture.
It has a number of speciality uses such as pattern making in foundry work, for drawing boards, pencils, picture frames, dowels, carving, blackboards, wooden toys, clogs, brush handles and battery separators, and it is also used for furniture parts, door knobs, ceilings, partitioning, matchsticks, matchboxes and packing cases. The roots are used as a substitute for cork and their wood for axe handles. The latex is used in the manufacture of chewing gum, in paints, as priming for concrete, or for sizing paper. Follicles are occasionally used as torches by the local population or burnt to repel mosquitos (Lemmens, Soerianegara and Wong, 1995).
In the period from 1980-1990 the export of jelutong sawn timber from Peninsular Malaysia was 32000-44000m3/year with a value of US$ 5.1-10.8 million a year; in 1992 it was 19000 m3 with a value of US$ 8.3 million (US$440/m3) (Lemmens, Soerianegara and Wong, 1995). In 1995, Malaysia (Peninsular) exported 5000 m3 of sawnwood at an average price of 710$/m3 (ITTO, 1996). The export from Sabah was 67000 m3 in 1987 with a value of US$4.5 million and 23000 m3 (55% as sawn timber, 45% as logs) in 1992 with a total value of US$ 3.5 million (US$ 215/m3 for sawn timber, US$ 82/m3 for logs). Japan imports comparatively large amounts of jelutong, mainly from Sarawak and Sabah (Lemmens, Soerianegara and Wong, 1995). In 1987, Indonesia exported 2,183,462US$ worth of this species as jelutong (WWF and IUCN, 1994-1995).
Jelutong is subject to a log export ban in Peninsular Malaysia, and special permission has been required to cut the tree in Thailand (Ministry of Agriculture and Cooperatives Decree of 1988).
Regulations on the methods of tapping the latex were introduced in the 1930s (Coppen, 1995).
In Peninsular Malaysia D. costulata is chosen for enrichment planting because it is easy to handle in the nursery, survives well when planted out, has a good rate of growth and has good market potential. Prolonged contact with acid water in peat forest harms young plants. D. costulata is a very light-demanding species and once a young tree is well established in full light, it tends to spread its crown and develop into a pronounced 'wolf tree'. Sudden opening of the canopy is favourable for its development (Lemmens, Soerianegara and Wong, 1995). D. costulata coppices readily and is extremely resistant to girdling (Lemmens, Soerianegara and Wong, 1995).