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Hevea brasiliensis (Willd.) Muell.-Arg.

Euphorbiaceae
Para rubber

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Source of Hevea or Para Rubber, obtained by tapping the trunks of the trees. The latex coagulates with the aid of acetic acid, formic acid, and alum. Cured rubber used for all types of rubber products. Seeds are source of Para Rubber seed oil, recommended for manufacture of soap. Although poisonous, seeds can be eaten as a famine food after processing. Boiling removes the poison and releases the oil which can be utilized for illumination. Seeds are sometimes eaten off the ground by cattle. Kernels (50–60% of the seed) contain 40–50% of a semi-drying pale yellow oil, used in soap making, paints, varnishes, and is effective against houseflies and lice. Press cake or extracted meal can be cautiously used as fertilizer or feed for stock (Reed, 1976).

Folk Medicine

Surprisingly, Duke and Wain (1981) contains no references to folk medicinal uses of Hevea. Most laticiferous plants have large folk medicinal roles.

Chemistry

Per 100 g, the poisonous seed is reported to contain 8.5 g H2O, 17.6 g protein, 48.5 g fat, 22.9 g total carbohydrate, 2.5 g ash, 120 mg Ca, and 430 mg P. Leaves contain a- and g-tocopherol, and plastochromanol-S. Ubiquinone 9 and 10 heveaflavone, vitexin, and isovitexin are also reported. The latex contains 60% water, 37% caoutchouc, 0.34% protein, 1.45% quebrachitol, 0.25% sugar, 0.53% ash, and 0.34% undetermined substances. Arachidylacohol, r, a-, b-, g-, and D-tocotrienol, hevein, L-inosit-2-methylether, b-indolylaceticacid, trigonelline, ergothioneine, and hercynine. Bark contains D-apiose (C5H10O5). Seeds contain the toxin linamarin (C10H17NO6). The seed oil (ca 40%) contains 7% palmitic-, 9% stearic-, 0.3% arachidic-, 30% oleic-, 30–50% linoleic-, and 2–23% linolenic-acids (List and Horhammer, 1969–1979).

Description

Tree up to 40 m tall, with girth 2.6–3.3 m; stems smooth and straight; trunk unbranched up a long way and then with much-branched leafy canopy; bark grayish; taproot well-developed; leaves alternate, trifoliolate, stipulate, petioles 7.5–10(-70) cm long; leaflets obovate, apically acuminate, entire, basally acute, penninerved, 10–15(-50) cm long, 3–6(-15) cm broad, elliptic-lanceolate in outline; flowers numerous, monoecious, creamy, yellow or green, in axillary pubescent panicles, sweet-scented, small; female flowers apical, the more numerous male flowers lateral in the inflorescence; petals absent; fruit a 3-lobed, 3-seeded ellipsoidal capsule, each carpel with 1 seed; seeds ellipsoidal, variable in size, 2.5–3 cm long, mottled brown, lustrous, weighing 2–4 g each. Seeds collected July–September in India (Reed, 1976).

Germplasm

Reported from the South American and, secondarily, the Indonesia-Indochina Centers of Diversity, rubber, or cvs thereof, is reported to tolerate disease, drought, high pH, insects, laterite, low pH, slopes, virus, and waterlogging (Duke, 1978). There are many improved varieties and cultivars in areas where Para Rubber is cultivated commercially. These vary in size, productivity of latex, and disease resistance (Reed, 1976). (2n = 36, 34,72)

Distribution

Native to the Amazon region; Brazil, Venezuela, Ecuador, Colombia, Peru, and Bolivia. Introduced to many other tropical regions of the world, as Indonesia, Malaysia, Liberia, India, Sri Lanka, Sarawak, and Thailand (Reed, 1976).

Ecology

Ranging from Subtropical Wet (without frost) to Tropical Dry to Tropical Wet Forest Life Zones, rubber is reported to tolerate annual precipitation of 10.2 to 42.9 dm (mean of 24 cases = 24.5), annual temperature of 23.1 to 27.5°C (mean of 24 cases = 25.6), and pH of (4.0) 4.3 to 8.0 (mean of 18 cases = 5.7) (Duke, 1978). A rain-forest species of the Amazon Basin, rubber is now an Asian crop, with Asia producing 92% of the world's natural rubber in Malaysia, Thailand, Sri Lanka, South Vietnam, and Sarawak. Most rubber is between 15°N and 10°S latitude, with hot equable humid climates, evenly distributed annual precipitation of 19 to 26 dm or more and temperatures between 23° and 35°C. Tolerates but does not flourish in areas with pronounced dry seasons and temperature fluctuations. Also tolerates some waterlogging and a wide pH range (4–8) but does better in acid soils. Lime is harmful, and shallow or poorly drained or peaty soils should be avoided. Thrives best in deep well-drained loamy soil, covered by natural undergrowth or leguminous cover-crop and protected from erosion (Reed, 1976).

Cultivation

Propagated by seeds or vegetatively by buddings or by a combination of both. Fruits burst open when ripe and the seeds are scattered up to 33 m from tree. Seeds gathered and sown fresh as they lose viability rapidly (only 7–10 days), extended to 4–6 weeks, if packed in charcoal powder or sawdust with 15–20% moisture in special containers. Buds collected from seedling trees used for budding. Area to be planted to rubber trees is cleared, then lined and marked for roads and drainage. Planting pits are dug, 75 x 75 x 75 cm, or 90 x 90 x 90 cm, and filled with surface soil and manure. Seedlings are raised in nurseries or directly in the field. Seeds germinate in 1–3 weeks, depending on climatic conditions and freshness of seed. Seedlings are 1–1.3 m tall in 6 months. About 100,000 plants/ha is average for a seedling plot, of which 60,000 to 70,000 should reach standard pulling size in 10–15 months. Then plants are uprooted, the stem cut back to 45–60 cm, the taproot 45–70 cm, and the lateral roots to 10 cm. Seedlings make good cuttings but rubber-bearing trees take very poorly or not at all. Transplanting to field done during monsoon. Tapping stands of 250–300 trees per hectare are recommended, obtained by thinning budwood densities of 375 to 450 or seedling densities of 500 to 600. Wider spacing might be used, intercropping coffee or cocoa, perhaps in conjunction with ipecac. A fodder crop such as Cajanus, might be tried for lac production, instead of the usually recommended covercrops (Centrosema, Calopogonium, Flemingia, Pueraria, Psophocarpus). After a few years under legumes, no N fertilizer may be needed, but phosphorus, magnesium, and potassium may be limiting in some areas. Potassium deficiency is frequent in Vietnam (Reed, 1976).

Harvesting

Tapping begins when trees are 5–8 years old, depending on the area, and increases every year until a maximum at about 20 years, then yield sustained for 40–50 years or more. Tapping consists of removal by excision of a thin cut of bark about 1 mm deep at regular intervals, thus opening the latex vessels in the bark, which are arranged in concentric cylinders and run in counter-clockwise spirals up the trunk. Usually the cuts run half-way around the trunk, but may encircle the tree. Several types of cuts are used. Only the basal part (1.3 m) of the trunk is tapped (most latex vessels develop here). Special knives are used to cut the proper depth and angle. Latex is collected through a small spout fixed in the bark in cups placed at end of cut, large enough to collect one-day's flow. Trees are tapped early in morning when flow of latex is highest; flow decreases with temperature and usually ceases in about 3 hours. An average tapper can tap 200–300 trees in 3 hours. Then the tapper starts back through the grove and empties the cups into large pails or buckets, sometimes adding a few drops of dilute ammonium solution to prevent coagulation. Rubber yield can be increased treating the bark below the tap with yield-stimulating mixtures containing plant hormones and selective weed-killers with hormone properties, as Stimalax, Eureka, 2,4-D, 2,4,5-T in palm oil (Reed, 1976). Copper sulfate also enhances latex flow (Rogers, 1981).

Yields and Economics

Rubber is produced year round, with great fluctuations month to month. Average prewar yields for unselected trees was about 300–450 kg latex/ha; about twice that for bud-grafted trees of approved clones, and 700–2,000 kg latex/ha for improved plantings. Average number of tappings per year is 120–140 in India, 160 in Malaysia. Some Malayan clones yield 2,250 kg/year, in best years 4,300 kg. Major world supply of natural rubber at present is obtained from Malaysia, Sumatra, Java, Indochina (Thailand is third largest), and Sri Lanka, with smaller quantities from Sarawak, India, Burma, and Equatorial Africa, and the rain-forests of tropical South America. Production in Thailand rose from 97,108 MT in 1953 to 258,000 MT in 1968. World production of Para rubber is 1.9–2.2 million tons. (Indonesia [38%], Malaysia [33%], Thailand [7%], Sri Lanka [5%], Indochina [5%], and India [1.2%]). Major consumers are United States (average 1 kg per capita), United Kingdom, West Germany, and France. The U.S. rubber products industry employs more than 500,000 people, producing more than $17 billion worth of goods and consuming 3.4 million MT rubber/yr. Natural rubber accounts for 1/3 of the world's rubbers, tires and tire accessories using nearly 3/4 of U.S. natural rubber consumption in 1974 (Rogers, 1981).

Energy

I open my discussion of Hevea as an energy plant with two quotes. Pankhurst (1983) has higher energetic yields for rubber than I have seen elsewhere("rubber latex yields equivalent to 62 barrels oil/ha/yr.") Rogers (1981) says that natural rubber, occupying 6.9 million ha, "ranks as one of our most important biomass products in today's industrialized world." Such quotes led me to include rubber in my energy thinking. Some people have equated the hydrocarbons of latex with petroleum. With yields as high as 6–8 MT rubber/ha reported, it is safer to compare this with a sustainable yield of 15–20 barrels of oil per hectare. Rubber is often planted at wide spacing, intercropped with coffee or cocoa. On small holdings, intercropping is often practiced, but annuals should be more than a meter away, bananas more than 2 m. In intercropping situations such as these, there could be 1–5 MT of prunings, dead limbs, leaves, etc. per hectare. Assuming that leaf-litter fall in these simulated forest agroecosystems is equal to that in natural forest ecosystems, rubber plantations, like other forest plantations, might yield 5–12 MT/ha/yr. Five may be a reasonable assumption. Leaf fall values of 5 MT/ha/yr are reported for San Carlos, Venezuela, 8–10 in an Ivory Coast Forest, 12 in Khao Chong Forest in Thailand, 7.4–10.7 near Belem, Brazil, 6.7 near Manaus. Most values in tropical forests are greater than 7 MT/ha/yr and several exceed 10.

Biotic Factors

About 90 species of fungi are known to attack Hevea trees, the most prevalent ones being the following: Botryodiplodia elactica and B. theobromae, Colletotrichum heveae (leaf spot), Fomes lamaensis (brown root rot), Gloeosporium heveae (die-back), Oidium heveae (powdery mildew), Pellicularis salmonicolor (pink disease), Phytophthora palmivora (causing fruit rot, leaf-fall, black thread, and die-back), Polystichus occidentalis and P. personii (white spongy rot), Sphaerella heveae (rim bright), Sphaerostilbe repens (red rot) and Ustulina maxima (charcoal rot). It is also attacked by Bacterium albilineans, and parasitized by Loranthus spp. Nematodes isolated from Hevea brasiliensis include: Helicotylenchus cavenessi,H. dihystera, H. erythrinae, Meloidogyne incognita acrita, M. javanica, Pratylenchus coffeae, P. brachyurus. (Golden, p.c., 1984) Insect pests include the following species: Scale insects (Aspidiotus cyanophylli and Parasaissetia nigra). White ants cause serious damage to trees at all ages. Snails can be serious pests to young trees. Various animals can damage the trunks (Reed, 1976). The Hevea tree is subject to many types of diseases that must be controlled for economic production. Three types of root disease, classified as white, red, and brown, are controlled by cutting away diseased tissue and applying prophylactic coatings. Panel diseases, classified as black stripe, moldy rot, and panel necrosis, are minimized by spraying or coating specific fungicides. Stem disease, consisting of pink disease, stem canker, and dieback is reduced by brushing on specific fungicides. Leaf disease, consisting of abnormal leaf fall, Gloeosporium leaf disease, powdery mildew, and bird's eye spot, is controlled by a variety of sprays, including copper oxychloride, sulfur dust, and others applied by spray or dusting techniques (Rogers, 1981).

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw