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Description: Excoecaria agallocha is a small to medium-sized tree up to 12 m (40 ft.) tall, with acrid, toxic milky latex and glossy leaves 4-12 cm (2-5 in) long. The young leaves are pinkish, but become bright red when they are ready to drop off the tree. Its tiny, wind pollinated flowers are produced in dense spikes. Because it is dioceous (male and female flowers are segregated on separate plants), when the flowers are blooming, the trees can appear to be surprisingly different. E. agallocha bears small, round fruit capsules that explode when ripe to disperse the seeds via water. The seeds have an air space within the seed coat which helps them float. The bark of the tree is rough and grayish.
Distribution: E. agallocha is native from India to parts of Micronesia including areas of Palau, Yap, the Marianas and Chuuk, as well as in Western Polynesia. It is common on the seaward margin of the coastal forest on coral limestone, sometimes in mangrove forests, but not too far inland. Thus, this tree is principally found in the landward edge of mangrove forests and can often be found at or just above the high tide mark.
A key characteristic of this species is the toxic milky latex that exudes from broken leaves, bark and twigs, a sap that “can blister skin, hurt eyes and may even cause temporary blindness” (the Malay name for E. agallocha is Buta-buta, which is also its name on Guam, meaning “blind”). Indeed, the poisonous latex of E. agallocha can cause severe inflammation of the eyes and may leave a person blind for weeks. Even the smoke of its burning wood is caustic and can cause severe irritation to the eyes. For example, the famous Captain Bligh (1792) wrote in his travel account of the Voyage of the Bounty what occurred on Saturday the April 25th 1789 on Nomuka [Annamooka] a small island in the southern part of the Ha’apai group of islands in the Kingdom of Tonga where Bligh and the Bounty had spent three days collecting firewood and water; the mutiny on the Bounty occurred the day after it left Nomuka:
“On the 25th at daylight the wooding and watering parties went on shore. I had directed them not to cut the kind of tree [E. agallocha] which, when Captain Cook wooded here in 1777, blinded for a time many of the woodcutters” [e.g., see Bligh, William. A Voyage to the South Sea. 1792 from Project Gutenberg].
However, as toxic as the sap of E. agallocha may be, smoke from the bark is sometimes used to treat leprosy, and its wood, if processed carefully, is used in some areas as firewood and converted into charcoal. In addition, even though its wood is soft, white and light with a fine grain and rots quickly, it has some other valuable economic uses. For example, in Bangladesh, the relatively weak wood of this tree is an important source for making inexpensive planks as well as matches, matchboxes and pulp for paper. In some areas, the milky sap is used to stun fish, and some indigenous peoples in New Guinea use the sap as an ingredient in arrow poison, while in Fiji, the bark is sometimes used to treat severe pain caused by the stings of poisonous fish (e.g. see Mastaller 1997:97-98,102). It appears that over much of its natural range of distribution the mangrove species E. agallocha has been used in traditional medicines to treat leprosy, probably because the active alkaloids in the milky latex produced by this species are effective in reducing the pain of lepers when used in bathing water. Actually, E. agallocha has been widely used in folklore medicine for the treatment of several diseases. Recently, E. agallocha has been tested for modern medical uses with modern clinical trials indicating that the plant may have anti-HIV, anti-cancer, anti-bacterial and anti-viral properties. For example, a study by Patil et al. (2011:147-155) investigated the “anti HIV and anticancer properties of active fraction of stem ethanol extracts of the plant,” with results that “clearly indicate strong anti HIV and anticancer properties in stem extracts of E. agallocha.” Furthermore, antimicrobial (antibacterial, antiviral and antifungal) agents from mangrove plants and their endophytes indicate that E. agallocha is a valuable medicinal resource needing further research. For example, Ibrahim and Effendy (2013) listed many active bioactive agents found in E. agallocha or its endophytes including Alkaloids, carotenoids, chalcones, cyclitol, diterpenes, excoecaria toxins, fluratoxin, glycerides of fatty acids, lipids and waxes, phorbol esters, polyphenols, polysaccharides, proteins, saponins, steroids, sugars, tannins, triterpenes, phomopsin A, B, C and, cytosporon B and C. (also see e.g., Prihanto et al. 2012). Although the milky sap of this mangrove plant can to irritating and toxic, it does have a legasy of traditional use in medicine for treatment of various diseases such as epilepsy, ulcers, leprosy, rheumatism, and paralysis. These traditional treatments reportedly involve various parts of E. agallocha, including the leaves, roots, woods, stems, bark, latex, and seeds. (see Mondal et al. 2016 for an extensive profile on the “Blind-your-eye Mangrove Excoecaria Agallocha, including aspects of its ethnobotany, phytochemistry and pharmacology).
Uses by Island or Island Group:
Uses in Palau: Excoecaria agallocha is sometimes used for firewood in Palau, but it “is also known to be poisonous to the eyes” (Kitalong et al. 2011, also see Defillips et al.1988).
Uses in Yap: According in Okabe (see Defillips et al. 1988), sap extracted from the bark of Excoecaria agallocha is drunk with water once a day to alleviate constipation. It is mixed with other plants for medicine. Falanruw (2015:84) briefly described the dangers of contact with the toxic sap of this member of the Euphorbia family which is noted for a number of species with mildly to strongly poisonous latex: “If the bark [E. agallocha]is scratched or leaves broken, irritating latex is secreted; the sap or even smoke from burning wood of this tree is very irritating to the eyes.”
Uses in Guam: More than a hundred years ago Safford (1905:271) commented on Excoecaria agallocha:
“When the tree is cut or bruised the milky juice flows copiously from the wound and soon hardens like rubber. It is so acrid that it will blister the skin and is almost blinding if it gets into the eyes. The smoke of the burning wood is also very irritating; in Fiji it is thought to be a remedy for leprosy. The wood is white, soft, and spongy. In India fishing floats are sometimes made from the roots.”
For notes on the presence of mangroves on Guam, including Excoecaria agallocha, see Mueller-Dombois and Fosberg 1998.
Uses in Chuuk: The Chuukese name for Neechiichi has been interpreted in a number of ways; one described by Goodenough (2002:155) refers to a “Dripping Place” which is “appropriate to Girschner’s reference to a tree with poisonus sap, presumably the Excoecaria agallocha, known in Chuuk by several names: owusuus, rowusuus, wiisuusu, wusuus).” According to Goodenough, the variation “in what is reported, therefore, may reflect different interpretations of the name in different localities and by different informants.” According to Goodenough and Sugita (2002:369), in Chuuk, the fruit of E. agallocha is used as medicine for eye trouble.”