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Morus alba L.

Moraceae
White mulberry, Russian mulberry, Silkworm mulberry, Moral blanco

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 unpublished.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

Trees are extensively grown (e.g. southern Europe, India) for their leaves as food for silkworms. Fruits may be eaten raw or cooked. Fruits are an ingredient of a particularly seductive drink known as Mulberry Wine. Wild birds, poultry, and hogs are fond of fruits. Mulberry leaves are sometimes eaten as a vegetable and are useful as a cattle fodder. Being nutritious and palatable, they are said to improve milk yield of dairy animals. Wood is valued for sporting goods due to its elasticity and flexibility when steamed, being considered as good as ash. Sapwood is white to yellowish-white, heart-wood golden brown, darkening after exposure; light to moderately heavy, straight-grained, not liable to split, but shows tendency to warp, moderately durable under cover, easy to work and finish, used mainly for hockey sticks, tennis and badminton rackets and racket presses, cricket bats, house building materials, agricultural implements, and furniture. Furnishes a medium grade fuel wood. Stem bark is fibrous and used in China and Europe for paper making. Twigs are used as binding material and for making baskets. Trees often used as ornamentals, roadsides or boundary markers (Reed, 1976; C.S.I.R., 1948–1976).

Folk Medicine

According to Hartwell (1967–1971), the fruit juice is used in folk remedies for tumors of the fauces. Reported to be antidotal, antiphlogistic, antitussive, antivinous, astringent, bactericide, diaphoretic, ditiretic, emollient, escharotic, expectorant, fungicide, laxative, nervine, purgative, refrigerant, restorative, sedative, tonic, and vermifuge, white mulberry is a folk remedy for aphtha, armache, asthma, bronchitis, bugbite, cachexia, cold, constipation, cough, debility, diarrhea, dropsy, dyspepsia, edema, epilepsy, fever, headache, hyperglycemia, hypertension, inflammation, insomnia, melancholy, menorrhagia, snakebite, sorethroat, stomatitis, tumors, vertigo, and wounds (Duke and Wain, 1981). Medicinally, fruits are laxative, refrigerant in fevers, and used locally as remedy for sore throat, dyspepsia, and melancholia. Roots and bark are purgative, anthelmintic, and astringent; leaves considered disphoretic and emollient; a decoction of leaves being used as a gargle for inflammation of throat (Reed, 1976).

Chemistry

Per 100 g, the fruit is reported to contain 87.5 g H2O, 1.5 g protein, 0.49 g fat, 8.3 g carbohydrates, 1.4 g fiber, 0.9 g ash, 80 mg Ca, 40 mg P, 1.9 mg Fe, 174 IU vit. A, 9 mg thiamine, 184 mg riboflavin, 0.8 mg nicotinic acid, and 13 mg ascorbic acid. Dry leaves contain 18–28.8% protein, 11.3–0.7% MgO, 0.8–13.6% soluble sugars, 0.6–1.4% P2O5, 2–3.9% K2O, 1.4–2.4% CaO, 0.2–0.7% MgO, 0.8–1.8% Al2O3, 0.05–0.26% Fe2O3, 1.8–2.6% SiO2, and 0.3–0.56% SO4 (C.S.I.R., 1948–1976). Substances which attract the silkworm larvae to the leaves have been identified as citral, linalyl acetate, linalol, terpinyl acetate, and hexenol, the first 3 being more effective. b-sitosterol (ca 0.2% in leaves), along with some sterols and a water-soluble substance, is the main factor which stimulates the biting action; the amount of food eaten by larvae is controlled by the concentration of b-sitosterol. Protein perparations from young mulberry leaves form an excellent supplement to protein-deficient diets. Non-protein nitrogen accounts for ca 22% of the total nitrogen in young leaves and ca 14% in mature leaves. Amino acids identified in the free form are: phenylalanine, leucine, valine, tyrosine, proline, alanine, glutamic acid, glycine, serine, arginine, aspartic acid, cystine, threonine, sarcosine, gamma-amino-butyric acid, pipecolic acid, and 5-hydroxy pipecolic acid. The leaves are a good source of ascorbic acid, with 2–3 mg/g, of which over 90% is present in the reduced form. They contain also carotene, vitamin B1, folic acid, folinic acid, and vitamin D. Phytate phosphorus accounts for 18.2% of total phosphorus. Volatile constituents identified in steam-distillates of the leaves are: n-butanol, beta-gamma-hexenol, methyl-ethyl acetaldehyde, n-butylaldehyde, isobutylaldehyde, valeraldehyde, hexaldehyde, alpha-beta-hexenal, acetone, methyl-ethyl ketone, methyl-hexyl ketone, butylamine, and acetic, propionic, and isobutyric acids. Leaves also contain calcium malate, succinic, and tartaric acids, xanthophyll and isoquercitrin (quercetin 3-glucoside) and tannins; adenine, chorine, and trigonelline bases are present in young leaves. Analysis of leaves gave (dry weight basis): protein, 14.0; EE, 6.8; NFE, 49.7; total ash, 13.8; calcium (CaO, 2.74; and phosphorus (P2O5) 0.45% (C.S.I.R., 1948–1976). According to Hager's Handbook, the wood contains 0.3–0.44% morin, dihydromorin, dihydrokaempferol, 2,4,4',6-tetra-hydroxybenzophenone, maclurin, and ca 2% hydroxyresveratrol. Seeds contain 33–38% fatty oil (with linoleic-, stearic-, oleic-, myristic-, palmitoleic-, and arachidic-acids) and ca 25% protein (List and Horhammer, 1969–1979).

Description

Small to medium-sized monoecious or dioecious shrub or tree, up to 15 m tall, wide-spreading, round-topped, trunk attaining 60 cm in diameter; leaves alternate, stipulate, variable in shape, lobed or unlobed, cordate, dentate, acuminate, long-petiolate, 12 x 8 cm on fruiting branches, up to 25 x 20 cm on vigorous non-fruiting branches, usually smooth above, glabrous or pubescent along veins beneath, thin, light green; flowers small, greenish-yellow, in dense spikes to 2 cm long; sepals 4; stamens 4; pistils with two styles; staminate spikes soon deciduous; pistillate spikes maturing into an aggregate fruit (syncarp) of drupelets; syncarp ovoid to oblong-cylindric, 1–5 cm long, white, pinkish or purplish to nearly black, edible long before ripe, sweet, but insipid; seeds brown, 1–1.2 mm long, 12,000–13,000/oz. Fl. Mar.–May, fr. Summer.

Germplasm

Reported from the China-Japan Center of Diversity, white mulberry, or cvs thereof, is reported to tolerate disease, drought, frost, hydrogen fluoride, low pH, poor soil, salt, shade, slope, and weeds (Duke, 1978). It is also said to tolerate aerial sprays of 2,4,5-T but not ground treatment. Numerous cvs have been adapted in various silk-producing regions of the world, differing in their adaptability to various soils and climates (as those suited for cold climate, for areas with severe winters, or for mild climate; some are early, others late or intermediate); resistance to diseases; food value of leaf for silkworms; and suitability for use as stock or scion in grafting. Japan has about 700 types of which 21 are extensively cultivated. Most important cv grown in India is M. alba var. muticaulis Loud., fast growing, adapted to field culture, and giving high yield of large, tender, thick leaves. In India, mulberry is either grown as a field crop (plants kept in form of bushes and the leaves harvested several times a year for the multivoltine race of silkworms) or as a tree (leaves harvested only once a season for rearing univoltine races of silkworms). In Bengal, cultivation of the var. atropurpurea along borders of bush plantations has been recommended. Largest acreage of mulberry in India is in Mysore, where more than 75% of total mulberry raw silk production occurs. There has been some selection of mulberry in India, the selection 'K.M.', in West Bengal, gives 50% more leaves than local types, and is popular in Mysore for grafting purposes. Also strains 'Selected I' and 'Selected V' evolved in Mysore are promising. Forty-four cvs, some local, others introduced, have been studied in Thailand. The Russian cvs (M. alba var. tatarica) are often planted as windbreaks, as they are very hardy and thrive under greatest neglect. For this purpose, they are planted 2.6–7 m apart, making excellent screens and standing pruning well. Used as rootstocks for other mulberries, they are very popular in the Great Lakes Region of the United States. Raised from seed and quite variable, the fruits are inferior, suitable only for birds. 'New American', considered the best cv, 'Trowbridge' and 'Thorburn' are the leading kinds of fruit-bearing mulberries for the North. (2n = 28)

Distribution

Native of China, white mulberry is cultivated throughout the world wherever silkworms are raised, and is occasionally cultivated elsewhere in Europe, North America, and Africa. Having escaped, trees often appear on roadsides, along fencerows, and as ornamentals.

Ecology

Ranging from Cool Temperate Steppe to Warm through Tropical Very Dry to Moist Forest Life Zones, white mulberry is reported to tolerate annual precipitation of 4.4 to 40.3 dm (mean of 28 cases = 9.8), annual temperature of 5.9 to 27.5°C (mean of 28 cases = 16.6), and pH of 4.9 to 8.0 (mean of 23 cases = 6.7) (Duke, 1978, 1979). According to Wyman (1974), it tolerates average annual minimum temperatures of -10 to -20°F (-23.3 to -28.9°C). White mulberry grows well on wide variety of soils. It withstands drought, once well established. However, it is liable to wind damage. In India, it is cultivated up to 3,300 m elevation, but can grow as well at sea-level.

Cultivation

Mulberry trees can be propagated by seeds, cuttings, or graftings. Seeds should be treated with camphor water before sowing to ward off disease. Thin layer of soil and ashes spread over seed after sowing. Beds kept moist. Seeds germinate in 9–14 days, depending on the season. When seedlings are about 7.5 cm tall, they are thinned and weeded. For bush mulberries, seedlings 10–15 cm tall are used as transplants; for trees, seedlings are allowed to grow 1.3 m and trained before transplanting. Cuttings are obtained from exhausted bushes at pruning time. Branches are cut into pieces 22–30 cm long with 3 buds and planted immediately. Sometimes cuttings are tied into bundles and kept buried in soil 6–9 cm deep, kept watered, and after about a month when buds have shoots about 5 cm long, are taken out of mud and planted. Cuttings root quickly, and with cultivation and irrigation, they may attain a height of 75 cm in 6 weeks. Mulberry plants from seedlings are more expensive, but give better plants than those from cuttings. Seedlings usually planted 2 to a pit 4" pits spaced 60–75 cm apart. Root grafting is usually practiced in India. Stocks are seedlings of any type; the scion are selected from high yielding, quick-growing types with large leaves of good food value. Rooted cuttings are planted in pits or furrows. In dryland culture, pit system is uged. Cuttings placed in prepared pits, 30 cm in diameter and 22 cm deep, spaced 75 cm apart, in rows 75 cm apart. Planted in July after SW monsoon has set in. Usually 3 cuttings are put in each pit and watered; 75,000 to 120,000 cuttings/ha. When irrigation is used, cuttings are planted in furrows in April or May, 10 cm apart, the furrows being 22 cm apart. With this very close planting, 110,000 to 200,000 cuttings/ha are required. Grafted plants develop a better root system than those from either seedlings, cuttings, or layerings, and are used exclusively in Japan. Grafted trees are planted 1.6 m apart each way, about 4,000/ha, and are especially suitable for irrigated areas. Various techniques are employed to prune and train mulberry plants. After each pruning, the field is cultivated and manured.

Harvesting

Fruits are picked or shaken on drop cloth's when in season. Not being attractive for marketing, they are usually consumed locally. For harvesting leaves, mulberry bushes under irrigation attain a height of about 1.3 m in 10 weeks, when the leaves are ready for picking. Under rainfed conditions, first picking may be done 12–17 weeks after planting. About 10 pickings per season for irrigated plants and 6 or 7 for rainfed crops. Best time for picking leaves is in the evening. Harvested leaves are stored in small loose heaps in cool room and protected from heating, fermentation, or drying out. Bushes may be productive for as many as 15 years, after which old plants are pulled out, the land planted to a green manure crop and then replanted to mulberry bushes.

Yields and Economics

Yield of mulberry leaves varies according to the soil, moisture supply, manuring, and cultural practices. Bushes grown under rainfed conditions yield 4,000–7,000 kg/ha annually; under irrigation, from 10,000–14,000 kg/ha and selected varieties, as 'Selected I' and 'Selected V' yield as high as 22,000 kg/ha. Yields of leaves from tree mulberries are not available. Different trees vary greatly in fruit production. Sericulture is the most important commercial use for white mulberry. Young, fully developed leaves are best for feeding silkworm larvae. In Thailand, local silkworms produce 300–800 m of fiber per cocoon compared with 1,600 m for Japanese silkworms, and 1,400 m for a cross between them. Those of us who have seen solid coats on the ground of white fruits of the white mulberry or red to purple fruits of other species, realize that there is a lot of sugar there that could be converted to alcohol.

Energy

Finding rather high yields of ethanol in peracetic acid treatments and four days incubation of the sawdust, Lee commented, "the yield of ethanol from wood sawdust can be increased from 1% to 6% if the treatment for delignification is improved. It is concluded that Populus species and Morus show great potential for ethanol production. We have established about 300,000 ha of improved, fast growing Populus hybrids (mostly P. x euramericana and P. alba x glandulosa) throughout the country. In Korea...a 45,000 ha plantation has been established with mulberry trees mainly to produce leaves for silkworms... Most of the stems and branches produced by mulberry trees so far are utilized for heating or cooking and as a supporting material for horticultural crops. Recently, preliminary studies on yields of ethanol from mulberry trees show promising possibilities. Also, if the conversion of mulberry tree biomass to fuels is economically feasible, planting mulberry trees will be greatly advantageous to Korean farmers. Other fuel sources might be organic wastes, mill residues, logging residues and agricultural by-products such as rice, barley, or wheat straw. Remarkable yields of energy may be expected on the assumption that the biomass produced from all existing plantations is converted to fuels" (Lee, no date). With 10% sulfuric acid sawdust hydrolyzed for one hour yields 28% sugar.

Biotic Factors

The following are listed as affecting Morus alba, in Agriculture Handbook No. 165: Acrospermum foliicolum, Agrobacterium rhizogenes (hairy root), Armillaria mellea (root rot), Botryosphaeria ribis, Cercospora moricola (leaf spot), Cercosporella mori (leaf spot), Ciboria carunculoides, Cytospora sp. (twig canker), Dermatea mori, Dothiorella sp., D. mori (canker, twig blight), Fusarium lateritium var. mori (canker, twig blight), Gibberella baccata, Helicobasidium purpureum (root rot), Massaria epileuca, M. olivacea, Meloidogyne spp. (root knot nematodes), Mycosphaerella mori (leaf spot), Myxosporium diedickei (twig blight), Nectria sp. (canker), Nectria cinnabarina, Nectria verrucosa, Phymatotrichum omnivorum (root rot), Physalospora obtusa, Polyporus farlowii (heart rot), P. gilvus (wood rot), P hispidus (heart rot), Pseudomonas mori (bacterial spot, blight), Rosellinia aquila (root rot), Schizophyllum commune (wood rot), Sclerotinia sp. (canker), Sphaeropsis sp., S. sepulta, Stereum cinerascens (wood rot), Tryblidiella nigrocinnabarina, T. rufula var. microspora, Valsa morigena, Valsaria insitiva, and the leaf mottling virus. In addition, Browne (1968) lists the following as affecting this species: mulberry yellow net virus; Cephaleuros virescens (Algae); Auricularia auricula-judae, Botryosphaeria obtusa, Cerotelium fici, Cerrena unicolor, Corticium salmonicolor, Diploidia morina, Fomes robiniae, F. senex, Gibberella moricola, Hendersonula toruloidea, Inonotus cuticularis, I. hispidus, Macrophomina phaseoli, Nectria coccinea, Phloeospora mori, Phyllactinia guttata, Phyllosticta morifolia, Polyporus squamosus, Sclerotinia fuckeliana, S. sclerotiorum, Sphaeropsis mori, Thyrostroma mori, Valsa ambiens, and Xylaria polymorphs (Fungi). Dendrophthoe falcata, Loranthus sp. (?), Viscum album (Angiospermae); Tetranychus telarius (Acarina), Anoplophora chinensis, Apriona cinerea, A. germari, Batocera rufomaculata, Celosterna scabrator, Gonocephalum vagum, Mimastra cyanura, Olenecamptus bilobus, Phryneta leprosa, Sthenias grisator, and Taeniotes scalaris (Coleoptera). Aleuroplatus pectiniferus, Ceroplastes ceriferus, Chunrocerus niveosparsus, Drosicha stebbingi, Hemiberlesia lataniae, Icerya purchasi, Parasaissetia nigra, Parthenolecanium persicae, Planococcus kenyae, Pseudaulacaspis pentagona, Pseudococcus filamentosus, Pulvinaria maxima, and Quadraspidiotus perniciosus. (Hemiptera). Anacanthotermes macrocephalus (Isoptera); Acria emarginella, Archips micaceanus, Ascotis selenaria, Diacrysia obliqua, Euproctis lunata, E. sulphurescens, Glyphodes pyloalis, Hyposidra talaca, Indarbela tetraonis, Labdia semicoccinea, Metanastria hyrtaca, Penicillaria nugatrix, and Spodoptera litura. (Lepidoptera). Choroedocus illustrius, and Schistoceria gregaria (Orthoptera). Reed (1976) adds the following: Aecidium mori (rust), Cytospora atra (bronze canker), Diplodia butleria (stem rot), Ganoderma applanatum (white sap rot), G. lucidum (heart rot), Polyporus tulipiferae (white spongy sap rot), Thyrostoma mori (Coryneum mori, causes reduction in leaf production), Trametes badia (butt rot), and Ustilago haesendockii (smut leaf). Nematodes include Melodoigyne javanica and M. sp. According to Reed (1976), insects causing most damage to mulberry are: Phenococcus hirsutus (sucks sap of stem, leaf or petiole, causing severe curling and crinkling of leaves and swelling and twisting of apical regions), Pseudodendrothrips ornatissima (thrips), and white grubs and termites.

References

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