Mulberry

Morus spp.

1. Identification and origin

Morus spp. is a genus of the Moraceae family that includes several species known as mulberries, notably Morus alba L., Morus nigra L. and Morus rubra L.. The origin varies according to the species: M. alba is native to East Asia, M. nigra to Western Asia and M. rubra to North America. Mulberries have been cultivated for millennia for the production of fruits (mulberries), timber and, above all, as food for the silkworm (Bombyx mori).

2. Economic importance

The mulberry is of economic importance in three main areas:

• Fruit growing: production of mulberries for fresh consumption, processing (jams, juices, vinegars) and pastry.
• Sericulture: Morus alba is the food base of the silkworm, being essential for the production of natural silk.
• Timber and ornamental uses: strong timber of good workability; trees widely used in rows and for shading.

The growing demand for fruits rich in antioxidants has increased commercial interest.

3. Botanical characterisation

Trees or shrubs of medium habit, with a rounded crown and simple, alternate leaves, with serrated and often lobed margins (above all in M. alba). The flowers are small, unisexual, grouped in cylindrical inflorescences. The fruit is a compound infructescence (sorosis), fleshy, of variable colouration (white, red, purple or black). Reproduction is by seed, cutting or grafting, depending on the species and the production objective.

4. Soil and climate requirements

Mulberries adapt well to temperate and Mediterranean climates, tolerating heat and periods of moderate drought. They prefer deep, fertile and well-drained soils, with a pH between 5.5–7.5. Morus alba is more tolerant of cold and drought; M. nigra prefers more humid environments and rich soils. They are sensitive to prolonged waterlogging.

5. Main pests

• Aphids (Aphididae): deformations and production of honeydew.
• Scale insects (Coccoidea): sap sucking and vegetative decline.
• Fruit fly: Ceratitis capitata may attack ripe fruits.
• Defoliating caterpillars: various species of Lepidoptera.
• Mites (Tetranychidae): silvering and reduction of the photosynthetic area.

6. Main diseases

• Powdery mildew: Phyllactinia corylea and Uncinula spp. cause white mycelium on leaves.
• Anthracnose: Colletotrichum spp. causes leaf spots and necrosis.
• Cankers: Botryosphaeria spp. and other opportunistic fungi.
• Root rots: Armillaria spp. and Phytophthora spp. in poorly drained soils.
• Occasional bacterioses: leaf spots and necrosis under humid conditions.

7. General crop management

It includes the use of certified plants, planting in well-drained soils, formative and cleaning pruning, weed control and monitoring of pests and diseases. Regular irrigation improves the size and quality of the fruits, although the species is relatively hardy. The removal of dry or infected branches and the maintenance of good ventilation reduce sanitary problems. Harvesting should be carried out when the fruits reach the colouration and texture characteristic of maturity.

Bibliographic references

• EPPO Global Database – Morus spp..
• CABI – Crop Factsheets – Morus spp..
• FAO – Technical documents on hardy fruit trees.
• Orwa, C. et al. (2009). Agroforestree Database: Morus species.
• Ercisli, S. & Orhan, E. (2007). Chemical composition of white (Morus alba), red (Morus rubra) and black (Morus nigra) mulberry fruits. Food Chemistry.
• Poljak, I. et al. (2017). Morphological and genetic diversity of mulberry species. Scientia Horticulturae.