Citrus

Citrus spp.

1. Identification and origin

Citrus fruits (Citrus spp.) are evergreen tree and shrub species of the Rutaceae family, native to Southeast Asia. The genus includes widely cultivated species and hybrids, such as Citrus sinensis (L.) Osbeck (sweet orange), Citrus reticulata Blanco (mandarin), Citrus limon (L.) Osbeck (lemon), Citrus paradisi Macfad. (grapefruit) and Citrus aurantifolia (Christm.) Swingle (lime). They are currently one of the most important fruit-tree groups worldwide.

2. Economic importance

Citrus fruits have enormous global economic relevance, being consumed fresh and as juice, concentrate, essential oils and processed products. The citrus industry is strategic in Mediterranean, subtropical and tropical regions, with a strong impact on exports, agro-industry and employment. The by-products (peel, seeds, pulp) are used in animal feed, cosmetics and the chemical industry.

3. Botanical characterisation

Evergreen trees or shrubs, with a rounded, dense canopy. The leaves are simple, leathery, with aromatic oil glands. The flowers are white, highly fragrant and hermaphrodite. The fruits are hesperidia, with an epicarp rich in essential oils and a segmented pulp. The root system is relatively shallow, sensitive to waterlogging and root asphyxia.

4. Soil and climate requirements

They prefer subtropical and Mediterranean climates, with mild winters and hot summers. They are sensitive to frost, especially during the flowering and fruiting stages. They develop best in deep, well-drained soils, with a pH between 5.5 and 7.0.
They require a regular water supply, but without soil saturation. Excessive salinity reduces vigour and productivity.

5. Main pests

• Fruit fly (Ceratitis capitata): punctures and rot in the fruits.
• Scale insects (Coccidae, Diaspididae): sap sucking and sooty mould.
• Aphids (Aphididae): leaf curling and transmission of viruses.
• Citrus leafminer (Phyllocnistis citrella): mines in young leaves and reduced growth.
• Lemon moth (Prays citri): damage to flowers, young fruits and shoots, which can compromise fruiting.
• Mites (Tetranychidae, Eriophyidae): silvering and leaf drop.

6. Main diseases

• Citrus canker (Xanthomonas citri subsp. citri): necrotic lesions on leaves and fruits.
• Black spot (Phyllosticta citricarpa): lesions on fruits and commercial losses.
• Root rots (Phytophthora spp.): gummosis and decline.
• Citrus tristeza (CTV): a virus disease transmitted by aphids, causing decline in sensitive rootstocks.
• Alternaria brown spot (Alternaria alternata): leaf necrosis and fruit drop in mandarins.

7. General crop management

Management includes choosing adapted rootstocks, formation and aeration pruning, balanced fertilisation and controlled irrigation. Monitoring of fruit fly, scale insects, leafminer and Prays citri is essential. Preventing Phytophthora requires good drainage and avoiding wounds to the crown. Harvesting should be carried out at the optimum point of ripeness, avoiding mechanical damage that reduces storage life.

Bibliographic references

• EPPO Global Database – Citrus spp..
• CABI Crop Compendium – Citrus spp..
• Davies, F. S., & Albrigo, L. G. (1994). Citrus. CAB International.
• Timmer, L. W. et al. (2000). Compendium of Citrus Diseases. APS Press.
• Spiegel‑Roy, P., & Goldschmidt, E. E. (1996). Biology of Citrus. Cambridge University Press.