Apple tree

Malus domestica

1. Identification and origin

The apple tree (Malus domestica Borkh.), belonging to the Rosaceae family, is one of the oldest and most widely cultivated temperate fruit trees in the world. The species results from a complex process of hybridisation and domestication involving mainly Malus sieversii (Ledeb.) M.Roem. (Central Asia) and Malus sylvestris (L.) Mill. (Europe). Domestication began more than 4,000 years ago in the region of Kazakhstan, with subsequent spread to Europe, Asia and, later, to the American continent.

2. Economic importance

The apple is one of the most produced fruits globally, with high economic value and a strong presence in the food industry. It is consumed fresh, processed (juices, cider, purées, dehydrated products) and used in pastry. The main producers include China, the United States, Poland, Turkey, Italy and France. In Portugal, production stands out in the regions of Beira Alta, Beira Interior, Oeste and Trás‑os‑Montes, with designations of origin such as Maçã de Alcobaça and Maçã Bravo de Esmolfe.

3. Botanical characterisation

A deciduous tree of medium size (3–8 m), with a rounded canopy and short productive branches. The leaves are simple, ovate, serrated and pubescent on the lower surface. The flowers, white to pink, appear in corymbs and are essentially entomophilous, with a strong dependence on pollinators. The fruit is a pome, with a thin epicarp, fleshy mesocarp and seeds housed in five locules. The root system is relatively shallow, especially when grafted onto dwarfing rootstocks.

4. Soil and climate requirements

The apple tree is typical of temperate climates, requiring an accumulation of winter chilling (600–1,500 hours < 7 °C, depending on the cultivar) to break dormancy. It prefers moderate temperatures during growth and cool nights in the ripening phase. It develops best in deep, well-drained soils of medium texture, with a pH between 6.0 and 7.0. It is sensitive to waterlogging and benefits from regular watering in dry regions. The choice of rootstock influences vigour, tolerance to heavy soils, disease resistance and productivity.

5. Main pests

• Codling moth (Cydia pomonella): The main pest of the fruit, causing galleries and commercial losses.
• Woolly apple aphid (Eriosoma lanigerum): Forms colonies on branches and roots, causing deformities and decline.
• Green aphids (Aphis pomi, Dysaphis plantaginea): Leaf curling and transmission of viruses.
• Leaf miner (Phyllonorycter blancardella): Leaf galleries and reduction of photosynthesis.
• Mites (Panonychus ulmi, Tetranychus urticae): Chlorosis and loss of vigour.
• Fruit fly (Ceratitis capitata): Damage to late cultivars.
• Nematodes (Meloidogyne spp., Pratylenchus spp.): Root decline and lower productivity.

6. Main diseases

• Apple scab (Venturia inaequalis): The most important disease of the apple tree, causing lesions on leaves and fruits.
• Powdery mildew (Podosphaera leucotricha): White coating on leaves and shoots, affecting growth and fruiting.
• Fire blight (Erwinia amylovora): A devastating disease, causing necrosis, wilting and death of branches.
• Cankers (Neonectria ditissima, Botryosphaeria spp.): Necrosis and death of branches.
• Post-harvest rots (Penicillium expansum, Botrytis cinerea): Significant losses in storage.
• Downy mildew (Peronospora farinosa): Less common, but serious under humid conditions.
• Viruses (e.g.: apple mosaic virus, chlorosis virus): Reduction of vigour and productivity.

7. General crop management

Apple tree management involves:

• Choosing cultivars and rootstocks adapted to the climate, soil and chilling requirements.
• Formative and fruiting pruning, essential to balance vigour and production.
• Cross-pollination, ensuring the presence of compatible cultivars and beehives.
• Fertility management with a focus on nitrogen, calcium and boron for fruit quality.
• Controlled watering, avoiding waterlogging and water deficits during the fruit-filling phase.
• Phytosanitary monitoring, with special attention to apple scab, codling moth and fire blight.
• Fruit thinning, promoting larger sizes and reducing biennial bearing.
• Harvesting at the optimal point, considering firmness, colour, soluble solids content and commercial destination.
• Storage in a controlled atmosphere, prolonging post-harvest conservation.

Bibliographic references

• EPPO Global Database. Malus domestica – pests and diseases.
• CABI Invasive Species Compendium. Malus domestica – datasheets.
• Ferree, D. C., & Warrington, I. J. (Eds.). (2003). Apples: Botany, Production and Uses. CABI.
• Tromp, J., Webster, A. D., & Wertheim, S. J. (2005). Fundamentals of Temperate Zone Tree Fruit Production. Backhuys Publishers.
• Jackson, J. E. (2003). The Biology of Apples and Pears. Cambridge University Press.