Maize

Zea mays

1. Identification and origin

Maize (Zea mays L.) is a cereal of the Poaceae family, native to Mesoamerica, where it was domesticated around 9,000 years ago from teosinte (Zea mays ssp. parviglumis Iltis & Doebley). The crop spread widely after the European expansion, becoming one of the most widely grown cereals worldwide. Today it is produced in tropical, subtropical and temperate regions, thanks to the great genetic diversity that exists among varieties and hybrids.

2. Economic importance

Maize is the cereal with the largest global production, with uses in animal feed (fodder, silage), the food industry (starches, flours, oils, syrups), biofuels (ethanol) and direct human consumption (sweet corn, cornmeal). In Portugal it is part of intensive and extensive production systems, being relevant for silage production on livestock farms. Internationally, it stands out for its high productivity, industrial versatility and strategic importance in food security.

3. Botanical characterization

An annual plant, erect in habit, with robust stalks that can reach 1.5–4 m in height. The leaves are long and lanceolate, with a sheath that surrounds the stalk. The male inflorescence (tassel) is located at the top of the plant, while the female inflorescence (ear) appears in the leaf axils, displaying long, filamentous stigmas. Pollination is predominantly anemophilous. The grain is a caryopsis, with great morphological variability among varietal types, including dent, flint, sweet and popcorn maize.

4. Soil and climate requirements

Maize adapts well to hot climates, requiring high temperatures for germination and development. It prefers deep, fertile and well‑drained soils, with a pH between 5.5 and 7.5. It has high water requirements, especially between flowering and grain filling, being sensitive to prolonged water deficits. It responds markedly to fertilization, especially to nitrogen, and benefits from a good availability of organic matter.

5. Main pests

• Aphids (Aphididae): sap sucking and transmission of viral diseases
• Fall armyworm (Spodoptera frugiperda): destruction of the whorl and young leaves
• European corn borer (Ostrinia nubilalis): tunnels in the stalk and ear
• Western corn rootworm (Diabrotica virgifera virgifera): root damage
• Corn fly (Atherigona spp.): damage to seedlings
• Weevils and moths in storage (Curculionidae, Pyralidae): post‑harvest losses

6. Main diseases

• Common rust (Puccinia sorghi): orange pustules on the leaves
• Southern rust (Puccinia polysora): brown pustules and early defoliation
• Northern leaf blight (Exserohilum turcicum): elongated spots and leaf necrosis
• Fusarium diseases (Fusarium spp.): ear rots and risk of mycotoxins
• Stalk rot (Stenocarpella maydis): weakening and breakage of the stalk
• Viral diseases (MRDV, MDMV, SCMV): mosaics and chlorosis

7. General crop management

Management includes the choice of hybrids adapted to the local cycle and conditions, sowing at a suitable time and the use of certified seed. Weed control is essential in the first weeks, given the crop's low initial competitiveness. Fertilization must be balanced, with special attention to nitrogen. Irrigation must avoid water stress at flowering and grain filling. Maize is also used in rotations to improve soil structure and reduce the pressure of pests and diseases. Harvesting takes place when the grain reaches the moisture content appropriate to its destination (silage or dry grain).

Bibliographic references

• EPPO Global Database – Zea mays
• CABI Crop Protection Compendium – Zea mays
• Flint‑Garcia, S. A. (2013). Genetics and consequences of crop domestication. Journal of Agricultural and Food Chemistry, 61(35), 8267–8276.
• Shiferaw, B., Prasanna, B. M., Hellin, J., & Bänziger, M. (2011). Crops that feed the world 6: Maize. Food Security, 3, 307–327.