Hops

Humulus lupulus

1. Identification and origin

Hops (Humulus lupulus L.), belonging to the Cannabaceae family, is a perennial climbing plant native to Europe, western Asia and North America. It has been cultivated for several centuries, mainly for the use of its female inflorescences (cones), essential in the brewing industry due to their aromatic, bitter and preservative properties.

2. Economic importance

Hops is a strategic crop for beer production, providing bitter compounds (α-acids), volatile aromas and antimicrobial properties. The cones are used fresh, dried or processed into pellets and extracts. The main producers include the United States, Germany, the Czech Republic, Slovenia and China. There is also growing interest in the use of hops in phytotherapy and cosmetics due to its sedative and antioxidant properties.

3. Botanical characterisation

A vigorous climbing plant, with twining stems that can reach 6–10 m in length. The leaves are opposite, palmate, with 3–5 lobes and a serrated margin. The species is dioecious, with separate male and female plants; only the female plants produce the cones used commercially. The cones are compound inflorescences, containing lupulin glands rich in resins and essential oils. The root system is deep and rhizomatous, allowing annual regrowth.

4. Soil and climate requirements

It prefers cool temperate climates, with long and bright summers. It requires deep, fertile, well-drained soils, with pH between 6.0 and 7.5. It is sensitive to waterlogging and benefits from regular irrigation during vegetative growth. The crop requires support structures (trellises) and good sun exposure to maximise cone production.

5. Main pests

• Hop aphid (Phorodon humuli): sap-sucking and transmission of viruses.
• Mites (Tetranychus urticae): chlorosis and fine webbing in dry conditions.
• Caterpillars (Noctuidae): defoliation and damage to inflorescences.
• Whitefly (Trialeurodes vaporariorum): honeydew and sooty mould.
• Nematodes (Pratylenchus spp., Meloidogyne spp.): root lesions and plant decline.

6. Main diseases

• Downy mildew (Pseudoperonospora humuli): one of the most serious diseases, causing necrosis, deformations and loss of cones.
• Powdery mildew (Podosphaera macularis): white coating on leaves and cones, affecting quality and production.
• Root rots (Phytophthora spp.): wilt and plant death in waterlogged soils.
• Verticillium wilt (Verticillium albo‌-atrum): vascular wilt and progressive decline.
• Grey mould (Botrytis cinerea): rotting of cones, especially in humid conditions.

7. General crop management

It includes the choice of cultivars adapted to the local climate, installation of vertical supports, training and pruning of the stems, regular irrigation without waterlogging, balanced fertilisation and rigorous monitoring of downy mildew, powdery mildew and hop aphid. Crop rotation and improved drainage reduce the incidence of soil diseases. Harvesting should be carried out when the cones show a dry texture and an intense aroma.

Bibliographic references

• EPPO Global Database. Humulus lupulus – pests and diseases.
• CABI Invasive Species Compendium. Humulus lupulus – datasheets.
• Neve, R. A. (1991). Hops. Chapman & Hall.
• Beatson, R. A., et al. (2019). Hop breeding and genetics. In: Kole, C. (Ed.), The Hops Genome. Springer.
• Hieronymus, S. (2012). For the Love of Hops: The Practical Guide to Aroma, Bitterness and the Culture of Hops. Brewers Publications.