Cowpea

Vigna spp.

1. Identification and origin

The cowpea belongs to the genus Vigna Savi, a diverse group of the Fabaceae family that includes more than 100 species distributed mainly across tropical and subtropical regions. Within this genus, several species of agricultural importance stand out:

• Vigna unguiculata subsp. unguiculata (L.) Walp. — cowpea, black-eyed bean or yardlong bean. Five cultivation groups are distinguished — Unguiculata, Biflora, Sesquipedalis, Textilis and Melanophthalmus — which represent morphological and use variations, from grain types to long-pod or “black-eye” forms.
• Vigna radiata (L.) R. Wilczek — mung bean.
• Vigna mungo (L.) Hepper — urd bean.
• Vigna angularis (Willd.) Ohwi & H. Ohashi — adzuki bean.
• Vigna subterranea (L.) Verdc. — bambara groundnut.

The cowpea proper corresponds to Vigna unguiculata (L.) Walp., a species native to West Africa, where it was domesticated millennia ago. Its high drought tolerance and ecological adaptability favoured its expansion into East Africa, South Asia, the Americas and Mediterranean regions, becoming a food and forage legume of great relevance.

2. Economic importance

It is a legume of great food and agronomic relevance, especially in tropical and subtropical regions. It stands out for its high drought tolerance, its nutritional value (protein, fibre, minerals) and its role in the biological fixation of nitrogen. It is of growing importance in low-input agricultural systems and in the markets for dry legumes. Countries such as Nigeria, Niger, Brazil and Burkina Faso are major producers.

3. Botanical characterisation

An annual, herbaceous plant with a variable growth habit (prostrate, semi-erect or climbing). The leaves are compound, trifoliate, with oval or rhomboid leaflets. The flowers are papilionaceous, generally white, yellow or violet. The pods are elongated, cylindrical, containing reniform seeds of variable colouring (cream, brown, black, mottled). The root system is deep and well adapted to drought conditions.

4. Soil and climate requirements

It adapts well to warm and dry climates, tolerating high temperatures and periods of water deficit. It prefers light to medium soils, well drained, with a pH between 5.5 and 7.0. It is more tolerant to acidity and drought than other legumes, but sensitive to waterlogging. Moisture is critical during flowering and pod filling.

5. Main pests

• Cowpea weevil (Callosobruchus maculatus): severe damage to stored seeds.
• Whitefly (Bemisia tabaci): sap sucking and transmission of viruses.
• Aphids (Aphis craccivora): leaf curling and transmission of viruses.
• Caterpillars (Noctuidae): leaf consumption and damage to young pods.
• Root-knot nematodes (Meloidogyne spp.): root deformations and reduction of growth.

6. Main diseases

• Downy mildew (Phytophthora vignae): root rots and death of seedlings.
• Anthracnose (Colletotrichum lindemuthianum): dark lesions on leaves and pods.
• Powdery mildew (Erysiphe polygoni): whitish coating on the leaves.
• Angular leaf spot (Pseudocercospora cruenta): brown angular lesions on the leaves.
• Viruses (CABMV, CPMMV): mosaics, deformations and reduction of vigour.

7. General crop management

This includes the choice of adapted and drought-tolerant varieties, sowing in well-drained soils, crop rotation with cereals and other legumes, weed control, regular monitoring of pests and diseases and supplementary irrigation in critical phases. Harvesting should be carried out when the pods reach physiological maturity, ensuring quality and conservation of the grain.

Bibliographic references

• EPPO Global Database. Vigna unguiculata – pests and diseases.
• CABI Invasive Species Compendium. Vigna unguiculata – datasheets.
• Timko, M. P., & Singh, B. B. (2008). Cowpea, from Africa to the world. In: C. Kole & T. C. Hall (Eds.), Compendium of Transgenic Crop Plants: Transgenic Legume Grains and Forages (pp. 1–20). Wiley‑Blackwell.
• Boukar, O., et al. (2019). Cowpea (Vigna unguiculata): Genetics, genomics and breeding. Plant Breeding.
• Carvalho, M., et al. (2017). Nutritional and phytochemical composition of cowpea. Food Research International.