striga

Striga, commonly known as witchweed, is a genus of parasitic plants in the family Orobanchaceae. The genus contains about 25–30 species native to tropical Africa and parts of Asia, with some species reported in other regions. Striga plants are obligate root parasites; they attach to the roots of host plants via a specialized structure called the haustorium and withdraw water and nutrients, often severely reducing host growth.

Biology and morphology: Striga species are herbaceous annuals or short-lived perennials. They typically emerge as slender shoots from infected host roots, with reduced leaves and green to pale stems. Flowers are tubular and often brightly colored, arranged in spikes or racemes. The seeds are extremely small and produced in large numbers; they can persist in soil for many years awaiting a suitable host.

Ecology and impact: Striga primarily attacks cereals and legumes such as maize, sorghum, millet, cowpea, and groundnut. Infestations can cause substantial yield losses and contribute to food insecurity in affected regions. Germination is stimulated by chemical signals released by host roots, notably strigolactones.

Management: Control relies on integrated strategies, including resistant crop varieties, crop rotation with non-hosts, improved soil fertility, and trap crops that induce suicidal germination. Management is challenging due to seed longevity and a broad host range; chemical control is limited in field settings.

Notable species include Striga hermonthica (witchweed), Striga asiatica, and Striga gesnerioides.