Striga, commonly known as witchweed, is a genus of parasitic flowering plants in the family Orobanchaceae (order Lamiales), with older classifications having placed it in Scrophulariaceae. The genus contains an uncertain number of species — estimates suggest more than 40 — distributed naturally across parts of Africa, Asia, and Australia.
Witchweeds are obligate hemiparasites of the roots of other plants. They require a living host for germination and initial development, though established plants can then survive independently. The plants are recognizable by their bright-green stems and leaves and small, vividly colored and attractive flowers.
Several species are among the most destructive agricultural weeds known, particularly in sub-Saharan Africa where they parasitize staple cereal crops such as sorghum, maize, millet, and rice in savanna farming systems. Crop losses extend beyond Africa to other tropical and subtropical regions, and the genus has also established itself as a pest in parts of the Americas. Striga gesnerioides, a distinctive species in the genus, parasitizes cowpea and other broadleaf crops rather than grasses.
The generic name derives from the Latin strīga, meaning "witch," a reference that gives rise to the common name witchweed.
Etymology
The genus name Striga derives from the Latin strīga, meaning "witch," which also gives rise to the widely used common name witchweed.
Distribution
Striga occurs naturally across parts of Africa, Asia, and Australia, with the highest species diversity and agricultural impact concentrated in sub-Saharan African savannas. The genus has also spread to tropical and subtropical regions of the Americas, where it causes losses in cereal and other crops.
Ecology
Witchweeds are obligate root hemiparasites: their seeds will not germinate without chemical signals (strigolactones) released by a suitable host's roots, and seedlings must attach to host roots to survive early development. Hosts include sorghum, maize, millet, rice, cowpea, and sugarcane. Although classified as hemiparasites (retaining some photosynthetic capacity), they draw water, nutrients, and carbohydrates from their hosts, suppressing growth severely even before the parasite emerges above ground.
Conservation
Some Striga species are the focus of intensive control research rather than conservation concern, as they threaten food security across sub-Saharan Africa. However, several rarer species in the genus have restricted ranges and may face habitat pressure.
Cultural Uses
Witchweeds have no established beneficial cultural or medicinal use; the name "witchweed" itself reflects the historical perception of the plants as mysterious and destructive agents that invisibly devastated crops before emerging from the soil.
