Striga
Striga, commonly known as witchweed,[1] is a genus of parasitic plants that occur naturally in parts of Africa, Asia, and Australia. It is in the family Orobanchaceae. Some species are serious pathogens of cereal crops, with the greatest effects being in savanna agriculture in Africa. It also causes considerable crop losses in other regions, including other tropical and subtropical crops in its native range and in the Americas.
Witchweeds are characterized by bright-green stems and leaves and small, brightly colored and attractive flowers.[2] They are obligate hemiparasites of roots and require a living host for germination and initial development, though they can then survive on their own.[3]
The genus is classified in the family Orobanchaceae,[4] although older classifications place it in the Scrophulariaceae.[5]
Although most species of Striga are not pathogens that affect human agriculture, some species have devastating effects upon crops, particularly those planted by subsistence farmers.[7] Crops most commonly affected are corn, sorghum, rice and sugarcane.[2][8] Three species cause the most damage: Striga asiatica, S. gesnerioides, and S. hermonthica.
Witchweed parasitizes maize, millet, sorghum, sugarcane, rice, legumes, and a range of weedy grasses.[9] It is capable of significantly reducing yields, in some cases wiping out the entire crop.[2]
Host plant symptoms, such as stunting, wilting, and chlorosis, are similar to those seen from severe drought damage, nutrient deficiency, and vascular disease.[2][9][10]
