Here, we investigate continent-scale patterns of host specialization in the parasitic plant Striga hermonthica. A root hemiparasite of the broomrape family (Orobanchaceae), S. hermonthica is characterized by a complex life cycle. Seeds can remain viable in soils for up to ~14 years (Bebawi et al. 1984) until germination, which requires detection of specific hormones (strigolactones) present in host root exudates (Cook et al. 1966). Other host-derived molecules trigger the formation of the haustorium (Cui et al. 2018), a specialized feeding structure used to invade host tissues and form vascular connections. Through these connections, parasitic plants suppress host immune responses (Shahid et al. 2018)and acquire water and nutrients to support their own development, emergence, and reproduction (Clarke et al. 2019).  S. hermonthica is widespread across diverse abiotic environments in East and West Africa where it parasitizes grasses including maize, pearl millet, sorghum, sugarcane, and rice and is a major constraint to food security (Rodenburg et al. 2016, Runo and Kuria 2018).   Compared to pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor), which both have centers of domestication in Africa (Winchell et al. 2017, Burgarella et al. 2018), maize is a relatively recent host and has few natural resistances to Striga (Rich and Ejeta 2008, Timko et al. 2012).