Strigolactones have diverse functions as plant hormones and as ecological signals to communicate with soil microbes. Strigolactones are also exploited by parasitic plants, including noxious parasitic weeds called Striga hermonthica, as germination cues that enable efficient parasitism to their host plants. Recent understanding for the mechanism of strigolactone perception by α/β-hydrolase receptors has provided opportunities to dissect the diverse functions with synthetic strigolactones. Here, we introduce the design principle of the synthetic strigolactones, which relies on a hybrid of two functions encoded in the two substructures, ABC-ring and D-ring. The principle discussed here has been applied to develop a Striga-selective suicide germination stimulant acting at femtomolar-range.