The present invention provides a compound that has an activity equal to or higher than that of natural strigolactone, can be chemically synthesized by a convenient step and at low cost, exhibits stability in environments, and has no or weak seed germination-promoting effect on plants of the genus Striga or Orobanche. Specifically, the present invention provides a compound represented by the general formula (III) or a salt thereof, wherein X represents a lower alkyl group or the like Q represents a single bond or the like and ring C represents a 6-membered ring represented by the formula (IVa) or the like wherein R1, R2, R3, and R4 each independently represent a carbon atom or the like, Z1 and Z2 are bonded to the ring atoms of ring C and each independently represent a hydrogen atom, a halogen atom, or the like, and the groups R5, R6, R7, Z3, Z4, and Z5 are as defined in the specification.
