Farnesyl pyrophosphate synthase involved in murgantiol biosynthesis, a male-released aggregation pheromone, by catalyzing the formation of (2E,6E)-farnesyl diphosphate. (2E)-geranyl diphosphate + isopentenyl diphosphate = (2E,6E)-farnesyl diphosphate + diphosphate Binds 2 Mg(2+) ions per subunit. Pheromone biosynthesis. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the FPP/GGPP synthase family.