Our laboratory bioassays demonstrated a strongly synergistic effect on P. myriotylum growth when E. adenophorum oil extracts were mixed with commonly-used synthetic fungicides (mefenoxam, mancozeb, iprodione or azoxystrobin). Moreover, the antifungal activity of oil extracts was higher than that of iprodione. The precise mechanism of this synergistic inhibition of P. myriotylum growth is not known. It is likely, however, that the synergistic effect is due to the components of the mixture targeting different sites in P. myriotylum mycelial cells . Mefenoxam inhibits ribosomal RNA (rRNA) biosynthesis , while mancozeb inhibits pyruvic acid oxidation. The antifungal activity of iprodione is related to its intervention effects on protein kinase in the signal transduction pathway. The mechanism of action of E. adenophorum oil extracts is not clear, but the mode of action of its major component—terpene—is speculated to involve membrane disruption by lipophilic compounds . The low-molecular weight and highly lipophilic compounds can easily diffuse across cell membranes to induce biological reactions . The synergy could conceivably be the result of a general increase in stress when different cellular processes are attacked simultaneously . Or, to be more precise, membrane disruption may allow a greater quantity of synthetic fungicides to reach the target sites successfully.