Technical Abstract: Fungal infections of vineyard grapes compromise the yield and organoleptic properties of wines, and there is a need for more effective fungal control measures. The aim of the present work is to evaluate the potential of a novel lipopeptide fungicidal formulation to control these diseases. A mixture of rhamnolipids (RLs) and the lipodepsinonapeptide syringomycin E (SYRE) showed greater inhibitory activities than SYRE alone against fungi isolated from grape berries and stems of a heavily infected vineyard in Louisiana. The fungal species tested were: Aspergillus japonicus, Cladosporium cladosporioides, Curvularia brachyspora, Greeneria uvicola, Nigrospora sphaerica, Trichoderma sp., Penicillium sclerotiorum and P. thomii. SYRE gave 50% killing of germinating conidia of all these fungal species at concentrations between 0.75 and 3 µM and the SYRE + RL mixture gave 50% killing between 0.75 and 1 µM SYRE. Non-germinated conidia of C. brachyspora, but not of the other fungi, were killed by SYRE alone or SYRE + RLs (both giving 50% killing at < 1 µM SYRE). The RLs alone did not affect the growth of either germinating or non-germinated conidia of these fungi. These results demonstrate the strong and broad fungicidal properties of SYRE and show that when mixed with RLs, it is even more lethal to a wide range of grape-associated fungi when in the germination stage.