1. Floral and Nursery Plants Research Unit, U.S. National Arboretum, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA
2. State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
3. North East Area, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland, USA