1. Department of Plant Pathology, Entomology and Microbiology, Iowa State University, 1344 Advanced Teaching and Research Building, 2213 Pammel Drive, Ames, IA 50011, USA
2. School of Economics and Management, China University of Petroleum (Beijing), Beijing, China
3. Department of Horticulture, Iowa State University, 106 Horticulture Hall, Ames, IA 50011, USA
4. Dyson School of Applied Economics and Management, Cornell University, Ithaca, New York 14853, USA