1. Department of Plant Physiology Swammerdam Institute for Life Sciences University of Amsterdam P.O. Box 94215 1090 GE Amsterdam The Netherlands
2. Department of Population Biology Institute for Biodiversity and Ecosystem Dynamics University of Amsterdam P.O. Box 94240 1090 GE Amsterdam The Netherlands
3. Department of Crop Protection Faculty of Bioscience Engineering Ghent University B‐9000 Ghent Belgium