1. 1Institute for Agricultural and Fisheries Research, Burg. Van Gansberghelaan 96, 9820 Merelbeke, Belgium
2. 3Plant Pathology and Microbiology Department, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
3. 2Institute for Agricultural and Fisheries Research, Burg. Van Gansberghelaan 96, 9820 Merelbeke, Belgium
4. 4Institute for Agricultural and Fisheries Research, Burg. Van Gansberghelaan 96, 9820 Merelbeke, Belgium, Laboratory for Agrozoology, Ghent University, Coupure links 653, 9000 Ghent, Belgium;, Email: maurice.moens@ilvo.vlaanderen.be