Kolk, A., and A. Sierpiski. 1999. The infestation of Polish forests by insect pests in 1998 and the forecast for 1999. Pages 89-93 In B. Forster, M. Knizek, and W Grodzki (eds.), Methodology of forest insect and disease survey in Central Europe. Proceedings of the Second Workshop of the IUFRO Working Party 7.03.10, April 20-23, 1999, Sion-Châteauneuf, Switzerland. Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland.