This report was prepared by Suranant Subhadrabandhu, Professor of Horticulture, Department of Horticulture, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand, under the valuable guidance and encouragement of M.K. Papademetriou, Senior Plant Production and Protection Officer, FAO Regional Office for Asia and the Pacific (FAO/RAP). Appreciation is expressed to F.J. Dent for editing this valuable document. Also, the unfailing support of Mrs Valai Visuthi, who provided assistance in formatting the manuscript, is greatly appreciated.