category b Chapter - Research pt.21/10/09; no link to full text available pa.13/9/11. PERMISSION: 'Cannot grant permission for publisher version, however permission for author versions to be used in the repositories has been granted providing a link to each book on the website is included: http://bookshop.cabi.org/?page=2633&pid=1985&site=191. Added keywords, editors, palce of pub., 21.9.12-MMM