The B-type Bemisia tabaci in Yancheng area have the following characteristics: single biotype,plenty of proper host plants,frequent transfer,yearly-expanding occurrence area,ahead of occurrence time,aggravating damage,tender distribution and transfer.Yearly-expanding protective cultivation area,high temperature and drought condition,abundant food chains which consist of many suitable host plants,resistance to pesticides and difficult prevention are the important reasons for causing the outbreak of Bemisia t...