Abstract: An investigation was carried out in fields with different Bemisia tabaci population density to study the spatial distribution and population behavior of B.tabaci（Gennadius） on the leafy mustard， Brassica juncea var.foliosa Bailey. Spatial distribution pattern of B.tabaci was determined by methods of aggregation index， Iwao linear regression model and Taylor power law model. The results showed that the spatial distribution of adult B.tabaci fitted an aggregate distribution， characterized by a raised aggregation degree as population increased. The M*-m linear model of Iwao （M*=1.1181 m+0.5764） and V～m power law model of Taylor （V=1.1539 m1.429） were established. By Blackith aggregation population mean analysis， when m<4.315 1， the aggregation pattern of B.tabaci is caused by certain environment factors such as climate， cultivation conditions， plant fertility status; when m≥4.315 1， the aggregation behavior of B.tabaci is caused by the comprehensive influence of the pest and environmental conditions. Additionally， the theoretical sampling number model N=1962/D2（1.5764/m+01181） and the sequential sampling model Tn=1.5764/（D02-0.1181/n） were proposed for B.tabaci in leafy mustard fields.

Key words: leafy mustard （Brassica juncea）, Bemisia tabaci, spatial distribution pattern, sampling technique