Spatial patterns ofleaf-curling plum aphid,Brachycaudus helichrysi, aggregates and alate colonization of sunflower fields were studied over several years. Monte Carlo test procedures, based on indices of aggregation and spatial autocorrelation statistics, were used for spatial data analysis. In most cases, neighboring plants were colonized and infested independently. Over large areas, spatial structures could exist but temporal changes in spatial patterns from week to week were often observed for alatae as well as for apterae. Heterogeneity in plant development seemed to be of importance for alate landing, apterous multiplication, and their spatial patterns. The implications for pest management and sampling are discussed.