Spatial Pattern of Abundance of the Black Bean Aphid, Aphis fabae, in Britain

(1) Populations of Aphisfabae Scop. were monitored in Britain on its primary winter host, Euonymus europaeus L., on the two principal secondary summer crop hosts, springsown Viciafaba L. and sugar beet, and during the spring, summer and autumn migrations. This unique year-round monitoring was used to examine the spatial dynamics of the aphid in 1969-86. (2) Changes in the mean spatial pattern of abundance of the aphid during a single annual cycle reflect a sequence of changing host plants. (3) The longer-term dynamics and survival of the aphid depend on the spatial pattern of abundance in the non-crop environment. Thus, the wide distribution of wild hosts in late summer affects the numbers of autumn migrants, and the regional variation in abundance of E. europaeus affects the success of the aphid in finding sites for overwintering eggs. (4) Spatial patterns of abundance of other aphid pest species are compared with that of A. fabae. (5) The implications of varying spatial patterns of abundance are discussed in relation to pest forecasting.