The distribution and abundance of the spindle tree, Euonymus europaeus, in southern England with particular reference to forecasting infestations of the black bean aphid, Aphis fabae.
Abstract
A method is discussed for determining distribution and abundance of the spindle tree (Euonymus europaeus). This could be used for other hedgerow species. The work forms part of a study on forecasting of crop infestations of Aphis fabae Scop. based on overwintering populations on spindle for which corrections need to be made for the varying abundance of this winter host. In southern England, spindle occurs in hedgerows, scrubland and woodland and is generally associated with calcareous soils where it is sometimes 'common' (126-625 bushes/10 km2) or locally 'abundant' (>625/10 km2) except on open downland where hedgerows are scarce or where the chalk and limestone are overlain by acidic soils. Elsewhere, spindle is widely distributed, often at densities of about 6-25 bushes/10 km2 though it is 'absent' or 'very rare' (<5 bushes/10 km2) in some large areas such as the Fenland and much of the Midlands. It is, however, 'occasional' to 'common' (26-625 bushes/10 km2) in some non-calcareous areas, notably over parts of the Old Red Sandstone in Herefordshire and southern Shropshire and over Weald Clay. The data were used to make adjustments to forecasts in 16 areas in southern England. This notably improved forecasts in areas of high spindle density in contrast to areas of low density. The correction factors will therefore be applied only in high density areas.