APHIDS

K.G. Preston-Mafham

Over 500 species of aphids have been recorded in the British Isles. Of these, around 110 species have been listed for Cornwall. However, in the majority of cases the records are very old, often dating back to the early years of the last century. Many of the more recent records derive from phenological studies undertaken at the Duchy College site at Rosewarne. It is therefore impossible to ascertain the true status of any aphid species in Cornwall, and the ease with which new species can be added to the list (e.g. Macrosiphum cholodkovskyi on Meadowsweet Filipendula ulmaria from three sites in 2008) merely serves to emphasize the inadequate state of our knowledge. A shortage of modern identification literature and the difficulty of actually using any that is available tends to restrict the study of aphids, and there is currently nobody in Cornwall working on this group in any depth. Only about 30% of aphids are regularly seen, and only about 10% are common pests (Carter, 1993). The rarer species tend to be those which are restricted to a single host plant, which itself may be scarce in Cornwall. However, even when the host plants are varied and widespread, they are not necessarily widely colonised. Thus, the nationally common Pea Aphid Acyrthosiphon pisum seems only occasionally to take advantage of its wild host plants (e.g. vetches) in Cornwall. By contrast, the Beech Aphid Phyllaphis fagi seems to be present on its host (itself not native in Cornwall) almost wherever it occurs, exposure to wind seeming to be the main limiting factor. A number of non-British species have become established in Cornwall, of which the Lupin Aphid Macrosiphum albifrons (first seen in Cornwall in 1981) has had a devastating impact on Tree Lupins Lupinus arboreus grown as pioneer crops on the china clay tips.