Laboratory and field studies on the relation of arabis mosaic virus to its nematode vector Xiphinema diversicaudatum (Micoletzky)

SUMMARY Xiphinema diversicaudatum is widely distributed in southern Britain, mainly in heavy soils, but also in the peat soil of the Fens and in medium textured soils in the south‐west. Patches of plants infected with arabis mosaic virus (AMV) in a range of crops including some, like celery and marrow, not before known to be hosts, coincide with patches of soil infested with X. diversicaudatum. Roots of some plants infested with the nematode carried small galls; not all such plants were infected with, or even susceptible to, AMV. Adult X. diversicaudatum transmitted AMV more readily than larvae, but none of 103 nematodes, transferred when moulting, infected healthy plants. X. diversicaudatum were still infective after 24 days in moist peat, free from plants. X. diversicaudatum is common in several districts in soil from old hedgerows but not in the adjacent fields. Hedgerow trees seem to be hosts of the nematode and at least one, elder, is also a host of AMV. In other districts, plants with AMV occur in crops near to infested hedges or isolated trees, and on land taken into cultivation after being derelict. In the Tamar Valley, Devon, X. diversicaudatum is common in pastures; white clover in these often contains AMV. Planting such fields with strawberry leads to disease outbreaks. A few X. diversicaudatum occur down to 3 ft. in soil, but most are at 3–9 in. At a site where arable land has reverted to woodland, the nematodes apparently have spread from a hedge into the woodland at an average rate of 1 ft. per year over a period of 75 years. It is suggested that both X. diversicaudatum and AMV are common constituents of natural woodland in Britain and that their incidence has decreased since the advent of agriculture.