EFFECTIVENESS OF SOIL SAMPLING FOR VIRUS-VECTOR NEMATODES IN MAFF CERTIFICATION SCHEMES FOR FRUIT AND HOPS

In fruit and hop certification schemes of the Ministry of Agriculture, Fisheries and Food, sites used for the propagation of high‐grade virus‐tested stocks are soil sampled to detect vector nematodes before planting. Of 326 sites in England and Wales sampled for Foundation and Elite strawberry certification between 1963 and 1976, vector nematodes were detected in 22 per cent of sites, and most of these sites were rejected. Consideration of the theoretical aspects of sampling for vector nematodes, and of virus acquisition and transmission shows that, although soil sampling will reduce the risk of re‐infection by nematode‐borne viruses, it cannot prevent re‐infection. However, nematode‐transmitted virus infections are seldom detected during growing‐season inspections of strawberry runners entered for certification, which suggests that in practice the risks are small, probably because few vector populations are transmitting virus. Copyright © 1979, Wiley Blackwell. All rights reserved