Abstract

There are more than 30 viruses and virus diseases in Rubus and Ribes crops worldwide and several of those occurring in Europe can severely damage crop production and/or quality. Planting virus-tested certified material away from likely sources of infection is essential for control but, because of the longevity of these crops (more than 10 years), satisfactory control of incoming virus infection over the life of the crop is often difficult to achieve. In Ribes the major pathological problem is the black currant reversion disease and its gall mite vector, both of which cause serious damage. The only other virus disease of significance is gooseberry vein banding, the causal agent of which is transmitted by aphids. Rapid and sensitive detection assays have recently been developed at the Scottish Crop Research Institute (SCRI) for the viruses involved in these 2 virus diseases. Effective control of reversion disease and its vector using resistance genes to these organisms in cultivars is very promising. However, the species structure, ecology and virus vector capabilities of other eriophyid mites found on Ribes needs further study to assess the likely stability of currently deployed gall mite resistance genes. In Rubus, the most widespread virus and the most difficult to control is the pollen-borne raspberry bushy dwarf virus (RBDV). Cultivars with resistance genes to the common isolates of this virus are effective in preventing infection but the occurrence of resistance-breaking isolates of this virus pose problems for control. Aphid-borne viruses are also widespread and are very damaging. The effective control of most of these viruses has been achieved through the use of cultivars carrying genes for resistance to the main aphid vector, Amphorophora idaei. However, these viruses have been increasing in incidence in crops due to the ability of the aphid to overcome these resistance genes. The viruses causing raspberry leaf spot mosaic disease are lethal in sensitive raspberry cultivars and their spread is unlikely to be controlled effectively by the application of aphicides. raspberry vein chlorosis virus transmitted by the small raspberry aphid, Aphis idaei, is common in several crops posing problems for control. Soil-borne viruses, although very damaging when they occur in crops, are usually only localized in occurrence, but they may be of more widespread significance following the withdrawal of soil sterilants used commonly in horticulture to control nematodes.