Incidence and Ecology of Blackberry yellow vein associated virus.

Symptoms of leaf vein yellowing and bush decline in blackberry were attributed to infection by a novel crinivirus named Blackberry yellow vein associated virus (BYVaV). The disease is an emerging threat to blackberry production because it can cause substantial yield loss. The objective of this study was to identify the source and means of spread of BYVaV. A survey of blackberry plants for BYVaV from wild, cultivated, and nursery stocks was conducted. Insect traps and healthy blackberry sentinel plants were placed among symptomatic plants in a production field throughout two growing seasons to monitor the occurrence of potential vectors and virus spread. Virus indicator plants were grafted with BYVaV-infected blackberry because this virus was latent in some blackberry cultivars, but indicator plants failed to express symptoms when infected with BYVaV. Reverse-transcription polymerase chain reaction detection revealed the occurrence of BYVaV in blackberry nurseries in the United States, in production fields in Arkansas, South Carolina, and North Carolina, and in wild blackberry populations in Arkansas. Whiteflies (Trialeurodes packardii and T. ruborum), potential vectors of BYVaV, were observed on sticky traps placed in blackberry fields and were found colonizing blackberry plants; however, transmission studies failed to produce whitefly-mediated transmission of BYVaV. Further understanding of the disease etiology is needed to devise viable management strategies for this disease.