Submitted to: Crop Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/6/2011
Publication Date: 4/15/2011
Publication URL: handle.nal.usda.gov/10113/58490
Citation: Oudemans, P., Hillman, B., Linder-Basso, D., Polashock, J.J. 2011. Visual inspections of nursery stock fail to protect new plantings from Blueberry scorch virus infection. Crop Protection. 30:871-875. Interpretive Summary: Blueberry scorch virus (BlScV) is an important disease of highbush blueberry that is rapidly spreading throughout the North American growing regions and has recently been reported as occurring in Europe. The virus is transmitted by sucking insects, and spread in fields tends to be down the rows and outward in a circular pattern. We noticed in many newly-planted fields that the incidence of infected bushes was random, suggesting a method of spread independent of the insects. In order to determine how the virus was spreading, nurseries were surveyed and found to harbor BlScV-infected plants that were being used for propagation of new plants. Forty percent of the plants propagated from infected plants were found to be infected with BlScV. This study identifies infected nursery stock as an important source of BlScV spread and underscores the importance of having nursery stock used for propagation virus tested. The results are important for blueberry nurseries, retailers, and growers.
Technical Abstract: Blueberry scorch virus (BlScV) is one of the most pervasive pathogens of highbush blueberry. The virus is aphid-vectored and exhibits a latent period between infection and symptom expression of up to 4 years. In many cases, we have observed BlScV symptom expression in new fields that is inconsistent with aphid-vectored introduction and spread. It was, therefore, speculated that the virus is also introduced through infected nursery stock. To examine this possibility, we first surveyed selected nurseries to determine if mother plants, used for propagation by cuttings, were BlScV-infected. Two nurseries were found to harbor symptomless infected mother plants (cv. Duke). Cuttings were collected from infected and non-infected plants and rooted in propagation beds. The survival and infection of cohorts from each mother plant were determined one year after planting. A greater proportion of cuttings survived from non-infected mother plants (0.7) than from infected mother plants (0.5). Of the cohort from infected mother plants that survived, 40% tested positive for BlScV. We further tracked the appearance of infected plants in a ‘Duke’ planting that originated from a nursery with BlScV-infected mother plants. Symptom-expressing plants were rogued out each year for 6 years, after which BlScV-infected plants no longer appeared. This study identifies infected nursery stock as an important source of BlScV dissemination and underscores the importance of having symptomless mother plants virus tested.