Search

Twig and blossom blight, and stem dieback, has become an impediment to highbush blueberry (Vaccinium corymbosum L.) production in British Columbia. Periodic assessment of disease symptoms and patho...

Phomopsis vaccinii cause a serious disease of blueberry, cranberry and other Vaccinium crops in the North America and Europe as well. Over 1000 species names are described by Phomopsis spp., but their biology and life style are mostly unknown. Identification of P. vaccinii by methods of classical phytopathology is difficult and complicate, because many species are morphologically similar to P. vaccinii, and P. vaccinii itself has diverse patterns of colony morphology. For this investigation P. vaccinii isolates were obtained from five cranberry plantations in different locations of Latvia (Babite, Alsunga, Rucava, Ape and Pargauja municipality) from berries affected by viscid rot at harvest and storage in 2010. Altogether 44 P. vaccinii isolates were cultivated on potato dextrose agar for description of colony morphology. In order to find some relationships between samples, the isolates were arranged in different groups on the basis of mycelium color and structure (zoning), reverse pigmentation, pycnidium formation time, size, location, number and size of conidia. During this study the colonies of P. vaccinii from cranberry in Latvia showed different morphological features in culture and no relationships between growing regions and groups of isolates were found. P. vaccinii is easy to confuse with other Phomopsis species if only classical phytopathological methods are used.

Vaccinium twig blight (caused by Phomopsis vaccinii, teleomorph Diaporthe vaccinii) is a major endemic disease on blueberries and cranberries in the Eastern and Northwestern USA and Canada. It has also been found in Europe, Chile and China. Publications on its occurrence in the USA and Canada indicate that the pathogen is limited to cool climates. Published data on worldwide occurrence were inventoried and supplemented with National Plant Diagnostic Network (NPDN) data in the USA. These occurrence and long-term climate data were entered in the niche models MaxEnt and Multi-Model Framework to predict the potential global distribution of the disease. Precipitation in the driest quarter and mean annual temperature contributed most to the prediction. The results indicate that P. vaccinii is not limited to cool climates, although the optimal annual average temperature is 10 °C according to the MaxEnt model. The models correctly predicted that the climate in the central and eastern USA and the west coast of the USA and Canada would be conducive to blueberry twig blight. Large areas in Europe, eastern Australia and New Zealand, and smaller areas in South America and East Asia would be conducive too. For the first time, the NPDN database was shown to be an important source of information for the prediction of the potential global distribution of a plant pathogen.

As requested by the European Commission, the EFSA Panel on Plant Health (PLH) Panel assessed the risk of Diaporthe vaccinii in the EU, focusing on entry, establishment, spread and impacts on cultivated and wild Vaccinium species, the principal hosts being American and European cranberry and blueberry. Several outbreaks occurred in the EU since 1956, but most were eradicated except in Latvia. The Panel considered entry via fruits and plants for planting. The risk of establishment from discarded infected berries is much lower than from infected plants for planting, of which, potted plants and cuttings pose the greatest risk, while plug plants, derived from tissue culture and grown in pest free structures, pose a low risk. Nine per cent of the EU is highly suitable for establishment of the pathogen, mostly in the SE and NE. Following establishment, the pathogen could spread naturally over short range, and by human assistance over long range. Calculations with an integrated model for entry, establishment and spread, indicate that with current regulations, over a period of 5 years, a few hundred cultivated Vaccinium plants and several thousand Vaccinium plants in natural ecosystems would contract the disease. The associated loss of commercial production is small, less than one tonne of berries per year. On natural vegetation, the median impact after 5 years was estimated to be negligible affecting a negligible proportion of the natural Vaccinium population (2 x 10 8). However, the uncertainty of this estimate was high, due to uncertainty about the rate of spread; in a worst-case scenario (99th percentile), almost 1% of plants in natural areas would become infected. Complete deregulation (scenario A1) was predicted to increase the impact substantially, especially in natural areas, while additional measures (scenario A2) would effectively eliminate the entry of infected plants for planting, further reducing the impacts below the current situation.

The European Commission requested the EFSA Panel on Plant Health to perform a pest categorisation of Diaporthe vaccinii Shear, the fungal agent responsible for twig blight, canker, viscid rot, fruit rot and storage rot of several Vaccinium species. The pest is listed in Annex IIAI of Directive 2000/29EC. D. vaccinii is a single taxonomic entity and methods exist for its discriminative detection. The host is restricted to Vaccinium species, the main cultivated hosts being blueberries and cranberries. Hosts are cultivated throughout Europe, and wild Vaccinium species are common components of forests. Conditions are conducive to disease development in most areas of Europe, but not in all Member States (MSs). The disease is currently present in Latvia with restricted distribution and the pest is under surveillance in The Netherlands. In the one Latvian report, storage losses were observed on cranberry, but these losses were caused by a complex of pathogens, including D. vaccinii, which was isolated with a low incidence. Detection methods are available but cultural and morphological identifications should be confirmed with molecular tools owing to the presence of other Phomopsis species on Vaccinium in Europe. The pathogen can spread via the movement of (asymptomatic) infected or contaminated host plants for planting. No information exists on any methods applied for the control of D. vaccinii in the EU. D. vaccinii does not have the potential to be a quarantine pest as it does not fulfil one of the pest categorisation criteria defined in International Standard for Phytosanitary Measures No 11, that of having a severe impact. Data are not sufficient to conclude on pest categorisation of D. vaccinii based on the criteria of the International Standard for Phytosanitary Measures No 21 because there is no information about the level of potential consequences as a result of the use of infected host plants for planting. © European Food Safety Authority, 2014

Upright dieback, caused by Phomopsis vaccinii Shear (teleomorph Diaporthe vaccinii Shear), is an economically important disease that could threaten blueberry and cranberry production. Diagnosis of the disease by traditional phytopathological methods is difficult. We report the successful detection of P. vaccinii by direct tissue blot immunoassay (DTBIA) and plate-trapped antigen enzyme-linked immunosorbent assay (PTA-ELISA). The infected samples obtained from Lithuania are the findings reported on the fungus in Europe.