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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 pathogenicity test confirmed Phomopsis vaccinii to be the major causal agent of the disease. Symptomatic tissues sampled at 7- to 10-day intervals in the 2014 and 2015 growing seasons were examined for presence of pycnidia, their developmental stages, and conidial presence in relation to phenological status of blueberry. Based on histological analysis, pycnidia were grouped into a series of developmental stages, referred to as pre-conidial, early-conidial, conidial, conidial-release and post-conidial stages. These different stages of development coincided with the phenological stages of blueberry plants during the growing season. Pycnidia at the conidial and conidial-release stages were predominantly found on symptomatic tissues sampled from bud-break to bloom; these pycnidia had high conidial contents of 1.0–2.0 × 104 conidia pycnidium−1. Pycnidia at the post-conidial stage were mostly found on symptomatic tissues sampled from green-fruit to post-harvest, under warm and dry weather conditions. Pycnidia at the pre-conidial stage were predominantly observed on symptomatic tissues sampled during latter parts of the growing season, from bud-set to leaf-fall. Mycelial growth of P. vaccinii isolates on potato dextrose agar was measured in response to temperatures from 4 to 32°C; the optimum growth occurred between 20 and 28°C. The number of pycnidia produced on quarter-strength potato dextrose agar at different incubation conditions varied amongst P. vaccinii isolates, and the optimum production was recorded at 16°C with a photoperiod of 14 h light/10 h dark or 14 h UV-A/10 h. Percentage germination of conidia of P. vaccinii isolate 11 BB 14 on water agar was higher at 16, 20 or 24°C than at 8 or 12°C. Conidia at 16°C reached 50% germination at ≥56 h incubation, whereas conidia at 20 and 24°C reached 50% germination at ≥72 h. Percentage germination of conidia at 8 and 12°C remained <50% during 104 h incubation. These findings provide an improved understanding of the role of pycnidia in the epidemiology of twig and blossom blight and stem dieback caused by P. vaccinii on highbush blueberry. [ABSTRACT FROM AUTHOR]

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 × 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. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

Stem diseases of blueberry (Vaccinium spp.) can cause significant crop loss as well as loss of entire bushes. Stem diseases are also more difficult to control with fungicides than foliar or fruit diseases. A screening program was initiated to test blueberry cultivars for resistance to two pathogenic fungi: botryosphaeria stem blight and phomopsis twig blight. An attached stem assay was developed to compare the host response with both fungi. The relative resistance of 50 blueberry cultivars was assessed using stem lesion lengths, analyzed on a log scale, taken at 4 weeks postinoculation. For Botryosphaeria stem blight, mean lesion length ranged from about 10 mm in resistant cultivars to about 140 mm in susceptible cultivars. The half-high cultivars Northsky, Northblue, and Chippewa, and the Iowbush cultivar Putte were among the most resistant. Phomopsis twig blight lesions ranged in mean length from about 18 to 98 mm. Similar to results for Botryosphaeria stem blight, resistance was limited to half-high ('Northsky' and 'Chippewa') and lowbush ('Blomidon', 'Chignecto', and 'Cumberland') cultivars. Individual cultivars resistant to one pathogen were not necessarily resistant to the other; although, overall, the resistances were correlated. Approximate 95% confidence intervals were established for all cultivars to predict mean performance across years. The cultivars tested varied in resistance, but the largest single factor affecting lesion length was the fungal isolate used for inoculations. These data enable us to identify cultivars resistant to both diseases that can be used for planting in problem areas, as well as selection of parental material for breeding cultivars with improved resistance. [ABSTRACT FROM AUTHOR]

The present note is the first report about detection of Phomopsis canker on highbush blueberries in Lithuania. Phomopsis vaccinii was isolated from diseased plants into pure culture, and morphologic characteristics of cultures on different media were described. This fungus was included into the A1 list of Quarantine Pests of European and Mediterranean Plant Protection Organization (EPPO) and to the list of Quarantine Pests of Lithuania. [ABSTRACT FROM AUTHOR]

Upright dieback, caused byPhomopsis vacciniiShear (teleomorphDiaporthe vacciniiShear), 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 ofP. vacciniiby 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. [ABSTRACT FROM AUTHOR]