Blueberry Scorch Virus Research Articles

High-resolution mapping of Blueberry scorch virus incidence using RGB and multispectral UAV images and deep learning

High-resolution mapping of Blueberry scorch virus incidence using RGB and multispectral UAV images and deep learning

Development of a Multiplex PCR for Simultaneous Detection of Blueberry Red Ringspot Virus and Blueberry Scorch Virus Including an Internal Control

Blueberry red ringspot virus (BRRSV) and blueberry scorch virus (BlScV) are included in the quarantine virus list managed by the Korean Animal and Plant Quarantine Agency. A multiplex polymerase chain reaction (PCR) assay with an internal control was developed for the simultaneous detection of both viruses. The specific primers used here were designed based on the highly conserved regions of the genomic sequences of each virus, obtained from the National Center for Biotechnology Information nucleotide databases. The primers were designed to amplify a partial sequence within coat protein (CP) for detecting BRRSV and a partial sequence within the CP-16 kDa for detecting BlScV. 18S ribosomal RNA (rRNA) was used as internal control, and the primer set used in a previous study was modified in this study for detecting 18S rRNA. Each conventional PCR using the BRRSV, BlScV, and 18S rRNA primers exhibited a sensitivity of approximately 1 fg plasmid DNA. The multiplex PCR assay using the BRRSV, BlScV, and 18S rRNA primers was effective in simultaneously detecting the two viruses and 18S rRNA with a sensitivity of 1 fg plasmid DNA, similar to that of conventional PCR assays. The multiplex PCR assay developed in this study was performed using 14 blueberry cultivars grown in South Korea. BRRSV and BlScV were not detected, but 18S rRNA was all detected in all the plants tested. Therefore, our optimized multiplex PCR assay could simultaneously detect the two viruses and 18S rRNA in field samples collected from South Korea in a time-efficient manner. This approach could be valuable in crop protection and plant quarantine management.

A binomial sampling method for estimating the density of blueberry aphid, Ericaphis fimbriata (Hemiptera: Aphididae), in commercial highbush blueberry

Abstract An accurate and efficient sampling method is an important tool for insect pest management because it allows for consistent measurements across many samples. There are currently no proposed standardised sampling plans or spray thresholds for the aphid Ericaphis fimbriata Richards (Hemiptera: Aphididae) on highbush blueberry (Vaccinium corymbosum Linnaeus) in British Columbia, Canada, despite it being the primary vector for blueberry scorch virus (BlScV). A standard sampling plan for this pest would allow for rapid and consistent measurements of aphid abundance in commercial fields and would allow for more detailed study of the relationship between aphid abundance, damage, and the spread of BlScV. Binomial sampling plans use the presence:absence of a pest within a sample unit to estimate the proportion of infested sample units. Pest density (proportion of measured samples with individuals present) is linked to abundance (number of individuals), and the relationship between these two measures can be modelled mathematically. In the present study, we collected data on aphid density and aphid abundance in six varieties of highbush blueberry grown in the Fraser Valley, British Columbia. These data were used to construct a distribution-free binomial model that, when given a measure of aphid density, can predict aphid abundance within a given sample.

Blueberry latent virus in highbush blueberry (Vaccinium corymbosum L.) in Bosnia and Herzegovina

A small-scale survey for blueberry viruses in Bosnia and Herzegovina was performed in 2018. A total of 20 samples from three locations were collected and analyzed for the presence of 11 viruses. ELISA assays were performed for blueberry scorch virus, blueberry shock virus, blueberry shoestring virus, blueberry leaf mottle virus, tobacco ringspot virus, and tomato ring spot virus. The samples were tested for blueberry red ringspot virus by PCR, and blueberry fruit drop associated virus, blueberry latent virus, blueberry mosaic associated virus, blueberry necrotic ring blotch virus, blueberry virus A, and blueberry leaf mottle virus by RT-PCR. The analyses confirmed the presence of BlLV in eight samples with no other virus detected in any of the samples.

Alien species of aphids (Hemiptera: Aphididae) found in Serbia, new to the Balkan Peninsula

New alien species of aphids (Illinoia liriodendri (Monell), Wahlgreniella nervata (Gillete), Takecallis arundicolens (Clarke) and Tinocallis takachihoensis Higuchi) have been found for the first time in Serbia. These records are new for the Balkan Peninsula. Data of Ericaphis scammelli (Mason), species recently mentioned in Serbia, are also presented in the text. The species have been found during the last five years at four sites (Belgrade, Zemun, Mladenovac and Bojnik) on five cultivated plants. Ericaphis scammelli is a pest of blueberry and a vector of Blueberry scorch virus. The other four develop colonies on decorative plants: I. liriodendri has been found on Liriodendron tulipifera, W. nervata on Rosa sp., T. arundicolens on Pseudosasa japonica and T. takachihoensis on Ulmus x hollandica. The origin of three of the species (E. scammelli, I. liriodendri and W. nervata) is North America and two (T. arundicolens and T. takachihoensis) have come from East Asia. Their morphology, biology and the damage they inflict are discussed here, as well as their potential economic and environmental threat. Only parthenogenetic viviparous females of all 5 species have been collected. Their biology has not been studied enough in Europe and needs further examination. Original drawings of all species are presented.

Blueberry scorch virus Detected on Blueberry Plants Imported Into China

Blueberry scorch virus (BlScV), a member of the Carlavirus genus in the Betaflexiviridae family, was first reported in the United States. Scorch caused by BlScV is a serious disease of blueberry and can lead to great loss of yield. At present, the disease has also been reported in Germany, Canada, Italy, and the Netherlands (Ciuffo et al. 2005; Kalinowska et al. 2013; Wegener and Punja 2004). However, the disease had never been reported on blueberry in China. Symptoms caused by BlScV range from asymptomatic to severe blighting of flowers and leaves depending on blueberry cultivars and virus strain. In 2015, 57 imported samples of highbush blueberry cultivars showing virus-like symptoms in an isolated blueberry orchard in Fujian Province (south China) were collected and tested for BlScV by DAS-ELISA using specific antiserum according to the manufacturer’s protocol (Agdia, U.S.A.). Among the samples, one was positive for BlScV in DAS-ELISA. To confirm the presence of the virus, RT-PCR was performed using BlScV-specific primers. A set of BlScV-specific primers, forward primer (5′-CTCAAGCCGCAGCGTCACA-3′) and reverse primer (5′-CACCAGTGTACTCCGTTTCGAGA-3′), was designed to amplify a 667-bp fragment of the coat protein gene of BlScV. Total RNA was extracted from the extracts of ELISA-positive sample using an RNA extraction kit (Qiagen, Germany). The first-strand cDNA was synthesized using cDNA synthesis kit (Promega, U.S.A.) according to the manufacturer’s instructions with the N6 random primer (Promega, U.S.A.). PCR was carried out using GoTaq Master Mix following the manufacturer’s protocol (Promega, U.S.A.). The program used for PCR amplification was 94°C for 3 min, followed by 35 cycles at 94°C for 30 s, 53°C for 30 s, and 72°C for 1 min, followed by a final extension at 72°C for 10 min. The expected 667-bp fragment was purified, ligated to pGEM-T easy vector (Takara, Japan), and sequenced. The obtained sequence was deposited in GenBank (accession no. KX977562) and analyzed. Further sequence comparison revealed that the amplicon nucleotide sequence was 97.6% identical to the sequence of an isolate of BlScV from the United States (KP232989), which confirmed the presence of BlScV. To our knowledge, this is the first report of BlScV in blueberries in China. In recent years, a number of blueberry cultivars from abroad have been introduced to China, and thus BlScV-infected blueberry has the potential to be an important long-distance vector. Considering that BlScV could become an important threat to blueberry production, all the imported blueberry bushes in the orchard were destroyed to prevent the spread of the virus.

Incidence of viruses in highbush blueberry (Vaccinium corymbosum L.) in Serbia

A large-scale survey for highbush blueberry (Vaccinium corymbosum L.) viruses in Serbia was performed from 2011 to 2015. A total of 81 leaf samples from 15 locations were collected and analyzed for the presence of 8 viruses. Serological ELISA assay was performed to determine the presence of: Blueberry scorch virus (BlScV), Blueberry shock virus (BlShV), Blueberry shoestring virus (BSSV), Blueberry leaf mottle virus (BLMoV), Tobacco ringspot virus (TRSV) and Tomato ringspot virus (ToRSV). All samples were tested for the presence of Blueberry red ringspot virus (BRRV) by PCR and for Blueberry mosaic-associated virus (BlMaV) by RT-PCR test. The analyses confirmed the presence of BlMaV in 8 (9.9%) samples and BRRV in 1 (1.2%) sample. No BlScV, BlShV, BLMoV, BSSV, TRSV or ToRSV viruses were detected in any of the analyzed samples.

Genetic variability of blueberry scorch virus isolates from highbush blueberry in New York State.

The genetic variability of blueberry scorch virus (BlScV) isolates from New York was determined within a portion of the RNA-dependent RNA polymerase gene and the triple gene block and coat protein (CP) genes. Phylogenetic analysis of 19 New York isolates and other isolates for which sequence information is available in GenBank revealed two distinct clades, regardless of the coding region analyzed, and limited variability within (0.029 ± 0.007) and between (0.183 ± 0.032) phylogroups. Recombination events were identified in the CP gene of three New York isolates, and codons of the five BlScV genes characterized were found to be under neutral or negative selective pressure.

First Report of Blueberry scorch virus in Elderberry in Poland.

Blueberry scorch virus (BlScV) is a member of the genus Carlavirus and one of the most widespread pathogens of highbush blueberry (Vaccinium corymbosum L.). The virus was first reported in the United States and has been reported in several countries in Europe, including Italy, Germany, the Netherlands, and Poland. Symptoms of scorch disease in highbush blueberry include necrosis of flower blossoms and leaves, shoot blight, and chlorosis. Sometimes BlScV infection is symptomless or limited to single blossoms and shoots, but all highbush blueberry cultivars are susceptible to virus infection. Cranberry (V. macrocarpon L.) and wild black huckleberry (V. membranaceum L.) are known as natural and symptomless hosts of BlScV (1). In June 2012, during the research concerning the occurrence of BlScV in plants outside Vaccinium sp., 15 leaf samples from five elderberry bushes (Sambucus nigra L., family Adoxaceae) were randomly collected from the Lodzkie region in Central Poland and three were positive in double antibody sandwich (DAS)-ELISA using specific antiserum (Agdia Inc., Elkhart, IN). To confirm the presence of the virus, total nucleic acid was extracted from ELISA-positive elderberry samples according to established protocol (T. Malinowski. Proc. 4th Int. EFPP Symposium, 445, 1996) and used in one step reverse transcription PCR. Primers were developed against the published NJ-2, BC-1, and BC-2 sequences of BlScV (GenBank Accession Nos. NC_003499, AY941198, and AY941199, respectively). The forward primer, RDP_1 (5'-ATGGCACTCACATACAGAAGTCC-3'), and the reverse primer, RDP_2 (5'-TGCCTCTTCAATGCACGATGTTC-3'), were used to amplify a 420-bp fragment of the RNA-dependent RNA polymerase gene of the virus. Amplicons of expected size were obtained from three DAS-ELISA-positive samples, while no products were observed for the negative control (DAS-ELISA-negative elderberry tissues). Sequence of one selected PCR product revealed 100, 88, and 87% nucleotide sequence identity and 100, 96, and 96% amino acid sequence identity with BC-2, NJ-2, and BC-1, respectively. BlScV-infected elderberry bushes were asymptomatic. As BlScV is transmitted by aphids in a non-persistent manner, infected elderberry bushes near highbush blueberry plantings may play an important role in virus spread. The potential for BlScV infection of plants outside family Ericaceae should be investigated. To the best of our knowledge, this is the first report of BlScV infecting elderberry. Reference: (1) R. R. Martin et al. Viruses 4:2831, 2012.

Molecular characterization of two distinct strains of blueberry scorch virus (BlScV) in northern Italy

During blueberry scorch virus (BlScV) surveys of highbush blueberries in Italy between 2005 and 2010, we initially discovered infected orchards only in Piedmont. Since 2009, however, three infected orchards have also been found in Trentino, where a new host species, Vaccinium ashei, was found to be infected by BlScV. Molecular characterization of isolates during the study period suggests that two very distinct epidemics are now present in Italy: the Piedmont isolates belong to a new BlScV strain, whereas the Trentino isolates are almost identical to the Washington State strain.

Visual inspections of nursery stock fail to protect new plantings from Blueberry scorch virus infection

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 in the host plant of up to 5 years. In many cases, we have observed BlScV symptom expression in new fields that appears inconsistent with aphid-vectored introduction and spread. It was, therefore, speculated that the virus may be 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 from one nursery 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 significantly 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 also surveyed the distribution of infected, symptomatic plants in recent ‘Duke’ plantings that originated from nurseries with BlScV-infected mother plants and compared distribution with older plantings with more advanced BlScV outbreaks. In all cases, the distribution of BlScV symptom development in young fields was random, which is consistent with introduction from planting stock. Older plantings showed a strong clustered distribution, which is consistent with aphid transmission. This study identifies infected nursery stock as an important source of BlScV dissemination and underscores the importance of having symptomless mother plants virus tested.

Seasonal variation in Blueberry scorch virus concentration in highbush blueberry and implications for disease monitoring and management

Seasonal variation in relative Blueberry scorch virus (BlScV) concentration was determined for three infected highbush blueberry, Vaccinium corymbosum, cultivars in a commercial field in southwestern British Columbia, Canada. Relative virus concentration per g of infected blueberry flower clusters and leaf terminal tissue varied during the season with significant cultivar-by-time interactions. Flower clusters had the highest BlScV concentration per g of tissue and could be collected in early May for disease surveys. Timing of leaf sample collection for BlScV surveys, transmission studies and virus purification should be based on studies of temporal variation in BlScV concentration for the principal cultivars in a production area.

Characterization of hydrangea chlorotic mottle virus, a new member of the genus Carlavirus

An isolate of the tentative carlavirus species Hydrangea chlorotic mottle virus (HdCMV) was found in New Zealand (NZ) in 2007. The host range, serological properties and complete genome sequence of this isolate were determined in this study. While the NZ isolate shared 98% nucleotide sequence identity with the US isolate of HdCMV, differences in titre and host range were found. The HdCMV-NZ genome sequence of 8,433 nt possessed a typical carlavirus organisation with six open reading frames. HdCMV is most closely related (60.4% nt identity) to blueberry scorch virus, a relationship also suggested by serology. These data suggest that HdCMV is a new carlavirus species.

EMERGING AND REEMERGING VIRUS DISEASES OF BLUEBERRY AND CRANBERRY

It should be expected that as blueberry cultivation continues to expand into new areas, the plants will become exposed to viruses that have not previously been observed in blueberry. Since the last symposium in 2004, Blueberry scorch virus continues to be a major concern in the USA Pacific Northwest and it has also been detected in New England as well as the Netherlands and Italy in Europe. In the past, blueberry mosaic symptoms appeared to spread very slowly or not at all, while in recent years, the disease has been spreading within fields and appearing in new fields. Blueberry mosaic symptoms have been observed in many production areas. A high molecular weight double-stranded RNA (dsRNA) has been detected in plants with mosaic symptoms indicating the presence of a virus, but the virus has yet to be characterized. Blueberry red ringspot virus has been detected in the southeastern USA. A virus has been detected in plants exhibiting Blueberry fruit drop symptoms in the Pacific Northwest. In cranberry, funky flower symptoms have been observed in the northeastern USA for the past 10 years. Recently, Cucumber mosaic virus has been detected in plants exhibiting funky flower symptoms. Efforts to demonstrate a causal relationship between Cucumber mosaic virus and disease symptoms are underway. Tobacco streak virus was first reported from cranberry plants imported into Scotland and has since been detected in New Jersey. A breakthrough in detection of viruses in Vacciniu#n species has come from the development of a dsRNA extraction method that works reliably with blueberry and cranberry. Cloning and sequencing of purified dsRNA has been the most successful means for the characterization of viruses of woody plants that can not be transmitted to herbaceous hosts. INTRODUCTION There were ten virus and virus-like diseases of blueberry and two of cranberry

Temporal trends in the transmission of Blueberry scorch virus in British Columbia, Canada

Every 2 weeks during the 2001–2003 growing seasons, 10–20 highbush blueberry, Vaccinium corymbosum ‘Berkeley’ (Ericaceae), trap plants were placed in two commercial fields in which the proportion of plants infected with Blueberry scorch virus (BIScV, all strain BC-2) ranged from 0.14 to 0.54. In 2003, Nicotiana occidentalis (Solanaceae) trap plants were placed in the same fields. After 2 weeks of field exposure, trap plants were removed and tested for BIScV for up to 5 years using serological and molecular assays. Aphids were sampled from trap plants, surrounding crop plants, and yellow-pan water traps. Nine of 938 trap plants (eight blueberry and one N. occidentalis) became infected with BIScV strain BC-2 between 13 May and 23 July. No transmission was recorded outside this time period. In three blueberry trap plants, BIScV was detected 2 years after field exposure. On crop plants, 0.4–7.0 aphids per leaf terminal were observed at peak density in June or July. In water traps, 35.6 (range 1–102) alatae were caught per month from May to July. The proportion of trap plants becoming infected during the transmission period was 0.0–0.04 depending on year and field. The data support the view that BIScV is not efficiently transmitted by aphids. The number of N. occidentalis trap plants that became infected was similar to blueberry, but aphid species infesting the two plants differed.

Primary and Secondary Parasitoids (Hymenoptera) of Aphids (Hemiptera: Aphididae) on Blueberry and Other <I>Vaccinium</I> in the Pacific Northwest

Blueberry scorch virus, a commercially important Carlavirus in highbush blueberry, Vaccinium corymbosum L., is vectored by aphids (Hemiptera: Aphididae). We surveyed the aphids, primary parasitoids (Hymenoptera: Aphelinidae, Braconidae), and associated secondary parasitoids (Hymenoptera: Charipidae, Megaspilidae, Pteromalidae) on highbush blueberry and other Vaccinium in the Pacific Northwest from 1995 to 2006, with samples concentrated in 2005 and 2006, to lay the groundwork for augmentative biological control. Ericaphis fimbriata (Richards) was the principal aphid. The dominant parasitoid species were Praon unicum Smith, Aphidius n. sp., A. sp., and Aphidius ervi Haliday. Their frequency in relation to the other primary parasitoids varied significantly with geographical area; P. unicum dominated the frequency distribution in southwestern British Columbia, A. n. sp., west of the Cascades, and A. sp. and A. ervi east of the Cascades. Among the secondary parasitoids, pteromalids dominated, and their frequency in relation to the other secondary parasitoids was lowest in southwestern British Columbia. The parasitization rate for P. unicum and A. n. sp. in southwestern British Columbia increased from May or June to a maximum of 0.080 +/- 0.024 and 0.090 +/- 0.084 (SD), respectively, in late July or early August. P. unicum emerged in the spring 4 wk before A. n. sp. The parasitization rate for P. unicum was lower in conventional than organic fields. Whereas aphid density increased monotonically, P. unicum had two spring peaks. A simulation model showed that these peaks could reflect discrete generations. Releases of insectary-reared P. unicum at 150 or 450 DD above 5.6 degrees C, summing from 1 January, may effectively augment the natural spring populations by creating overlapping generations.

First Report of Blueberry scorch virus in Black Huckleberry in British Columbia.

Blueberry scorch virus (BlScV), an aphid-borne carlavirus, causes a serious disease of highbush blueberry (Vaccinium corymbosum L.) in North America and Europe. Symptoms of BlScV infection on highbush blueberry include necrosis of flower blossoms and young leaves, shoot blight, and chlorosis. Currently, cranberry (Vaccinium macrocarpon L.) is the only other natural host of BlScV. In July 2004, wild black huckleberry (Vaccinium membranaceumL.) was sampled in the Kootenay Region of southeastern British Columbia. Foliar tissues were sampled during 2004 from 11 bushes from a clearing on the side of a mountain near Crawford Bay, BC, Canada and tested by double-antibody sandwich-ELISA using polyclonal antiserum (Agdia Inc., Elkhart, IN). BlScV was detected in 6 of the 11 bushes sampled and in the positive control (BlScV-infected blueberry leaf tissue) and was not detected in the negative control (healthy blueberry leaf tissue). To confirm the presence of the virus, total nucleic acid was extracted from ELISA-positive huckleberry samples according to an established protocol (A. Rowhani et al. Proc. Int. Counc. Stud. Viruses Virus-Like Dis. Grapevine, Extended Abstr. 13:148, 2000). Reverse transcription-PCR was performed using pd(T)12-18 random primer (Amersham Biosciences, Piscataway, NJ) for reverse transcription and BlScV-specific primers developed against the published NJ-2 sequence of BlScV (GenBank Accession No. NC_003499). Using the forward primer, BS708F, (5'-TCAATCCGTGGTGCTACGAG-3'), and the reverse primer, BS1188R, (5'-ACAGTGCGCAATGTTCCAGT-3'), a 480-bp amplicon was obtained from each of the ELISA-positive samples, while no ampli-cons were observed for the negative control (ELISA-negative huckleberry tissue). Direct sequencing of one selected amplicon revealed 90, 84, and 77% nucleotide sequence identity and 97, 96, and 88% amino acid sequence identity with strains NJ-2, BC-1 (GenBank Accession No. AY941198) and BC-2 (GenBank Accession Nos. AY941199), respectively. BlScV-infected huckleberries were asymptomatic. The presence of BlScV in alternate hosts has implications for disease epidemiology. Testing for BlScV in Vaccinium species in and around commercial highbush blueberry plantings, as well as lowbush blueberry (V. angustifolium Aiton), rabbiteye blueberry (V. ashei Reade), other native Pacific Northwest species (V. ovatum Pursh and V. parvifolium Smith), and ornamental Vaccinium species is warranted. To our knowledge, this is the first report of BlScV infecting black huckleberry.

The complete nucleotide sequence of Passiflora latent virus and its phylogenetic relationship to other carlaviruses

A virus identified as Passiflora latent virus (PLV) was isolated from passion fruit plants. Particle morphology, host range and serological properties suggested that this virus belongs to the genus Carlavirus. The complete genomic sequence of PLV was determined by sequencing overlapping cDNA fragments. The genome consisted of 8386 nt, excluding the poly (A) tail and contained six open reading frames, typical of carlaviruses. The overall similarities of the predicted amino acid sequence of PLV to those of other carlaviruses ranged from 25 to 73%. Phylogenetic analysis indicated that PLV was closely related to lily symptomless virus and blueberry scorch virus. This is the first report of the complete nucleotide sequence and genome structure of PLV.

Epidemiology and identification of strains of Blueberry scorch virus on highbush blueberry in British Columbia, Canada

Blueberry scorch virus (BlScV), first discovered in British Columbia, Canada, in 2000, causes a potentially serious disease on highbush blueberry (Vaccinium corymbosum). The epidemiology of BlScV was studied over four consecutive years (2001–2004) in British Columbia. In 2001, leaf tissue sampled from 40 commercial fields tested positive for BlScV, when using a polyclonal antibody in a double antibody sandwich – enzyme-linked immunosorbent assay. In 2002, 2003, and 2004, BlScV was detected in an additional 19, 49, and 12 previously uninfected fields, respectively. Disease spread was studied in more detail by mapping BlScV distribution in three commercial blueberry fields. The percent increase in diseased plants ranged from 4.4% to 5.2% from 2001 to 2002, and from 4.2% to 9.6% from 2002 to 2004. Symptoms on blueberry cultivars in May included necrosis of blossoms and young leaves, leaf chlorosis, and shoot blight; line patterns on the leaves of some infected cultivars were observed in October. BlScV was also detected in two additional Vaccinium spp., namely cranberry (V. macrocarpon) and black huckleberry (V. membranaceum). Reverse transcription – polymerase chain reaction with BlScV-specific primers was used to obtain partial sequences of the coat-protein gene for 12 BlScV isolates from blueberry in British Columbia. These sequences were compared with each other and with those of strains from United States (NJ-1, NJ-2, and WA-2) and two strains recently described in British Columbia (BC-1 and BC-2). The 12 British Columbia isolates shared 88%–100% homology with each other and were more closely related to BC-2 and NJ-2 than to BC-1, NJ-1, and WA-2. The high incidence of BlScV in highbush blueberry in British Columbia, the range of symptoms, the presence of BlScV in other Vaccinium spp., and the variability in sequences of the coat-protein gene among strains suggest that the virus is widespread and that different strains are now established in British Columbia.

Spatial and temporal distribution of winged aphids (Hemiptera: Aphididae) frequenting blueberry fields in southwestern British Columbia and implications for the spread of Blueberry scorch virus

AbstractAlate aphids were sampled in five fields of commercial blueberry, Vaccinium corymbosum L. (Ericaceae), during 2001 and 2002 using yellow tile, green tile, and Tremclad® yellow water traps. Eighty-seven species were identified among a total of 7722 alatae. Several of the species are known virus vectors, including Aphis fabae Scopoli, Brachycaudus helichrysi (Kaltenbach), Hyalopterus pruni (Geoffroy), Hyperomyzus lactucae (L.), Myzus persicae (Sulzer), Rhopalosiphoninus staphyleae (Koch), and Rhopalosiphum padi (L.). The number of species caught varied with year, and the number of species and the total number of alatae varied with field, trap colour, and season. More species were caught in 2001 than in 2002, in yellow than in green traps, and in the summer than in the spring or the autumn, and more alatae were caught in Tremclad® yellow traps than in yellow or green tile traps, and in the autumn than in the spring or the summer. However, numerous interactions limit generalizations. Analyses of the data for individual species revealed similar patterns and interactions. The effects of year, field, trap colour, and season varied with species. Given nonpersistent virus transmission and the large numbers of alatae caught of species that are known virus vectors, there is considerable potential for spread of Blueberry scorch virus by migrant aphids. Field- or area-specific and season-specific control strategies could be developed once the virus vector status of the different species is known. In addition, given the number of significant interactions observed in the data, there is a need to investigate alternative, generalized approaches to reducing virus transmission rates, such as applying whitewash or kaolin particle film to blueberry leaves.